A method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product

Abstract

The application provides a preparation method of a porous ultrahigh molecular weight polyethylene and polypropylene blended product, and belongs to the field of material processing methods. The method solves the problem of solid state processing difficulty of ultrahigh molecular weight polyethylene. The method comprises the following steps: blending ultrahigh molecular weight polyethylene and polypropylene according to a proportion, pressing the blend into a plate by using a hot pressing method, and cutting the pressed plate into a rectangular sample; performing solid state die drawing on the rectangular sample at a set temperature, keeping the rectangular sample at a constant temperature for a period of time, then stretching the rectangular sample to a shape stable according to a set die drawing speed, stopping the stretching, and keeping the sample at a constant deformation for a period of time, so as to obtain the blended product. The method is mainly used for preparing ultrahigh molecular weight polyethylene products.

Description

Technical Field

[0001] This invention belongs to the field of material processing methods, and in particular relates to a method for preparing a blend of porous ultra-high molecular weight polyethylene and polypropylene. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) has long molecular chains, numerous internal entanglements, and extremely poor melt flowability, making it unsuitable for direct processing using common industrial injection molding methods. Current processing methods for UHMWPE mainly include gel spinning, extrusion, hot pressing, and sintering. These methods either consume large amounts of solvents or energy, or fail to fully realize the material's potential. To further promote the development of my country's UHMWPE industry, the industry urgently needs cleaner, more environmentally friendly, energy-saving, and emission-reducing processing methods that meet the demands of industrial production.

[0003] Solid-state die drawing is a processing technique that stretches materials from a die in a solid state to achieve the desired microstructure and properties. Compared to extrusion, which also uses a die, the material does not need to be heated to a molten state, saving significant energy. This process requires no solvents and can produce samples with different degrees of orientation by adjusting the die shape and the initial size of the sample, thereby obtaining high-strength materials. These processed materials can be used to manufacture luggage, flooring, or other sheet materials. Therefore, this technology holds promise for processing ultra-high molecular weight polyethylene (UHMWPE), enabling the production of novel high-strength UHMWPE products without the addition of solvents. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method for preparing a blend of porous ultra-high molecular weight polyethylene and polypropylene to solve the problem of difficult solid-state processing of ultra-high molecular weight polyethylene.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product, comprising the following steps:

[0006] Step 1: Blend ultra-high molecular weight polyethylene and polypropylene in a certain proportion, press the blend into a sheet using a hot pressing method, and cut the pressed sheet into rectangular strips.

[0007] Step 2: Solid-state stretching of the rectangular sample at a set temperature. First, keep the rectangular sample at the set temperature for a period of time. Then, stretch the rectangular sample to a stable shape according to the set stretching speed. After that, stop stretching and let the sample remain constant under a fixed deformation for a period of time to obtain the blended product.

[0008] Furthermore, in step 1, ultra-high molecular weight polyethylene and polypropylene are blended in a mass ratio of 1:9 to 9:1.

[0009] Furthermore, in step 1, ultra-high molecular weight polyethylene and polypropylene are blended using a Banbury mixer.

[0010] Furthermore, in step 1, the blend is pressed into a sheet with a thickness of 1mm to 20mm using a hot pressing method.

[0011] Furthermore, the sheet material pressed in step 1 is rectangular or square.

[0012] Furthermore, in step 2, the rectangular sample is solid-state stretched in a range below the melting point of ultra-high molecular weight polyethylene. First, the rectangular sample is kept at a constant temperature for 10 minutes, and then stretched to a stable shape according to the set stretching speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 30 minutes to obtain the blended product.

[0013] Furthermore, in step 2, the rectangular sample is solid-state stretched within a temperature range 1-5°C above the melting point of ultra-high molecular weight polyethylene. The rectangular sample is first kept at a constant temperature for 10 minutes, and then stretched to a stable shape according to the set stretching speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 30 minutes to obtain the blended product.

[0014] Furthermore, in step 2, the rectangular sample is solid-state molded at a temperature 10°C or higher than the melting point of ultra-high molecular weight polyethylene. The rectangular sample is first kept at a constant temperature for 20 minutes, and then stretched to a stable shape according to the set molding speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 10 minutes to obtain the blended product.

[0015] Furthermore, the die-drawing speed is 1–500 mm / min.

[0016] Compared with existing technologies, the advantages of this invention are as follows: Addressing the difficulty of solid-state processing of ultra-high molecular weight polyethylene (UHMWPE), this invention employs solid-state molding technology to successfully achieve solid-state processing of UHMWPE / iPP blends. By blending UHMWPE with isotactic polypropylene (iPP) and utilizing their melting point difference, UHMWPE / iPP blend products with different microstructures and macroscopic morphologies are successfully prepared. The resulting products are highly oriented UHMWPE products with good mechanical strength. The mechanical properties, transparency, and surface feel of the UHMWPE / iPP blend products can be controlled by varying the molding temperature. These products can be used in sheet materials, strapping, and surface decoration. This processing method avoids the use of solvents, allows for the control of both microscopic and macroscopic morphology of the material, is simple, energy-saving, environmentally friendly, and produces diverse products.

[0017] This invention utilizes solid-state molding technology to prepare UHMWPE / iPP oriented materials with different degrees of orientation and varying micro and macroscopic morphologies, based on changes in the initial size of the sample and the solid-state stretching temperature. In particular, by adjusting the molding temperature, it is possible to prepare UHMWPE / iPP products with different levels of transparency. The prepared stretched strips exhibit a certain fiber orientation structure, and the UHMWPE / iPP strips prepared under partial stretching conditions possess micropores of several hundred nanometers in size, making them suitable for use as porous materials. Furthermore, the UHMWPE / iPP products prepared by solid-state molding possess strong mechanical properties. Depending on the micro and macroscopic morphology of the samples, the prepared UHMWPE products can be used in future applications such as sheet materials, strapping, and surface finishing. Attached Figure Description

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 These are macroscopic photographs and corresponding wide-angle views of the blended product prepared in Example 1 of the present invention;

[0020] Figure 2 These are macroscopic photographs and corresponding wide-angle views of the blended product prepared in Example 2 of this invention;

[0021] Figure 3 These are macroscopic photographs and corresponding wide-angle views of the blended product prepared in Example 3 of the present invention;

[0022] Figure 4 The images shown are scanning electron microscope (SEM) images of solid-state molded samples of the porous ultra-high molecular weight polyethylene and polypropylene blend described in this invention; wherein: Figure 4(a) is a scanning electron microscope image of the sample at 130℃. Figure 4 (b) is a scanning electron microscope image of the sample at 140℃. Figure 4 (c) is a scanning electron microscope image of the sample at 150℃.

[0023] Figure 5 This is the true stress-strain curve of the solid molded sample at different temperatures during the re-stretching process described in this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0025] See Figure 1-5 This embodiment describes a method for preparing a blend of porous ultra-high molecular weight polyethylene and polypropylene, which includes the following steps:

[0026] First, ultra-high molecular weight polyethylene and polypropylene are blended in a mass ratio of 1:9 to 9:1 using an internal mixer. The blend is then pressed into rectangular or square sheets with a thickness of 1 mm to 20 mm using a hot pressing method. The pressed sheets are then cut into rectangular strips of a certain size, which needs to match the mold size of the solid die stretching technology.

[0027] Example 1: A 5mm thick UHMWPE / iPP (5:5) rectangular strip was solid-state stretched below the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 130℃. The rectangular strip was first held at this temperature for 10 minutes, and then stretched at a stretching speed of 1-500mm / min until the shape stabilized. Stretching was then stopped, and the sample was allowed to remain under a fixed deformation for 30 minutes to obtain the blend product. The prepared blend product exhibited a certain degree of orientation and transparency. Its orientation and appearance are shown in the photographs. Figure 1 .

[0028] Example 2: A 5mm thick UHMWPE / iPP (5:5) rectangular strip was solid-state stretched at a temperature 1°C above the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 140°C. The rectangular strip was first held at this temperature for 10 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. Stretching was then stopped, and the sample was allowed to remain under a fixed deformation for 30 minutes to obtain the blend product. The prepared blend product exhibited a certain degree of orientation, but its transparency was slightly reduced. The degree of orientation and appearance are shown in the photograph. Figure 2 .

[0029] Example 3: A 5mm thick UHMWPE / iPP (5:5) rectangular strip was solid-state stretched at a temperature 10°C or higher than the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 150°C. The rectangular strip was first held at this temperature for 20 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. Stretching was then stopped, and the sample was allowed to remain under a fixed deformation for 10 minutes to obtain the blended product. The prepared blended product has a granular surface and is opaque, but the sample exhibits a certain degree of orientation. The degree of orientation and appearance are shown in the photograph. Figure 3 .

[0030] Example 4: A 20mm thick UHMWPE / iPP (1:9) rectangular sample was solid-state stretched in a range below the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 130℃. The rectangular sample was first kept at a constant temperature for 10 minutes, and then stretched at a stretching speed of 1 to 500 mm / min until the shape was stable. After that, the stretching was stopped, and the sample was kept constant under a fixed deformation for 30 minutes to obtain the blended product.

[0031] Example 5: A 20mm thick UHMWPE / iPP (1:9) rectangular strip was solid-state stretched at a temperature 3°C above the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 140°C. The rectangular strip was first held at this temperature for 10 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. Stretching was then stopped, and the sample was allowed to remain under a constant deformation for 30 minutes to obtain the blended product. The prepared blended product exhibited a certain degree of orientation, but its transparency was slightly reduced.

[0032] Example 6: A 20mm thick UHMWPE / iPP (1:9) rectangular sample was solid-state stretched at a temperature 10°C or higher than the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 150°C. The rectangular sample was first held at this temperature for 20 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. Stretching was then stopped, and the sample was held at a constant deformation for 10 minutes to obtain the blended product. The product transparency decreased.

[0033] Example 7: A 20mm thick UHMWPE / iPP (9:1) rectangular strip was solid-state stretched in a range below the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 130℃. The rectangular strip was first kept at a constant temperature for 10 minutes, and then stretched at a stretching speed of 1 to 500 mm / min until the shape was stable. After that, the stretching was stopped, and the sample was kept constant under a fixed deformation for 30 minutes to obtain the blended product.

[0034] Example 8: A 20mm thick UHMWPE / iPP (9:1) rectangular strip was solid-state stretched at a temperature 5°C above the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 140°C. The rectangular strip was first held at this temperature for 10 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. Stretching was then stopped, and the sample was allowed to remain under a constant deformation for 30 minutes to obtain the blend product. The prepared blend product exhibited a certain degree of orientation, but its transparency was slightly reduced.

[0035] Example 9: A 20mm thick UHMWPE / iPP (9:1) rectangular strip was solid-state stretched at a temperature 10°C or higher than the melting point of ultra-high molecular weight polyethylene. In this example, the temperature was 150°C. The rectangular strip was first held at this temperature for 20 minutes, and then stretched at a stretching speed of 1–500 mm / min until the shape stabilized. After that, the stretching was stopped, and the sample was held at a constant deformation for 10 minutes to obtain the blended product. The product surface was very rough and opaque.

[0036] By controlling the molding temperature of UHMWPE / iPP, materials with different surface textures were prepared. Blends stretched below the melting point of UHMWPE showed smooth and regular surfaces; blends prepared near the melting point of UHMWPE exhibited reduced surface smoothness; and blends prepared above the melting point of UHMWPE showed a noticeable grainy texture. Scanning electron microscopy revealed that the former contained only oriented fiber structures and lamellar crystals, while the latter also showed micropores, especially in the blend stretched at 150°C, where the micropores were highly uniform. (See [link to documentation]). Figure 4 .

[0037] Mechanical tests were conducted on the blended products after die stretching under different conditions. Regardless of the die stretching temperature, the samples could be stretched again upon re-stretching. Specific stretching curves are shown below. Figure 5 , is the tensile curve of the sample after molding at 30℃.

[0038] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing a blend of porous ultra-high molecular weight polyethylene and polypropylene, characterized in that: It includes the following steps: Step 1: Blend ultra-high molecular weight polyethylene and polypropylene in a certain proportion, press the blend into a sheet using a hot pressing method, and cut the pressed sheet into rectangular strips. Step 2: Solid-state stretching of the rectangular sample at a set temperature. First, keep the rectangular sample at the set temperature for a period of time. Then, stretch the rectangular sample to a stable shape according to the set stretching speed. After that, stop stretching and let the sample remain constant under a fixed deformation for a period of time to obtain the blended product.

2. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 1, ultra-high molecular weight polyethylene and polypropylene are blended in a mass ratio of 1:9 to 9:

1.

3. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 1, ultra-high molecular weight polyethylene and polypropylene are blended using a Banbury mixer.

4. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 1, the blend is pressed into a sheet with a thickness of 1mm to 20mm using a hot pressing method.

5. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: The sheet material pressed in step 1 is rectangular or square.

6. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 2, the rectangular sample is solid-state molded in a range below the melting point of ultra-high molecular weight polyethylene. First, the rectangular sample is kept at a constant temperature for 10 minutes. Then, the rectangular sample is stretched to a stable shape according to the set molding speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 30 minutes to obtain the blended product.

7. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 2, the rectangular sample is solid-state stretched within a temperature range of 1-5°C above the melting point of ultra-high molecular weight polyethylene. The rectangular sample is first kept at a constant temperature for 10 minutes, and then stretched to a stable shape according to the set stretching speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 30 minutes to obtain the blended product.

8. The method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to claim 1, characterized in that: In step 2, the rectangular sample is solid-state molded at a temperature 10°C or higher than the melting point of ultra-high molecular weight polyethylene. The rectangular sample is first kept at a constant temperature for 20 minutes, and then stretched to a stable shape according to the set molding speed. After that, the stretching is stopped, and the sample is kept constant under a fixed deformation for 10 minutes to obtain the blended product.

9. A method for preparing a porous ultra-high molecular weight polyethylene and polypropylene blend product according to any one of claims 6-8, characterized in that: The die-drawing speed is 1 to 500 mm / min.

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