Creep-resistant ultra-high molecular weight polyethylene material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer material forming, and discloses a creep-resistant ultra-high molecular weight polyethylene material as well as a preparation method and application thereof. The method comprises the following steps: firstly, carrying out hot pressing on ultrahigh molecular weight polyethylene powder under a static pressure condition, and then carrying out compression and extension in pulse vibration mould pressing equipment in a cyclic displacement mode to realize orientation regulation and control of the material, so as to form a melt blank with an excellent orientation structure; and finally, cooling to cure and shape. According to the invention, the viscoelasticity of the material is utilized, the orientation structure of the material is precisely regulated and controlled through the cyclic displacement technology of pulse vibration molding equipment, more ordered orientation crystal structures are formed inside by adjusting the amplitude and frequency, the mechanical property and creep resistance of the material are improved, and the mechanical property and creep resistance of the material are improved. And more reliable application of the ultra-high molecular weight polyethylene material in artificial joints with high stress and high performance requirements is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material forming, and particularly relates to a creep-resistant ultra-high molecular weight polyethylene material, a preparation method thereof, and an application thereof. Background Art

[0002] Ultra-high molecular weight polyethylene has excellent comprehensive properties and is widely used in various fields, especially in the field of artificial joints. With the gradual trend of artificial joint replacement surgery towards younger age groups, the requirements for material strength are also continuously increasing. Creep behavior under high stress will exacerbate joint wear and shorten the service life of the joint. To meet the needs of young patients, reduce the revision and replacement of artificial joint prostheses, and thereby alleviate the pain of patients, it is urgent to further improve the creep resistance and mechanical properties of polymer materials.

[0003] Regulating the orientation structure is an effective method to improve creep resistance and mechanical properties. How to effectively regulate the orientation structure to prepare ultra-high molecular weight polyethylene with more excellent creep resistance and mechanical properties is an urgent problem to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to provide a creep-resistant ultra-high molecular weight polyethylene material, a preparation method thereof, and an application thereof, so as to solve the problem of poor creep resistance and mechanical properties of existing polymer materials.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of a creep-resistant ultra-high molecular weight polyethylene material, comprising the following steps:

[0007] Hot-press ultra-high molecular weight polyethylene powder under static pressure conditions to obtain a prefabricated melt blank;

[0008] Perform pulse vibration molding on the prefabricated melt blank to obtain a melt blank;

[0009] Cool the melt blank to obtain a creep-resistant ultra-high molecular weight polyethylene material;

[0010] The pulse vibration molding adopts a cyclic displacement mode.

[0011] Preferably, in the above-mentioned preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the temperature of the hot-pressing is 150-160°C; the pressure of the hot-pressing is 12-17 MPa; the time of the hot-pressing is 1-10 min.

[0012] Preferably, in the above-mentioned preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the amplitude of the pulse vibration molding is 0-1 mm.

[0013] Preferably, in the above preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the frequency of the pulsed vibration molding is 0.1-20 Hz.

[0014] Preferably, in the above preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the time of the pulsed vibration molding is 2-30 min.

[0015] Preferably, in the above preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the waveform of the cyclic displacement mode is one of a sine wave, a square wave, and a triangular wave.

[0016] Preferably, in the above preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the temperature of the pulsed vibration molding is 140-155 °C.

[0017] Preferably, in the above preparation method of a creep-resistant ultra-high molecular weight polyethylene material, the cooling rate is 1-30 °C / min.

[0018] The present invention also provides a creep-resistant ultra-high molecular weight polyethylene material prepared by the preparation method of a creep-resistant ultra-high molecular weight polyethylene material.

[0019] The present invention also provides an application of a creep-resistant ultra-high molecular weight polyethylene material in the preparation of artificial joint materials.

[0020] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention provides a preparation method of a creep-resistant ultra-high molecular weight polyethylene material, including the following steps: placing ultra-high molecular weight polyethylene powder in a mold, and performing hot pressing treatment under static pressure conditions to obtain a dense preformed melt blank; then, placing the preformed melt blank in a pulsed vibration molding device, and performing compression and stretching on it through a cyclic displacement mode to achieve orientation regulation of the material, thereby forming a melt blank with an excellent orientation structure; subsequently, stopping the cyclic displacement mode, and performing a cooling operation on the melt blank to solidify and shape it. The present invention makes full use of the excellent viscoelastic properties of the ultra-high molecular weight polyethylene material itself, and precisely regulates the orientation structure of the material by adopting the cyclic displacement technology of the pulsed vibration molding device. During the hot pressing process, by adjusting the parameters of the amplitude and frequency, more ordered orientation crystal structures are formed inside the material. This optimized processing method not only effectively improves the mechanical properties of the material, but also significantly enhances its creep resistance, and finally prepares an ultra-high molecular weight polyethylene material with a high degree of orientation and excellent comprehensive properties, providing a more reliable application for it in artificial joints with high stress and high performance requirements. Detailed Embodiments

[0022] The present invention provides a preparation method of a creep-resistant ultra-high molecular weight polyethylene material, comprising the following steps:

[0023] Thermally pressing ultra-high molecular weight polyethylene powder under hydrostatic pressure to obtain a prefabricated melt blank;

[0024] Performing pulse vibration molding on the prefabricated melt blank to obtain a melt blank;

[0025] Cooling the melt blank to obtain a creep-resistant ultra-high molecular weight polyethylene material;

[0026] The pulse vibration molding adopts a cyclic displacement mode.

[0027] In the present invention, the temperature of the thermal pressing is preferably 150 - 160 °C, more preferably 152 - 157 °C, and still more preferably 155 °C; the pressure of the thermal pressing is preferably 12 - 17 MPa, more preferably 14 - 16 MPa, and still more preferably 15 MPa; the time of the thermal pressing is preferably 1 - 10 min, more preferably 2 - 6 min, and still more preferably 5 min.

[0028] In the present invention, the prefabricated melt blank is placed in the mold cavity of a pulse vibration molding device; the volume of the prefabricated melt blank ≤ the volume of the mold cavity.

[0029] In the present invention, no limitation is imposed on the pulse vibration molding device, and a device well-known to those skilled in the art can be selected. Specifically in the examples, the pulse vibration molding device adopted in the present invention refers to Patent CN113021725A.

[0030] In the present invention, during the pulse vibration molding process, the midpoint of the periodic displacement amplitude in the cyclic displacement mode (i.e., the middle plane of the movement trajectory of the upper template from the highest position to the lowest position) is set to be equal to the initial stacking thickness of the prefabricated melt blank in the mold cavity.

[0031] In the present invention, the amplitude of the pulse vibration molding is preferably 0 - 1 mm, more preferably 0.1 - 0.6 mm, and still more preferably 0.4 mm.

[0032] In the present invention, the frequency of the pulse vibration molding is preferably 0.1 - 20 Hz, more preferably 1 - 10 Hz, and still more preferably 2 Hz.

[0033] In the present invention, the time of the pulse vibration molding is preferably 2 - 30 min, more preferably 4 - 10 min, and still more preferably 5 min.

[0034] In the present invention, the waveform of the cyclic displacement mode is preferably one of a sine wave, a square wave, and a triangular wave, more preferably a sine wave or a triangular wave, and still more preferably a sine wave.

[0035] In the present invention, the temperature of the pulse vibration molding is preferably 140-155 °C, more preferably 150-155 °C, and still more preferably 155 °C.

[0036] In the present invention, the cooling rate is preferably 1-30 °C / min, more preferably 5-10 °C / min, and still more preferably 9 °C / min. After obtaining the oriented melt blank in the present invention, the cyclic displacement mode is stopped, and the melt blank is cooled and shaped. The cooling and shaping can fix the orientation of the molecular chain segments in the blank layer, thereby further improving the creep resistance and mechanical properties.

[0037] The present invention also provides a creep-resistant ultra-high molecular weight polyethylene material prepared by a preparation method of a creep-resistant ultra-high molecular weight polyethylene material.

[0038] The present invention also provides an application of a creep-resistant ultra-high molecular weight polyethylene material in the preparation of artificial joint materials.

[0039] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] Example 1

[0041] This embodiment provides a preparation method of a creep-resistant ultra-high molecular weight polyethylene sheet, including the following steps:

[0042] (1) Pour ultra-high molecular weight polyethylene (UHMWPE) powder with a viscosity-average molecular weight of 5 million into a square non-overflow mold, and perform hot pressing under a constant pressure. The pressure is 15 MPa, the temperature is 155 °C, and the time is 5 min to obtain a prefabricated melt blank.

[0043] (2) Place the prefabricated melt blank at the central position of the square non-overflow mold, and the prefabricated melt blank is smaller than the cavity size. Then, perform hot pressing under a pulse vibration molding cyclic displacement to obtain an oriented melt blank with a biaxial orientation ratio of 4; wherein, the hot pressing temperature is 155 °C, the time is 5 min, and the hot pressing is performed under a sine wave pulse vibration molding cyclic displacement. The frequency of the cyclic displacement is 2 Hz, and the amplitude is 0.4 mm to obtain a melt blank; the size of the melt blank is the same as that of the prefabricated melt blank.

[0044] (3) Stop the cyclic displacement mode, and cool the melt blank at 9 °C / min to obtain a biaxially oriented creep-resistant ultra-high molecular weight polyethylene sheet.

[0045] The anti-creep performance and mechanical properties of the ultra-high molecular weight polyethylene sheet prepared in Example 1 were tested. Under the conditions of 37 °C and 15 MPa, after a constant load of 5 h, the creep strain was 5.78%; the tensile performance was tested according to the standard GB / T 1040.2-2022, and the tensile strength was 115.7 MPa.

[0046] Example 2

[0047] This example provides a method for preparing a creep-resistant ultra-high molecular weight polyethylene sheet. For details, refer to Example 1. The difference is that the frequency of cyclic displacement in step (2) is 1 Hz.

[0048] The anti-creep performance and mechanical properties of the ultra-high molecular weight polyethylene sheet prepared in Example 2 were tested. Under the conditions of 37 °C and 15 MPa, after a constant load of 5 h, the creep strain was 8.75%; the tensile performance was tested according to the standard GB / T 1040.2-2022, and the tensile strength was 100.5 MPa.

[0049] Example 3

[0050] This example provides a method for preparing a creep-resistant ultra-high molecular weight polyethylene sheet. For details, refer to Example 1. The difference is that the frequency of cyclic displacement in step (2) is 5 Hz.

[0051] The anti-creep performance and mechanical properties of the ultra-high molecular weight polyethylene sheet prepared in Example 3 were tested. Under the conditions of 37 °C and 15 MPa, after a constant load of 5 h, the creep strain was 6.54%; the tensile performance was tested according to the standard GB / T 1040.2-2022, and the tensile strength was 110.4 MPa.

[0052] Example 4

[0053] This example provides a method for preparing a creep-resistant ultra-high molecular weight polyethylene sheet. For details, refer to Example 1. The difference is that the frequency of cyclic displacement in step (2) is 0.5 Hz.

[0054] The anti-creep performance and mechanical properties of the ultra-high molecular weight polyethylene sheet prepared in Example 4 were tested. Under the conditions of 37 °C and 15 MPa, after a constant load of 5 h, the creep strain was 10.05%; the tensile performance was tested according to the standard GB / T 1040.2-2022, and the tensile strength was 90.1 MPa.

[0055] Comparative Example 1

[0056] This comparative example provides a method for preparing an unoriented ultra-high molecular weight polyethylene sheet. Specifically, refer to Example 1. The difference lies in that in step (2), the prefabricated melt blank is not subjected to any treatment (i.e., always kept in a hydrostatic state without applying cyclic displacement), but is directly placed in a mold cavity with the same size as it for hot pressing to obtain an unoriented ultra-high molecular weight polyethylene sheet.

[0057] The ultra-high molecular weight polyethylene sheet prepared in Comparative Example 1 was tested for creep resistance and mechanical properties. Under the conditions of 37 °C and 15 MPa, after 5 h of constant load, the creep strain was 21.64%; the tensile properties were tested according to the standard GB / T 1040.2-2022, and the tensile strength was 38.2 MPa.

[0058] Comparative Example 2

[0059] This comparative example provides a method for preparing an oriented ultra-high molecular weight polyethylene sheet. Specifically, refer to Example 1. The difference lies in that in step (2), under a hydrostatic state, compression and stretching are carried out by using hydrostatic pressure (i.e., no cyclic displacement is applied to the melt, always kept fixed at the midpoint of the amplitude without generating up and down amplitudes) to obtain an oriented ultra-high molecular weight polyethylene sheet.

[0060] The ultra-high molecular weight polyethylene sheet prepared in Comparative Example 2 was tested for creep resistance and mechanical properties. Under the conditions of 37 °C and 15 MPa, after 5 h of constant load, the creep strain was 11.64%; the tensile properties were tested according to the standard GB / T 1040.2-2022, and the tensile strength was 80.6 MPa.

[0061] In summary, the present invention provides a self-reinforcing forming method based on cyclic displacement technology for enhancing the oriented structure of ultra-high molecular weight polyethylene. During the processing, through the repeated action of cyclic displacement, the molecular chains are continuously arranged in an orderly manner, thereby significantly increasing the oriented structure inside the material. This method makes full use of the viscoelastic characteristics of ultra-high molecular weight polyethylene, realizes the efficient and precise regulation around the material's own characteristics, and completes the optimization process of its self-reinforcement. The ultra-high molecular weight polyethylene prepared by the processing method of the present invention not only exhibits excellent high strength and high creep resistance, but also has better use stability. While meeting the requirements of high stress and high performance, this material provides a more reliable and long-life solution for fields such as artificial joints, and is expected to significantly reduce the burden on patients and improve the overall performance of medical devices.

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a creep-resistant ultra-high molecular weight polyethylene material, characterized in that: The following steps are involved: hot pressing the ultra-high molecular weight polyethylene powder under static pressure to obtain a prefabricated melt blank; The prefabricated melt blank is subjected to pulse vibration compression molding to obtain a melt blank; Cooling the melt to obtain a creep-resistant ultra-high molecular weight polyethylene material; The pulse vibration compression molding adopts a cyclic displacement mode.

2. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 1, characterized in that: The temperature of the hot pressing is 150-160° C.; the pressure of the hot pressing is 12-17 MPa; and the time of the hot pressing is 1-10 min.

3. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 2, characterized in that: The amplitude of the pulse vibration compression molding is 0 to 1 mm.

4. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to any one of claims 1 to 3, characterized in that: The frequency of the pulse vibration compression molding is 0.1-20 Hz.

5. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 4, characterized in that: The pulse vibration compression molding process lasts for 2 to 30 minutes.

6. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 5, characterized in that: The waveform of the cyclic displacement mode is one of a sine wave, a square wave and a triangle wave.

7. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 6, characterized in that: The temperature of the pulse vibration compression molding is 140-155°C.

8. The method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to claim 4, characterized in that: The cooling rate is 1-30°C / min.

9. A creep-resistant ultra-high molecular weight polyethylene material obtained by the method for preparing a creep-resistant ultra-high molecular weight polyethylene material according to any one of claims 1 to 8.

10. Use of the creep-resistant ultra-high molecular weight polyethylene material according to claim 9 in the preparation of artificial joint materials.