Photoelastic Analysis of Thermo-degradable Polymer for Biomedical use

• Main Authors: Yung-Hsun Shih, 施永勳
• Other Authors: Sheng-Yang Lee
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/89272382536679257696

碩士 === 台北醫學院 === 口腔復健醫學研究所 === 90 === Thermal degradable polymer (e.g. polylactic acid) is characterized by its photo-elasticity. During the polymerization process, its crystallization and mechanical properties are critically affected by temperature, pressure and other processing condition. Whether the magnitude and location of the residual stress inside a polymer are also affected by the processing conditions is unclear. This study used polymerization of lactic acid into #20 (pure PLLA) and #30 (95% PLLA and 5% PDLA) under different processing conditions (e.g. heating temperature, heating time) as experimental model. Photoelastic analysis apparatus,MTS, were used to examine the distribution of residual stress inside the polymerized product and its relationship with the breaking point; X-ray diffractometer and Gel Permeation Chromatography were used to examine the relationship between crystallization, molecular weight and distribution of residual stress. The results showed a non-linear log regression in stress (i.e.no.of fringe order ) of #20 and #30 under different processing temperature. The fringe order in #20 was gradually reduced with the processing temperature increasing from 170°C to 190°C, indicating a degradation of PLLA and a reduction of internal stress under higher temperature. The stress in #30 was however the lowest at a processing temperature of 160°C when the temperature was increased from 150°C to 170°C. These results suggest that photoelastic analysis is a convenient and non-invasive technique that can be used to accurately examine the internal stress of a polymer product. It can be used as an important indication for the best processing procedure for high-molecule injection processes and quality control of the products. Key words: PLA, photoelastic analysis, crystallnility, annealing, Bending modulus