The tensile creep (and other tensile) properties of ultra-high molecular weight polyethylene (UHMW PE) have been determined before and after electron beam irradiation and compared with similar results on normal molecular weight high-density polyethylene (NMW PE). In both polymers, irradiation increases the tensile modulus and the yield stress whilst reducing creep. The major effects occur over the first 20 MRad irradiation dose, though creep strain continues to diminish with dose in UHMW PE up to 64 MRad. Most of the effects can be attributed to crosslinking in the amorphous phase, though the rise in yield stress seems to require crosslinking in the crystalline phase, and the initial rise in modulus in UHMW PE seems to reflect a rise in crystallinity. Comparison with other polymers shows that the creep behaviour of UHMW PE remains relatively poor, even after irradiation. The improvements obtained may, however, be significant in applications where creep resistance is of secondary importance compared with, say, impact and wear resistance, in which UHMW PE excels. 相似文献
采用干法纺丝工艺,以超高分子量聚乙烯(PE–UHMW)纤维专用树脂为原料,制备高性能PE–UHMW纤维,通过电子拉力机、扫描电子显微镜、差示扫描量热仪对不同后拉伸倍率的纤维进行力学性能和微观结构分析。结果表明,随着拉伸倍率的增加,纤维初生丝结晶度由49.57%逐渐提高至72.17%,拉伸倍率50倍以后,结晶度逐渐趋于平稳;随着拉伸倍率的增加,纤维的力学性能逐渐增强,在拉伸倍率达到83.3倍时,纤维的力学性能达到最佳,纤维断裂强度为31.53 c N/dtex,断裂伸长率为2.69%,断裂模量为1 054.78 c N/dtex;纤维微观表面结构也发生有规律的变化。 相似文献
The role of entanglements in obtaining a homogeneous product of ultra high molecular weight polyethylene (UHMW‐PE) has been explored. Studies performed in this report show that a disentangled state before melting is a prerequisite to obtain homogeneous products of an intractable polymer like UHMW‐PE. The disentangled state is obtained directly from the reactor by controlling the polymerisation conditions or in the solid state when there is enhanced chain mobility along the c‐axis of a unit cell. The disentangled state is maintained in the melt over a period of time, invoking implications in polymer rheology. This approach is applicable to polymers in general. The homogeneous fully sintered UHMW‐PE, obtained for the first time, shows a considerable decrease in oxygen permeability, and increase in toughness and fatigue resistance. Such homogeneous products of UHMW‐PE are of beneficial in highly demanding applications, especially in knee‐prosthesis, where the polymer is used as an inlay between the human bone and a metal or ceramic part, which slides against the polyethylene component during normal gait.
Phase diagram for the extended chain crystals. 相似文献