期刊
ULTRASONICS SONOCHEMISTRY
卷 21, 期 1, 页码 376-386出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ultsonch.2013.07.007
关键词
Micro-molding; Ultrasound technology; Polylactide; Polymer degradation; Processing
资金
- MCINN/FEDER
- AGAUR [MAT2009-11503, MAT2012-36205, 2009SGR-1208]
A new ultrasonic micro-molding system was used to process polylactide (PLA) and fabricate reduced dimension specimens. Plasticization and molding of PLA were achieved by applying ultrasonic waves after feeding the polymer into a plasticizing chamber. Chemical and physical characteristics of processed PLA varied depending on the processing window (i.e. changes in ultrasonic wave amplitude between 14.2 and 48.1 mu m and molding pressure between 0.5 in 6 bars). In terms of chemical effects, the application of ultrasound can lead to lower molecular weights (e.g. decreases of more than 45% in the weight average molecular weight), revealing partial degradation of the material. Also, the processed materials exhibited slightly higher thermal degradability than pure PLA because ultrasonic vibrations break molecular linkages and worsen the polymer structure. Finally, the processing conditions for the preparation of PLA specimens could be optimized without causing degradation and preserving structural characteristics and mechanical properties. Specifically, the use of an amplitude of 48.1 mu m and a pressure of 3 bars gave samples with the same molecular weight as the raw material (i.e. 117,500 g/mol as opposed to 117,300 g/mol for M-w). (C) 2013 Elsevier B.V. All rights reserved.
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