Effects of crystallization and loading-rate on the mode I fracture toughness of biodegradable poly(lactic acid)
Effects of crystallization and loading-rate on the mode I fracture toughness of biodegradable poly(lactic acid)
复制标题
结晶和加载速率对生物可降解聚乳酸I型断裂韧性的影响
DOI：
10.1023/a:1016520518959
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
K. Arakawa
中科院分区：
文献类型：
--
作者：
M. Todo;N. Shinohara;K. Arakawa
生物可降解聚合物由于其降解后的可吸收性和无毒性而被提议作为用于人体的生物材料。例如，聚乙交酯和聚乳酸（PLA）正被考虑用于骨固定和骨填充材料[1，2]。作为用于人体硬组织的生物材料，这些聚合物必须具有与人体组织相当的机械性能。虽然对聚合物生物材料的需求正在增加，但其变形和断裂行为的细节尚未完全了解，并且很少尝试研究机械行为与微观结构之间的关系[3]。本研究的目的是了解PLA的I型断裂行为。PLA样品在四种不同的条件下成型，并使用偏光显微镜对其微观结构进行了表征。在低和高加载速率（1 mm/min和1 m/s）下测量模式I临界应力强度因子KIC。根据实验结果分析了成型温度、微观结构和加载速率对KIC的影响。采用岛津公司生产的聚乳酸微丸（LactyR# 9030），其平均分子量为140 000。玻璃化转变温度和熔点分别为60.5 ℃和149.5 ℃。PLA在180 ℃熔融后在不同条件下模塑。模塑条件见表I。使用常规热压机制造5 mm厚的PLA板用于模式I断裂测试。对于每种条件，还使用热板和载玻片制造薄膜，以使用偏光显微镜研究其微观结构。
Biodegradable polymers have been proposed as a biomaterials for use in the human body because of their absorbable nature and non-toxicity after degradation. For example, polyglycolide and poly (lactic acid)(PLA) are being considered for bone fixation and bone filling materials [1, 2]. As such biomaterials for hard tissue of human body, these polymers must possess mechanical properties comparable to human tissue. Although the demand for polymeric biomaterials is increasing, the details of their deformation and fracture behavior have not fully been understood yet and few attempts have been made to study the relationship between the mechanical behavior and microstructure [3]. The aim of the present study is to understand the mode I fracture behavior of PLA. PLA samples were molded under four different conditions, and their microstructures were characterized using a polarizing microscope. The mode I critical stress intensity factor, KIC, was measured at a low and a high loading-rate (1 mm/min and 1 m/s). The effects of molding temperature, ie microstructure and loading-rate on KIC were then assessed based upon the experimental results. Fracture micromechanism was also studied by polarizing and scanning microscopies.PLA pellets (LactyR# 9030) were provided by Shimadzu Co. Ltd. The average molecular weight was 140 000. The glass transition temperature and the melting point were 60.5◦ C and 149.5◦ C, respectively. PLA was molded under different conditions after melting at 180◦ C. Molding conditions are given in Table I. PLA plates of 5 mm thick were fabricated using a conventional hot press for Mode I fracture testing. For each condition, a thin film was also fabricated using a hot plate and slide glasses to study its microstructure using a polarizing microscope.