A METHOD OF FABRICATING PARTICLEBOARD FROM
CELLULOSIC PLANT MATERIAL
A) TECHNICAL FIELD
[0001] The present invention generally relates to the field of fabricating
shaped boards, using agricultural waste products. The present invention
particularly relates to the composite boards such as particleboards and fiber
boards comprising cellulosic plant material. The present invention also relates to
method of making composite boards from cellulosic plant material.
B) BACKGROUND OF THE INVENTION
[0002] Particleboard is also known as chipboard. The particleboard is an
engineered wood product manufactured with the following components: wood
chips, sawmill shavings or sawdust, and a synthetic resin or other suitable binder.
These aforementioned components are pressed and extruded. Oriented strand
board (OSB) also known as flake board and wafer board. OSB is similar but uses
machined wood flakes offering more strength. All of these are composite
materials that belong to the spectrum of fiberboard products.
[0003] Particleboard is cheaper, denser and more uniform than
conventional wood and plywood. The particleboard is substituted for them when
appearance and strength are less important than cost. Different grades of particle
board have different densities. The particleboard with higher density has greater
strength.
[0004] The advantages of using particleboard over plywood is that the
particleboard is more stable (unless it gets wet), much cheaper to buy and more
convenient to use.
[0005] Particleboard is manufactured by mixing wood particles or flakes
together with a resin and converting the mixture into a sheet.
[0006] Using wood for manufacturing particleboard has following
negative effects. The natural resources ecosystem “forests” are affected and lost.
The loss of forest leads to ecological imbalance and global warming. The number
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of forests is decreasing. Further the need for alternative and engineered wood is
increasing which can replace the wood in various applications.
[0007] Straw is an agricultural by-product, the dry stalks of cereal plants
after the grain and chaff have been removed. Straw makes up about half of the
yield of cereal crops such as barley, oats, rice, wheat and rye. Straw is a valuable
renewable biomass resource if used properly. The straw has many uses such as
using in fuel, livestock bedding and fodder, thatching and basket making. There
are many alternative uses of straw. The most developed commercial uses include
feeding animals, producing electrical power and heat via combustion. Many
different kind of product can be made with straw. From old time’s straw has
making huts, crafts, horticulture and hats.
[0008] The straw is a lignocellulosic material produced as a byproduct
from agricultural crop production. Straw is mainly composed of cellulose,
hemicelluloses, lignin, nitrogenous compound and ash.
[0009] Open field burning is currently the most common and also perhaps
the most polluting agronomic particle for straw disposal. This disposal technique
although inexpensive and rapid is a controversial practice in many areas of the
world. The smoke and various gases including hydrocarbons that are emitted
during open burning create public health concerns. The especially high emission
rate of fine particulate matter and the consequent effects on visibility and
perceived effects on health have been largely responsible for the increasing
worldwide regulation or prohibiting of agricultural crop residue burning.
However off-field utilization may be a preferred approach.
[0010] Straw is generally not utilized for board production with the use of
conventional formaldehyde based resins because its fiber cells are surrounded by
a layer of wax/silica. This layer prevents the water based formaldehyde resins -
which are widely used today in the industrial fiber board manufacture.
[0011] There is a huge unused quantity of agricultural (straw) residues
around the globe. The estimated worldwide availability of wheat and rice straw
in several countries has increased with increase in the agriculture output.
According to the data, China, India and the USA appear to be the major straw
(mainly wheat and rice straw) producing countries.
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[0012] India is the second largest producer of straw residues. Hence this
straw residue is easily available and found to make commercial products on large
scale.
[0013] In the morphological structure, straw from wheat or rice is less
homogeneous than softwoods or hardwoods. When compared to wood, straw
contains relatively large number of cell elements and epidermal cells which
comprises a high amount of ash and silica. In a cross section, the epidermic cells
are the outermost surface cells and are covered by a thin waxy layer. This layer
lowers the wet-ability of straw with water based formaldehyde resins. Also straw
has a quite different chemical composition compared to wood. Straw has a higher
content of hemicelluloses, ash and silica, but a lower content of lignin compared
with wood.
[0014] Traditionally, rice straw and wheat straw is burnt after harvesting
the crops. Straw is a lignocelluloses biomass material and can have many
commercial uses for agriculture and industrial applications. Increasing
environmental and public health concerns with conventional straw disposal
methods, such as open-field burning, have made the alternative uses of straw
attractive in many countries. The challenge is developing an economically viable
options that can produce and market straw products to offset the harvesting and
processing costs.
[0015] Table 1 below illustrates the biochemical composition of the wheat
straw, rice straw and spruce wood:
[0016] There are hindrances with the manufacturing of the particle boards
because of hindrance in bonding of resin with straw to make
particleboard/strawboard. It adds additional processes and cost. Main problem
with using the straw to make a board is that there is a layer of wax and silica on
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the straw and it is more prominent in case of rice straw. Most of the cheap resins
available in the market are water based formaldehyde resins. So it is not possible
to make bonding between straw surface and urea formaldehyde resin without
some suitable treatment of the straw to remove that wax layer or to use some
other non water based high cost resin. These resins have problem in adhering to
the outermost wax layer so costly resins have to be used. Other option is to treat
the straw with chemicals or by thermal and mechanical treatment.
[0017] In polymer chemistry and material science, resin is a “solid or
highly viscous substance usually containing pre-polymers with reactive groups”.
Such viscous substances are plant derivatives or synthetic in nature. Synthetic
resins are material with a property of interest that is similar to natural plant
resins, they are viscous liquids that are capable of hardening permanently.
Otherwise chemically they are very different from the various resinous
compounds secreted by plants. The synthetic resins are of several classes. Some
synthetic resins are manufactured by esterification or soaping of organic
compounds. Some are thermosetting plastics in which the term “resin” is loosely
applied to the reactant or product or both.
[0018] In recent years, particle and fibre boards have been made with
other sources of cellulose fibre, such as agricultural biomass including corn
stover, rice straw, wheat straw, switch grass, and sugar cane bagasse. However,
many of these particle and fibre boards require the use of expensive items and do
not meet the required standard for use in structural applications in construction.
They also often are not suitable for applications where nails or screws are
required.
[0019] There is a need for particle and fibre boards that are made from
less expensive wood derived cellulosic material and/or cellulosic material that is
from readily available, fast growing cellulose sources or from agricultural waste
materials that are inexpensive to produce and meet the required standards for
structural applications in construction.
[0020] Hence, there is a need for a method for fabricating particleboards
from rice or wheat straw. Also there is a need for the particleboards fabricated
from straw for replacing wood based particleboard.
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C) OBJECTIVES OF THE INVENTION
[0021] The primary objective of the present invention is to provide a
method for fabricating particleboard from rice or wheat straw.
[0022] Another objective of the present invention is to provide
particleboards fabricated from straw (rice or wheat) for replacing the
use/application of wood based particleboard.
[0023] Yet another objective of the present invention is to analyze suitable
resin for fabricating particleboards from rice or wheat straw.
[0024] Yet another objective of the present invention is to analyze the
effect of changing the particle size of the rice or wheat straw on the strength of
the particleboard.
[0025] Yet another objective of the present invention is to provide a cost
effective method for fabricating the particleboard using rice or wheat straw.
[0026] Yet another objective of the present invention is to chemically treat
the wheat or rice straw for increasing the roughness of straw surface and
eliminating the need for expensive adhesive/resin.
[0027] Yet another objective of the present invention is to determine
moisture content, density and static bending strength of the wheat and rice straw
particleboard.
[0028] Yet another objective of the present invention is to subject the
wheat/rice straw particleboard to screw and nail withdrawal test.
[0029] Yet another objective of the present invention is to provide the
particleboards fabricated from straw (rice or wheat) for saving the forests and
reducing the pollution.
[0030] These and other objects and advantages of the present invention
will become readily apparent from the following detailed description taken in
conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0031] The various embodiments of the present invention provide
particleboard fabricated from natural cellulose based material. The embodiments
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of the present invention also provide a method for fabricating particleboard from
rice or wheat straw. The particleboards fabricated from straw (rice or wheat)
replace the use/application of wood based particleboard.
[0032] According to one embodiment of the present invention, the method
of fabricating particleboard from straw comprises of the following steps. The
straw is procured from villages. The straw is chopped using a fodder cutting
machine to obtain straw particles. The straw particles are separated using a sieve
into a plurality of groups based on particle size. The straw particles are divided
into two groups based on the particle length of the straw particles. The straw
particles in one group have a short length straw particle. The straw particles in
another group have long length straw particle. The length of the straw particles
of one group is more than that of the another group. The sieved straw particles
are chemically treated of the two groups with an alkali solution for a
predetermined time. The alkali solution is drained out of the straw particles of
the two groups after the predetermined time. The straw particles of the two
groups are rinsed for a plurality of times with water to remove alkali. The straw
particles of the two groups are sun dried to remove moisture content from the
straw particles. The straw particles of the two groups are heated in an oven to
remove the moisture content from the straw particles. Resin is sprayed on the
dried straw particles of the two groups and the two groups of resin sprayed straw
particles are mixed to obtain a mixture. The straw particles of the two groups are
mixed by a manual mixer. The mixture comprises of straw particles and the
resin. The resin is an urea formaldehyde resin. The mixture is placed in a mould
for casting and pressed with curing press to obtain a pre-pressed mixture. The
pre-pressed mixture is pressed in a CurinCat hot press machine for a
predetermined time under a predetermined pressure to obtain a particle board.
The predetermined time is 10 minutes. The predetermined pressure is obtained
by applying a load of 100 Kg f/cm3. The particleboards fabricated from straw
particles comprising the long length straw particle and short length straw particle
are obtained separately. The particleboards are cut in a rectangular shape. The
particleboards are subjected for physicochemical tests. The physiochemical tests
are a moisture content determination test, screw and nail withdrawal test and
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static bending strength determination test. The straw particles are rinsed with
water for five times. The resin is a urea formaldehyde resin.
[0033] According to one embodiment of the present invention, the straw
for fabricating the particleboard is selected from a group consisting of wheat
straw and rice straw.
[0034] According to one embodiment of the present invention, the straw
particles of short particle length have a length in a range of 1.5-3.5 mm. The
straw particles of long particle length have a length in a range of 3.5-12 mm.
[0035] According to one embodiment of the present invention, the alkali
is sodium hydroxide (NaOH) solution. The sodium hydroxide solution has a
predetermined concentration. The predetermined concentration of sodium
hydroxide solution is 1% v/v. The straw particles are treated with sodium
hydroxide solution for a predetermined time of 12 hours. The straw particles are
treated with alkali solution to obtain a rough surface.
[0036] According to one embodiment of the present invention, the
moisture content determination test is performed to ascertain that the
particleboard comprising small length straw particle have a moisture content of
6.37% when compared to the particleboard comprising long length straw particle
having a moisture content of 6.74%.
[0037] According to one embodiment of the present invention, the screw
withdrawal test is performed to ascertain that the particleboard comprising small
length straw particle have a capacity of 414.04 N when compared to the
particleboard comprising long length straw particle having a capacity of 318 N.
[0038] According to one embodiment of the present invention, the static
bending strength is performed to ascertain modulus of rupture and modulus of
elasticity. The particleboard comprising small length straw particle have a
modulus of rupture 2.732 N/mm2 when compared to the particleboard
comprising long length straw particle having a modulus of rupture 1.772N/mm2.
The particleboard comprising small length straw particle have a modulus of
elasticity 549.68 N/mm2 when compared to the particleboard comprising long
length straw particle having a modulus of elasticity 453.629N/mm2.
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[0039] According to one embodiment of the present invention, the
composition for fabricating particleboard from straw comprises of an alkali
treated straw particles and
[0040] A resin. The straw for fabricating the particleboard is selected from
a group consisting of wheat straw and rice straw. The resin is an urea
formaldehyde resin. The alkali for treating the straw particles is sodium
hydroxide. The straw particles are divided into two groups based on the particle
length of the straw particles. The straw particles in one group have a short length
straw particle and in another group has long length straw particle. The length of
the straw particles of one group is more than that of the another group.
[0041] According to one embodiment of the present invention, the straw
particles of short particle length have a length in a range of 1.5-3.5 mm. The
straw particles of long particle length have a length in a range of 3.5-12 mm.
[0042] According to one embodiment of the present invention, the
detailed work plan for the fabrication of the particleboard from rice or wheat
straw consists of the following steps: (a) studying about the availability and
composition of straw, (b) conducting research about the related problems, (c)
visiting a nearby plant of wood manufacturer engineering units to have a deeper
understanding, (d) obtaining the rice or wheat straw from the nearby villages, (e)
understanding the technology used to manufacturing the boards and modify it to
make it cost effective, (f) making arrangements to make the board in the institute,
(g) making sample particleboard product from the rice or wheat straw and testing
the strength and other properties, and (h) comparing the particleboards by
varying the resin, raw material and layout of straw.
[0043] According to one embodiment of the present invention, the ureaformaldehyde
(UF) resins are the main binders for wood composite boards, such
as particleboards, fiberboards or hardwood plywood. In the use of UF resins,
water solubility, adhesion, high curing rate and low cost are the attractive
properties. The adhesion of urea formaldehyde (UF) resin to the straw fiber has
been demonstrated in a research using an innovative chemi-thermo-mechanical
(CTM) pre-treatment of the straw.
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[0044] The urea formaldehyde (UF) resins are synthesized only from two
reactive components (urea and 45-50% aqueous solution of formaldehyde), the
variety of reactions in synthesis, storage and curing make urea formaldehyde
(UF) resins the object for research. Changing synthesis conditions of resins
provides relatively good possibilities of designing the structure and technical
properties of resins.
[0045] According to one embodiment of the present invention, the raw
straw (rice or wheat straw) is obtained from a nearby village. The general
method for fabrication of particleboard is as follows. The straw is chopped into
small particles using the fodder cutting machine. The straw is separated based on
the particle size. The particle size is in a range of 12-21mm particle size. The
straw is subjected to chemical treatment with 1% NaOH solution. This chemical
treatment process of straw involves soaking the straw particles in a 1% NaOH
solution at atmospheric temperature and pressure for 12 hours, after which the
NaOH solution is drained out of straw. Then straw particles are rinsed
thoroughly five times with water to remove alkali (NaOH) and then dried. Urea
formaldehyde resin is sprayed on these straw particles and they are mixed evenly
with help of hands to obtain a mixture. The mixture is then put in a mold for
casting and pressed. The mold is then removed and the mixture is carefully
placed in the curing press. The pre-pressed mixture is then again pressed in the
CurinCat hot press machine for 10 minutes to cure the particleboard. The
CurinCat hot press machine compresses the particleboard under a load of 100
Kgf/cm2 for 10 minutes. The particleboard is removed from curing press and cut
into a proper rectangular shape.
[0046] According to one embodiment of the present invention, the
chemical treatment of the rice or wheat straw by sodium hydroxide (NaOH)
solution is an important step for getting roughness on the surface of the straw.
For determining the duration of time period for keeping the straw in contact with
the NaOH solution is decided using the experimentation to get maximum
roughness in the least possible time.
[0047] According to one embodiment of the present invention, seven
samples of straw particles (rice or wheat straw) are soaked in the 1% w/v sodium
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hydroxide (NaOH) solution and taken out after fixed intervals of time. The straw
particles are washed with distilled water to remove the NaOH content from the
surface of the straw. The straw particles are then dried. The roughness is
measured using a roughness meter and the values are noted. It is observed that
the surface roughness of the straw particle becomes constant after treating the
straw particle with NaOH for 12 hours. The soaking time for straw particles is
determined to be 12 hours.
[0048] According to one embodiment of the present invention, after the
optimization of the duration of chemical treatment of the straw, the particleboard
is fabricated from rice straw. Following are the steps for fabricating the
particleboard from rice straw: the rice straw is chopped into small particles using
the fodder cutting machine. The straw particles are separated based on the
particle size. The particle size is in a range of 12-21 mm. The straw particles are
subjected to chemical treatment. The straw particles are treated with 1% w/v
NaOH solution. The chemical treatment process includes soaking the straw
particles in a 1% w/v NaOH solution at atmospheric temperature and pressure for
12 hours. After 12 hours NaOH solution is drained out of straw. The straw
particles are rinsed thoroughly five times with water to remove the alkali
(NaOH). The straw particles are dried. The urea formaldehyde resin is sprayed
on the straw particles. The urea formaldehyde resin and the straw particles are
mixed evenly with hands. The mixture is put in a mould for casting and pressed.
The mould is removed and the mixture is placed in the curing press. The prepressed
mixture is then again pressed in the CurinCat hot press machine for 10
minutes to cure the particleboard. The CurinCat hot press machine compresses
the particleboard under a load of 100 Kgf/cm2 for 10 minutes. The particleboard
is removed from the curing press. The particleboard is cut into rectangular shape.
[0049] According to one embodiment of the present invention, the
particleboard is tested for strength. It is observed that the strength and the
bonding of the particleboard are low. The modulus of rupture for the synthesized
particleboard is found to be 0.82 N/mm2 when compared to 10 N/mm2 in the
standard particle board. It is found that the mixing of the resin with the straw
particles is not good and the moisture content in the straw is high which cause
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the generation of steam during drying. The steam and moisture content loosens
the bonding between the straw and the resin. For overcoming the problem of the
non-uniform mixing the blender is made using local resources available.
[0050] According to one embodiment of the present invention, with the
blender the straw particles are mixed with the urea formaldehyde resin and the
improved particleboards are fabricated. The new particleboards are made with
very low amount of moisture content or no moisture.
[0051] According to one embodiment of the present invention, after
reduction of the moisture in straw particles, the particleboard with improved
physical property is fabricated from straw. Following are the steps for fabricating
the particleboard from straw with improved physical property. The straw is
chopped using fodder cutting machine. The straw particles are separated using a
sieve made at the institute into two groups based on the straw particle sizes. The
first group of straw particles have a particle size between 1.5-3.5 mm and the
other straw particle size is between 3.5-12 mm. Both the groups of straw
particles are chemically treated with 1% NaOH. In the chemical treatment
process the straw particles are soaked in a 1% NaOH solution at atmospheric
temperature and atmospheric pressure for 12 hours. After 12 hours the NaOH
solution is drained out of the straw particles. The straw particles are rinsed
thoroughly five times with water to remove alkali and dried. Both the groups of
straw particles are sun dried to remove moisture content. The sun dried straw
particles are heated in an oven to remove the extra moisture present in the straw
which is a big problem in particleboard fabrication. Urea formaldehyde resin is
sprayed on the dried straw particles. The straw particles and the sprayed urea
formaldehyde resin are mixed in a blender using manual force to obtain an
uniform straw mixture comprising straw particles and urea formaldehyde resin.
The mixture is placed in the mould for casting and pressing. The mould is
removed and the mixture is placed in the curing press. The pre-pressed mixture is
then again pressed in the CurinCat hot press machine for 10 minutes to cure the
particleboard. The CurinCat hot press machine compresses the particleboard
under a load of 100 Kg f/cm2 for 10 minutes. The particleboard is removed from
the curing press. The particleboard is cut into rectangular shape. The
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particleboards obtained are tested according to the Indian Standards to compare
the fabricated particleboard with standard particleboard available in market.
[0052] According to one embodiment of the present invention, the particle
size and the binder (urea formaldehyde resin) are factors determining the strength
of the particleboard. The smaller and average particle size of the straw yields a
particleboard with increased physical properties.
[0053] According to one embodiment of the present invention, the
particleboard fabricated from straw with improved physical property is subjected
for the determination of moisture content according to Indian Standards (IS),
screw and nail withdrawal test according to Indian Standards (IS) and
determination of the static bending strength according to the Indian Standards
(IS).
[0054] According to one embodiment of the present invention, the
particleboards fabricated with the new method are tested according to the Indian
Standards. Further the comparison between the particleboards and the standard
particleboard from market is made.
[0055] According to one embodiment of the present invention, the
quantity of the resin and the additive added for the fabrication of particleboard
from the rice or wheat straw is calculated and optimized. The calculation for the
amount of resin and the additive to be added to the straw for the fabrication of
the particleboard is done based on the following relations:
Amount of solid content of resin to be added= 10% of the weight of straw
Amount of solid content in the resin= 40%
Amount of ammonium chloride (hardener) = 0.5% of the solid content of
resin.
[0056] According to one embodiment of the present invention, the
moisture content and the density of the particleboard is determined according to
the Indian Standard (IS). The particleboard specimens should be of the full
thickness of the particleboard and should be 7.5 cm wide and 15 cm long. Each
sample of the particleboard is weighed accurately and the initial weight is
recorded as M1 (M1= weight of the sample before heating). The samples of
particleboard are dried in a ventilated oven at a temperature of 103°C until the
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mass is constant to 0.2% between two successive weighing made at an interval of
not less than 1 hour. The particleboard sample is cooled and weighed. The
weight is recorded as M2 (M2= weight of the sample after heating). Moisture
content is calculated by using the following formula:
Moisture content= [(M1-M2)/M2]*100
[0057] According to one embodiment of the present invention, the screw
and nail withdrawal test is conducted according to the Indian Standard (IS). The
nails are commonly used to join two pieces of boards. The strength with which
the nails bind the particleboards in taken into consideration. The nail withdrawal
test is used to determine the binding force of the nails when used with the
particleboards. In the nail withdrawal test, a nail is inserted inside the board with
the head portion of the nail protruding out. A universal testing machine is used to
pull the nail from the particleboard. The machine captures the force requirement
during the test. In the nail withdrawal test both the nail and the screws can be
used.
[0058] The procedure of the nail withdrawal test comprises of the
following steps. The length and width of the test sample particleboard is taken in
150 mm and 75 mm respectively. The thickness is made more than 30 mm by
adding three layers of particleboard using adhesive and clamps. Two wooden
screws of number 8 mm and 50 mm length are threaded into the particleboard
specimens/samples at right angle to the face up to half of their length in a prebore
of 2.5 mm. The holes are at mid-width at about 5 cm from the ends of the
specimen. The particleboard samples are tested on Universal testing Machine
(UTM). The specimen is inserted in the fixture with the head of the screw or nail
up. In the assembly for the screw or nail withdrawal test the rate of load is
applied to the specimen by a uniform motion at a rate of 1.5 mm/min.
[0059] According to one embodiment of the present invention, the static
bending strength of the particleboard is determined according to the Indian
Standard (IS). The static bending tests are used to determine the load carrying
capacity of the boards.
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[0060] The procedure of the static bending test comprises of the following
steps. A predetermined size of the particleboard specimen/sample is prepared as
per the standard protocol. The particleboard specimen/sample is placed under an
universal testing machine. The static bending test is conducted at a temperature
of 27°C±2°C. The load and the deflection is recorded at plurality of time
intervals. The specimen/sample particleboard is placed in a manner where both
the ends of the specimen/sample particleboard rest on planks. The middle/center
of the sample/specimen particleboard has equal distance from the ends. The
specimen/sample particleboard is continuously pressed at the middle/center. The
reaction force of the specimen/sample particleboard is measured by the machine.
[0061] The particleboard sample/specimens to be tested for static bending
strength are of 75 mm width is the nominal thickness is greater than 6 mm (t is
thickness in centimeter). The length of the specimen is 50+24 L (L is span length
in centimeters). The span between the supports is 24 t. The particleboard sample
is loaded at the center with the rate of loading calculated by the following
formula:
N=ZL2/6t
Where,
N= rate of loading in cm/min
Z= 0.0015
L=span length in cm
T= thickness in cm
[0062] These and other aspects of the embodiments herein will be better
appreciated and understood when considered in conjunction with the following
description and the accompanying drawings. It should be understood, however,
that the following descriptions, while indicating preferred embodiments and
numerous specific details thereof, are given by way of illustration and not of
limitation. Many changes and modifications may be made within the scope of
the embodiments herein without departing from the spirit thereof, and the
embodiments herein include all such modifications.
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E) BRIEF DESCRIPTION OF THE DRAWINGS
[0063] The other objects, features and advantages will occur to those
skilled in the art from the following description of the preferred embodiment and
the accompanying drawings in which:
[0064] FIG. 1 is a flow chart illustrating a method of fabricating
particleboard from straw, according to one embodiment of the present invention.
[0065] FIG. 2 is a graph illustrating the effect of soaking straw particles
in alkali solution for different time periods for optimizing roughness of the straw
particles, according to one embodiment of the present invention.
[0066] FIG. 3 is a photograph illustrating the perspective view of the
particleboard fabricated form the straw, according to one embodiment of the
present invention.
[0067] Although the specific features of the present invention are shown
in some drawings and not in others. This is done for convenience only as each
feature may be combined with any or all of the other features in accordance with
the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0068] In the following detailed description, reference is made to the
accompanying drawings that form a part hereof, and in which the specific
embodiments that may be practiced is shown by way of illustration. These
embodiments are described in sufficient detail to enable those skilled in the art to
practice the embodiments and it is to be understood that the logical, mechanical
and other changes may be made without departing from the scope of the
embodiments. The following detailed description is therefore not to be taken in a
limiting sense.
[0069] The various embodiments of the present invention provide
particleboard fabricated from natural cellulose based material. The embodiments
of the present invention also provide a method for fabricating particleboard from
rice or wheat straw. The particleboards fabricated from straw (rice or wheat)
replace the use/application of wood based particleboard.
17
[0070] According to one embodiment of the present invention, the method
of fabricating particleboard from straw comprises of the following steps. The
straw is procured from villages. The straw is chopped using a fodder cutting
machine to obtain straw particles. The straw particles are separated using a sieve
into a plurality of groups based on particle size. The straw particles are divided
into two groups based on the particle length of the straw particles. The straw
particles in one group have a short length straw particle. The straw particles in
another group have long length straw particle. The length of the straw particles
of one group is more than that of the another group. The sieved straw particles
are chemically treated of the two groups with an alkali solution for a
predetermined time. The alkali solution is drained out of the straw particles of
the two groups after the predetermined time. The straw particles of the two
groups are rinsed for a plurality of times with water to remove alkali. The straw
particles of the two groups are sun dried to remove moisture content from the
straw particles. The straw particles of the two groups are heated in an oven to
remove the moisture content from the straw particles. Resin is sprayed on the
dried straw particles of the two groups and the two groups of resin sprayed straw
particles are mixed to obtain a mixture. The straw particles of the two groups are
mixed by a manual mixer. The mixture comprises of straw particles and the
resin. The resin is an urea formaldehyde resin. The mixture is placed in a mould
for casting and pressed with curing press to obtain a pre-pressed mixture. The
pre-pressed mixture is pressed in a CurinCat hot press machine for a
predetermined time under a predetermined pressure to obtain a particle board.
The predetermined time is 10 minutes. The predetermined pressure is obtained
by applying a load of 100 Kg f/cm3. The particleboards fabricated from straw
particles comprising the long length straw particle and short length straw particle
are obtained separately. The particleboards are cut in a rectangular shape. The
particleboards are subjected for physicochemical tests. The physiochemical tests
are a moisture content determination test, screw and nail withdrawal test and
static bending strength determination test. The straw particles are rinsed with
water for five times. The resin is a urea formaldehyde resin.
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[0071] According to one embodiment of the present invention, the straw
for fabricating the particleboard is selected from a group consisting of wheat
straw and rice straw.
[0072] According to one embodiment of the present invention, the straw
particles of short particle length have a length in a range of 1.5-3.5 mm. The
straw particles of long particle length have a length in a range of 3.5-12 mm.
[0073] According to one embodiment of the present invention, the alkali
is sodium hydroxide (NaOH) solution. The sodium hydroxide solution has a
predetermined concentration. The predetermined concentration of sodium
hydroxide solution is 1% v/v. The straw particles are treated with sodium
hydroxide solution for a predetermined time of 12 hours. The straw particles are
treated with alkali solution to obtain a rough surface.
[0074] According to one embodiment of the present invention, the
moisture content determination test is performed to ascertain that the
particleboard comprising small length straw particle have a moisture content of
6.37% when compared to the particleboard comprising long length straw particle
having a moisture content of 6.74%.
[0075] According to one embodiment of the present invention, the screw
withdrawal test is performed to ascertain that the particleboard comprising small
length straw particle have a capacity of 414.04 N when compared to the
particleboard comprising long length straw particle having a capacity of 318 N.
[0076] According to one embodiment of the present invention, the static
bending strength is performed to ascertain modulus of rupture and modulus of
elasticity. The particleboard comprising small length straw particle have a
modulus of rupture 2.732 N/mm2 when compared to the particleboard
comprising long length straw particle having a modulus of rupture 1.772N/mm2.
The particleboard comprising small length straw particle have a modulus of
elasticity 549.68 N/mm2 when compared to the particleboard comprising long
length straw particle having a modulus of elasticity 453.629N/mm2.
[0077] According to one embodiment of the present invention, the
composition for fabricating particleboard from straw comprises of an alkali
treated straw particles and a resin. The straw for fabricating the particleboard is
19
selected from a group consisting of wheat straw and rice straw. The resin is an
urea formaldehyde resin. The alkali for treating the straw particles is sodium
hydroxide. The straw particles are divided into two groups based on the particle
length of the straw particles. The straw particles in one group have a short length
straw particle and in another group has long length straw particle. The length of
the straw particles of one group is more than that of the another group.
[0078] According to one embodiment of the present invention, the straw
particles of short particle length have a length in a range of 1.5-3.5 mm. The
straw particles of long particle length have a length in a range of 3.5-12 mm.
[0079] According to one embodiment of the present invention, the
detailed work plan for the fabrication of the particleboard from rice or wheat
straw consists of the following steps: (a) studying about the availability and
composition of straw, (b) conducting research about the related problems, (c)
visiting a nearby plant of wood manufacturer engineering units to have a deeper
understanding, (d) obtaining the rice or wheat straw from the nearby villages, (e)
understanding the technology used to manufacturing the boards and modify it to
make it cost effective, (f) making arrangements to make the board in the institute,
(g) making sample particleboard product from the rice or wheat straw and testing
the strength and other properties, and (h) comparing the particleboards by
varying the resin, raw material and layout of straw.
[0080] According to one embodiment of the present invention, the ureaformaldehyde
(UF) resins are the main binders for wood composite boards, such
as particleboards, fiberboards or hardwood plywood. In the use of UF resins,
water solubility, adhesion, high curing rate and low cost are the attractive
properties. The adhesion of urea formaldehyde (UF) resin to the straw fiber has
been demonstrated in a research using an innovative chemi-thermo-mechanical
(CTM) pre-treatment of the straw.
[0081] The urea formaldehyde (UF) resins are synthesized only from two
reactive components (urea and 45-50% aqueous solution of formaldehyde), the
variety of reactions in synthesis, storage and curing make urea formaldehyde
(UF) resins the object for research. Changing synthesis conditions of resins
20
provides relatively good possibilities of designing the structure and technical
properties of resins.
[0082] According to one embodiment of the present invention, the raw
straw (rice or wheat straw) is obtained from a nearby village. The general
method for fabrication of particleboard is as follows. The straw is chopped into
small particles using the fodder cutting machine. The straw is separated based on
the particle size. The particle size is in a range of 12-21mm particle size. The
straw is subjected to chemical treatment with 1% NaOH solution. This chemical
treatment process of straw involves soaking the straw particles in a 1% NaOH
solution at atmospheric temperature and pressure for 12 hours, after which the
NaOH solution is drained out of straw. Then straw particles are rinsed
thoroughly five times with water to remove alkali (NaOH) and then dried. Urea
formaldehyde resin is sprayed on these straw particles and they are mixed evenly
with help of hands to obtain a mixture. The mixture is then put in a mold for
casting and pressed. The mold is then removed and the mixture is carefully
placed in the curing press. The pre-pressed mixture is then again pressed in the
CurinCat hot press machine for 10 minutes to cure the particleboard. The
CurinCat hot press machine compresses the particleboard under a load of 100
Kgf/cm2 for 10 minutes. The particleboard is removed from curing press and cut
into a proper rectangular shape.
[0083] According to one embodiment of the present invention, the
chemical treatment of the rice or wheat straw by sodium hydroxide (NaOH)
solution is an important step for getting roughness on the surface of the straw.
For determining the duration of time period for keeping the straw in contact with
the NaOH solution is decided using the experimentation to get maximum
roughness in the least possible time.
[0084] According to one embodiment of the present invention, seven
samples of straw particles (rice or wheat straw) are soaked in the 1% w/v sodium
hydroxide (NaOH) solution and taken out after fixed intervals of time. The straw
particles are washed with distilled water to remove the NaOH content from the
surface of the straw. The straw particles are then dried. The roughness is
measured using a roughness meter and the values are noted. It is observed that
21
the surface roughness of the straw particle becomes constant after treating the
straw particle with NaOH for 12 hours. The soaking time for straw particles is
determined to be 12 hours.
[0085] Table 2 below illustrates the roughness of straw after being soaked
in NaOH solution for different time periods:
NaOH
Treatment
Time S. N. Ra Rasd Rmax Rmin
15min 1 0.399 0.0945 0.458 0.248
30min 2 0.434 0.0805 0.57 0.3255
1Hr 3 0.591 0.082 0.7295 0.4775
2Hr 4 0.851 0.133 0.502 0.6145
5Hr 5 0.8755 0.1205 1.0055 0.657
12Hr 6 1.1485 0.491 1.824 0.9035
24Hr 7 1.218 0.5905 2.5355 0.891
[0086] According to one embodiment of the present invention, after the
optimization of the duration of chemical treatment of the straw, the particleboard
is fabricated from rice straw. Following are the steps for fabricating the
particleboard from rice straw: the rice straw is chopped into small particles using
the fodder cutting machine. The straw particles are separated based on the
particle size. The particle size is in a range of 12-21 mm. The straw particles are
subjected to chemical treatment. The straw particles are treated with 1% w/v
NaOH solution. The chemical treatment process includes soaking the straw
particles in a 1% w/v NaOH solution at atmospheric temperature and pressure for
12 hours. After 12 hours NaOH solution is drained out of straw. The straw
particles are rinsed thoroughly five times with water to remove the alkali
(NaOH). The straw particles are dried. The urea formaldehyde resin is sprayed
on the straw particles. The urea formaldehyde resin and the straw particles are
mixed evenly with hands. The mixture is put in a mould for casting and pressed.
22
The mould is removed and the mixture is placed in the curing press. The prepressed
mixture is then again pressed in the CurinCat hot press machine for 10
minutes to cure the particleboard. The CurinCat hot press machine compresses
the particleboard under a load of 100 Kgf/cm2 for 10 minutes. The particleboard
is removed from the curing press. The particleboard is cut into rectangular shape.
[0087] According to one embodiment of the present invention, the
particleboard is tested for strength. It is observed that the strength and the
bonding of the particleboard are low. The modulus of rupture for the synthesized
particleboard is found to be 0.82 N/mm2 when compared to 10 N/mm2 in the
standard particle board. It is found that the mixing of the resin with the straw
particles is not good and the moisture content in the straw is high which cause
the generation of steam during drying. The steam and moisture content loosens
the bonding between the straw and the resin. For overcoming the problem of the
non-uniform mixing the blender is made using local resources available.
[0088] According to one embodiment of the present invention, with the
blender the straw particles are mixed with the urea formaldehyde resin and the
improved particleboards are fabricated. The new particleboards are made with
very low amount of moisture content or no moisture.
[0089] According to one embodiment of the present invention, after
reduction of the moisture in straw particles, the particleboard with improved
physical property is fabricated from straw. Following are the steps for fabricating
the particleboard from straw with improved physical property. The straw is
chopped using fodder cutting machine. The straw particles are separated using a
sieve made at the institute into two groups based on the straw particle sizes. The
first group of straw particles have a particle size between 1.5-3.5 mm and the
other straw particle size is between 3.5-12 mm. Both the groups of straw
particles are chemically treated with 1% NaOH. In the chemical treatment
process the straw particles are soaked in a 1% NaOH solution at atmospheric
temperature and atmospheric pressure for 12 hours. After 12 hours the NaOH
solution is drained out of the straw particles. The straw particles are rinsed
thoroughly five times with water to remove alkali and dried. Both the groups of
straw particles are sun dried to remove moisture content. The sun dried straw
23
particles are heated in an oven to remove the extra moisture present in the straw
which is a big problem in particleboard fabrication. Urea formaldehyde resin is
sprayed on the dried straw particles. The straw particles and the sprayed urea
formaldehyde resin are mixed in a blender using manual force to obtain an
uniform straw mixture comprising straw particles and urea formaldehyde resin.
The mixture is placed in the mould for casting and pressing. The mould is
removed and the mixture is placed in the curing press. The pre-pressed mixture is
then again pressed in the CurinCat hot press machine for 10 minutes to cure the
particleboard. The CurinCat hot press machine compresses the particleboard
under a load of 100 Kg f/cm2 for 10 minutes. The particleboard is removed from
the curing press. The particleboard is cut into rectangular shape. The
particleboards obtained are tested according to the Indian Standards to compare
the fabricated particleboard with standard particleboard available in market.
[0090] According to one embodiment of the present invention, the particle
size and the binder (urea formaldehyde resin) are factors determining the strength
of the particleboard. The smaller and average particle size of the straw yields a
particleboard with increased physical properties.
[0091] According to one embodiment of the present invention, the
particleboard fabricated from straw with improved physical property is subjected
for the determination of moisture content according to Indian Standards (IS),
screw and nail withdrawal test according to Indian Standards (IS) and
determination of the static bending strength according to the Indian Standards
(IS).
[0092] According to one embodiment of the present invention, the
particleboards fabricated with the new method are tested according to the Indian
Standards. Further the comparison between the particleboards and the standard
particleboard from market is made.
[0093] According to one embodiment of the present invention, the
quantity of the resin and the additive added for the fabrication of particleboard
from the rice or wheat straw is calculated and optimized. The calculation for the
amount of resin and the additive to be added to the straw for the fabrication of
the particleboard is done based on the following relations:
24
Amount of solid content of resin to be added= 10% of the weight of straw
Amount of solid content in the resin= 40%
Amount of ammonium chloride (hardener) = 0.5% of the solid content of
resin.
[0094] According to one embodiment of the present invention, the
moisture content and the density of the particleboard is determined according to
the Indian Standard (IS). The particleboard specimens should be of the full
thickness of the particleboard and should be 7.5 cm wide and 15 cm long. Each
sample of the particleboard is weighed accurately and the initial weight is
recorded as M1 (M1= weight of the sample before heating). The samples of
particleboard are dried in a ventilated oven at a temperature of 103°C until the
mass is constant to 0.2% between two successive weighing made at an interval of
not less than 1 hour. The particleboard sample is cooled and weighed. The
weight is recorded as M2 (M2= weight of the sample after heating). Moisture
content is calculated by using the following formula:
Moisture content= [(M1-M2)/M2]*100
[0095] Table 3 below illustrates the result obtained after conducting the
density and moisture content test of the particleboard fabricated from straw:
Small Particle board Large Particle board IS Particle board
(Flat pressed single
layer)
Initial mass
(M₁)(g) 111.45 118.44
Over-dry
mass(M₀) 104.78 110.96
(g)
Moisture
content (%) 6.37 6.74 10
Length (mm) 151.12 151.10 10
Width (mm) 76.09 76.06
Thickness
(mm) 15.23 13.12
Density (kg/m) 636.40 785.50
25
[0096] According to one embodiment of the present invention, the screw
and nail withdrawal test is conducted according to the Indian Standard (IS). The
nails are commonly used to join two pieces of boards. The strength with which
the nails bind the particleboards in taken into consideration. The nail withdrawal
test is used to determine the binding force of the nails when used with the
particleboards. In the nail withdrawal test, a nail is inserted inside the board with
the head portion of the nail protruding out. A universal testing machine is used to
pull the nail from the particleboard. The machine captures the force requirement
during the test. In the nail withdrawal test both the nail and the screws can be
used.
[0097] The procedure of the nail withdrawal test comprises of the
following steps. The length and width of the test sample particleboard is taken in
150 mm and 75 mm respectively. The thickness is made more than 30 mm by
adding three layers of particleboard using adhesive and clamps. Two wooden
screws of number 8 mm and 50 mm length are threaded into the particleboard
specimens/samples at right angle to the face up to half of their length in a prebore
of 2.5 mm. The holes are at mid-width at about 5 cm from the ends of the
specimen. The particleboard samples are tested on Universal testing Machine
(UTM). The specimen is inserted in the fixture with the head of the screw or nail
up. In the assembly for the screw or nail withdrawal test the rate of load is
applied to the specimen by a uniform motion at a rate of 1.5 mm/min.
[0098] Table 4 below illustrates the result obtained after conducting the
screw withdrawal test of the particleboard fabricated from straw:
Small particle board Large particle board IS flat pressed single
layered
Max. Load (1)
(N) 391.00 320.62
Max. Load (2)
(N) 437.08 315.80
Average Max.
Load 414.04 318.21 1250
(N)
26
[0099] According to one embodiment of the present invention, the static
bending strength of the particleboard is determined according to the Indian
Standard (IS). The static bending tests are used to determine the load carrying
capacity of the boards.
[00100] The procedure of the static bending test comprises of the
following steps. A predetermined size of the particleboard specimen/sample is
prepared as per the standard protocol. The particleboard specimen/sample is
placed under an universal testing machine. The static bending test is conducted at
a temperature of 27°C±2°C. The load and the deflection is recorded at plurality
of time intervals. The specimen/sample particleboard is placed in a manner
where both the ends of the specimen/sample particleboard rest on planks. The
middle/center of the sample/specimen particleboard has equal distance from the
ends. The specimen/sample particleboard is continuously pressed at the
middle/center. The reaction force of the specimen/sample particleboard is
measured by the machine.
[00101] The particleboard sample/specimens to be tested for static
bending strength are of 75 mm width is the nominal thickness is greater than 6
mm (t is thickness in centimeter). The length of the specimen is 50+24 L (L is
span length in centimeters). The span between the supports is 24 t. The
particleboard sample is loaded at the center with the rate of loading calculated by
the following formula:
N=ZL2/6t
where,
N= rate of loading in cm/min
Z= 0.0015
L=span length in cm
T= thickness in cm
27
[00102] Table 5 below illustrates the result obtained after conducting the
bending test of the particleboard fabricated from straw:
Small fiber particle board Long fiber particle board IS flat
pressed
single
layered
particle
board
Sample no 1 2 Avg. 1 2 Avg.
Modulus of 2.282 3.182 2.732 1.469 2.075 1.772 10
rupture
(N/mm2)
Modulus of
541.3
49 558.019 549.68 423.439 483.82 453.629 2000
Elasticity
( N/mm2)
[00103] Table 6 below illustrates the result obtained after analyzing the
physiochemical properties of the particleboards fabricated from long straw
particles and short straw particles:
Properties Small Straw
Fiber
Particleboard
Long Straw
Fiber
particleboard
IS flat pressed
single layered
particleboard
Moisture
content (%)
6.37 6.74 10
Density (Kg/m) 630.40 785.5 500-800
Screw
Withdrawal
load (Max.) (N)
414.04 318.21 1250
MOR (Modulus
of Rupture)
(N/mm2)
2.732 1.772 11
28
MOE (Modulus
of elasticity)
(N/mm2)
549.68 453.629 2000
[00104] According to one embodiment of the present invention, the
particleboards fabricated after drying the moisture content illustrate increased
strength when compared to the particleboards fabricated without completely
removing the moisture content. The particleboard fabricated with shorter straw
particles illustrates increase in the higher values of plurality of physiochemical
tests when compared to the particleboards fabricated with straw particles of long
length. The long length straw particles do not mix with the urea formaldehyde
resin uniformly when compared to the short length straw particles. The strength
of the particleboard fabricated from straw is comparable or at par with standard
particleboard. The particleboard fabricated from straw are used for low strength
applications.
[00105] FIG. 1 is a flow chart illustrating a method of fabricating
particleboard from straw, according to one embodiment of the present invention.
The method of fabricating particleboards from straw comprises of the following
steps. The straw is procured from the villages (101). The straw is wheat straw or
rice straw. The straw is chopped using the fodder cutting machine to obtain straw
particles (102). The straw particles are separated using a sieve into plurality of
groups based on particle size (103). The straw particles are divided into two
groups based particle size. The straw particles with particle size 1.5-3.5 mm are
placed in one group and the straw particles with particle size 3.5-12 mm are
placed into another group. The straw particles are chemically treated with alkali
for 12 hours (104). Both the group are treated with 1% v/v NaOH solution for 12
hours. The alkali solution is drained out of the straw particles after 12 hours
(105). The straw particles are rinsed plurality of times with water to remove
alkali (106).The straw particles of both the groups are rinsed five times with
water to remove the alkali. The straw particles are sun dried to remove the
moisture content (107). The straw particles are heated in oven to completely
remove the moisture content (108). Both the group of straw particles are
29
subjected to sun drying and heating in oven.The resin is sprayed on dried straw
particles and mixing to obtain a mixture (109). The resin is urea formaldehyde
resin. The straw particles of both the groups are mixed with urea formaldehyde
resin in a manual mixer to obtain a mixture. The mixture is placed in a mould for
casting and pressing with curing press to obtain a pre-pressed mixture (110). The
pre-pressed mixture is pressed in a CurinCat hot press machine for 10 minutes
under a load of 100 Kg f/cm3 and obtaining particleboard from straw of short
particle length and straw of longer particle length (111). Two different
particleboards are obtained. One particleboard fabricated from short length straw
particles and the other particleboard fabricated from long length straw particles.
The particleboards are cut and the particleboards are subjected for
physicochemical tests (112). The particleboards are cut into rectangular shape.
The particleboard are subjected to plurality of physiochemical tests. The
physiochemical tests are moisture content determination test, screw and nail
withdrawal test and determination of static bending strength. The tests are
conducted according to Indian Standards (IS).
[00106] FIG. 2 is a graph illustrating the effect of soaking straw particles
in alkali solution for different time periods for optimizing roughness of the straw
particles, according to one embodiment of the present invention. The alkali
solution is NaOH 1% v/v. FIG. 2 illustrates that the surface roughness of the
straw particles becomes constant after 12 hours. Based on the observations, the
soaking time for straw particles in NaOH 1% v/v is kept 12 hours.
[00107] FIG. 3 is a photograph illustrating the perspective view of the
particleboard fabricated form the straw, according to one embodiment of the
present invention. The FIG. 3 illustrates the uncut particleboards fabricated from
straw.
[00108] The foregoing description of the specific embodiments will so
fully reveal the general nature of the embodiments herein that others can, by
applying current knowledge, readily modify and/or adapt for various applications
such specific embodiments without departing from the generic concept, and,
therefore, such adaptations and modifications should and are intended to be
30
comprehended within the meaning and range of equivalents of the disclosed
embodiments.
[00109] It is to be understood that the phraseology or terminology
employed herein is for the purpose of description and not of limitation.
Therefore, while the embodiments herein have been described in terms of
preferred embodiments, those skilled in the art will recognize that the
embodiments herein can be practiced with modification within the spirit and
scope of the appended claims.
[00110] Although the embodiments herein are described with various
specific embodiments, it will be obvious for a person skilled in the art to practice
the embodiments herein with modifications. Although the embodiments herein
are described with various specific embodiments, it will be obvious for a person
skilled in the art to practice the embodiments herein with modifications.
G) ADVANTAGES OF THE INVENTION
[00111] The embodiments of the present invention provide a method for
fabricating particleboard from rice or wheat straw.
[00112] The embodiments of the present invention provide particleboards
fabricated from straw (rice or wheat) for replacing the use/application of wood
based particleboard.
[00113] The embodiments of the present invention analyze suitable resin
for fabricating particleboards from rice or wheat straw.
[00114] The embodiments of the present invention analyzes the effect of
changing the particle size of the rice or wheat straw on the strength of the
particleboard.
[00115] The embodiments of the present invention provide a cost effective
method for fabricating the particleboard using rice or wheat straw.
[00116] The embodiments of the present invention provide chemical
treatment for the wheat or rice straw for increasing the roughness of straw
surface and eliminating the need for expensive adhesive/resin.
31
[00117] The embodiments of the present invention determines the
moisture content, density and static bending strength of the wheat and rice straw
particleboard.
[00118] The embodiments of the present invention provides particleboards
fabricated from straw which withstands the screw and nail withdrawal test.
[00119] The embodiments of the present invention provide the
particleboards fabricated from straw (rice or wheat) for saving the forests and
reducing the pollution.
[00120] The foregoing description of the specific embodiments will so
fully reveal the general nature of the embodiments herein that others can, by
applying current knowledge, readily modify and/or adapt for various applications
such specific embodiments without departing from the generic concept, and,
therefore, such adaptations and modifications should and are intended to be
comprehended within the meaning and range of equivalents of the disclosed
embodiments.
[00121] It is to be understood that the phraseology or terminology
employed herein is for the purpose of description and not of limitation.
Therefore, while the embodiments herein have been described in terms of
preferred embodiments, those skilled in the art will recognize that the
embodiments herein can be practiced with modification within the spirit and
scope of the appended claims.
[00122] Although the embodiments herein are described with various
specific embodiments, it will be obvious for a person skilled in the art to practice
the embodiments herein with modifications. Although the embodiments herein
are described with various specific embodiments, it will be obvious for a person
skilled in the art to practice the embodiments herein with modifications.

We Claim:
1. A method of fabricating particleboard from straw, the method comprises
the steps of:
procuring straw from villages;
chopping the straw using a fodder cutting machine to obtain straw
particles;
separating the straw particles using a sieve into a plurality of
groups based on particle size, and wherein the straw particles are divided
into two groups based on the particle length of the straw particles, and
wherein the straw particles in one group have a short particle length and
wherein the straw particles in another group have a long particle length
and wherein a length of the straw particles of one group is more than that
of the another group;
chemically treating the sieved straw particles of the two groups
with an alkali solution for a predetermined time;
draining the alkali solution out of the straw particles of the two
groups after the predetermined time;
rinsing the straw particles of the two groups for a plurality of
times with water to remove alkali;
sun drying the straw particles of the two groups to remove a
moisture content from the straw particles;
heating the straw particles of the two groups in an oven to remove
the moisture content from the straw particles;
spraying a resin on the dried straw particles of the two groups and
mixing the two groups of resin sprayed straw particles to obtain a mixture,
and wherein the straw particles of the two groups are mixed by a manual
mixer, and wherein a mixture comprising straw particles and the resin is
obtained, and wherein the resin is an urea formaldehyde resin;
placing the mixture in a mould for casting and pressing with
curing press to obtain a pre-pressed mixture;
pressing the pre-pressed mixture in a CurinCat hot press machine
for a predetermined time under a predetermined pressure to obtain a
33
particle board, and wherein the predetermined time is 10 minutes and
wherein the predetermined pressure is obtained by applying a load of 100
Kg f/cm3, and wherein particleboards fabricated from straw particles
comprising the long particle length and short particle length are obtained
separately;
cutting the particleboards in a rectangular shape; and
subjecting the particleboards for physicochemical tests, and
wherein the physiochemical tests include a moisture content
determination test, a screw and nail withdrawal test and a static bending
strength determination test, and wherein the straw particles are rinsed with
water for five times, and wherein the resin is a urea formaldehyde resin.
2. The method according to claim 1, wherein the straw for fabricating the
particleboard is selected from a group consisting of a wheat straw and a
rice straw.
3. The method according to claim 1, wherein the straw particles of short
particle length have a length in a range of 1.5-3.5 mm, and wherein the
straw particles of long particle length have a length in a range of 3.5-12
mm.
4. The method according to claim 1, wherein the alkali is sodium hydroxide
(NaOH) solution, and wherein the sodium hydroxide solution has a
predetermined concentration, and wherein the predetermined
concentration of sodium hydroxide solution is 1% v/v, and wherein the
straw particles are treated with sodium hydroxide solution for a
predetermined time of 12 hours, and wherein straw particles are treated
with alkali solution to obtain a rough surface.
5. The method according to claim 1, wherein the moisture content
determination test is performed to ascertain that the particleboard
comprising small length straw particle have a moisture content of 6.37%
when compared to the particleboard comprising long length straw particle
having a moisture content of 6.74%.
34
6. The method according to claim 1, wherein the screw withdrawal test is
performed to ascertain that the particleboard comprising small length
straw particle have a capacity of 414.04 N when compared to the
particleboard comprising long length straw particle having a capacity of
318 N.
7. The method according to claim 1, wherein the static bending strength is
performed to ascertain modulus of rupture and modulus of elasticity, and
wherein the particleboard comprising small length straw particle have a
modulus of rupture 2.732 N/mm2 when compared to the particleboard
comprising long length straw particle having a modulus of rupture
1.772N/mm2, and wherein the particleboard comprising small length
straw particle have a modulus of elasticity 549.68 N/mm2 when compared
to the particleboard comprising long length straw particle having a
modulus of elasticity 453.629N/mm2.
8. A composition for fabricating particleboard from straw, the composition
comprises:
an alkali treated straw particles; and
a resin;
wherein straw for fabricating the particleboard is selected from a group
consisting of a wheat straw and a rice straw, and wherein the resin is an
urea formaldehyde resin, and wherein the alkali for treating the straw
particles is sodium hydroxide, and wherein the straw particles are divided
into two groups based on the particle length of the straw particles, and
wherein the straw particles in one group have a short particle length and
wherein the straw particles in another group have a long particle length
and wherein a length of the straw particles of one group is more than that
of the another group.
35
9. The composition according to claim 8, wherein the straw particles of short
particle length have a length in a range of 1.5-3.5 mm, and wherein the
straw particles of long particle length have a length in a range of 3.5-12
mm.