Description:FIELD OF THE INVENTION:
The present invention relates to a polypropylene composite material. The invention specifically relates to a functionalized polypropylene composite material and more specifically it relates to a process for the preparation of functionalized polypropylene composite materials using Glass fiber and Talc. The functionalized polypropylene composite material of the present invention has high stiffness and toughness with very high heat deflection temperature and long-term thermal stability for high temperature applications.

BACKGROUND OF THE INVENTION:
Polypropylene (PP) is one of the most important thermoplastic materials in the world and is widely used in our daily life for a wide range of applications compared to many other commodity polymers. It is the second most produced polyolefin after polyethylene and benefited from its lower cost, excellent chemical resistance against most organic materials, light weight, hydrophobic nature along with desirable mechanical and thermal properties.

Generally, polypropylene being a commodity thermoplastic has desirable thermal resistance which makes it hard to enter high service temperature applications such as under the bonnet components of passenger and commercial vehicles where mostly engineering polymers or filled polymers are used. The conventional process to get these properties is to blend the engineering polymers with fillers / fibers to make particulate / fiber reinforced composites and extrude in single screw extruder or twin-screw extruder. All these composites are dried, and injection molded and evaluated.

The conventional process for functionalization / melt grafting / cross-linking polypropylene involves a macroradical formation through various possible routes, for instance via thermal decomposition of peroxides for graft copolymerization and high energy irradiation (gamma and electron beams) for cross-linking of PP.

There are various prior known methods for preparing polypropylene composite materials along with cross linking and the same are disclosed herein below.

In CN112500641A, modified polypropylene composite material prepared by mixing polypropylene with glass fiber, liquid paraffin, silane coupling agents, ethylene-octylene copolymer along with specific compound antioxidant, specific beta nucleating agent and phthalic acid Tripropylene glycol diacrylate and ethoxylated trimethylolpropane triacrylate mixture as grafting agent to synergistically improve the aging resistance of the polypropylene, acid and alkali. All these materials are mixed in a mixer and extruded in Twin Screw Extruder in temperature range 180 – 235°C and rotating speed of screw is 100 – 600 / minute.

TW201224044A describes a process for making cross-linkable high melt strength polypropylene resins using cross-linkable silane-grafted polypropylene compositions. The processes generally include contacting a polyolefin, a multifunctional monomer and a silane compound in the presence of a radical initiator, wherein the polyolefin is selected from polypropylene, polyethylene, combinations thereof and copolymers thereof. More specifically cross-linkable vinyl triethoxy decane graft type polypropylene compositions made.

CN110872418A describes a method for the preparation of Polypropylene compositions. In this method, Polypropylene was blended with high molecular weight polypropylene, high molecular weight copolymer, crosslinking agent, calcium stearate, antioxidants, antibacterial agent, ultraviolet absorber, fillers glass fiber, calcium carbonate, and kaolin and extruding in a twin-screw extruder at 190 °C to 230 °C, with draw ratio of 40 and a screw diameter of 35 cm. The composition is used in the production of a hollow barrel with good mechanical strength and antibacterial properties with antibacterial rate is =99.9% without any reduction in mechanical properties.

CN101735545B describes the preparation of a high-rigidity light composite board for roof of automobile with high stiffness, high toughness, permanent moisture resistance, mildew resistance and no peculiar smell. This composite was made by blending polypropylene resin, high density polyethylene, polyfunctional monomer, GFPP resin, PE talc resin, PE resin, EAA resin, nano-powder catalyst, accelerating agent, initiator, antioxidant, wetting dispersant, foaming agent in high speed mixer and adding this mixture to a single or double-screw extruding machine with barrel temperature of 165 to 190 °C, the mold head temperature of 165 to 180 °C, the nip gap is 2.0 to 4.0 mm. The composite non-woven fabric of the extruded foam board is molded by thermoplastic molding process into single-face composite non-woven fabrics, after compression molding and cutting the edge material to obtain high-rigidity light composite board for roof of automobile.

Most of these processes mentioned above are single step processes of mixing all polymers, monomers, additives, cross linking agents, antioxidants, foaming agents etc, in Haake mixer, single screw extruder / twin screw extruder in situ. During these processes there are unwanted reactions between the Polymers / monomers / initiators / additives leading to unwanted side reactions, homopolymer formation etc. leading to lesser properties.

Hence, there is a need to further improve the thermal properties of polypropylene for high service temperature applications such as under the bonnet components of passenger and commercial vehicles.

SUMMARY OF THE INVENTION:
This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended to determine the scope of the invention.

The present invention provides a functionalized polypropylene composite comprising:
a) 40 wt.% to 90 wt.% of a functionalized polypropylene;
b) 10 wt.% to 40 wt.% of a fiber or 10 wt.% to 40 wt.% of a filler; and
c) 1 wt.% to 10 wt.% of an additive, wherein the additive comprises a compatibilizer, an antioxidant, carbon black and a processing aid, and
wherein the functionalized polypropylene comprises 90 wt.% to 99 wt.% of a polypropylene and 1 wt.% to 10 wt.% of a functional monomer.

In one of the embodiments of the present invention, the functionalized polypropylene composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the fiber; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid.

In another embodiment of the present invention, the functionalized polypropylene composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the filler; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid.

The present invention also provides a process for preparing a functionalized polypropylene composite, comprising:
(i) synthesizing a functionalized polypropylene;
(ii) blending the functionalized polypropylene with a fiber or a filler along with a compatibilizer, a processing aid, carbon black and an antioxidant in a mixer and extruding in an extruder to obtain a compounded material;
(iii) optionally thermally aging the compounded material; and
(iv) conditioning compounded material to obtain the functionalized polypropylene composite.

The present invention provides the functionalization/crosslinking of polypropylene and blending with fibers and fillers which helps in increasing the thermal stability of the polypropylene composites for the high service temperature applications.

The present disclosure relates to a process for the preparation of Functionalized polypropylene composites by the following process.

Synthesis of Functionalized Polypropylene (FPP) by reacting pristine polypropylene (PP) with different multifunctional monomers using different peroxides through reactive processing in Twin Screw Extruder with a variation in peroxide, monomers concentrations, temperature profile and Screw RPM.

The functionalized PP was dry blended with E- Glass fiber, Fillers along with standard additives like processing aids, colorants, antioxidants and compatibilizers in a high-speed mixer and extruded in Twin Screw Extruder in the form of granules.

The above obtained granules of functionalized PP reinforced with Glass fiber and other fillers were dried and molded into different test specimens by injection molding and evaluated their thermo-mechanical and thermal ageing properties.

Wherein, polypropylene selected is a homo, co or a random copolymer with ethylene having a Melt Flow Index in the range of 3 – 12 g/10 min and the Fibers are E-glass fibers with variation in length. Fillers are selected from Talc, CaCO3, and like with variation in particle size. These fibers/fillers are used as such or in a combination thereof.

DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates SEM picture of Glass Fiber reinforced Pristine Polypropylene.

Figure 2 illustrates SEM picture of Glass Fiber reinforced Functionalized Polypropylene.

DETAILED DESCRIPTION OF THE INVENTION:
The present disclosure addresses the drawbacks of the prior art and provides for a functionalized polypropylene composite material. Further, the present invention also provides a process for the preparation of functionalized polypropylene composite material with long-term thermal stability for high-temperature applications. The synthesized functionalized polypropylene composite material is simple, efficient and thermally stable as compared to other materials produced by existing methods.

For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present disclosure, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.

It must be noted that as used herein and in the appended claims, the singular forms "a", "and", and "the" include plural referents unless the context dictates otherwise. Thus, for example, reference to "a compound" includes a plurality of such compounds, and reference to "the step" includes reference to one or more steps and equivalents thereof known to those skilled in the art, and so forth.

The term “some” as used herein is defined as “none, or one, or more than one, or all.” Accordingly, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would all fall under the definition of “some.” The term “some embodiments” may refer to no embodiments or to one embodiment or to several embodiments or to all embodiments. Accordingly, the term “some embodiments” is defined as meaning “no embodiment, or one embodiment, or more than one embodiment, or all embodiments.”

The terminology and structure employed herein is for describing, teaching and illuminating some embodiments and their specific features and elements and does not limit, restrict or reduce the spirit and scope of the claims or their equivalents.

More specifically, any terms used herein such as but not limited to “includes”, “comprises”, “has”, “consists” and grammatical variants thereof is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. The specification will be understood to also include embodiments which have the transitional phrase “consisting of” or “consisting essentially of” in place of the transitional phrase “comprising.” The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim, except for impurities associated therewith. The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed disclosure.

Whether or not a certain feature or element was limited to being used only once, either way it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do NOT preclude there being none of that feature or element, unless otherwise specified by limiting language such as “there NEEDS to be one or more” or “one or more element is REQUIRED.”

As used herein, the term “about” is used to indicate a degree of variation or tolerance in a numerical or quantitative value. It indicates that the disclosed value is not intended to be strictly limiting, and may vary by plus or minus 5%, without departing from the scope of the invention.

Unless otherwise defined, all terms, and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by one having an ordinary skill in the art.

Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements presented in the attached claims. Some embodiments have been described for the purpose of illuminating one or more of the potential ways in which the specific features and/or elements of the attached claims fulfil the requirements of uniqueness, utility and non-obviousness.

Use of the phrases and/or terms such as but not limited to “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or variants thereof do NOT necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or alternatively in the context of more than one embodiment, or further alternatively in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

As used herein the terms “method” and “process” have been used interchangeably.

The present invention relates to a functionalized polypropylene composite.

In some embodiments, the functionalized polypropylene composite comprises:
a) 40 wt.% to 90 wt.% of a functionalized polypropylene;
b) 10 wt.% to 40 wt.% of a fiber or 10 wt.% to 40 wt.% of a filler; and
c) 1 wt.% to 10 wt.% of an additive, versus the total weight of the composite,
wherein the additive comprises a compatibilizer, an antioxidant, carbon black and a processing aid, and
wherein the functionalized polypropylene comprises 90 wt.% to 99 wt.% of a polypropylene and 1 wt.% to 10 wt.% of a functional monomer, versus the total weight of the functionalized polypropylene.

In another embodiment, the functionalized polypropylene composite comprises:
a) 40 wt.% to 90 wt.% of a functionalized polypropylene;
b) 10 wt.% to 40 wt.% of a fiber or 10 wt.% to 40 wt.% of a filler; and
c) 1 wt.% to 10 wt.% of an additive, versus the total weight of the composite,
wherein the additive consists of compatibilizer, antioxidant, carbon black and processing aid, and
wherein the functionalized polypropylene comprises 90 wt.% to 99 wt.% polypropylene and 1 wt.% to 10 wt.% of functional monomers and other additives, versus the total weight of the functionalized polypropylene.

In one of the embodiments of the present invention, the functionalized polypropylene composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the fiber; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid, versus the total weight of the composite.

In another embodiment of the present invention, the functionalized polypropylene composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the filler; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid, versus the total weight of the composite.

In an embodiment of the present invention, the antioxidant comprises 0.05 wt.% to 0.5 wt.% primary antioxidant; and 0.05 wt.% to 0.5 wt.% secondary antioxidant.

In an embodiment of the present invention the polypropylene is selected from polypropylene homopolymer, polypropylene copolymer and polypropylene random copolymer or a combination thereof. In yet another embodiment of the present invention, the functional monomer is selected from trimethylolpropane triacrylate (TMPTA) and pentaerythritol tetraacrylate (PETA) or a combination thereof.

In another embodiment of the present invention, the fiber is a glass fiber. The glass fiber is electrical glass fiber, wherein the diameter of the electrical glass fiber is 14-micron, and length of the electrical glass fiber is 4 mm. In yet another embodiment of the present invention, the filler is selected from talc, carbon black and calcium carbonate or a combination thereof. In one of the preferred embodiments of the present invention, the filler is talc with particle size varying from 3 to 10 microns.

In another embodiment of the present invention, the compatibilizer is polypropylene homopolymer or copolymer or random copolymer grafted with 2 wt.%. of maleic anhydride (PP-g-MA). In one of the preferred embodiments, the compatibilizer is polypropylene homopolymer or copolymer or random copolymer grafted with 2 wt.%. of maleic anhydride (PP-g-MA) with maleic anhydride content of 1 wt.%. In yet another embodiment of the present invention the processing aid is polyisobutylene. In one of the preferred embodiments, the processing aid is polyisobutylene (PIB) with a molecular weight of 4000 – 5000.

In another embodiment of the present invention, the antioxidant is selected from pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010) and Tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) or a combination thereof. In yet another embodiment of the present invention wherein the antioxidant comprises a primary antioxidant and a Secondary Antioxidant. The primary antioxidant is Irganox 1010. The Secondary Antioxidant is Irgafos 168.

In another embodiment of the present invention, the filler is carbon black having a density of 18.5 to 23.5 lb/ft3.

The present invention provides a process for preparing a functionalized polypropylene composite, comprising:
(i) synthesizing a functionalized polypropylene;
(ii) blending the functionalized polypropylene with a fiber or a filler along with a compatibilizer, a processing aid, carbon black and an antioxidant in a mixer and extruding in an extruder to obtain a compounded material;
(iii) optionally thermally aging the compounded material; and
(iv) conditioning the compounded material to obtain the functionalized polypropylene composite.

In one of the embodiments of the present invention, there is provided a process for preparing the functionalized polypropylene composite, wherein the process comprises:
(i) synthesizing the functionalized polypropylene;
(ii) blending the functionalized polypropylene with the fiber along with the compatibilizer, the processing aid, carbon black and the antioxidant in the mixer and extruding in the extruder to obtain the compounded material;
(iii) thermally aging the compounded material to obtain a thermally aged compounded material; and
(iv) conditioning the thermally aged compounded material to obtain the functionalized polypropylene composite.

In one of the embodiments of the present invention, there is provided a process for preparing the functionalized polypropylene composite, wherein the process comprises:
(i) synthesizing the functionalized polypropylene;
(ii) blending the functionalized polypropylene with the filler along with the compatibilizer, the processing aid, carbon black and the antioxidant in the mixer and extruding in the extruder to obtain the compounded material; and
(iii) conditioning of the compounded material to obtain the functionalized polypropylene composite.

In one of the preferred embodiments of the present invention, the process for preparing functionalized polypropylene composite material with high heat deflection temperature and long-term thermal stability for high-temperature applications, comprising:

- (a) Compounding Functionalized PPs (PP-g-TMPTA & PP-g-PETA) with a compatibilizer, a processing aid, a colorant, a primary antioxidant and a secondary antioxidant in a high-speed mixer obtain a compounded material; and
- (b) The compounded material was transferred to hopper of Extruder having L/D ratio of 40, Screw diameter – 18 mm and maintaining the barrel temperature profile of 160 – 230 °C, Screw RPM – 100-200.
- (c) The Glass fibres are fed from side feeder which is connected at the Zone-5 of the barrel of the extruder. These fibers and Functionalized PP homogeneously mixed during melt state and extruded into strands.
- (d) The extrudates were cooled under water and made into 3-4 mm granules and dried for 4 hours at 80 °C.
- (e) The compounded granules were molded into ASTM test specimens / articles, conditioned for 48 hours, and subjected to thermal aging and evaluated their mechanical properties.

In yet another embodiment of the present invention, the process of preparing Functionalized polypropylene composite material is conducted in a twin-screw extruder.

In one of the embodiments of the present invention the Functionalized polypropylene composite is prepared by:
(i) synthesis of the functionalized polypropylene;
(ii) blending the functionalized polypropylene with a filler in a mixer and feeding into an extruder to obtain a functionalized polypropylene composite material;
(iii) optionally, thermally aging the above functionalized polypropylene composite material; and
(iv) conditioning of functionalized polypropylene composite material to obtain the functionalized polypropylene composite.

In one of the embodiments of the present invention the functionalized polypropylene composite is prepared by:

- (a) Compounding Functionalized PPs (PP-g-TMPTA & PP-g-PETA) with talc filler, compatibilizer, a processing aid, a colorant, a primary antioxidant and a secondary antioxidant in a high-speed mixer obtain a compounded material;
- (b) The compounded material was transferred to hopper of Extruder having L/D ratio of 40, Screw diameter – 18 mm and maintaining the barrel temperature profile of 160 – 230 °C, Screw RPM – 100-200;
- (c) The above compounded functionalized polypropylene - talc filler composite materials were homogeneously mixed during melt state and extruded into strands;
- (d) The extrudates were cooled under water and made into 3-4 mm granules and dried for 4 hours at 80°C; and
- (e) The compounded granules were molded into ASTM test specimens / articles, conditioned for 48 hours, and subjected to thermal aging and evaluated their mechanical properties.

In another embodiment of the present invention, there is provided a process for preparing the functionalized polypropylene composite, wherein the fiber is a glass fiber. The filler is selected from talc, carbon black and calcium carbonate or a combination thereof. The compatibilizer is polypropylene homopolymer or copolymer or random copolymer grafted with 2 wt.%. of maleic anhydride (PP-g-MA). The processing aid is polyisobutylene. The antioxidant is selected from pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010) and Tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) or a combination thereof.

In one of the embodiments of the present invention, the functionalized polypropylene is synthesized by:
(i) compounding a polypropylene with a functional monomer and an initiator with a solvent under inert atmosphere in a high-speed mixer for about 5 to about 30 minutes at room temperature to obtain a compounded material;
(ii) transferring the compounded material to a extruder and grafting /copolymerization in melt stage at about 5 rpm to about 200 rpm, for about 5 minutes to about 20 minutes, at about 160°C to about 230 °C to obtain the functionalized polypropylene. The initiator used in the synthesis of the functionalized polypropylene is selected from Luperox 101 (2,5-Bis(tert-butyl peroxy)-2,5-dimethylhexane) and Trigonox–301 (3,6,9-Triethyl-3,6,9-trimethyl-1,2,4,5,7,8-hexoxonane).

In another embodiment of the present invention, the mixer or extruder includes Torque mixer, Micro compounder, Single Screw Extruder or a Twin-Screw extruder.

In one embodiment of the present invention, the polypropylene used in the synthesis of the functionalized polypropylene is selected from polypropylene homopolymer, polypropylene copolymer and polypropylene random copolymer or a combination thereof. The functional monomer is selected from trimethylolpropane triacrylate (TMPTA) and pentaerythritol tetraacrylate (PETA) or a combination thereof.

In another embodiment of the present invention, the functional monomer is selected from trimethylolpropane triacrylate (TMPTA), Pentaerythritol Tetraacryalte (PETA) or like materials. In yet another embodiment of the present invention, the functional monomer is multifunctional monomer.

In one of the embodiments of the present invention, the Functionalized Polypropylene obtained above in melt stage is cooled in air / water bath and made into granules and dried for about 4-6 hours at about 80°C.

In one of the embodiments of the present invention, the thermal ageing of functionalized polypropylene composite is conducted in hot air oven, wherein the temperature of thermal ageing is about 100°C to about 150 °C, and the thermal ageing is carried out for about 250 hours to about 300 hours.

In another embodiment of the present invention, the Functionalized polypropylene composite material shows excellent stiffness and toughness balance as indicated by increase in mechanical properties which further increased during thermal aging compared to Pristine PP – Glass fiber.

In yet another embodiment of the present invention, the functionalized polypropylene composite materials show excellent heat deflection temperature, and crystallization temperature by incorporation of Talc and Glass fiber into Functionalized PP. The HDT values increased to 159°C from 90°C for pristine PP.

In yet another embodiment of the present invention, the functionalized polypropylene – Glass fiber composites show better dispersion and less fiber pull out compared to polypropylene – GF composites.

The present application describes a functionalized polypropylene composite material. Further, the present invention also provides a method for preparing functionalized polypropylene composite material with high heat deflection temperature and long-term thermal stability for high-temperature applications as described herein.

Functionalized Polypropylene was synthesized through melt grafting by reacting polypropylene with Trimethylolpropane triacrylate (TMPTA) and other Functional Monomers in twin screw extruder initiated by the peroxide initiators - Luperox 101 (2,5-Bis(tert-butyl peroxy)-2,5-dimethylhexane) and Trigonox-301(3,6,9-Triethyl-3,6,9-trimethyl-1,2,4,5,7,8-hexoxonane) as 40% solution in hydrocarbons by variation of monomer, initiator concentrations, temperature profile and screw rpm under nitrogen atmosphere. The extruded functionalized polypropylene made into granules.

The functionalized polypropylene composite was produced by dry blending Functionalized PP with E-Glass Fiber in the second step along with compatibilizer, processing aid, colorants, and antioxidants in a high-speed mixer and extruded in twin screw extruder under optimized processing conditions.

Functionalized polypropylene – filler (Talc, Carbon Black, CaCO3) composite materials were also made under identical conditions as described herein.

Functionalized polypropylene composite materials were injection molded and evaluated their thermal ageing properties, thermal stability for high service temperature applications.

Wherein, polypropylene selected is a homo, co or a random copolymer with ethylene having a Melt Flow Index in the range of 3 – 12 g/10 minute and the Fibers are E-glass fibers with variation in length. Fillers are selected from Talc, CaCO3 and like with variation in particle size. These fibers / fillers are used as such or in a combination thereof.

High toughness, high Stiffness, and high LTTS, high heat deflection temperature properties were obtained for functionalised PP / GF composites compared to pristine PP homopolymer / GF composites.

The synthesized functionalized polypropylene composite materials are cost effective simple, efficient, environment friendly, and thermally stable as compared to other existing methods.

MATERIALS
Polymers / Copolymers / Compatibilizers: PP: Polypropylene: MFI: 12 g/ 10 minute; MFI: 3 gm / 10 minute; PP-g-TMPTA - Polypropylene grafted with Trimethylolpropane triacrylate; PP-g-MA – Polypropylene grafted with Maleic Anhydride (2wt%)- MFR – 100 gm/10 minutes).

Processing Aid: PIB – Polyisobutylene, Number Average molecular Weight: 4500-5000 which enhances flowability.

Monomers: TMPTA: Trimethylolpropane triacrylate; PETA: Pentaerythritol tetraacrylate.

Radical Initiators: Luperox 101 - 2,5-Bis(tert-butyl peroxy)-2,5-dimethylhexane; Trigonox – 301: Trigonox 301 (3,6,9-Triethyl-3,6,9-trimethyl-1,2,4,5,7,8-hexoxonane) 40% solution in hydrocarbons. These initiators initiate the graft copolymerization.

Fibers: Glass Fiber – Electrical Glass Fiber (14-micron diameter, 4 mm length)

Fillers: Talc: Particle Size: 3.30 to 3.80 Micron, Bulk density: 0.18 to 0.24 g/cc.

Colorant: Carbon Black – Density: 18.5 to 23.5 lb/ft3, Ash content: 1.5% max., Iodine number: 238 to 278 g/Kg.

Antioxidants: Irganox 1010: Primary antioxidant (pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl] propionate); Irgafos 168: Secondary antioxidant (Tris-(2,4-di-tert-butyl phenyl) phosphite.

EVALUATION OF THERMO-MECHANICAL PROPERTIES
Injection Molding:
The dried granules of Functionalized PP / Filler and Functionalized / Fiber composite materials were injecting molded into Tensile, Impact, and Flexural specimens as per ASTM D4101.

Melt Flow Index
Melt Flow Index (MFI) of the Functionalized PP, FPP – Talc, FPP – GF composites were measured as per ASTM D-1238 test method at 230°C, 2.16 kg load.

Thermo-Mechanical Properties:
The injection molded test specimens were conditioned for 40 hours at 23°C and 50% RH and their Tensile Properties (ASTM D638), Flexural Properties (ASTM D790), Izod impact properties (ASTM D256) and Heat deflection Temperature at 0.45MPa (ASTM D648) such as Tensile strength (TS), Tensile Modulus (TM), Flexural Strength (FS), Flexural Modulus (FM), Impact Strength (IS), Heat Deflection Temperature (HDT) were measured.

Long Term Thermal Stability:
Thermal ageing, which is an important property when it comes to long-term thermal stability (LTTS) property. LTTS property is essential in high-service temperature applications. Thermal ageing is conducted in a hot air oven. The temperature of the oven is set at 150 °C. The thermal ageing is conducted for 300 hours. The tensile, flexural and notched impact specimens are hung in the oven tray with the help of paper clip and the ageing is done for 300 hours. After thermal ageing, the specimens are taken out and kept for conditioning at 23 °C and 50% RH for 40 hours. After the conditioning, the specimens are tested for all mechanical properties.

Scanning Electron Microscopy
SEM images are captured at the cross-section of the impact fractured specimens in liquid nitrogen.

Differential Scanning Calorimetry
The Melting temperature (Tm), Crystallization Temperature (Tc) and other properties of Functionalized PP and their composite samples were measured by using Differential Scanning Calorimeter (DSC) with a heating rate of 10 °C / minute under nitrogen.

EXAMPLES
Example 1: Preparation of Functionalized polypropylene
Functionalized Polypropylene (FPP) was prepared by mixing Polypropylene (PP) with radical initiator viz. Luperox 101 and monomer viz. Trimethylolpropane Triacryalte (TMPTA). The initiator and monomer were dissolved in hexane solvent and added to PP. The entire mixture was transferred to a tumbler mixer and mixed for 10 – 15 minutes. The Polypropylene granules coated with TMPTA/Luperox 101 mixture are fed into the extruder hopper of a Twin-Screw Extruder. All these additions were conducted under nitrogen atmosphere. The above mixture was extruded in a Twin-Screw Extruder with a temperature profile maintained at 150 to 210°C (from feed to die – total 10 zones) and the screw rotation speed is set as 150 rpm. The twin screw is having L/D of 40 and screw diameter of 18 mm. The monomer concentration was varied from 1 to 10 wt.% and initiator concentration was varied from 100 – 1000 ppm. Vacuum degassing unit is attached at 8th zone of the barrel. The polymer melt comes out of a two-hole die, which is cooled in a water bath and taken to a pelletizer to pelletize the granules. The collected granules were dried for 2 hours at 80°C.

In a similar way functionalized PP-g-PETA was also prepared by replacing PETA in place of TMPTA by following the above procedure.

In a similar way both Functionalized Polypropylenes, viz., PP-g-TMPTA and PP-g-PETA were also synthesized in a similar way except replacing Luperox-101 with Trigonix – 301.

The functionalized polypropylene (PP-g-TMPTA and PP-g-PETA) graft copolymers were characterized by IR / Gravimetry / DSC / TGA. The unreacted monomer and homopolymer removed by extracting with suitable solvents like acetone, hexane. Extent of grafting measured by Gravimetry, IR and Soxhlet extraction using decalin solvent. Thermo-mechanical properties of PP / TMPTA and PP/PETA graft copolymers are given in Tables 1 and 2.

Table 1: Preparation of Functionalized Polypropylene
Functionalized Polypropylene Polypropylene (PP) % TMPTA / PETA (%) Luperox -101 / Trigonox – 301 (ppm)
1 100 0 0
2 97.5 2.5 250
3 95 5.0 250
4 92.5 7.5 250
5 90.0 10.0 250
6 97.5 2.5# 250
# PETA

Table 2: Thermo-mechanical properties of Functionalized Polypropylene

FPP (Details
Table 1) MFI (g/10 min) TS at yield (MPa) FS (MPa) FM (MPa) IS (J/m) HDT at 0.45 MPa (°C) Tm (°C) Tc (°C)
1 14 31 42 1543 22 90 164 118
2 16 25 48 1910 21 108 164 124
3 17 25 49 1860 21 112 164 126
4 13 28 50 1860 17 112 164 126
5 13 27 54 1880 16 112 164 126
6 23 27 51 1803 21 108 164 125

Addition of TMPTA or PETA, almost all properties which includes Melt Flow Index (MFI), Flexural Strength (FS), Flexural Modulus (FM), Heat Deflection Temperature (HDT) and Crystallization Temperature (Tc) increased whereas slight decrease in Tensile Strength (TS) and Impact Strength (IS). The increase in Flexural strength, Flexural modulus, and HDT mainly due to incorporation of monomers (TMPTA / PETA) into PP matrix which in turn increased cross-linking and the stiffness in functionalized PP. The crystallization temperature has increased significantly functionalized PPs by about 8 °C from 118 °C to 126 °C due to nucleating effect of graft copolymers (PP-g-TMPTA & PP-g-PETA) in Polypropylene matrix. There is no significant change in melting temperature (Tm) indicating that the polypropylene polymer architecture is intact, and no degradation observed under the conditions studied.

Example 2: Preparation of Functionalized Polypropylene – Talc Composites
Functionalized Polypropylene (FPP) and Talc composites were prepared by blending Functionalized polypropylene (FPP) with Talc (10 – 40 wt.%) with primary antioxidants, secondary antioxidants, compatibilizers in a tumbler mixer for 5 – 15 minutes. After blending, the FPP – Talc composites were fed through hopper into Twin Screw Extruder (TSE) and extruded with a temperature profile of 160 to 210 °C and the screw rotation speed of 150 rpm. The TSE is having L/D ratio of 40 and screw diameter of 18 mm. The extrudates were made into 2-4 mm granules, dried at 80 °C for 4-6 hours and injection molded into different test specimens and measured their thermo-mechanical properties. Various compositions and properties are given in Tables 3 – 4.

Table 3: Functionalized PP and Talc Composites
FPP / Talc Composites (FPP) wt.% PP
(wt.%) Talc
(wt. %) PP-g-MA (wt.%) Carbon black Antioxidants (wt.%) PIB (wt.%)
1 0 100 0 0 0 0 0
2 100 0 0 0 0 0 0
3 75 0 20 4 0.5 0.25 0.25
4 55 0 40 4 0.5 0.25 0.25

Table 4: Thermo-Mechanical Properties of Functionalized PP / Talc Composites
FPP / Talc composites
(Details in Table 3) MFI (g/10 min) TS (MPa) FS (MPa) FM (MPa) IS (J/m) HDT (°C) Tm (°C) Tc (°C)
1 14 31 42 1543 22 90 164 118
2 24 25 48 1910 21 108 164 124
3 16 36 62 3554 27 131 163 128
4 10 37 70 3987 22 138 162 129

The addition of talc to functionalized PP has increased melt flow index (MFI), tensile strength (TS), flexural strength (FS), flexural modulus (FM) and Heat Deflection Temperature (HDT) and crystallization temperature (Tc). MFI increased due to incorporation of co-monomers into functionalized graft copolymers – Talc composites. The increase in FM, FS, IS, TS is due to increase in stiffness. The FS & FM increased drastically due to synergistic effect of Talc and graft copolymers presence in FPP – Talc composites. The HDT increased by more than 20°C due to cross-linking of comonomers in FPP-Talc composites. The Tc increased by 10°C due to nucleating effect of TMPTA in FPP – Talc composites.

Example 3: Preparation of Functionalized Polypropylene – Glass fiber Composites
Functionalized PP (FPP) and Glass Fiber composites (20 – 40 wt.% were prepared by melt mixing of FPP with Glass fiber as described here. FPP granules and fibres were dried for 2 hours at 80°C before addition. The dried Functionalized PP granules were mixed with 0.25% - 1 wt.% of Polyisobutylene (PIB) in a tumbler mixer for 2 minutes. Once PIB coated as thin layer, another set of additives (0.25 to 2 wt.%) which includes Antioxidants (primary / secondary), Fillers especially carbon black (0.2 – 1 wt.%), PP-g-MA compatibilizer (4 wt.%) were fed into the tumbler mixer so that all these additives / fillers are coated uniformly on the FPP granules. The coated FPP granules with additives and fillers were transferred to the main hopper of the Twin Screw Extruder which feeds materials into the Zone-1 of the barrel. The Glass fibres are fed from side feeder which is connected at the Zone-5 of the barrel. The vacuum degassing unit is attached in the Zone-8 of the barrel. The temperature profile is maintained at 160 to 230 °C (Zone-1 to Zone 10). The screw rotation speed is set as 100 rpm. The extrusion of FPP, PIB and other additives were carried out in above TSE and the melt extrudates comes out of a two-hole die are cooled in a water bath and pelletized into 2-4 mm granules.

For comparison polypropylene – Glass Fiber composites made under identical conditions in the above compositions except replacing functionalized PP with Polypropylene. The collected granules were dried for 2 hours at 80 °C. After 48 hours, they were molded into different articles / test specimens. The FPP – GF composite compositions are given in Table 5 & their thermo-mechanical, thermal aging studies especially Long-Term Thermal Stability (LTTS) properties are given in Tables 6 and 7.

Table 5: Functionalized Polypropylene – Glass Fiber Composites
FPP / GF composites PP FPP (wt.%) Glass fiber (wt.%) PP-g-MA (wt.%) Carbon black Antioxidants (wt.%) PIB (wt.%)
1 100 0 0 0 0 0 0
2 75 - 20 4 0.5 0.25 0.25
3 0 75 20 4 0.5 0.25 0.25
4 0 55 40 4 0.5 0.25 0.25

Table 6: Thermo-Mechanical properties of Functionalized PP – Glass Fiber Composites
FPP/ GF Composites Tensile Strength @ Yield
(MPa) Flexural Strength
(MPa) Flexural Modulus
(MPa) Impact Strength (J/m) Elongation @ Yield (%) HDT @ 0.45 (°C) Crystallisation temperature (°C)
1 31 42 1543 20 14 90 118
2 49 62 3860 45 7 157 124
3 59 90 4230 48 5 158 128
4 85 115 8900 80 4 159 128

Functionalized PP – GF composites showed higher tensile strength (double), Flexural strength (double), Flexural Modulus (four times), and impact strength (four times) than PP – GF composites by increasing the concentration of GF and FPP in FPP – GF composites. This clearly indicated that the stiffness and toughness balance in functionalized polypropylene increased due to cross-linking of functionalized monomers & bonding between the glass fibers and FPP matrix (Table 6). The heat deflection temperature increased by > 65oC due to synergistic effect of Glass fibers and cross-linking of functional monomers in FPP – GF composites.

Table 7: Thermo- Mechanical Properties of Functionalized PP – Glass Fiber Composites after Thermal Aging
FPP / GF composites TS @ Yield
(MPa) FS
(MPa) FM
(MPa) Notched
IS @ 23oC (J/m) E @ Yield (%) HDT @ 0.45 (°C) Tc
(°C)
1 24 44 1732 13 11 105 118
2 44 65 3428 37 8 157 125
3 61 93 5004 55 6 159 126
4 89 117 8920 83 3 159 126

Thermal aging of FPP – GF composites further increased the mechanical properties such as Tensile strength (3 times), Flexural strength (2 times), Flexural Modulus (4 times), Impact strength (6 times) and heat deflection temperature and crystallization temperature (Table 7) due to cross-linking during thermal aging.

Table 8: Retention of Tensile Strength and Flexural Strength in FPP – GF and PP-GF Composites after thermal aging studies
PP/GF and FPP / GF composites Tensile strength at yield (MPa) Retention of Property (%) Flexural strength (MPa) Retention of Property (%)
Before Aging After Aging Before Aging After Aging
PP/GF 49 44 -9 62 65 4
FPP / GF 59 61 4 90 93 4

The tensile strength and Flexural strength were retained in FPP – GF composites after thermal aging for 300 hours at 150 °C compared to pristine PP – GF composites due to cross-linking of functional monomers in FPP – GF composites (Table 8).

Table 9: Retention of Flexural Modulus and Impact Strength in FPP-GF and PP-GF Composites after thermal aging studies

PP/GF and FPP / GF composites Flexural Modulus (MPa) Retention of Property (%) Notched Impact Strength @ 23°C Retention of Property (%)
Before Aging After Aging Before Aging After Aging
PP/GF 3860 3428 -11 45 37 -17
FPP / GF 4230 5004 18 48 51 6.9

Functionalized PP – GF composites showed improved mechanical properties such as Flexural modulus, Notched impact strength after thermal aging whereas PP – GF composites showed deterioration. This is due to better homogenization between FPP and GF leading to higher bonding between Functionalized PP matrix and Glass Fibers as seen in Figures 1 and 2. This higher bonding leads to less pull out in FPP – GF composites compared to PP – GF composites (Table 9).

Advantage of the present invention:
Applications of developed functionalized polypropylene / GF composites:
• Under the bonnet components of Passenger and Commercial vehicles.
• Components such as Air intake manifolds, HVAC housings, Fans and shrouds, Parts for cooling systems and technical components exposed to high heat and loads.
• Dashboard components of Passenger vehicles
• Dishwasher, washing machine, and refrigerator components where thermal stability is required. , Claims:1. A functionalized polypropylene composite comprising:
a) 40 wt.% to 90 wt.% of a functionalized polypropylene;
b) 10 wt.% to 40 wt.% of a fiber or 10 wt.% to 40 wt.% of a filler; and
c) 1 wt.% to 10 wt.% of an additive wherein the additive comprises a compatibilizer, an antioxidant, carbon black and a processing aid; and
wherein the functionalized polypropylene comprises 90 wt.% to 99 wt.% of a polypropylene and 1 wt.% to 10 wt.% of a functional monomer.
2. The composite as claimed in claim 1, wherein the composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the fiber; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid.
3. The composite as claimed in claim 1, wherein the composite comprises 40 wt.% to 90 wt.% of the functionalized polypropylene; 10 wt.% to 40 wt.% of the filler; 1 wt.% to 10 wt.% of the compatibilizer; 0.1 wt.% to 1 wt.% of the antioxidant; 0.1 to 5 wt% of carbon black and 0.1 wt.% to 10 wt.% of the processing aid.
4. The composite as claimed in claim 1, wherein the polypropylene is selected from polypropylene homopolymer, polypropylene copolymer and polypropylene random copolymer or a combination thereof and the functional monomer is selected from trimethylolpropane triacrylate (TMPTA) and pentaerythritol tetraacrylate (PETA) or a combination thereof.
5. The composite material as claimed in claim 1, wherein the fiber is a glass fiber; and the filler is selected from talc, carbon black and calcium carbonate or a combination thereof.
6. The composite material as claimed in claim 1, wherein the compatibilizer is polypropylene homopolymer or copolymer or random copolymer grafted with 2 wt.%. of maleic anhydride (PP-g-MA); and the processing aid is polyisobutylene.
7. The composite material as claimed in claim 1, wherein the antioxidant is selected from pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010) and Tris(2,4-di-tert-butylphenyl)phosphite (Irgafos 168) or a combination thereof.
8. A process for preparing a functionalized polypropylene composite, comprising:
(i) synthesizing a functionalized polypropylene;
(ii) blending the functionalized polypropylene with a fiber or a filler along with a compatibilizer, a processing aid, carbon black and an antioxidant in a mixer and extruding in an extruder to obtain a compounded material;
(iii) optionally thermally aging the compounded material; and
(iv) conditioning the compounded material to obtain the functionalized polypropylene composite.
9. The process as claimed in claim 8, wherein the process comprises:
(i) synthesizing the functionalized polypropylene;
(ii) blending the functionalized polypropylene with the fiber along with the compatibilizer, the processing aid, carbon black and the antioxidant in the mixer and extruding in the extruder to obtain the compounded material;
(iii) thermally aging the compounded material to obtain a thermally aged compounded material; and
(iv) conditioning the thermally aged compounded material to obtain the functionalized polypropylene composite.
10. The process as claimed in claim 8, wherein the process comprises:
(i) synthesizing the functionalized polypropylene;
(ii) blending the functionalized polypropylene with the filler along with the compatibilizer, the processing aid, carbon black and the antioxidant in the mixer and extruding in the extruder to obtain the compounded material; and
(iii) conditioning of the compounded material to obtain the functionalized polypropylene composite.
11. The process as claimed in claim 8, wherein the functionalized polypropylene is synthesized by:
(i) compounding a polypropylene with a functional monomer and an initiator with a solvent under inert atmosphere in a high-speed mixer for about 5 to about 30 minutes at room temperature to obtain a compounded material;
(ii) transferring the compounded material to an extruder and graft copolymerizing in melt stage at about 5 rpm to about 200 rpm, for about 5 minutes to about 20 minutes, at about 160°C to about 230 °C to obtain the functionalized polypropylene,
wherein the initiator is selected from luperox 101 (2,5-Bis(tert-butyl peroxy)-2,5-dimethylhexane) and trigonox–301 (3,6,9-Triethyl-3,6,9-trimethyl-1,2,4,5,7,8-hexoxonane).
12. The process as claimed in claim 8, wherein the thermal ageing of functionalized polypropylene composite is conducted in hot air oven, wherein the temperature of thermal ageing is about 100°C to about 150 °C, and the thermal ageing is carried out for about 250 hours to about 300 hours.