A continuous fiber cloth / UHMWPE composite material and its bilayer co-extrusion molding process

Abstract

This invention relates to a continuous fiber cloth / UHMWPE composite material and its two-layer co-extrusion molding process. The process includes the following steps: extruding ultra-high molecular weight polyethylene (UHMWPE) matrix material through a single-screw extruder; heating the UHMWPE material to above its melt temperature in the screw extruder's feeding section; then conveying the melt into a die forming section; and undergoing melt-compression molding in the die forming section to prepare a melt preform. Molding methods include extrusion molding, injection molding, and compression molding. First, pre-attach films to both sides of the fiber cloth surface; then pass the fiber cloth through a specific cavity into the die, and before the cooling section, co-extrude it with the melt preform to form a continuous fiber cloth / UHMWPE composite material. Compared with existing technologies, this invention effectively solves the problems of dimensional accuracy, temperature resistance, and cut resistance of existing UHMWPE products, promoting the development of the UHMWPE product industry.

Description

Technical Field

[0001] This invention relates to the field of polymer processing and molding, specifically to a continuous fiber cloth / UHMWPE composite material and its two-layer co-extrusion molding process. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a type of polyethylene (PE) with a viscosity-average molecular weight greater than 1.5 million. It is a novel thermoplastic engineering plastic. Due to its long molecular chains and extremely high molecular weight, it possesses excellent mechanical properties, impact resistance, wear resistance, self-lubrication, and chemical corrosion resistance. UHMWPE is currently the most wear-resistant plastic discovered, so its sheets, pipes, and profiles are widely used in petrochemical, machinery, textile, papermaking, mining, food processing, and sports equipment industries, with large packaging containers and pipes being the most prevalent applications. Furthermore, based on its excellent physiological inertness, UHMWPE has been used in the medical and health fields, including heart valves, orthopedic surgical parts, and artificial joints.

[0003] Products made from UHMWPE (Ultra-High Temperature PVC) possess high strength and impact resistance, maintaining excellent toughness and strength even at -40℃. However, UHMWPE has a significant drawback: poor high-temperature resistance and, while wear-resistant, poor scratch resistance. With the widespread application of UHMWPE products, their shapes and sizes are becoming increasingly diverse, leading to ever-increasing demands for dimensional accuracy, high-temperature resistance, and cut resistance, especially for irregularly shaped parts such as guide rails, sliders, and gears. However, due to its relatively high shrinkage rate of approximately 2-3%, it is highly susceptible to dimensional instability during molding, including warping, ellipticing, and uneven localized shrinkage. Summary of the Invention

[0004] The purpose of this invention is to overcome at least one of the defects of the prior art by providing a continuous fiber cloth / UHMWPE composite material and its bilayer co-extrusion molding process. This effectively solves the problems of dimensional accuracy, temperature resistance, and cut resistance in existing UHMWPE products, thus promoting the development of the UHMWPE product industry.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention utilizes a fiber cloth / UHMWPE double-layer co-extrusion molding process. Based on the product's shape, thickness, and application requirements, a suitable mold is designed, along with a reasonable temperature distribution to create a stepped temperature distribution. This allows for precise adjustment of product dimensions. Furthermore, a suitable fiber cloth is selected to achieve cut resistance and improve the temperature resistance of the UHMWPE product. The specific solution is as follows:

[0007] A bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material, the process comprising the following steps:

[0008] Ultra-high molecular weight polyethylene (UHMWPE) matrix material is extruded through a single-screw extruder. In the feeding section of the screw extruder, the UHMWPE material is heated to above the melting temperature. The melt is then conveyed into the die forming section, where it undergoes melt-compression molding to prepare a melt preform. Molding methods include extrusion molding, injection molding, and compression molding.

[0009] First, a film is pre-attached to both sides of the fiber cloth surface. Then, the fiber cloth is passed through a pre-composite heating roller through a specific cavity 1. Before the cooling section, it is co-extruded with the melt preform to form a continuous fiber cloth / UHMWPE composite material. Then, it is cooled and shaped through a specific cavity 2 and pulled out by a traction machine.

[0010] Furthermore, the fiber cloth is a blend of ultra-high molecular weight polyethylene (UHMWPE) fiber and heat-resistant fiber. Other fiber blends are primarily used to address the drawback of UHMWPE fiber's poor heat resistance; generally, UHMWPE fiber has a temperature resistance of 120-140℃, while aramid, carbon fiber, and glass fiber have temperature resistances exceeding 200℃. UHMWPE fiber possesses high strength and high modulus, excellent abrasion resistance, and cut resistance; blending it increases the operating temperature while further enhancing its superior abrasion resistance and cut resistance.

[0011] Furthermore, the ratio of the area occupied by the ultra-high molecular weight polyethylene fiber to the heat-resistant fiber in the fiber cloth is (2-5):1, and the areal density of the fiber cloth is 60-200 g / m². 2 The blended fabric is woven using plain or twill weave.

[0012] Furthermore, the heat-resistant fiber is a fiber with a temperature resistance of not less than 200℃, including one or more of polypropylene fiber, nylon fiber, aramid fiber, carbon fiber, glass fiber, polyester fiber, viscose fiber or acrylic fiber; the ultra-high molecular weight polyethylene fiber has a strength of 25-40 cN / dtex and a fineness of 50-1600D, preferably, a fiber strength of 30-35 cN / dtex and a fineness of 500-1000D.

[0013] Furthermore, the molecular weight of the ultra-high molecular weight polyethylene is 1 million to 6 million.

[0014] Furthermore, the specific steps are as follows:

[0015] (1) The ultra-high molecular weight polyethylene matrix material is extruded through a single screw extruder. In the feeding section of the screw extruder, the ultra-high molecular weight polyethylene material is heated to above the melting temperature. Then the melt is conveyed into the die forming section. In the die forming section, it is melt-pressed and compressed to prepare a melt preform.

[0016] (2) First, the fiber cloth is pre-attached to both sides of the surface of the fiber cloth. Then, the fiber cloth is passed through a pre-composite heating roller through a specific cavity 1. Before the cooling section, it is co-extruded with the melt preform to form a continuous fiber cloth / UHMWPE composite material. Then, it is cooled and shaped through a specific cavity 2 and pulled out by a traction machine.

[0017] Furthermore, in step (1), the extrusion temperature of the single screw is controlled to gradually increase from 150 to 280°C; the forming section of the mold is provided with a flow-dividing section, a compression section and a shaping section in sequence, and the temperature is controlled to gradually decrease from 250 to 180°C in a stepped manner, wherein the flow-dividing section is 235-280°C, the compression section is 200-235°C and the shaping section is 150-200°C.

[0018] Furthermore, in step (2), the specific cavity has a multi-point staged temperature control effect on both the inner and outer sides. The temperature inside the cavity is controlled at 150-180℃, and the temperature outside is controlled at 135-160℃. The temperature of the composite co-extrusion is 150-180℃, the compression ratio of the composite section is (1.1-1.8):1, and the pressure of the template in the specific cavity 1 is automatically adjusted and controllable by the pressure sensor.

[0019] Furthermore, the film includes ultra-high molecular weight polyethylene (UHMWPE) film and EVA film. When laminated, a four-layer composite fiber cloth is formed, consisting of UHMWPE film / EVA film / fiber cloth / EVA film. The UHMWPE film is located on the outside of the cavity and has a thickness of 0.2-1 mm, while the EVA film has a thickness of 0.2-0.5 mm.

[0020] A continuous fiber cloth / UHMWPE composite material prepared by the double-layer co-extrusion molding process described above.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The present invention designs a reasonable temperature distribution to form a stepped temperature distribution. By using mold temperature controllers, chillers and other related temperature control equipment, the temperature difference is precisely adjusted to control the material cooling rate and shrinkage speed, thereby achieving the purpose of precisely adjusting the product size.

[0023] (2) This invention utilizes ultra-high molecular weight polyethylene fiber blended with other fibers, combining the high strength and high modulus of ultra-high molecular weight polyethylene fiber, excellent anti-cut performance, and the excellent temperature resistance of aramid fiber, carbon fiber and other fibers, and composites them on the surface of ultra-high molecular weight polyethylene products, thereby improving the defects of ultra-high molecular weight polyethylene that is wear-resistant but not scratch-resistant, and low-temperature resistant but not high-temperature resistant, thus expanding the service life and application range of the products.

[0024] (3) The specific cavity of this invention has the functions of extrusion shaping and adjusting shrinkage rate. The shape of the inner cavity is the same as that of the die head, following the shape of the product. Generally speaking, most of the cavities formed nowadays are cooled and shaped, and few can be controlled, or have their shrinkage rate of two or more materials adjusted in a controllable manner during the composite process. The specific cavity of this invention achieves controllable adjustment of the shrinkage rate of two or more materials during the composite process through a pressure sensor and a high and low temperature mold temperature controller. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the extrusion composite molding process of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] A continuous fiber cloth / UHMWPE composite material and its bilayer co-extrusion molding process include the following steps:

[0028] (1) Ultra-high molecular weight polyethylene (UHMWPE) material is extruded through a single-screw extruder. In the feeding section of the screw extruder, the UHMWPE material is heated to above the melting temperature. The melt is then conveyed into the die forming section, where it is melt-compressed to form a melt preform. The UHMWPE fiber strength is 25-40 cN / dtex, and the fineness is 50-1600D, preferably 30-35 cN / dtex and 500-1000D. The matrix is ​​UHMWPE powder with a molecular weight of 1 million to 6 million. The extrusion temperature of the single screw is controlled to gradually increase from 150-280℃. The die forming section is sequentially equipped with a flow-dividing section, a compression section, and a shaping section, and the temperature is controlled to gradually decrease from 250-180℃ in a stepped manner, with the flow-dividing section at 235-280℃, the compression section at 200-235℃, and the shaping section at 150-200℃.

[0029] (2) Ultra-high molecular weight polyethylene (UHMWPE) / EVA films are pre-laminated on both sides of the fiber cloth surface to form a four-layer composite fiber cloth consisting of UHMWPE film / EVA film / fiber cloth / EVA film. This fiber cloth is then passed through a specific cavity into a mold and co-extruded with the melt preform before the cooling section. The lamination temperature is 150-180℃, and the compression ratio of the lamination section is (1.1-1.8):1, thus forming a co-extruded product. The fiber cloth is prepared by blending UHMWPE fibers with one or more other fibers. Other fibers include one or more of polypropylene fibers, nylon fibers, aramid fibers, carbon fibers, glass fibers, polyester fibers, viscose fibers, and acrylic fibers. The UHMWPE fibers are woven with other fibers using a plain or twill weave. The area ratio of UHMWPE fibers to other fibers is (2-5):1, and the areal density of the fiber cloth is 60-200 g / m³. 2 The specific cavity has a multi-point staged temperature control effect on both the inner and outer sides, with the temperature inside the cavity controlled at 150-180℃ and the temperature on the outer side controlled at 135-160℃.

[0030] Example 1

[0031] A continuous fiber fabric / UHMWPE composite material and its two-layer co-extrusion molding process are disclosed. The process involves extruding ultra-high molecular weight polyethylene (UHMWPE) profiles using raw materials with a molecular weight of 2 million. First, the UHMWPE material is heated to a temperature above its melting point. The melt is then extruded into a high-pressure melt in the compression section of a die. A fiber fabric is then produced by blending UHMWPE fibers and aramid fibers at an area ratio of 2:1, with a fiber fabric surface density of 60 g / m³. 2 The extruded material is laminated with ultra-high molecular weight polyethylene (UHMWPE) film / EVA film on both sides of its surface. The UHMWPE film on the outer side is 1 mm thick, and the EVA film on the inner side is 0.2 mm thick. This film is then laminated with the high-pressure melt in the setting section at a lamination temperature of 180℃. The compression ratio in the lamination section is 1.5:1. After cooling, it is formed into the finished product. The mold forming section is divided into a flow-dividing section, a compression section, and a setting section, with heating temperatures ranging from 250℃, 210℃, and 180℃, respectively. The temperature inside the cavity is controlled at 160℃, and the temperature outside the cavity is controlled at 150℃. The mechanical properties of the extruded product are shown in Appendix Table 1.

[0032] Example 2

[0033] A continuous fiber fabric / UHMWPE composite material and its two-layer co-extrusion molding process are disclosed. The process involves extruding ultra-high molecular weight polyethylene (UHMWPE) profiles using raw materials with a molecular weight of 3.5 million. First, the UHMWPE material is heated to a temperature above its melting point. The melt is then extruded into a high-pressure melt in the compression section of a die. A fiber fabric is then produced by blending UHMWPE fibers and nylon fibers at an area ratio of 5:1, with a fiber fabric surface density of 90 g / m³. 2The extruded material is laminated with ultra-high molecular weight polyethylene (UHMWPE) film / EVA film on both sides of its surface. The UHMWPE film on the outer side is 0.3 mm thick, and the EVA film on the inner side is 0.5 mm thick. This film is then laminated with the high-pressure melt in the setting section at a lamination temperature of 150℃. The compression ratio in the lamination section is 1.2:1. After cooling, it is formed into the finished product. The mold forming section is divided into a flow-dividing section, a compression section, and a setting section, with heating temperatures ranging from 225℃, 200℃, and 150℃, respectively. The temperature inside the mold cavity is controlled at 150℃, and the temperature outside the mold cavity is controlled at 135℃. The mechanical properties of the extruded product are shown in Appendix Table 1.

[0034] Example 3

[0035] A continuous fiber cloth / UHMWPE composite material and its two-layer co-extrusion molding process are disclosed. The process involves extruding ultra-high molecular weight polyethylene (UHMWPE) sheets with a raw material molecular weight of 4.5 million. First, the UHMWPE material is heated to a temperature above its melting point. The melt is then extruded into a high-pressure melt in the compression section of a die. A fiber cloth is then produced by blending UHMWPE fibers and carbon fibers at an area ratio of 3:1, with a fiber cloth surface density of 150 g / m³. 2 The extruded material is laminated with ultra-high molecular weight polyethylene (UHMWPE) film / EVA film on both sides of its surface. The UHMWPE film on the outer side is 0.5 mm thick, and the EVA film on the inner side is 0.3 mm thick. This film is then laminated with the high-pressure melt in the setting section at a lamination temperature of 175℃. The compression ratio in the lamination section is 1.3:1. After cooling, it is formed into the finished product. The mold forming section is divided into a flow-dividing section, a compression section, and a setting section, with heating temperatures ranging from 235℃, 210℃, and 160℃, respectively. The temperature inside the cavity is controlled at 180℃, and the temperature outside the cavity is controlled at 160℃. The mechanical properties of the extruded product are shown in Appendix Table 1.

[0036] Table 1 Mechanical properties of products from Examples 1-3

[0037]

[0038] *Note: The sliding friction coefficient test adopts a reciprocating method, and the test conditions are a pressure of 5N and a frequency of 1Hz.

[0039] Comparative Example 1

[0040] A molding process for extruding ultra-high molecular weight polyethylene (UHMWPE) profiles using raw material with a molecular weight of 2 million involves first heating the UHMWPE material to a temperature above its melting point. The melt is then compressed in the compression section of a die, becoming a high-pressure melt. This high-pressure melt is then directly cooled in a cooling section to form the finished product. The die forming section is divided into a flow distribution section, a compression section, and a shaping section, with heating temperatures ranging from 250°C, 210°C, and 180°C, respectively.

[0041] Comparative Example 2

[0042] A molding process for extruding ultra-high molecular weight polyethylene (UHMWPE) sheets using raw materials with a molecular weight of 3 million involves first heating the UHMWPE material to a temperature above its melting point. The melt is then compressed in the compression section of a die, becoming a high-pressure melt. This high-pressure melt is then directly cooled in a cooling section to form the finished product. The die forming section is divided into a flow distribution section, a compression section, and a shaping section, with heating temperatures ranging from 235°C, 210°C, and 160°C, respectively.

[0043] Comparative Example 3

[0044] A molding process for extruding ultra-high molecular weight polyethylene (UHMWPE) profiles using raw materials with a molecular weight of 2 million involves first heating the UHMWPE material to a temperature above its melting point. The melt is then extruded into a high-pressure melt in the compression section of a die. A fiber fabric is then produced by blending UHMWPE fibers with aramid fibers at an area ratio of 2:1, with a fiber fabric surface density of 60 g / m². 2 The inner surface of the EVA film is 0.2mm thick, and then it is laminated with the high-pressure melt in the shaping section at a lamination temperature of 180℃. The compression ratio of the lamination section is 1.5:1. After that, it is directly cooled and formed into the product in the cooling section. The mold forming section is divided into a flow distribution section, a compression section, and a shaping section, with heating temperatures ranging from 250℃, 210℃, and 180℃, respectively. The temperature inside the cavity is controlled at 160℃, and the temperature outside the cavity is controlled at 150℃.

[0045] Table 2 Mechanical properties of products from Comparative Examples 1-3

[0046]

[0047] *Note: The sliding friction coefficient test adopts a reciprocating method, and the test conditions are a pressure of 5N and a frequency of 1Hz.

[0048] Warpage data indirectly confirms the effectiveness of dimensional accuracy adjustments. Both the UHMWPE sheet and UHMWPE fiber are processed from UHMWPE resin. In this invention, the sheet is formed through extrusion molding; relevant physical properties can be found in Table 2. UHMWPE has a very high melt viscosity, poor flowability, and poor adhesion. Without a film laminated onto the fiber, it is difficult to simply co-extrude the fiber cloth and the UHMWPE matrix together. The absence of a UHMWPE film laminate on the outside of the fiber cloth can be reflected in a different coefficient of friction.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material, characterized in that, The specific steps of this process are as follows: (1) The ultra-high molecular weight polyethylene matrix material is extruded through a single screw extruder. In the feeding section of the screw extruder, the ultra-high molecular weight polyethylene material is heated to above the melting temperature. Then the melt is conveyed into the die forming section. In the die forming section, it is melt-compressed to prepare a melt preform. The extrusion temperature of the single screw is controlled to gradually increase from 150 to 280°C. The die forming section is provided with a flow distribution section, a compression section and a shaping section in sequence. The temperature is controlled to gradually decrease from 250 to 180°C in a stepped manner. The flow distribution section is 235-280°C, the compression section is 200-235°C and the shaping section is 150-200°C. (2) First, pre-attach the film to both sides of the fiber cloth surface, and then combine the fiber cloth with the melt preform in the cavity. The temperature of the composite co-extrusion is 150-180℃, the temperature inside the cavity is controlled at 150-180℃, and the temperature outside is controlled at 135~160℃. The compression ratio during the composite is (1.1-1.8):

1. The ultra-high molecular weight polyethylene has a molecular weight of 1 million to 6 million. The film includes ultra-high molecular weight polyethylene (UHMWPE) film and EVA film. When laminated, a four-layer composite fiber cloth is formed, consisting of UHMWPE film / EVA film / fiber cloth / EVA film. The UHMWPE film is located on the outside of the cavity and has a thickness of 0.2-1 mm. The EVA film has a thickness of 0.2-0.5 mm.

2. The bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material according to claim 1, characterized in that, The fiber cloth is a fiber cloth prepared by blending ultra-high molecular weight polyethylene fiber and heat-resistant fiber.

3. The bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material according to claim 2, characterized in that, The ratio of ultra-high molecular weight polyethylene fiber to heat-resistant fiber in the area of ​​the fiber cloth is (2-5):1, and the areal density of the fiber cloth is 60-200 g / m². 2 The blended fabric is woven using plain or twill weave.

4. The bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material according to claim 2, characterized in that, The heat-resistant fiber is a fiber with a temperature resistance of not less than 200℃, including one or more of polypropylene fiber, nylon fiber, aramid fiber, carbon fiber, glass fiber, polyester fiber, viscose fiber or acrylic fiber; the ultra-high molecular weight polyethylene fiber has a strength of 25-40 cN / dtex and a fineness of 50-1600 D.

5. The bilayer co-extrusion molding process for a continuous fiber cloth / UHMWPE composite material according to claim 4, characterized in that, The ultra-high molecular weight polyethylene fiber has a strength of 30-35 cN / dtex and a fineness of 500-1000 D.

6. A continuous fiber cloth / UHMWPE composite material prepared by the double-layer co-extrusion molding process as described in any one of claims 1-5.

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