EP4294876A1

EP4294876A1 - A polymer composite and a process for its preparation

Info

Publication number: EP4294876A1
Application number: EP21939158.8A
Authority: EP
Inventors: Keki Hormusji Gharda; Prakash D TRIVEDI; Jaimin C ZAVERI; Amit Kundu; Shantanu Bhowmik; Jennifer Vinodhini; Sudheendra K
Original assignee: Gharda Chemicals Ltd
Current assignee: Gharda Chemicals Ltd
Priority date: 2021-04-30
Filing date: 2021-09-17
Publication date: 2023-12-27
Also published as: WO2022229693A1

Abstract

The present disclosure relates to a polymer composite. The polymer composite of the present disclosure is lightweight, has good mechanical and thermal insulation properties. The present disclosure further relates to a simple and economical process for preparing the polymer composite.

Description

A POLYMER COMPOSITE AND A PROCESS FOR ITS PREPARATION

FIELD:

The present disclosure relates to a polymer composite and a process for its preparation.

ABBRE VATIONS :

ABPBI: Poly(2, 5 -benzimidazole);

PAEK: Poly aryl ether ketone;

PEK: Poly ether ketone; PEEK:Poly ether ether ketone;

PEKK: Poly ether ketone ketone; and PDMS: Poly dime thylsiloxane

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

Polymeric composite materials are widely used in aerospace, defence and aviation industries. Conventional polymeric composites that can be used in the above mentioned industries, are lightweight and have several advantages such as low density, improved stiffness and toughness. However, at high temperatures these polymer composite materials tend to lose these properties, which may lead to fire hazards and accidents, resulting in loss of life and property. The smoke and fume emissions from the combustion of these polymeric composites are also a cause of concern for human life.

Therefore, there is felt a need for a polymeric composite material which can overcome the above-mentioned drawbacks. OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative. Another object of the present disclosure is to provide a polymer composite.

Still another object of the present disclosure is to provide a polymer composite which is fireproof, light weight and possesses good mechanical properties.

Yet another object of the present disclosure is to provide a polymer composite which is highly resistant to heat and firetransfer.

Yet another object of the present disclosure is to provide a simple and economical process for preparation of a polymer composite.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to a polymer composite. The polymer composite comprises a core comprising a silicone rubber substrate having an operative first surface and an operative second surface; a first sheet comprising a mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, the first sheet being adhered on the first operative surface of the substrate; a second sheet comprising a mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, the second sheet being adhered on the second operative surface of the substrate; and ABPBI fibres wound on the core to form the polymer composite. The silicone rubber substrate can comprise one rubber sheet or multiple rubber sheets.

Further, the present disclosure relates to a process for preparing a polymer composite. The process comprises treating a silicone rubber substrate by using a nitrogen plasma to obtain a plasma treated silicone rubber substrate. A first sheet is formed by i) treating ABPBI by using nitrogen plasma to obtain a nitrogen plasma treated ABPBI ii) Separately, PAEK is treated by using nitrogen plasma to obtain a nitrogen plasma treated PAEK. iii) The treated ABPBI and the treated PAEK are stacked alternately to obtain a stacked ABPBI-PAEK. iv) The stacked ABPBI-PAEK is compression molded at a temperature in the range of 300 °C to 450 °C and at a pressure in the range of 1 bar to 10 bar for a time period in the range of 30 minutes to 120 minutes to obtain a molded ABPBI-PAEK. v) The molded ABPBI-PAEK is cured for a time period in the range of 5 hours to 15 hours to obtain the first sheet. Substeps i) to v) are repeated to obtain a second sheet. A core is formed by adhering the first sheet to an operative first surface of the substrate and the second sheet to an operative second surface of the substrate. ABPBI fibres are wound on the core to obtain the polymer composite.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING The present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1-a illustrates a photographic image of nitrogen plasma treatment instrument during the plasma treatment;

Figure 1-b illustrates a photographic image of ABPBI reinforced PEK composite; Figure 1-c illustrates a photographic image of polymer composite in accordance with the present disclosure;

Figure 2-a illustrates a photographic image wherein one side of the polymer composite is exposed to dry ice at -44 °C;

Figure 2-b illustrates a photographic image wherein the side of the polymer composite which is exposed to dry ice after 6 hours, has temperature of -29 °C;

Figure 2-c illustrates a photographic image of other side of the polymer composite which was exposed to 25 °C when the opposite side was exposed to dry ice;

Figure 3-a and 3-b illustrates photographic images (taken from different viewing angles) of combustion of one of the sides of the polymer composite using Bunsen burner; Figure 3-c illustrates a photographic image of the measurement of the temperature of one of the sides which is exposed to the Bunsen burner;

Figure 3-d illustrates photographic image of the measurement of the temperature of the other side of the polymer composite which is not exposed to the Bunsen burner;

Figure 4 illustrates a photographic image of the measurement of the compression strength of the polymer composite of the present disclosure;

Figure 5-a illustrates a photographic image of immersing the polymer composite of the present disclosure in a petrol; Figure 5-b illustrates a photographic image of the combustion of the polymer composite of the present disclosure;

Figure 5-c and 5- d illustrates photographic images (taken from different viewing angles) of the polymer composite at the end of the combustion process; Figure 6-a and 6-b illustrates a photographic image of the test for impact/shock absorption before and after the impact of the stone;

Figure 7 illustrates a photographic image of the float test of the polymer composite in accordance with the present disclosure;

Figure 8-a illustrates a simulated polymer composite model used for the simulation study; Figure 8-b illustrates a simulated temperature gradient profile across the polymer composite after 1 hour of the simulation study when the temperature of the ‘outer’ side is set at -30° C (243 K);

Figure 8-c illustrates a simulated temperature of the ‘inner’ side of the polymer composite over the period of 1 hour when the temperature of the ‘outer’ side is set at -30° C (243 K); Figure 8-d illustrates a simulated temperature profile across the polymer composite at different time over the period of 3 hours when the temperature of the ‘outer’ side of the polymer composite is set at -30° C (243 K);

Figure 9-a illustrates a simulated temperature gradient profile across the polymer composite after 9 minutes when the temperature of the ‘outer’ side of the polymer composite is set at 725° C (998 K);

Figure 9-b illustrates a simulated temperature of the ‘inner’ side of the polymer composite after 9 minutes when the temperature of the ‘outer’ side of the polymer composite is set at 725° C (998 K); and

Figure 9-c illustrates a simulated temperature profile across the polymer composite at different time over 9 minutes when the temperature of the ‘outer’ side is set at 725° C (998 K).

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing. Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, known processes or well-known apparatus or structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure are not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

Polymeric composite materials are widely used in aerospace, defence and aviation industries. Conventional polymeric composite used in the above mentioned industries are lightweight and have several advantages such as low density, improved stiffness and toughness. However, at high temperatures these polymer composite materials tend to lose their properties, which may lead to fire hazards and accidents, resulting in loss of life and property. The smoke and fume emissions from the combustion of these polymeric composites are also a major cause of concern for human life. The polymer composite of the present disclosure comprises a core and ABPBI fibres wound on the core to form the polymer composite. The core comprising a silicone rubber substrate having an operative first surface and an operative second surface; a first sheet comprising a mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, the first sheet configured to be adhered on the first operative surface of the substrate; a second sheet comprising mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, the second sheet configured to be adhered on the second operative surface of the substrate.

In an embodiment, the PAEK is in a form selected from a sheet and a film. In an exemplary embodiment, the PAEK is in the form of a film.

In accordance with the embodiments of the present disclosure, the PAEK is selected from Poly Ether Ketone (PEK), Poly Ether Ether Ketone (PEEK) and Poly Ether Ketone Ketone (PEKK).

Poly Ether Ketone (PEK) in the form of film, as used in the present disclosure, has a glass transition temperature of 158°C, crystallization temperature of about 170-180°C and melting temperature of 373 °C. PEK, which is a high-performance polymer shows good characteristics due to its strong rigid aromatic structure. PEK holds a good combination of properties such as high mechanical strength over a broad range of temperatures, chemical resistance, thermal stability and low smoke production during combustion. Hence, PEK film is used as a matrix material for the composite.

In an embodiment, the ABPBI is in the form of fibres. ABPBI (poly 2, 5 - benzimidazole) is a semi crystalline polymer containing benzimidazole that contributes to a high thermal stability. ABPBI is used as a reinforcing material for the PEK matrix due to its high Limiting Oxygen Index (LOI), high deflection temperature (HDT). ABPBI is non-flammable and it also retains the mechanical property at temperatures over 310°C.

ABPBI is a thermosetting polymer that cannot be melt processed up to 500° C. Due to very high glass transition temperature (Tg) of 485 °C and due to the absence of melting temperature (Tm) until 500° C, this polymer is difficult to melt process but is extremely stable at high temperatures. ABPBI fibers are directly solution spun. In accordance with the embodiments of the present disclosure, the predetermined weight ratio of the ABPBI to the PAEK in the first sheet is in the range of 0.5 to 0.8. In an exemplary embodiment, the weight ratio is 0.754.

In accordance with the embodiments of the present disclosure, the predetermined weight ratio of the ABPBI to the PAEK in the second sheet is in the range of 0.5 to to 0.8. In an exemplary embodiment, the weight ratio is 0.754.

In an embodiment of the present disclosure, the silicone rubber substrate is in the form of a rubber sheet. In another embodiment, the silicone rubber substrate comprises multiple rubber sheets with air gaps between the rubber sheets, thereby providing good insulation properties.

Silicone rubber used in the present disclosure is made from a gum based polydimethylsiloxane (PDMS) polymer. The PDMS polymer is chemically expanded when it is heat cured to create a closed cell sponge structure. The closed cell indicates that cells are non interconnecting, therefore they do not allow water to wick through the sponge. Silicone rubbers have superior mechanical properties owing to its non interconnecting cell structure. Silicone rubber of the present disclosure has excellent UV and ozone resistance due to the part of their inorganic backbone, which provides long term performance. Further, the silicone rubbers of the present disclosure are highly amorphous and thus do not have a melting point. Silicone rubbers used in the present disclosure also have good electrical properties and chemical properties. Silicone rubbers are resistant to high temperatures while maintaining their properties. They also show good flame retardant properties when compared with other types of rubbers.

In accordance with the embodiments of the present disclosure, the first sheet and the second sheet are adhered to the substrate with the help of a silicone adhesive.

In the present disclosure, the silicone adhesive is a RTV - 1 Silicone Adhesive (Room Temperature Vulcanizing Single Component Silicone Adhesive) which gets cured at room temperature. The operating temperature for the silicone adhesive is from -40 °C to 220°C. The silicone adhesive remains highly elastic even at lower temperatures because of the chemical structure. Other properties of the silicone adhesive include ease of operation, low viscosity, low shrinkage, high temperature resistance, non corrosive, chemical and ageing resistance. Silicone adhesive is also stable under high temperatures.

In accordance with the embodiments of the present disclosure, the compression strength of the polymer composite is in the range of 15MPa to 30MPa. In an exemplary embodiment, the compression strength is 20MPa.

In accordance with the embodiments of the present disclosure, the polymer composite has a density lower than water, preferably 0.7 g/cm .

In accordance with the embodiments of the present disclosure, a weight of the polymer composite is reduced by less than 1.5 wt% upon combustion. In an exemplary embodiment, the weight of the polymer composite is reduced by 1.3 wt.% upon combustion.

The advantages of the polymer composites of the present disclosure over the conventional composites are as follows:

1) The composite of the present disclosure is ultra light weight (density is 0.7 gm/cc, which is one of the lightest composites),

2) The composite of the present disclosure is thermally insulated even at a very low temperature of approximately -44 °C,

3) The composite of the present disclosure is thermally insulated under a very high temperature of approximately 726 °C,

4) The composite of the present disclosure has high impact strength, good compressive strength and most importantly it does not burn even when this composite is dipped in petrol and subjected to combustion. Moreover, there is virtually no emission of carbon di-oxide and carbon mono-oxide.

The polymer composites of the present disclosure are fire retardant, resistant to thermal degradation and are lighter in weight. Further, the polymer composites of the present disclosure are capable of creating barriers between the high temperature surface region and capable of inhibiting and impeding the transfer of heat, thus acting as an excellent fire resistant material.

The polymer composite of the present disclosure can be used in the field of defense such as a material for naval ships, hypersonic aircraft, long distance missiles and defence shelters across the border. Further, the polymer composite of the present disclosure can be used to fabricate the panels for fire proof building and elevators, panels for fire proof jacket, special purpose roofs/ shelters for extreme cold weather. Furthermore, the polymer composite of the present disclosure can be used as a light fire proof material for speed railway compartment, mass transport interior wall panels, ceiling and cladding. The polymer composite of the present application may comply with the global mass transport regulations of fire, smoke and toxicity norms / standards. Still further, the polymer composite of the present disclosure can be used as sound insulation/noise absorption material with fire proofing requirements such as underground metro rail tunnels or roads infrastructure. Other miscellaneous application of the composite are in the field of aerospace engineering and various air-transportation vehicles.

Further, the present disclosure relates to a process for preparing a polymer composite. The process is described in detail below.

First, the process comprises treating a silicone rubber substrate by using a nitrogen plasma to obtain a plasma treated silicone rubber substrate.

In accordance with the embodiments of the present disclosure, the thickness of the plasma treated silicone rubber substrate is in the range of 5 mm to 25 mm. In an exemplary embodiment, the thickness is 6 mm. In another exemplary embodiment, the thickness is 18 mm.

In the next step, a first sheet is formed by i) treating ABPBI by using nitrogen plasma to obtain a nitrogen plasma treated ABPBI ii) Separately, PAEK is treated by using nitrogen plasma to obtain a nitrogen plasma treated PAEK iii) The treated ABPBI and the treated PAEK are stacked alternately to obtain a stacked ABPBI-PAEK. iv) The stacked ABPBI- PAEK is compression molded at a temperature in the range of 300 °C to 450 °C and at a pressure in the range of 1 bar to 10 bar for a time period in the range of 30 minutes to 120 minutes to obtain a molded ABPBI-PAEK. v) The molded ABPBI-PAEK is cured for a time period in the range of 1 hour to 15 hours to obtain the first sheet.

In an exemplary embodiment, the compression molding is carried out at 400 °C for 1 hour and molded ABPBI-PEK is cured for 10 hours.

Curing of the molded ABPBI-PEK is carried out by allowing the lowering of the temperature of the molded ABPBI-PEK to room temperature (25 °C to 30 °C). The process of curing can take place at temperatures between 400 °C and room temperature and in 1 to 15 hours. In accordance with the embodiments of the present disclosure, the PAEK is selected from the group consisting of PEK, PEEK, and PEKK. In an exemplary embodiment, the PAEK is PEK.

In accordance with the embodiments of the present disclosure, the PAEK is in a form selected from a sheet and a film. In an exemplary embodiment, the PAEK is in the form of film having a thickness in the range of 0.10 mm to 0.15 mm.

In accordance with the embodiments of the present disclosure, the ABPBI is in the form of fibers. In an embodiment, the ABPBI is in the form of fabric woven from the fibres.

In accordance with the embodiments of the present disclosure, the weight ratio of the ABPBI to the PAEK in the first sheet is in the range of 0.5 to 0.8. In an exemplary embodiment, the weight ratio is 0.754. In accordance with the embodiments of the present disclosure, the plasma treated ABPBI has a Limited Oxygen Index (LOI) in the range of 95 to 97%. In an exemplary embodiment, LOI is 96%.

Generally, a material is called fire retardant when LOI of the sample is higher than atmospheric oxygen level concentration. Thus, the nitrogen plasma treated ABPBI show higher LOI value, making it one of the best suited materials for fire retardant.

Nitrogen plasma treatment of PAEK, ABPBI and silicone rubber are carried out to increase the interfacial interaction between PAEK, ABPBI and the silicone rubber. Because of the enhanced interfacial interaction, the polymer composite of the present disclosure has enhanced fire retardant, and mechanical properties. However, for non-structural applications, such composites can be made optionally without nitrogen plasma treatments.

Further, substeps i) to v) for preparing the first sheet are repeated to obtain a second sheet.

In accordance with the embodiments of the present disclosure, the weight ratio of ABPBI to PAEK in the second sheet is in the range of 0.5 to 0.8. In an exemplary embodiment, the weight ratio is 0.754.

In the next step, a core is formed by adhering the first sheet to an operative first surface of the substrate and adhering the second sheet to an operative second surface of the substrate. ABPBI fibers are wound on the core to obtain the polymer composite. In accordance with the embodiments of the present disclosure, the first sheet and the second sheet are adhered to the substrate with the help of a silicone adhesive.

In the polymer composite of the present disclosure, a barrier between high and low temperature region is created which reduces the heat transfer. The heat transfer from one side to the other side of the material is successfully prevented.

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment but are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the experiments should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.

EXPERIMENTAL DETAILS

Poly Ether Ketone (PEK) film that is used in the present disclosure has a thickness 0.1 mm. The PEK used in the present disclosure has a glass transition temperature of 145°C, crystallization temperature of about 170-180°C and melting temperature of 385°C. The molecular weight of PEK is in the range of 93,000-1,05,000 g/mol.

ABPBI [Poly (2, 5 - benzimidazole)] that is used in the present disclosure has a viscosity molecular weight and glass transition temperature of 28,000 - 30,000 and 485°C respectively.

Silicone rubber sheet used in the present disclosure has the thickness of 6 mm.

Experiment 1: Preparation of a polymer composite in accordance with the present disclosure: 1) Nitrogen plasma treatment: PEK film was cut into pieces having 100 mm x 100mm dimensions and cleaned with acetone to remove dirt particles present on the surface of the film. The chamber of the plasma treatment instrument was evacuated and purged with nitrogen gas. The cleaned PEK film(s) were introduced into the plasma treatment instrument and nitrogen plasma treatment was carried for 10 minutes to obtain nitrogen plasma treated

PEK films. For nitrogen plasma treatment, the vacuum chamber was evacuated to a pressure of 5.0xl0^~3 mbar. Nitrogen gas (99.99% purity) was introduced into the chamber at a flow rate of 22 L/min. Plasma was generated in the nitrogen atmosphere and the operating pressure _2 was 1.1x10 mbar and the power provided was 19 W. The duration of treatment was set to 600 seconds. The photographic image of the plasma treatment chamber during the plasma treatment is shown in figure 1-a.

The above-described plasma treatment process was also used for the plasma treatment of ABPBI fiber having dimension of 100 mm x 100mm and silicone rubber sheet/substrate having dimension of 100 mm x 100mm to obtain nitrogen plasma treated ABPBI fibers and a nitrogen plasma treated silicone rubber substrate. Nitrogen plasma enhances the adhesion characteristics of the silicone rubber substrate and the ABPBI-PEK sheet.

The limited oxygen index (LOI) of the untreated ABPBI fibers and the nitrogen plasma treated ABPBI fibers was measured using LOI test. The LOI for the nitrogen plasma treated ABPBI was found to be 96% and the LOI for the untreated ABPBI was found to be 94%. The LOI test indicated that the nitrogen plasma treated ABPBI required higher amount of oxygen for combustion as compared to untreated ABPBI.

2) Compression molding of ABPBI and PEK: Compression molded mixture of ABPBI-PEK composite was prepared by using layer by layer stacking method. Fifteen nitrogen plasma treated PEK and four nitrogen plasma treated ABPI fibers were stacked in an alternate fashion so that no 2 PEK and 2 ABPBI were in direct contact with each other. The stack of PEK-ABPBI nitrogen plasma treated sheets were compression molded for 1 hour at the pressure of 5 bar, at 400°C to obtain a compression molded mixture of ABPBI and PEK.

The compression molded mixture of ABPBI and PEK was then cured by cooling at a temperature in the range of 25 °C to 30 °C for 10 hours to obtain a sheet comprising a mixture of ABPBI and PEK. Two such sheets comprising a mixture of ABPBI and PEK were produced. The weight ratio of the ABPBI to the PEK in both the sheets was 0.754. The thickness of the sheets comprising a mixture of ABPBI and PEK was 2 mm.

The sheet comprising a mixture of ABPBI and PEK prepared in accordance with the present disclosure is shown in figure 1-b.

3) Preparation of the polymer composite: Polymer composite was prepared by adhering one sheet comprising a mixture of ABPBI and PEK on one side of the nitrogen plasma treated silicone rubber substrate having a thickness of 6 mm and adhering the other sheet comprising a mixture of ABPBI and PEK on the other side of the silicone rubber substrate. The treated silicone substrate and the two sheets comprising a mixture of ABPBI and PEK were bonded with silicone adhesive to obtain a core. The core was then convered with ABPBI fibre completely to obtain the polymer composite of the present disclosure.

The polymer composite of the present disclosure is shown in figure 1-c.

Characterization of the polymer composite of the present disclosure.

Demonstration of thermal insulation property:

Experiment 2:

Use of the cold conditions:

One of the sides of the polymer composite as prepared in experiment 1 of the present disclosure was exposed to dry ice at -44 °C, as shown in figure 2-a for 6 hours. The other side of the composite was exposed to room temperature of 25°C. After 6 hours, the temperature of the side exposed to dry ice got raised to -29°C due to sublimation of dry ice as shown in figure 2-b and the temperature of the other side (which was exposed to room temperature) got dropped to 14°C (from room temperature) as indicated in figure 2-c.

Experiment 3:

Use of the hot conditions:

The polymer composite of the present disclosure was exposed to fire through a Bunsen burner as shown in figure 3-a and 3-b. One side of the composite was exposed to more than 720°C for 10 minutes. The other side (which was not exposed to flame) of the polymer composite only showed 52.6°C after 10 minutes exposure to that flame. The difference in the temperatures of two sides of the composite is shown in figure 3-c and figure 3-d. The temperature of the side which was not exposed to fire increased from 30°C to only 52.6°C in 10 minutes.

The above experiment demonstrates that the temperature of one side of the polymer composite was very slightly affected by the temperature of the other side of the polymer composite. Hence, the polymer composite of the present application has excellent thermal insulation property.

Experiment 4:

Measurement of the compressive strength: The compressive strength of the polymer composite as prepared in the experiment 1 was measured as shown in figure 4. The compressive strength of the composite was 20MPa.

The polymer composite of the present disclosure showed good compressive strength due to the surface treatment carried out in nitrogen plasma. Strong interfacial interaction between the reinforcement and matrix is also one of the main reasons for achieving good compressive strength.

Experiment 5:

Demonstration of char formation on combustion: The polymer composite prepared in experiment 1 was infused in petrol completely as shown in figure 5-a. The polymer composite was then set to burn for 3 minutes as shown in figure 5-b. The combustion of the polymer composite produced very less amount of the smoke. No significant residue was formed on the surface of the polymer composite after combustion as shown in figure 5-c which demonstrates very less char formation as shown in figure 5-d. The weight of the polymer composite before and after the combustion was 145g and 143g respectively.

Experiment 6:

Demonstration of the capacity of shock/impact absorption: The polymer composite as prepared in experiment 1 was tested for impact strength wherein a 1.15 kg hard stone was dropped on the polymer composite from a height of 1.5 m as shown in figures 6-a and 6-b. After dropping the stone on the polymer composite, no significant deformation or damage was observed due to the impact absorption capacity of the polymer composite. This was due to the inclusion of silicone rubber substrate, which acts as an energy absorber, and the high impact resistance of PEK-ABPBI sheets attached to the silicone rubber substrate.

Experiment 7:

Demonstration of the lightweight nature of the polymer composite: The polymer composite which was infused with petrol and subjected to combustion was taken for a float test. The burnt polymer composite was immersed in water and it was observed that the burnt polymer composite floats on the water surface as shown in figure 7. This demonstrates that the burnt polymer composite is lighter than water, which in turns demonstrates its lightweight nature.

The density of the polymer composite was measured to be 0.7g/cm .

Experiment 8:

Simulation study was carried out using the composite prepared as per Experiment no. 1, wherein the silicone rubber substrate comprises 3 silicone rubber sheets_^

The conduction of heat through the polymer composite of the present disclosure was modelled using a software called FLUENT.

The simulation study was focused on evaluating the transient conduction through a composite consisting of 2 mm layers of the ABPBI reinforced PEK composite on either side and 18 mm layer of silicone rubber substrate in the middle as shown in figure 8-a. The 18 mm rubber substrate comprises 3 silicone rubber sheets each of 6 mm thickness, resulting in an effective thickness of 18 mm. Multiple rubber sheets ensure the presence of air gaps between the rubber sheets, as air is a great insulator.

Experiment 8-a - Use of the cold conditions for studying the thermal insulation in the simulated polymer composite of the present disclosure:

The modelling of the temperature gradient across the polymer composite was carried out by setting the value of the temperature on the ‘outer’ side at -30° C (243 K) and the temperature of the “inner” side was modelled using convective boundary conditions with a convective heat transfer coefficient of 20w/m which is typical for indoor conditions. The material properties used are as shown in the table below.

Table 1: Thermo-physical properties of the materials:

The above simulation was run for 3 hours by using a time step of 10 seconds. Initially, at t=0, the polymer composite was assumed to be at 298K (25 °C). The temperature gradient across the polymer composite using the above conditions after 1 hour is shown in figure 8-b. The variation in temperature of the ‘inner’ side of the polymer composite over the period of 1 hour is shown in figure 8-c which shows that the temperature of the ‘inner’ side was almost at a steady state value of 286 K (13°C) and there was no significant change after the first 30-40 minutes. This was well in agreement with the experimental findings and indicates that the temperature of the ‘outer’ side barely affects the temperature of the ‘inner’ side. The simulation was continued for 3 hours and the transient history of temperature distribution across the polymer composite is shown in Figure 8-d. Figure 8-d further shows the temperature variation across the polymer composite at various instances of time. According to figure 8-d, a significant temperature gradient between the ‘outer’ and ‘inner’ side of the composite was maintained even after 3hrs. At the end of 3 hours, the ‘inner’ side temperature dropped from 298 K to about 285 K, that is from 25 °C to 13 °C - which is indicative of the capability of the polymer composite material in providing the required thermal protection.

Experiment 8-b: Use of the hot conditions for studying the thermal insulation in the simulated polymer composite of the present disclosure:

In this part of the simulations, the same simulated polymer composite model was used as shown in figure 8-a. The temperature profiles were simulated by setting the temperature of the ‘outer’ side to 998 K (725° C), temperature of the ‘inner’ side to 300 K (27° C). Simulation was run for over 9 minutes. The temperature gradient across the polymer composite after 9 minutes is shown in figure 9-a. When the temperature of the ‘outer’ side of the polymer composite was set to 998 K (725° C), the temperature of the ‘inner’ side of the polymer composite during the course of 9 minutes changed slightly, which is shown in the figure 9-b. Figure 9-c demonstrates the temperature distribution within the polymer composite for various time intervals. According to figure 9-c, after 9 minutes, the temperature of ‘inner’ side reached to only 348 K (74°C) even if the temperature of the ‘inner’ side was set to 348 K (74°C).

The above simulations demonstrate that when the polymer composite is exposed to flame, the thermal energy does not diffuse through the material fast enough to cause any damage in a reasonable period of time.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of: the polymer composite which is lightweight, has good mechanical properties and thermal insulation properties; and a simple and economical process for preparation of a polymer composite.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments 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. 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 hem,,, _|„ raced with modification within the spirit and scope of the embodiments as described herein. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

CLAIMS:

1. A polymer composite comprising a) a core comprising i) a nitrogen plasma treated silicone rubber substrate having an operative first surface and an operative second surface; ii) a first sheet comprising a mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, said first sheet configured to be adhered on said first operative surface of said substrate; iii) a second sheet comprising a mixture of a nitrogen plasma treated ABPBI and a nitrogen plasma treated PAEK in a predetermined weight ratio, said second sheet configured to be adhered on said second operative surface of said substrate; and b) ABPBI fibers configured to be wound on said core to form the polymer composite.

2. The polymer composite as claimed in claim 1 , wherein said first sheet and said second sheet are adhered to said substrate with the help of a silicone adhesive.

3. The polymer composite as claimed in claim 1, wherein the compression strength of said polymer composite is in the range of 15MPa to 30MPa.

4. The polymer composite as claimed in claim 1, wherein said polymer composite has a density lower than water, preferably 0.7 g/cm .

5. The polymer composite as claimed in claim 1, wherein the weight of said polymer composite is reduced by less than 1.5 wt% upon combusion.

6. The polymer composite as claimed in claim 1, wherein said PAEK is selected from PEK (Polyether Ketone), PEEK (polyether-ether ketone) and PEKK (polyether ketone ketone).

7. A process for preparing a polymer composite, said process comprising the following steps: a. treating a silicone rubber substrate by using a nitrogen plasma to obtain a nitrogen plasma treated silicone rubber substrate; b. forming a first sheet by i. treating ABPBI by using nitrogen plasma to obtain a nitrogen plasma treated ABPBI; ii. separately treating PAEK by using nitrogen plasma to obtain a nitrogen plasma treated PAEK; iii. stacking alternately said treated ABPBI and said treated PAEK to obtain a stacked ABPBI-PAEK; iv. compression molding said stacked ABPBI-PAEK at a temperature in the range of 300 °C to 450 °C and at a pressure in the range of 1 bar to 10 bar for a time period in the range of 30 minutes to 120 minutes to obtain a molded ABPBI-PAEK; v. curing said molded ABPBI-PAEK for a time period in the range of 1 hours to 15 hours to obtain the first sheet; c. repeating substeps i) to v) to obtain a second sheet; d. forming a core by adhering said first sheet to an operative first surface of said nitrogen plasma treated silicone rubber substrate and said second sheet to an operative second surface of said nitrogen plasma treated silicone rubber substrate; e. winding ABPBI fibres on said core to obtain said polymer composite

8. The process as claimed in claim 7, wherein said first sheet and said second sheet are adhered to said substrate with the help of a silicone adhesive.

9. The process as claimed in claim 7, wherein said ABPBI is in the form of fibres.

10. The process as claimed in claim 7, wherein said ABPBI is in the form of fabric woven by using fibers.

11. The process as claimed in claim 7, wherein said plasma treated ABPBI has a Limited Oxygen Index in the range of 95 to 97%.

12. The process as claimed in claim 7, wherein said PAEK is in a form selected from a sheet and film.

13. The process as claimed in claim 7, wherein the weight ratio of said ABPBI to said PAEK is in the range of 0.5 to 0.8.

14. The process as claimed in claim 7, wherein the thickness of said plasma treated silicone rubber substrate is in the range of 5 mm to 25 mm.

15. The process as claimed in claim 7, wherein the silicone rubber substrate comprises one rubber sheet or multiple rubber sheets.