Mechanical properties of polylactide films and composites

• Main Authors: Hwang Huey-Ping, 黃慧平
• Other Authors: Sheng-Yang Lee
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/64906702632743635332

碩士 === 台北醫學院 === 口腔復健醫學研究所 === 86 === Poly-L-lactide(PLLA)is an excellent osteosynthesis material because it has good biocompatibility and it can be metabolized completely in humam body. On the other hand, commercial PLLA with a high molecular weight, over 5*10^6, was difficult to make, resulting in limited mechanical properties and an insufficient application in stress-bearing fracture sites. In this study, first, PLLA film samples were made of commercial available PLLA, and immersed in phosphate buffer solution(PBS) for 0, 1, and 3 weeks. After stretching, the deformation zones of the film samples produced during the stretching process were observed and analyzed to investigate the micro-deformation behavior of PLLA. Then, PLLA reinforced with 0,10wt%,30wt%,50wt% hydroxyapatite(HA) was fabricated into a block(40*3*4 mm^3) using a compression molding technique under several processing conditions. The composite samples were tested by material testing system, differential scanning calorimetry and gel permeability chromatography, and the morphology of the fracture surfaces were observed by a scanning electronic microscope to investidate their physical properties. The results show that the PLLA film samples were deformed by crazing rather than shear. During 3 weeks, no matter whether the film samples immersed in PBS or not, the yield strength of the film samples was not affected. There were no significant differences between the yield strength of crystal and non-crystal film samples, but the nucleation of the deformation zone of the crystal film samples happened in the non-crystal areas first. The flexural strength and the crystallinity of PLLA composite samples decrease as the HA contents increased, while the Young''s modulus was reversed. When the HA contents are the same, the Young''s modulus decreased as the HA particle size became larger, while the crystallinity of PLLA in the samples was reversed. The morphology of the fracture surfaces of the samples shows that the fracture of HA/PLLA composites is a mix-type fracture, and the space between HA nad PLLA interface becomes larger as the HA contents increase. The decreasing bonding strength between HA and PLLA might be the reason for a decrease in flexural strength.