Preparation method of oriented polymer block material

Abstract

The invention relates to the technical field of polymer material processing and modification, in particular to a method for preparing an oriented polyethylene block material. The invention aims to solve the technical problem that the high orientation degree is difficult to realize in the existing polymer block material processing. By applying shear deformation in a specific temperature interval which is 0.1-20 DEG C higher than the melting point of the polymer, the molecular chain orientation degree of the polymer material is remarkably improved. The core of the method is to select the specific temperature interval, so that the high orientation degree of a polymer molecular chain is effectively realized, and the overall performance of the material is remarkably improved. The selection of the temperature interval provides a new technical path for high performance of the polymer material, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material processing and modification, and in particular to a method for preparing an oriented polymer block material. Background Art

[0002] Polyethylene is an important polymer material widely used in packaging, construction, machinery, and other fields. In recent years, with the increasing demand for polyethylene material performance, researchers have been committed to improving its mechanical and optical properties through various processing techniques. Orientation treatment is an effective method. Through orientation treatment, the molecular chains of polyethylene are aligned in a specific direction, significantly improving the material's mechanical and optical properties.

[0003] In the prior art, one-dimensional fibers and two-dimensional films are common forms of oriented polyethylene materials. For example, Ye Z et al. [Macromolecular rapid communications, 2006, 27(15): 1217-1222] prepared oriented polyethylene fibers using extrusion equipment, and their tensile modulus can reach 20 GPa and their tensile strength can reach 1.3 GPa; Bobovitch AL et al. [Journal of applied polymer science, 2006, 100(5): 3545-3553] prepared oriented polyethylene films using a stretching process, and their tensile strength increased with increasing stretch ratio. These studies have shown that under these processing methods dominated by positive strain, the molecular chains of polyethylene can form a highly oriented structure, resulting in mechanical properties that are superior to those of unoriented polyethylene. However, these processing methods dominated by positive strain have obvious limitations: as the strain increases, the sample will undergo a significant size reduction in one or two dimensions, resulting in the shape of the final product being limited to a film or thin fiber, making it difficult to prepare a bulk material with larger three-dimensional dimensions.

[0004] In addition, significant progress has been made in research on the effects of shear strain on polyethylene structure. For example, Yang H et al. [Polymer, 2019, 184:12-1915] used a rotary shear system to produce high-density polyethylene oriented tubing with a "shish-kebab" structure at 100°C above the sample's melting point, significantly improving its mechanical properties. However, the processing temperature of this method is typically significantly higher than the melting point of polyethylene, which may cause the molecular chains to deorient during processing and cooling, thereby limiting the degree of molecular chain orientation in the final material and hindering further improvements in its mechanical properties.

[0005] In response to these deficiencies, the present invention proposes a new process based on the research results of the document [Scripta Materialia, 2012, 67(10):810-813]. This method can apply shear deformation near the melting point of the sample and, through subsequent cooling treatment, prepare a polyethylene bulk material with a highly oriented structure. Compared with the prior art, the method of the present invention overcomes the limitations of traditional methods in selecting processing temperatures by applying shear deformation within a specific temperature range near the melting point of the sample. This unique temperature range not only ensures the effectiveness of the shear deformation, but also optimizes the conditions for the subsequent cooling treatment, thereby achieving the preparation of a polyethylene bulk material with a highly oriented structure. Summary of the Invention

[0006] The present invention provides a method for preparing an oriented polymer block material by applying shear deformation in a specific temperature range near the melting point, thereby achieving the preparation of a material with high orientation, high crystallinity, and excellent mechanical properties. This method is applicable to polymer materials including, but not limited to, high-density polyethylene and ultra-high molecular weight polyethylene.

[0007] To achieve the above purpose, the technical solutions adopted in the present invention are as follows:

[0008] A method for preparing an oriented polymer block material, comprising the following steps:

[0009] 1) Using a crystalline polymer as raw material, an initial sample is prepared by a melt pelletizing casting process or mechanical processing;

[0010] 2) The initial sample is loaded into the sample holding chamber of the processing device, and the sample is heated to a temperature range of 0.1 to 20°C above its melting point by the temperature control system, and the temperature is maintained until the sample is completely melted and the temperature field is uniform and stable;

[0011] 3) The motor system drives the outer ring of the processing device to rotate, thereby driving the inner and outer walls of the sample to rotate relative to each other, causing the sample to undergo shear deformation, and the preset shear strain amount is achieved by accumulating the number of rotations;

[0012] 4) After processing is completed, an isotropic pressure of 0.1 to 100 MPa is applied to the processing device loaded with the sample, and the temperature is cooled to room temperature at a cooling rate of 5 to 200°C / min, so that the polymer completes the crystallization process in the directional shear field to form an oriented polymer block material with three-dimensional dimensions of not less than 1 mm.

[0013] Furthermore, the oriented polymer refers to the characterization of the crystal plane orientation by X-rays, wherein the characteristic crystal plane is defined as: based on the polymer crystallographic parameters, a crystal plane with a diffraction intensity of ≥25% within the 2θ angle range is selected in the X-ray diffraction pattern, and the orientation degree is calculated by the Hermans orientation function formula, and the value of the characteristic crystal plane is not less than 0.5.

[0014] Furthermore, the size of the block material in three dimensions is not less than 1 mm.

[0015] Furthermore, the polymer includes high-density polyethylene and ultra-high molecular weight polyethylene.

[0016] Furthermore, the melting point Tm is determined by differential scanning calorimetry (DSC) at a heating rate of 10°C / min, and the melting point is the peak temperature of the endothermic peak on the DSC curve.

[0017] Furthermore, the number of rotations is adjusted according to the actual required shear strain.

[0018] Furthermore, the processing device used in step 2) includes a core shaft; a lower washer; a sample; an outer ring; and an upper washer.

[0019] The beneficial effects of adopting the technical solution of the present invention are:

[0020] Compared to existing technologies, the method of this invention overcomes the limitations of traditional methods in processing temperature selection by applying shear deformation within a specific temperature range near the sample's melting point. This unique temperature range not only ensures the effectiveness of shear deformation but also optimizes the conditions for subsequent cooling, thereby achieving the preparation of highly oriented polyethylene bulk materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the internal structure diagram of the present invention.

[0022] Figure 2 These are the X-ray diffraction (XRD) results of ultra-high molecular weight polyethylene after deformation at 5°C and 15°C above the melting point.

[0023] Figure 3 This is a scanning electron microscope (SEM) micrograph of ultra-high molecular weight polyethylene before and after shear deformation by rotating the processing device 50 times at a temperature 5°C above the melting point.

[0024] Figure 4 This is a scanning electron microscope (SEM) micrograph of ultra-high molecular weight polyethylene before and after shear deformation by rotating the processing device 100 times at a temperature 15°C above the melting point. DETAILED DESCRIPTION

[0025] The following is a clear and complete description of the technical solutions in the embodiments of the invention in conjunction with the specific embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] The present invention is further described by the following specific examples:

[0027] The high-density polyethylene in the present invention is a polyethylene sheet produced by Dezhou Xinbeiyuan Wear-Resistant Materials Co., Ltd. w =8×10 4 .

[0028] The ultra-high molecular weight polyethylene in the present invention is a polyethylene sheet produced by Jiujiang Petrochemical. w =3×10 6 .

[0029] Example 1

[0030] Raw material: ultra-high molecular weight polyethylene

[0031] A method for preparing an oriented ultra-high molecular weight polyethylene block material comprises the following steps:

[0032] (1) Sample preparation: Samples were prepared by turning.

[0033] (2) Heating treatment: The sample is loaded into a processing device, heated to a temperature 5°C higher than the melting point, and the temperature is kept stable so that the ultra-high molecular weight polyethylene reaches a molten state. The processing device used includes a core shaft 1; a lower washer 2; a sample 3; an outer ring 4; and an upper washer 5.

[0034] (3) Processing: Under the above-mentioned stable temperature conditions, the sample was subjected to shear deformation treatment, and the processing device rotated 50 times.

[0035] (4) Cooling: The entire processing apparatus loaded with the sample is immersed in water, and a pressure of 100 MPa is applied to the upper and lower gaskets. The sample is cooled to room temperature by water cooling at a cooling rate of 100°C / min. After deformation, a circular ultra-high molecular weight polyethylene sample having dimensions greater than 1 mm in three dimensions is obtained. In this embodiment, the dimensions in three dimensions are 10 mm × 10 mm × 5 mm. Samples of 10 mm × 10 mm × 7 mm and 10 mm × 10 mm × 10 mm can also be prepared by replacing molds of different sizes.

[0036] Table 1 shows the orientation and crystallinity parameters of the corresponding samples before and after deformation. Figure 2 The XRD diffraction results of the corresponding samples before and after deformation are given. Figure 3The SEM microstructures of the samples before and after deformation are presented. XRD characterization results show an orientation degree of 0.711 and a crystallinity of 89.47%. Furthermore, the SEM microstructures show a molecular chain structure that tends to be parallel, confirming that this method can effectively prepare oriented ultra-high molecular weight polyethylene bulk materials.

[0037] Hermans orientation function formula: Where, cos 2 θ> is the statistical average of the cosine square of the angle between the normal direction of the characteristic crystal plane and the orientation direction.

[0038] Where, is the statistical average of the cosine square of the angle between the characteristic crystal plane normal direction and the orientation direction

[0039] Table 1 Changes in relevant parameters of ultra-high molecular weight polyethylene before and after deformation

[0040]

[0041] Example 2

[0042] Raw material: ultra-high molecular weight polyethylene

[0043] A method for preparing an oriented ultra-high molecular weight polyethylene block material comprises the following steps:

[0044] (1) Sample preparation: Samples were prepared by turning.

[0045] (2) Heating treatment: Load the sample into the processing device and heat it to a temperature 15°C higher than the melting point. Keep the temperature stable until the ultra-high molecular weight polyethylene reaches a molten state. Figure 1 As shown, the processing device used includes a core shaft 1; a lower washer 2; a sample 3; an outer ring 4; and an upper washer 5.

[0046] (3) Processing: Under the above-mentioned stable temperature conditions, the sample was subjected to shear deformation treatment, and the processing device rotated 100 times.

[0047] (4) Cooling: The entire processing device loaded with the sample was immersed in water. A pressure of 100 MPa was applied to the upper and lower gaskets. The sample was cooled to room temperature by water cooling at a cooling rate of 100°C / min. In this embodiment, the dimensions of the sample in three dimensions were 10 mm × 10 mm × 5 mm. Samples with dimensions of 10 mm × 10 mm × 7 mm and 10 mm × 10 mm × 10 mm can also be prepared by replacing molds of different sizes.

[0048] Table 1 shows the orientation and crystallinity parameters of the corresponding samples before and after deformation. Figure 2 The XRD diffraction results of the corresponding samples before and after deformation are given. Figure 4The SEM microstructures of the samples before and after deformation are presented. XRD characterization results show an orientation degree of 0.706 and a crystallinity of 97.14%. Furthermore, the SEM microstructures show a molecular chain structure that tends to be parallel, confirming that this method can effectively prepare oriented ultra-high molecular weight polyethylene bulk materials.

[0049] Other implementations

[0050] For those skilled in the art, the scope of the present invention should not be limited to the polyethylene materials mentioned in the above specific embodiments. The core of the method of the present invention lies in the selection of a specific temperature range (0.1 to 20°C higher than the melting point of the material) and the design and control of the shear deformation process based on this. By applying shear deformation within this temperature range, a high degree of orientation of the polyethylene molecular chains can be achieved. The selection of this temperature range is the key innovation of the present invention, which ensures the effectiveness and efficiency of the shear deformation process. Therefore, the method of the present invention is not only applicable to high-density polyethylene and ultra-high molecular weight polyethylene, but also to polyethylene materials with other molecular weight distributions. For the specific implementation of these materials, it can be achieved by appropriately adjusting the processing parameters (such as temperature, shear strain, etc.), and these adjustments are within the scope of the claims of the present invention and do not deviate from the core technical features of the present invention.

[0051] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent claim scheme. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing an oriented polymer block material, characterized in that: The preparation method of the oriented polymer block material comprises the following steps: 1) Using a crystalline polymer as raw material, an initial sample is prepared by a melt pelletizing casting process or mechanical processing; 2) The initial sample is loaded into the sample holding chamber of the processing device, and the sample is heated to a temperature range of 0.1-20°C above its melting point by the temperature control system, and maintained at this temperature until the sample is completely melted and the temperature field is uniform and stable; 3) The motor system drives the outer ring of the processing device to rotate, thereby driving the inner and outer walls of the sample to rotate relative to each other, causing the sample to undergo shear deformation, and the preset shear strain amount is achieved by accumulating the number of rotations; 4) After processing is completed, an isotropic pressure of 0.1 to 100 MPa is applied to the processing device loaded with the sample, and the temperature is cooled to room temperature at a cooling rate of 5 to 200°C / min to allow the polymer to complete the crystallization process in the directional shear field, forming an oriented polymer block material with three-dimensional dimensions of not less than 1 mm.

2. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The oriented polymer refers to the crystal plane orientation characterized by X-rays, wherein the characteristic crystal plane is defined as: based on the polymer crystallographic parameters, a crystal plane with a diffraction intensity within the 2θ angle range of ≥25% is selected in the X-ray diffraction pattern, and the orientation degree is calculated by the Hermans orientation function formula, and the value of the characteristic crystal plane is not less than 0.

5.

3. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The size of the bulk material in three dimensions is not less than 1 mm.

4. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The polymer includes high-density polyethylene and ultra-high molecular weight polyethylene.

5. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The melting point Tm is determined by differential scanning calorimetry (DSC) at a heating rate of 10°C / min. The melting point is the peak temperature of the endothermic peak on the DSC curve.

6. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The number of rotations is adjusted according to the actual required shear strain.

7. The method for preparing an oriented polymer block material according to claim 1, characterized in that: The processing device used in step 2) includes a core shaft (1); a lower washer (2); a sample (3); an outer ring (4); and an upper washer (5).

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