Fracture micromechanisms of bioabsorbable PLLA/PCL polymer blends
Fracture micromechanisms of bioabsorbable PLLA/PCL polymer blends
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DOI：
10.1016/j.engfracmech.2006.05.021
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发表时间：
2007-08
影响因子：
5.4
通讯作者：
M. Todo;Sang Dae Park;T. Takayama;K. Arakawa
中科院分区：
文献类型：
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作者：
M. Todo;Sang Dae Park;T. Takayama;K. Arakawa
聚（L-丙交酯）（PLLA）已被积极用作骨科和口腔手术中使用的可吸收骨固定器械的生物材料。最近，为了改善脆性PLLA的断裂性能，已经开发了PLLA和延性生物可吸收聚合物聚（ε-己内酯）（PCL）的聚合物共混物。本研究的目的是阐明PLLA/PCL共混物的断裂行为和增韧机制的细节。开发了具有不同PCL含量的PLLA/PCL共混物，然后测量裂纹起始时的临界能量释放速率Gin以评估PCL含量的影响。结果表明，PCL与PLLA共混后，Ginis值显著提高，当PCL含量为5wt%时，Ginis值最大提高了51%。通过偏光显微镜（POM）和扫描电子显微镜（SEM）观察了裂纹扩展行为，并对断裂机理进行了表征。PLLA/PCL复合材料在裂纹尖端形成了多条银纹，银纹由细长的原纤维和孔洞构成。断裂表面的扫描电子显微镜还表明，在裂纹尖端区域，由于高拉应力条件下，聚己内酯球晶的伸长，在表面形成了拉伸的原纤结构。因此，这些损伤形成被认为是主要的能量耗散机制，导致在断裂能的改善。
Poly(l-lactide) (PLLA) has actively been used as a biomaterial for resorbable bone fixation devices for use in orthopedic and oral surgeries. Recently, in order to improve the fracture properties of brittle PLLA, polymer blends of PLLA and a ductile bioabsorbable polymer, poly(ε-caprolactone) (PCL), have been developed. The aim of the present study is to elucidate details of the fracture behavior and toughening mechanisms of PLLA/PCL blends. PLLA/PCL blends with different PCL contents were developed, and the critical energy release rate at crack initiation, Gin, was then measured to assess the effect of PCL content. It was shown that Ginis dramatically improved by blending PCL with PLLA, and the maximum 51% of increase of Ginis acheived with 5wt% of PCL. Polarizing optical microscopy (POM) and scanning electron microscopy (SEM) of crack growth behavior were also performed to characterize the fracture mechanism. PLLA/PCL showed multiple craze formation in the crack-tip region, and elongated fibrils and voids construct the crazes. SEM of fracture surface also indicated that stretched fibril structures are formed on the surface as a result of elongation of PCL spherulites under high tensile stress condition in the crack-tip region. Thus, these damage formations are considered to be the primary energy dissipation mechanisms that resulted in the improvement of fracture energy.