A pp / pe-hips co-extruded composite sheet and a method for preparing the same

Abstract

The application relates to the technical field of composite sheet processing, in particular to a PPPE-HIPS co-extrusion composite sheet and a preparation method thereof, which sequentially comprises a surface layer, an intermediate layer and a surface layer, and is characterized in that the surface layer is prepared from the following raw materials in parts by weight: polypropylene A, polypropylene B, polypropylene C, a foaming agent, linear low-density polyethylene, the melt index of the polypropylene A under the test conditions of 230 DEG C and 2.16 kg is 0.2-0.5 g / 10 min; the melt index of the polypropylene B under the test conditions of 230 DEG C and 2.16 kg is 0.5-0.8 g / 10 min; the melt index of the polypropylene C under the test conditions of 230 DEG C and 2.16 kg is 1-1.5 g / 10 min; the intermediate layer is prepared from the following in parts by weight: high-impact polystyrene A, high-impact polystyrene B, high-impact polystyrene C, high-impact polystyrene, a filler and rubber; the relative molecular weight of the high-impact polystyrene A is 80000-120000; the relative molecular weight of the high-impact polystyrene B is 150000-220000; the relative molecular weight of the high-impact polystyrene C is 250000-280000; and the relative molecular weight of the high-impact polystyrene D is 290000-300000.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite sheet processing, more specifically, to a PP / PE-HIPS co-extrusion composite sheet and a preparation method thereof. BACKGROUND

[0002] With the continuous development and popularization of electronic products, the selection and design of their packaging materials become particularly important. Electronic products usually have delicate appearance designs, and the packaging is prone to friction and collision during transportation and handling, resulting in scratches on the product surface, affecting the product's aesthetic appearance and the user's first impression. In addition, the surfaces of some electronic products, such as screens and lenses, have high requirements for optical performance and touch sensitivity, and scratches may affect these properties, reducing user experience.

[0003] Among existing packaging materials, PP (polypropylene) and HIPS (high impact polystyrene) are two commonly used materials. PP sheets have good toughness and impact resistance, which can protect the product to some extent during transportation. However, PP materials also have some drawbacks, such as a significant decrease in impact strength at low temperatures, becoming brittle and easily breaking, thereby affecting the protection effect on electronic products.

[0004] HIPS materials have good processing performance, are easy to shape, and are suitable for mass production. They have excellent electrical insulation, making them suitable for packaging electronic products. However, HIPS is prone to friction and powder loss during use, which not only affects the cleanliness of the packaging but also may contaminate the product surface.

[0005] In order to improve the overall performance of packaging materials, people have tried to mix PP and HIPS. However, it was found during production that due to the large difference in molecular structure between PP and HIPS, their compatibility is poor, and after mixing, surface defects such as delamination and pitting may occur, affecting product quality and appearance.

[0006] Further, by using a multi-layer co-extrusion method to prepare sheets from PP and HIPS, and then performing vacuum forming treatment according to requirements, the corresponding packaging products are obtained. This method combines the advantages of both materials to some extent, but still faces some challenges in actual application.

[0007] Firstly, PP has good toughness and impact resistance, while HIPS has low elongation. The physical properties of the two are too different, and in co-extruded sheets, the thickness and proportion of each layer need to be designed reasonably to balance the overall mechanical properties of the sheet. If the design is not proper, the sheet may crack or deform when subjected to external forces during processing, especially when the sheet is thin, which is more likely to occur.

[0008] Secondly, PP and HIPS have different thermal expansion coefficients. When the temperature changes, the expansion and contraction degrees of each layer are different, which will generate thermal stress inside the sheet, affecting the dimensional stability and heat resistance of the sheet, and causing problems such as warping and cracking in the packaging product during the blister process, thereby affecting the protection effect of electronic products.

[0009] In summary, while PP and HIPS materials have certain advantages in electronic product packaging, their respective shortcomings and compatibility issues when mixed together limit their overall performance. While multi-layer co-extrusion can alleviate these shortcomings to a certain extent, it still requires overcoming numerous technical challenges during the design and processing process to achieve ideal packaging results. Summary of the Invention

[0010] In order to solve the problem that sheets produced by co-extrusion of PP and HIPS are difficult to maintain mechanical property balance and are prone to cracking, and have different expansion coefficients, and are prone to warping and cracking when the temperature changes, the present application provides a PP / PE-HIPS co-extruded composite sheet and its preparation method.

[0011] In the first aspect, the present application provides a PP / PE-HIPS co-extruded composite sheet, which adopts the following technical solution: a PP / PE-HIPS co-extruded composite sheet, comprising a surface layer, an intermediate layer and a surface layer in sequence, wherein the surface layer is prepared from the following raw materials in parts by weight:

[0012] Polypropylene A 5-10 parts

[0013] Polypropylene B10-20 parts

[0014] Polypropylene C 5-8 parts

[0015] 4-8 parts foaming agent

[0016] 5-10 parts linear low-density polyethylene

[0017] The melt index of polypropylene A at 230°C and 2.16 kg is 0.2-0.5 g / 10 min;

[0018] The melt index of polypropylene B at 230°C and 2.16 kg is 0.5-0.8 g / 10 min;

[0019] The melt index of polypropylene C at 230°C and 2.16 kg is 1-1.5 g / 10 min;

[0020] The intermediate layer is prepared from the following parts by weight:

[0021] 10-15 parts high impact polystyrene A

[0022] High impact polystyrene B 5-10 parts

[0023] High impact polystyrene C 8-12 parts

[0024] High impact polystyrene D 3-5 parts

[0025] 3-5 servings of filling

[0026] 3-5 parts of rubber;

[0027] The relative molecular weight of high impact polystyrene A is 80,000-120,000;

[0028] The relative molecular weight of high impact polystyrene B is 150,000-220,000;

[0029] The relative molecular weight of high impact polystyrene C is 250,000-280,000;

[0030] The relative molecular weight of high impact polystyrene D is 290,000-300,000.

[0031] By employing this technical solution, the combination of polypropylene with different melt indexes and linear low-density polyethylene in the surface layer, and the combination of high-impact polystyrene with different relative molecular weights, fillers, and rubber in the middle layer, effectively balances the sheet's overall mechanical properties, avoiding cracking or deformation caused by the significant differences in the physical properties of PP and HIPS. This maintains excellent mechanical properties, especially when producing thinner sheets. The sheet thickness can range from 0.3 to 3.5 cm, with the surface and middle layer thicknesses freely adjustable, eliminating the need for elaborate design. After blister forming, the resulting product exhibits excellent impact resistance and integrity, making it suitable for packaging a variety of electronic products.

[0032] At the same time, the above formula can alleviate the thermal stress caused by temperature changes, reduce the thermal stress caused by the difference in thermal expansion coefficients between PP and HIPS, improve the dimensional stability and heat resistance of the sheet, and reduce problems such as warping and cracking of the sheet during processing, thereby obtaining a complete packaging product.

[0033] The combination of polypropylene and linear low-density polyethylene on the surface layer, and the synergistic effect of high-impact polystyrene and rubber in the middle layer can effectively improve the wear resistance of the sheet, reduce friction and powder loss during use, maintain the cleanliness of the packaging, and avoid contamination of the product surface.

[0034] The rational design of the surface and middle layers gives the entire sheet excellent impact resistance, which can effectively protect electronic products during transportation and handling, preventing scratches or damage to the product surface due to external forces such as collision and friction, thereby improving the user's first impression of the product and usage experience.

[0035] Preferably, the polypropylene A is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

[0036] Preferably, the polypropylene B is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

[0037] Preferably, the polypropylene C is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

[0038] By adopting the above technical solution and rationally combining isotactic, atactic and syndiotactic polypropylene, as well as polypropylenes A, B and C with different melt indexes, the surface layer can improve wear resistance, heat resistance and processing performance while maintaining good mechanical properties, thereby effectively solving the problems of difficult mechanical property balance and easy cracking when co-extruding PP and HIPS to prepare sheets, as well as warping and cracking caused by different thermal expansion coefficients, thereby improving the overall performance and quality of the sheets.

[0039] Preferably, the linear low-density polyethylene has a melt index of 1-2 g / 10 min under test conditions of 230° C. and 2.16 kg.

[0040] By adopting the above technical solution, LLDPE possesses excellent flexibility and impact resistance. In composite sheets, the addition of LLDPE significantly improves the surface flexibility and impact resistance, enabling the sheet to better absorb and disperse energy when subjected to external forces, reducing the risk of breakage. The addition of LLDPE balances the rigidity of polypropylene with the toughness of high-impact polystyrene, ensuring the composite sheet maintains high strength while maintaining excellent flexibility.

[0041] Preferably, the foaming agent is at least one of an azo compound, a bicarbonate, a carbonate and a bicarbonate.

[0042] By adopting this technical solution, a large number of tiny bubbles are formed within the surface layer, reducing the density of the sheet. This also makes the packaging material lighter, making it easier to transport and use. The presence of these tiny bubbles also enhances the sheet's thermal insulation and cushioning properties. This improved thermal insulation means the packaging material can better protect electronic products from temperature fluctuations, reducing damage caused by temperature fluctuations. The improved cushioning properties effectively absorb and disperse external impacts, better protecting electronic products from collision damage during transportation and handling.

[0043] Preferably, the filler is at least one of zinc oxide, silicon dioxide, zinc carbonate, carbon black, kaolin, montmorillonite, diatomaceous earth, needle-shaped wollastonite and ceramic powder.

[0044] By adopting the above technical solution, the type of filler is optimized, the strength and hardness of the inner layer are further improved, and the deformation resistance of the sheet is enhanced. At the same time, the thermal expansion difference between PP and HIPS can be balanced, the thermal stress caused by temperature changes can be reduced, and the dimensional stability of the sheet can be improved.

[0045] Preferably, the rubber is at least one of polybutadiene, ethylene-propylene rubber, styrene-butadiene rubber and EPDM rubber.

[0046] By employing this technical solution and optimizing the type of rubber, the interaction between the flexibility of the rubber molecular chains and materials like HIPS strengthens the bond between the inner and outer layers, reduces the risk of delamination, and improves the overall stability of the sheet. Furthermore, the rubber's excellent elasticity and toughness absorb and disperse external impacts, enhancing the impact resistance of the inner layer and reducing the risk of damage from collisions. Furthermore, the rubber imparts excellent flexibility and elasticity to the inner layer, ensuring it maintains good performance across a wide range of ambient temperatures, resisting brittleness and improving the adaptability of the packaging material.

[0047] In a second aspect, the present application provides a method for preparing a PP / PE-HIPS co-extruded composite sheet, which adopts the following technical solution:

[0048] A method for preparing a PP / PE-HIPS co-extruded composite sheet comprises the following steps:

[0049] S1, mixing polypropylene A, polypropylene B, polypropylene C, linear low-density polyethylene and a foaming agent to obtain a mixture A;

[0050] S2. mixing high-impact polystyrene A, high-impact polystyrene B, high-impact polystyrene C, high-impact polystyrene D, a filler, and rubber to obtain a mixture B;

[0051] S3. Divide mixture A into two parts, and then add the two parts of mixture A and mixture B into three extruders respectively. The melts extruded from the three extruders are compounded in a co-extrusion head to obtain a PP / PE-HIPS co-extruded composite sheet.

[0052] By adopting this technical solution and utilizing a multi-layer co-extrusion method, the advantages of the surface and middle layers are combined to form a composite sheet with excellent overall performance. The surface layer provides excellent impact resistance and abrasion resistance, while the middle layer provides high impact resistance and dimensional stability. The overall sheet exhibits excellent mechanical properties, thermal stability, abrasion resistance, and cleanability. This PP / PE-HIPS co-extruded composite sheet production method, through rational material selection and process design, effectively solves the problems of mechanical property imbalance, cracking, and warping and cracking caused by different thermal expansion coefficients when co-extruding PP and HIPS sheets.

[0053] In summary, this application has the following beneficial effects:

[0054] 1. Excellent Mechanical Properties: Through the rational design of the surface and middle layers, the composite sheet exhibits excellent impact resistance, flexibility, and strength. The combination of polypropylene and linear low-density polyethylene in the surface layer enhances impact resistance and flexibility, while the high-impact polystyrene and rubber components in the middle layer further enhance impact resistance and flexibility, while the filler increases hardness and rigidity. This combined mechanical performance enables the sheet to effectively absorb and disperse energy when subjected to external impact, reducing the risk of cracking and deformation, making it particularly suitable for electronic product packaging requiring high mechanical properties.

[0055] 2. Easy to use: The formula in this application can make the surface layer and the middle layer of any thickness. There is no need to design the thickness of the middle layer and the surface layer with high precision. A sheet with excellent mechanical properties, stability, impact resistance, etc. can be obtained. It overcomes the problems of unbalanced mechanical properties and warping caused by differences in thermal expansion coefficients that may occur when a single material or simple co-extrusion is used. It provides a packaging material with excellent comprehensive performance, which can better meet the high requirements of electronic product packaging, effectively protect the safety of products during transportation and use, and at the same time maintain the cleanliness and aesthetics of the packaging. DETAILED DESCRIPTION

[0056] Example

[0057] Polybutadiene was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with the product model number P478063.

[0058] Ethylene-propylene rubber was purchased from China National Petroleum Corporation Jilin Chemical Industry Group Co., Ltd. with a brand number of 1035.

[0059] Styrene-butadiene rubber was purchased from Jining Tangyi Chemical Co., Ltd. with model number P28502115.

[0060] Example 1

[0061] A method for preparing a PP / PE-HIPS co-extruded composite sheet is prepared by the following method:

[0062] S1. Mix 500 g of polypropylene A, 1000 g of polypropylene B, 500 g of polypropylene C, 500 g of linear low-density polyethylene, and 400 g of azodicarbonamide to obtain a mixture A.

[0063] S2. Mix 1000 g of high-impact polystyrene A, 500 g of high-impact polystyrene B, 800 g of high-impact polystyrene C, 300 g of high-impact polystyrene D, 300 g of filler (silicon dioxide), and 300 g of rubber (polybutadiene) to obtain a mixture B;

[0064] S3. Divide mixture A into two parts, and then add the two parts of mixture A and mixture B into three extruders respectively. The melts extruded from the three extruders are compounded in a co-extrusion head to obtain a PP / PE-HIPS co-extruded composite sheet with a surface layer thickness of 0.5 cm and a middle layer thickness of 2.5 cm.

[0065] The melt index of polypropylene A (isotactic polypropylene) at 230°C and 2.16 kg is 0.2 g / 10 min;

[0066] The melt index of polypropylene B (syndiotactic polypropylene) at 230°C and 2.16 kg is 0.5 g / 10 min;

[0067] The melt index of polypropylene C (random polypropylene) at 230°C and 2.16 kg is 1 g / 10 min;

[0068] The molecular weight of high-impact polystyrene A is 80,000;

[0069] The molecular weight of high-impact polystyrene B is 150,000;

[0070] The molecular weight of high-impact polystyrene C is 250,000;

[0071] The molecular weight of high-impact polystyrene D is 290,000;

[0072] The melt index of the linear low-density polyethylene under the test conditions of 230° C. and 2.16 kg is 1 g / 10 min.

[0073] The difference between Example 2-3 and Example 1 is that the types, amounts and parameters of raw materials used to prepare the P / PE-HIPS co-extruded composite sheet are different. The specific differences are shown in Table 1:

[0074] Table 1 Raw material types, amounts and parameters for preparing P / PE-HIPS co-extruded composite sheets in Examples 1-3

[0075]

[0076]

[0077] Example 4

[0078] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this embodiment and Example 1 is that the thickness of the surface layer is 0.05 cm and the thickness of the middle layer is 0.2 cm.

[0079] Example 5

[0080] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this embodiment and embodiment 1 is that the thickness of the surface layer is 1 cm and the thickness of the middle layer is 1 cm.

[0081] Comparative Example

[0082] Comparative Example 1

[0083] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that low-density polyethylene is used instead of linear low-density polyethylene.

[0084] The melt index of the low-density polyethylene under the test conditions of 230° C. and 2.16 kg is 2.0 g / 10 min.

[0085] Comparative Example 2

[0086] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that low-density polyethylene is used instead of polypropylene A.

[0087] The melt index of the low-density polyethylene under the test conditions of 230° C. and 2.16 kg is 2.0 g / 10 min.

[0088] Comparative Example 3

[0089] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that the amount of polypropylene A is 1000g, the amount of polypropylene B is 0, and the amount of polypropylene C is 1000g.

[0090] Comparative Example 4

[0091] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that the amount of polypropylene A is 0 g, the amount of polypropylene B is 667 g, and the amount of polypropylene C is 1333 g.

[0092] Comparative Example 5

[0093] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that high-density polyethylene is used instead of high-impact polystyrene A.

[0094] The specific gravity of high-density polyethylene is 0.952g / cm 3 , the melt index under the test conditions of 230℃ and 2.16kg is 2.0g / 10min.

[0095] Comparative Example 6

[0096] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that the amount of high-impact polystyrene A is 0g, the amount of high-impact polystyrene B is 0, the amount of high-impact polystyrene C is 1891g, and the amount of high-impact polystyrene D is 709g.

[0097] Comparative Example 7

[0098] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that the amount of high-impact polystyrene A is 1733 g, the amount of high-impact polystyrene B is 867 g, the amount of high-impact polystyrene C is 0 g, and the amount of high-impact polystyrene D is 0 g.

[0099] Comparative Example 8

[0100] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that the amount of high-impact polystyrene A is 0g, the amount of high-impact polystyrene B is 1400g, the amount of high-impact polystyrene C is 600g, and the amount of high-impact polystyrene D is 600g.

[0101] Comparative Example 9

[0102] A method for preparing a PP / PE-HIPS co-extruded composite sheet. The difference between this comparative example and Example 1 is that high-density polyethylene is used instead of rubber.

[0103] The specific gravity of high-density polyethylene is 0.952g / cm 3 , the melt index under the test conditions of 230℃ and 2.16kg is 2.0g / 10min.

[0104] Detection method / test method

[0105] Dart impact strength: refer to ASTM D1708-03 Method B.

[0106] Comparative Examples 1, 2, 5, 6, and 9 were adjusted to a surface layer thickness of 0.05 cm, and the middle layer thickness was adjusted to 0.2 cm for Comparative Examples 10-14. Blister Forming Experiment: The PP / PE-HIPS co-extruded composite sheets produced in Examples 1-5 and Comparative Examples 1-14 were subjected to blister forming to form packaging boxes. The packaging boxes were then observed for cracking, warping, or deformation. The experimental data is shown in Table 2:

[0107] Table 2 Experimental data of Examples 1-5 and Comparative Examples 1-14

[0108] Examples or Comparative Examples Dart impact strength (g) Blister experiment Example 1 1100 intact Example 2 1200 intact Example 3 1340 intact Example 4 1100 intact Example 5 1100 intact Comparative Example 1 900 intact Comparative Example 2 1020 intact Comparative Example 3 960 intact Comparative Example 4 860 Warping Comparative Example 5 980 Deformation Comparative Example 6 910 Cracking Comparative Example 7 890 Cracking Comparative Example 8 900 Cracking Comparative Example 9 1010 Cracking Comparative Example 10 / Deformation Comparative Example 11 / Deformation Comparative Example 12 / Cracking Comparative Example 13 / Cracking Comparative Example 14 / Deformation

[0109] The experimental data of Example 1 and Comparative Examples 1-4 show that by preparing a PP / PE-HIPS coextruded composite sheet by combining polypropylenes having different melt indexes with linear low-density polyethylene in specific proportions, the sheet can be guaranteed to have good resistance to mechanical impact and will not crack, warp or deform during processing.

[0110] It can be seen from the experimental data of Example 1 and Comparative Examples 5-9 that by preparing PP / PE-HIPS co-extruded composite sheets by combining high-impact polystyrene of different molecular weights with rubber in specific proportions, it can be ensured that the sheets have good resistance to mechanical impact and will not crack, warp or deform during processing.

[0111] From the experimental data of Comparative Examples 1, 2, 5, 6 and 9, Comparative Examples 10-14, Examples 1, and Examples 4-5, it can be seen that the formula of the present application can be used to prepare sheets of different thicknesses without being restricted by thickness, and can also ensure that the sheets have good resistance to mechanical impact and will not crack, warp or deform during processing.

[0112] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A PP / PE-HIPS co-extruded composite sheet, comprising a surface layer, an intermediate layer and a surface layer in sequence, characterized in that: The surface layer is prepared from the following raw materials in parts by weight: Polypropylene A 5-10 parts Polypropylene B 10-20 parts Polypropylene C 5-8 parts 4-8 parts foaming agent 5-10 parts linear low-density polyethylene The melt index of polypropylene A at 230°C and 2.16 kg is 0.2-0.5 g / 10 min; The melt index of polypropylene B at 230°C and 2.16 kg is 0.5-0.8 g / 10 min; The melt index of polypropylene C at 230°C and 2.16 kg is 1-1.5 g / 10 min; The intermediate layer is prepared from the following parts by weight: High impact polystyrene A 10-15 parts High impact polystyrene B 5-10 parts High impact polystyrene C 8-12 parts High impact polystyrene D 3-5 parts 3-5 servings of filling 3-5 parts of rubber; The relative molecular weight of high impact polystyrene A is 80,000-120,000; The relative molecular weight of high impact polystyrene B is 150,000-220,000; The relative molecular weight of high impact polystyrene C is 250,000-280,000; The relative molecular weight of high impact polystyrene D is 290,000-300,000; the foaming agent is at least one of an azo compound, a carbonate and a bicarbonate; The rubber is at least one of polybutadiene, ethylene-propylene rubber, styrene-butadiene rubber and EPDM rubber.

2. The PP / PE-HIPS co-extruded composite sheet according to claim 1, characterized in that: The polypropylene A is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

3. The PP / PE-HIPS co-extruded composite sheet according to claim 1, characterized in that: The polypropylene B is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

4. The PP / PE-HIPS co-extruded composite sheet according to claim 1, characterized in that: The polypropylene C is at least one of isotactic polypropylene, atactic polypropylene and syndiotactic polypropylene.

5. The PP / PE-HIPS co-extruded composite sheet according to claim 1, characterized in that: The linear low-density polyethylene has a melt index of 1-2 g / 10 min under test conditions of 230° C. and 2.16 kg.

6. The PP / PE-HIPS co-extruded composite sheet according to claim 1, characterized in that: The filler is at least one of zinc oxide, silicon dioxide, zinc carbonate, carbon black, kaolin, montmorillonite, diatomaceous earth, needle-shaped wollastonite and ceramic powder.

7. A method for preparing the PP / PE-HIPS co-extruded composite sheet according to any one of claims 1 to 6, characterized in that: The method comprises the following preparation steps: S1, mixing polypropylene A, polypropylene B, polypropylene C, linear low-density polyethylene and a foaming agent to obtain a mixture A; S2. mixing high-impact polystyrene A, high-impact polystyrene B, high-impact polystyrene C, high-impact polystyrene D, a filler, and rubber to obtain a mixture B; S3. Divide mixture A into two parts, and then add the two parts of mixture A and mixture B into three extruders respectively. The melts extruded from the three extruders are compounded in a co-extrusion head to obtain a PP / PE-HIPS co-extruded composite sheet.

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