超高分子量聚乙烯辐射效应与改性研究

发布时间：2018-11-29 12:43

【摘要】：超高分子量聚乙烯(ultra-high molecular weight polyethylene,UHMWPE)化学结构简单、生物相容性突出、耐腐蚀、耐磨损,综合性能优异,被广泛应用于医疗、渔业、防护、工程等领域。UHMWPE也存在一些性能不足,比如表面能低、抗蠕变性差、耐温性低,此外耐磨性也有待提高,这限制了其在复合材料、工程领域的部分应用。因此,通过化学或物理方法改善其表面性质、提高抗蠕变性及耐磨性具有重要意义。辐射改性是一种有效改变高分子材料性能的方法,为此本论文以UHMWPE辐射效应为立足点,详细研究了UHMWPE的辐射氧化、接枝和交联,利用辐射氧化或辐射接枝提高UHMWPE表面润湿性,利用辐射交联提高UHMWPE抗蠕变性和耐磨性,另外借助共混辐射改性多壁碳纳米管(MWCNTs)改善了UHMWPE的力学性能。具体研究内容及结果如下:(1)、UHMWPE粉末的辐射氧化采用γ射线和电子束(EB)在空气中对UHMWPE粉末样品进行辐照,详细研究了粉末接受射线辐照后化学结构、润湿性和热稳定性变化情况,比较了吸收剂量和剂量率对材料结构、性质变化的影响并对氧化裂解程度进行计算。结果表明:UHMWPE粉末在空气中受γ射线/EB辐照后,裂解占主导地位;吸收剂量和剂量率对氧化裂解程度有显著影响。在低剂量率、高剂量条件下辐射氧化裂解更为严重,γ射线辐照300 kGy的样品可氧化裂解完全;此外,低剂量率辐照引发的氧化裂解程度可根据氧气扩散速度与剂量率进行估算。虽然UHMWPE粉末受到高剂量辐照后氧化裂解严重,但其热稳定性、润湿性变化较小。单纯辐射氧化对UHMWPE表面性质影响不大。(2)、UHMWPE粉末/薄膜预辐射接枝丙烯酸(AA)采用预辐射接枝方法,将γ射线辐照的UHMWPE粉末/薄膜在1 wt%AA溶液中进行反应,接枝少量AA以改善其亲水性。详细研究了UHMWPE粉末/薄膜受γ射线辐照、接枝AA、氢氧化钠(NaOH)中和处理后化学结构、表面润湿性变化情况。结果表明:UHMWPE粉末/薄膜表面成功接枝了AA,且粉末样品更有利于接枝反应进行,接枝少量AA后样品表面润湿性明显提高,中和处理进一步提高了润湿性。接枝6 wt%AA的粉末样品,用NaOH中和处理后可在水溶液中分散,表现出良好的亲水性。最终,通过接枝少量AA的方式制备了亲水性UHMWPE粉末。(3)、交联UHMWPE片材蠕变行为研究采用γ射线辐照和真空退火方式制备了交联的UHMWPE片材,详细研究了片材交联后凝胶含量、结晶度、蠕变和力学性能的变化。结果表明:UHMWPE片材辐射交联后凝胶含量、结晶度增加,抗蠕变性大幅提高,力学性能亦明显改善;300 kGy辐射交联的UHMWPE片材在270°C、0.06 MPa条件下拉伸4 h后依旧保持良好形貌,其杨氏模量亦由原始UHMWPE片材接近400 MPa增加到1400 MPa,增加幅度接近250%。此外,退火处理增加交联有利于片材抗蠕变性和模量提高。最终,通过辐射交联制备了具有良好抗蠕变性的UHMWPE板材。(4)、UHMWPE/X-UHMWPE复合材料摩擦行为研究采用辐射交联和共混方法将交联UHMWPE(X-UHMWPE)添加到常规UHMWPE中制备复合材料,详细研究了X-UHMWPE本身性质及复合材料摩擦行为。结果表明:UHMWPE粉末辐射交联后加工性能下降,高剂量辐照的样品难以熔融;在UHMWPE中添加少量X-UHMWPE使复合材料综合性能大幅改善,耐磨性大幅提高并保持较好延展性。如添加25 wt%150 kGy辐射交联的X-UHMWPE到常规UHMWPE中制备的复合材料,相对于原始UHMWPE而言,其耐磨性提高130%并保持90%的拉伸强度和70%的延展性。(5)、UHMWPE/MWCNTs复合材料力学行为研究采用γ射线辐照和共混方式将原始及经γ射线辐照(60 kGy)的MWCNTs添加到UHMWPE中制备复合材料,详细研究了MWCNTs经γ射线辐照(60 kGy)后结构及复合材料力学性能的变化。结果表明:MWCNTs经γ射线辐照后表面化学结构发生变化、缺陷增加但形貌变化微小;添加少量辐射改性的MWCNTs可有效提升复合材料力学性能,如添加2 wt%γ射线辐射改性的MWCNTs可提高20%的屈服强度;但引入少量MWCNTs难以有效提升复合材料的导热性质。
[Abstract]:The ultra-high molecular weight polyethylene (UHMWPE) has the advantages of simple chemical structure, outstanding biocompatibility, corrosion resistance, abrasion resistance and comprehensive performance, and is widely applied to the fields of medical treatment, fishery, protection, engineering and the like. The UHMWPE also has some poor properties, such as low surface energy, poor creep resistance, low temperature resistance, and increased wear resistance, which limits its application in the composite and engineering fields. Therefore, it is of great significance to improve the surface properties, improve the creep resistance and wear resistance by the chemical or physical method. The radiation modification is a method for effectively changing the properties of the high-molecular material. In this paper, the radiation oxidation, grafting and cross-linking of UHMWPE are studied in detail by the radiation effect of UHMWPE, and the wettability of the surface of the UHMWPE is improved by radiation oxidation or radiation grafting. The anti-creep and wear resistance of UHMWPE were improved by radiation cross-linking, and the mechanical properties of UHMWPE were improved by co-mixed radiation-modified multi-wall carbon nanotubes (MWCNTs). The specific research contents and results are as follows: (1) The radiation oxidation of UHMWPE powder is irradiated by X-ray and electron beam (EB) in air, and the chemical structure, wettability and thermal stability of the powder after radiation irradiation are studied in detail. The effect of absorbed dose and dose rate on the structure and properties of the material was compared, and the degree of oxidative cracking was calculated. The results show that the degradation of UHMWPE powder in air is dominated by X-ray/ EB irradiation, and the absorbed dose and dose rate have a significant effect on the degree of oxidative cleavage. In addition, the degree of oxidative cracking induced by low dose rate irradiation can be estimated according to the rate of oxygen diffusion and dose rate. Although the UHMWPE powder is subjected to high-dose irradiation, the oxidative cracking is severe, but the thermal stability and the wettability change are small. The effect of simple radiation oxidation on the surface properties of UHMWPE is not great. (2) The UHMWPE powder/ film pre-radiation grafted acrylic acid (AA) was grafted with a pre-radiation grafting method, and the X-ray irradiated UHMWPE powder/ film was reacted in a 1 wt% AA solution, and a small amount of AA was grafted to improve its hydrophilicity. The chemical structure and surface wettability of UHMWPE powder/ film under X-ray irradiation, grafting AA, sodium hydroxide (NaOH) and post-treatment were studied in detail. The results show that the surface of UHMWPE powder/ film is grafted with AA, and the powder sample is more beneficial to the grafting reaction, and the surface wettability of the sample after the grafting of a small amount of AA is obviously improved, and the wettability is further improved in the neutralization treatment. The powder sample of 6 wt% AA was grafted and dispersed in an aqueous solution after neutralization with NaOH to show good hydrophilicity. Finally, a hydrophilic UHMWPE powder was prepared by grafting a small amount of AA. (3) The cross-linked UHMWPE sheet was prepared by X-ray irradiation and vacuum annealing, and the changes of gel content, crystallinity, creep and mechanical properties of the cross-linked UHMWPE were studied in detail. The results show that the gel content, crystallinity, creep resistance and mechanical properties of UHMWPE sheet after radiation cross-linking are improved greatly, and the mechanical properties are improved obviously. The 300 kGy radiation cross-linked UHMWPE sheet is still in good shape after being stretched for 4 h under the condition of 270 掳 C and 0. 06MPa. The Young's modulus is also increased to 1400 MPa from the original UHMWPE sheet to 1400 MPa, and the increase is close to 250%. in addition, that increase of the degree of cross-linking of the anneal treatment facilitates the creep and modulus of the sheet. Finally, UHMWPE plates with good creep resistance were prepared by radiation crosslinking. (4) The friction behavior of UHMWPE/ X-UHMWPE composites was investigated by radiation cross-linking and blending. The composite materials were prepared by adding cross-linked UHMWPE (X-UHMWPE) to conventional UHMWPE, and the properties of the X-UHMWPE and the friction behavior of the composites were studied in detail. The results show that after the radiation cross-linking of UHMWPE powder, the processing property is decreased, and the sample with high dose irradiation is difficult to melt; a small amount of X-UHMWPE is added to the UHMWPE, so that the comprehensive performance of the composite material can be greatly improved, and the wear resistance is greatly improved and the ductility is maintained. such as the addition of 25 wt.% of the 150 kGy radiation cross-linked x-uhmwpe to the composite prepared in conventional uhmwpe, the wear resistance was increased by 130% and the tensile strength of 90% and the ductility of 70% were maintained with respect to the original uhmwpe. (5) The mechanical behavior of UHMWPE/ MWCNTs composite material was studied by X-ray irradiation and blending, and the MWCNTs were added to UHMWPE to prepare the composite material. The structure of MWCNTs and the change of the mechanical properties of the composite were studied in detail. The results show that the surface chemical structure of MWCNTs is changed by X-ray irradiation, the defect is increased, but the morphology is small, and the addition of small amount of radiation-modified MWCNTs can effectively improve the mechanical properties of the composite material, such as the addition of 2 wt% of the MWCNTs modified by the X-ray radiation can improve the yield strength of 20%; but it is difficult to effectively improve the thermal conductivity of the composite material by introducing a small amount of mwcnts.
【学位授予单位】：中国科学院研究生院(上海应用物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O632.12

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