Field of the invention
Present invention relates thermal insulating materials. More particularly, present invention provides thermal insulating materials comprising a filling of dried Eichhornia crassipes whole plant or petioles thereof, as thermal insulating material.

Background of the invention
The term thermal insulation refers to the use of materials, methods or processes to reduce the rate of heat transfer. This technique minimizes the transfer of heat energy from inside to outside and vice-versa, for the system by reducing the conduction, convection and radiation effects.
Various thermal insulating materials like acetate acrylic, beryllium oxide, ceramic glass, polyolefins, polystyrene, silicone rubber, polyurethane foam, loose fill, expanded perlite etc. are used for thermal insulation.
Expanded polystyrene is known in art for its insulation properties, however, expanded polystyrene suffers disadvantages of being inflammable. Though, fire-retardant grades are also available, for expanded polystyrene, it breaks down gradually when exposed to direct sunlight. Also, another disadvantage is that expanded polystyrene reacts with solvents used in the installation of fibreglass-reinforced plastic (such asstyrene-formulated polyesters) as well as with other organic solvents (petrol, kerosene, acetone, etc.).
Another material known in art for use as thermal insulating material is expanded perlite, which has good insulating efficiency, but is only effective when it is dry or in a loose granular state. The granules tend to absorb moisture and settle after installation. It becomes less effective as an insulation material with time.
Also, known in art is fibreglass, which suffers the disadvantage of having poor structural strength or compression resistance, a tendency to settle after installation if not properly installed, and its permeability to moisture.
One of the oldest known, most widely used conventional insulating materials is cork particularly in refrigeration industry. Corks are obtained from trees, which has led to scarcity of cork producing trees. Its main technical limitation is the tendency to absorb moisture. All these materials demand high input costs and have one or another limitation.
In view of foregoing, there arises a need to develop and explore novel insulating material, which does not suffer from disadvantages associated with conventional insulating materials, as mentioned above.

Summary of Invention:
An objective of the present invention is to provide, insulating materials comprising dried Eichhornia crassipes.
Yet another objective of the present invention is to provide insulating materials comprising dried whole plant of Eichhornia crassipes.
Yet another objective of the present invention is to provide insulating materials comprising dried petioles of Eichhornia crassipes.
According to an embodiment of the present invention, the plant should be dried in a range from 40 Degree Celsius to 80 Degree Celsius, preferably 60 Degree Celsius, before use as insulating material.
Yet according to another embodiment of the present invention, filled weight of petioles in the container for this experiment ranges from 30g/1000cc or 30g/l to 80g/1000cc or 80g/l, preferably 50g/l or 50g/1000cc.

Description of Figures:
Fig 1: Shows insulating containers. Fig 1A is single walled container, Fig 1B is double walled container and Fig 1C is double walled container with Eichhornia crassipes or Glasswool
Fig. 2: Regression curve for single container (cold treatment)
Fig. 3: Regression curve for double walled container (cold treatment)
Fig. 4: Regression curve for double walled container with Eichhornia crassipes (cold treatment)
Fig. 5: Regression curve for double walled container with glasswool (cold treatment)
Fig. 6: Thermal insulating capacity of Eichhornia crassipes petioles in cold treatment
Fig. 7: Thermal insulation capacity of Eichhornia crassipes petioles for heat retention.
Fig. 8: Regression curve for single container (hot treatment).
Fig. 9: Regression curve for double walled container (hot treatment)
Fig. 10: Regression curve for double walled container with Eichhornia crassipes petioles (hot treatment).
Fig.11: Regression curve for double walled container with glasswool (hot treatment)

Examples:
Material used
The petioles of Eichhornia crassipes were harvested and transversely cut into small pieces measuring about 5mm-10mm. The material was kept for sun-drying to remove the moisture from the material. After that, the material was oven-dried at 60°C and used for further studies.
Procedure for thermal insulation
To study the thermal insulation capacity of Eichhornia crassipes, an indigenous apparatus was designed (Fig. 1). Two steel containers of volume 3 litres (i) and 1 litre (ii) respectively were used for the study having concentric holes in both the lids with thermometers sealed with rubber stopper to prevent any breakage, and to conserve heat. All the experiments were performed in BOD incubator at constant temperature of 35°C which was considered as ambient temperature. Four types of experiments were designed. In the first experiment (Single walled Fig 1 A) container was filled with cold water and initial temperature recorded. Readings for change in temperature were taken after every hour till it approaches near ambient temperature. The same experiment was performed by taking hot water. In the second experiment (Double walled, Fig 1 B), the container (ii) was placed within container (i). Container (ii) was filled with cold water having same initial temperature as that of first experiment while the space left within two containers contains only air. The experiment was repeated by taking hot water. Third experiment (Double walled with Eichhornia crassipes, Fig 1 C) was similar to that of the second experiment, with the difference that the space between the two walls was filled with dried petioles of Eichhornia crassipes. The fourth experiment was same as that of third, only the difference was the replacement of Eichhornia crassipes with glasswool which is commercially used material for thermal insulation.
The density of the dried plant material used was found to be 0.026 g cm-3 and that of glasswool was 0.066 g cm-3. 50g of plant material was compared with equal weight of glasswool for thermal insulation.

Control Experiment:
Use of Eichhornia crassipes petioles for thermal insulation
Cold water temperature control
To study the thermal insulation properties of petioles of Eichhornia crassipes, two different sets of experiments with hot and cold water were performed. Observations were made in double walled containers, filled with dried petioles, containing hot or cold water in comparison to single walled container, empty double walled containers and commercially used glasswool.

Table 1: Thermal insulation of cold water with petioles of Eichhornia crassipes in comparison with single walled, double walled empty container, double walled container with glasswool.

No. of Hours
Temperature in Single Walled Container (°C)
Temperature in Double Walled Container with air (°C)
Temperature in Double Walled Container with Eichhornia crassipes (°C)
Temperature in Double Walled Container with Glasswool (°C)
0 1 1 1 1
1 21 7 5 7
2 33 10 8 10
3 35 14 11 12
4 35 18 14 15
5 35 21 17 17
6 35 23 20 19
7 35 25 21 20

Initial temperature of the cold water was observed to be 1ºC. After an hour, again the temperature was recorded which increased to 21ºC in single walled containers, 7ºC in double walled with air and container filled with glasswool and 5ºC in double walled container containing dried petioles of Eichhornia crassipes.
Table 2: Regression between temperature and time for cold experiment
S.No. Experimental setup Regression Equation Correlation coefficient (R)
1. Single container y = 6.4321ln(x) + 24.88 0.8438a
2. Double walled (empty) y = 3.107x + 4.428 0.9915a
3. Double walled (E.crassipes) y = 2.785x + 2.571 0.9949a
4. Double walled (Glasswool) y = 2.214x + 5.428 0.9919a
a= 0.001 level of significance

After another hour, reading was taken when it was seen that temperature in the single walled container reached to 33ºC, in empty double walled it was 10ºC whereas in double walled container with petioles it was only 8ºC, same temperature was recorded in glasswool filling experiment as that of double walled with air 10ºC . Similar trend was observed for next two hours. Readings were taken for fifth hour and it was observed that in single walled container temperature reached to 35ºC, in double walled empty container it was observed to be 21ºC whereas it was only 17ºC in double walled containers with Eichhornia crassipes petioles and in glasswool packing vessel. No more increase in temperature was observed in single walled container as it had reached to ambient temperature where as double walled container (empty) temperature increased to 23ºC and that for petiole filled container was 20ºC. Table 1 shows the results for the thermal insulation properties of Eichhornia crassipes. Regression analysis was done on the above results tabulated in Table 2 and showing in Fig. 2, 3, 4 and 5. The temperature profile trend for cold experiment was shown in Fig. 6.
Hot water temperature control
Experiment for hot water thermal insulation was performed. Initial temperature of the hot water was observed to be 94ºC. Reading was taken after an hour which revealed that temperature had dropped down to 63ºC in single walled container, where as it was 83ºC with double walled container and 85ºC in double walled container with Eichhornia crassipes and same for glasswool. After another hour temperature was recorded and found 53ºC in single walled container, 73ºC in empty double walled container and 78ºC in double walled container with dried petioles and 79ºC for glasswool. Similar trend of temperature fall was observed for next two hours also. Readings taken for the fifth hour revealed that temperature fall of 42ºC was observed for single walled container, 54ºC for double walled container (empty) and 63ºC for double walled container with Eichhornia crassipes and 65ºC for glasswool. Thereafter, water in single-walled container showed further decrease to 40ºC till seventh hour. At same time, temperature fell to 48ºC for empty double walled container whereas it was 56ºC in double-walled container with Eichhornia crassipes and 58ºC in glasswool filling as tabulated in Table 3 and shown in Fig. 7. Graphical representations of statistical analysis are shown in Fig. 8 to 11 and results are tabulated in Table 4 for regression and correlation coefficient studies.
Table 3: Thermal insulation of hot water with petioles of Eichhornia crassipes in comparison with single walled, double walled empty container and double walled container with glasswool.

No. of Hours
Temperature in Single Walled Container (°C)
Temperature in Double Walled Container with air (°C)
Temperature in Double Walled Container with Eichhornia crassipes (°C)
Temperature in Double Walled Container with Glasswool (°C)
0 94 94 94 94
1 63 83 85 85
2 53 73 78 79
3 48 63 71 74
4 45 58 66 69
5 42 54 63 65
6 41 51 60 60
7 40 48 56 58

Table 4: Regression between temperature and time for hot experiment
S.No. Experimental setup Regression Equation Correlation coefficient (R)
1. Single container y = -11.9ln(x) + 61.96 0.9939a
2. Double walled (empty) y = -18.4ln(x) + 83.83 0.9969a
3. Double walled (Eichhornia crassipes) y = -14.9ln(x) + 86.57 0.9929a
4. Double walled (Glasswool) y = -14.2ln(x) + 87.34 0.9813a
a= 0.001 level of significance

In the experiment to study the thermal proofing ability of dried petioles of Eichhornia crassipes, the plant showed promising results. Experiment was initiated with water at 1°C and was carried out for seven hours. In the single-walled container, water attained ambient temperature (35°C) after 3 h of observation, whereas in double-walled container with and without Eichhornia crassipes, the temperature was 14°C and 11°C respectively. 12°C temperature was recorded with glasswool filling comparatively less efficient than Eichhornia crassipes. These results reveal that Eichhornia crassipes has the capacity to withhold the energy of the system. Similar results were obtained when hot water, instead of cold water was taken. Initial temperature was recorded to be 94°C, which fell down to 42°C after 5 h, whereas it was 54°C and 63°C in double-walled containers and Eichhornia crassipes filled double-walled containers respectively after 5 h. In doubled walled container with glasswool, recorded temperature was 2°C higher than the temperature with Eichhornia crassipes filling i.e 65°C. Here Eichhornia crassipes proved at par efficient than glasswool. These results showed that petioles of Eichhornia crassipes have the capacity to conserve heat, and thus prove to be a suitable candidate for thermal proofing. The thermal insulation properties of Eichhornia crassipes can be attributed to its anatomy. The epidermis of petiole is single layered, and composed of parenchymatous cells. Cuticle is absent. Vascular bundles are embedded in outer parenchyma cells. Each vascular bundle has a bundle cap of sclerenechyma cells making up the petiole. The hexagonal air spaces are surrounded by bands of single layered parenchyma cells, which provide buoyancy to the plant for free flotation in the water bodies. The air spaces present in the petiole make it a good thermal insulating material. The mesh formed due to fibres of the Eichhornia crassipes petiole forms a membrane which traps air in its spaces and acts as an insulator of temperature.
These results showed that petioles of Eichhornia crassipes have the potential to conserve heat, and thus proves to be an apposite for thermal proofing.

Benefits of Eichhornia crassipes for thermal insulation over other commercially used products.
Eichhornia crassipes petioles are more economical and eco-friendly material for insulation of hot and cold materials because the other commercial products present in market glasswool, synthetic wool, asbestos and thermocol etc. are costlier and sometimes toxic to human beings. Fibreglass irritates the skin, eyes, and the respiratory system. Common symptoms include irritation of eyes, skin, nose, throat, dyspnoea (breathing difficulty); sore throat, hoarseness and cough.
The cost of using Eichhornia crassipes petioles for thermal insulation will be very less as comparative to other commercially available thermal insulating materials in market. It is a cheapest ever material for thermal insulation.

CLIAMS:WE CLAIM:
1. An insulating walled material comprising dried Eichhornia crassipes, between two layers of containers.
2. The insulating material as claimed in claim 1, wherein dried whole plant Eichhornia crassipes is used.
3. The insulating material as claimed in claim 1, wherein insulating materials comprises dried petioles of Eichhornia crassipes.
4. The insulating material as claimed in claim 1, wherein, the plant should be dried in a range from 40°C to 80°C, preferably 60°C, before use as insulating material.
5. The insulating material as claimed in claim 1, wherein, filled weight of petioles in the container for this experiment ranges from 30g/1000cc to 80g/1000cc, preferably 50g/l or 50g/1000cc.