期刊
POLYMER
卷 186, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2019.122014
关键词
Free volume; Thermal analysis; Internal stresses; Mechanical testing; Deformation mechanism
资金
- National Research Fund of Hungary [OTKA K 120039]
- Stipendium Hungaricum Scholarship Programme
- China Scholarship Council (CSC)
Injection molded specimens were prepared from poly(lactic acid) (PLA) and their properties were determined as a function of time to study physical ageing. The mechanical testing of specimens showed that properties change rapidly with time. The stiffness of the specimens increases considerably, while their deformability decreases drastically from 250% after injection molding to a few percent after less than a day of ageing. Thermal analysis showed that both relaxation enthalpy and the change in the glass transition temperature (T-g) of the polymer increased with time. T-g decreased with increasing ageing time that could not be explained by the generally accepted approach of decreasing free volume. The analysis of literature data showed that the decrease or increase of T-g depends on the temperature of ageing and on the rate of cooling. T-g decreases at relatively low ageing temperatures, while it increases when ageing temperatures are closer to the T-g of the polymer. Besides the decrease of free volume, the development of internal stresses also plays a role in the determination of the glass transition temperature. Internal stresses result in a decrease of T-g, while decreased free volume leads to an increase. Internal stresses determine deformation and failure mechanism as well; large stresses lead to crazing/cracking and finally to brittle failure, which may hinder the application of PLA in many areas.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据