Correlation between morphology and radiation resistance of polypropylene materials

医用聚丙烯固体材料经过辐照灭菌后，其力学性能会发生氧化降解。在本研究中，研究了形态对聚丙烯材料辐射降解的影响。结果表明：(1)热压成型条件对等规聚丙烯薄膜的结晶结构和球晶尺寸有很大的影响。聚丙烯熔体的快速冷却导致结晶和小尺寸球晶的近晶化，而缓慢冷却导致球晶生长良好，球晶由单斜晶组成。(2)辐照后，聚丙烯薄膜的断裂伸长率随辐照剂量的增加呈S形下降。导致50%残余伸长率的剂量被定义为临界剂量，它是抗辐射…的良好量度(3)用临界剂量法测量的聚丙烯薄膜的抗辐射性能随着薄膜中近晶晶体含量的增加而增加。(4)辐照前屈服应力较小的聚丙烯薄膜具有较高的抗辐射性能。在球晶尺寸相同的情况下，均聚薄膜的临界剂量大于共聚薄膜的临界剂量。(5)对于平均直径为10um的球晶薄膜，辐照前的屈服应力随着球晶平均直径的减小而迅速减小。含有10um以上球晶的薄膜在达到屈服点之前就会破裂，相应的抗拉强度随着球晶平均直径的增加而降低。(6)用25℃对二甲苯浸泡的方法来评价聚丙烯薄膜的室温重量膨胀率，随着球晶平均直径的减小，薄膜的室温重量膨胀率迅速增加。(7)对于含有较小球晶的薄膜，辐照前的屈服应力随着室温重量膨胀率的增大而增加，从而提高了抗辐射能力。较少

Polypropylene solid materials in medical use are subjected to radiation sterilization, which causes oxidative degradation of their mechanical properties. In this research, the influence of morphology on the radiation degradation of polypropylene materials was investigated. The results are summarized as follows:(1) The crystal structures, as verified by means of X-ray diffraction measurement, and the spherulitic size in the isotactic polypropylene films are strongly affected by the conditions of compression moulding on the hot press. Rapid cooling of the polypropylene melts produces smectic modification of crystallines and small sized spherulites, while slow cooling leads to well grown spherulites consisting of monoclinic crystallines.(2) Upon -irradiation, the elongation at break of polypropylene films decreases in a sigmoidal form as a function of radiation dose. The dose leading to 50 % residual elongation, which is defined as a critical dose, is a good measure of the radiation resis … More tance of polypropylene materials.(3) The radiation resistance of polypropylene films, as measured by the critical dose, increases as the content of smectic crystallines in the film increases.(4) The polypropylene films with smaller yield stress before irradiation show higher radiation resistance. The critical dose of homopolymer films is greater than that of copolymer films, when compared at the same size of spherulites contained.(5) For the films containing spherulites with 10 um mean diameter, the yield stress before irradiation decreases rapidly as the mean spherulitic diameter becomes smaller. The films containing spherulites with more than 10 um breaks down before reaching a yield point, and the corresponding tensile strength decreases with the increase in mean diameter of spherulites.(6) The weight swelling ratio of polypropylene films at room temperature, which is evaluated by immersion of the films in p-xylene at 25 C, increases rapidly with the decrease in mean diameter of spherulites.(7) For the films containing smaller sized spherulites, the yield stress before irradiation increases and thus the radiation resistance increases as the weight swelling ratio at room temperature becomes grater. Less