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ITS » Scientific Articles » Luar ITS
Posted by nurkhamidah@chem-eng.its.ac.id at 28/05/2013 14:34:07  •  1008 Views


EFFECTS OF CRYSTALLINITY AND MOLECULAR WEIGHT ON CRACK BEHAVIOR IN CRYSTALLINE OF POLYL-LACTIC ACID

Author :
NURKHAMIDAH, SITI ( 198405082009122004 )
WOO, EAMOR.M




ABSTRAK

The crack behavior and spherulitic morphology in melt-crystallized polyL-lactic acid PLLA were found to be molecular weight MW and crystallinity dependent along with other key factors. With increasing MW in PLLA the size of spherulites band spacing of ringbanded spherulites and degree of crystallinity decreased whereas cracks were increasingly less likely to occur. Multiple types of cracks that is circumferential andor radial cracks were massively present in low-MW PLLA PLLA-11k which had a high crystallinity. Upon cooling in PLLA- 11k at most crystallization temperatures Tcs cracksformed and the crack patterns were dependent on the lamellar morphology within the spherulites. Hexagonal rather than circular cracks occurred spontaneously during the cooling process of PLLA of a medium-MW gradePLLA-120k in PLLA film samples crystallized only at high Tc 135138C and cooled to ambient temperature. However no cracks of any types at all were present in PLLA films of high enough MWs PLLA-152k and PLLA-258kupon either slow air cooling or quench cooling when the samples were dipped into liquid nitrogen. Apparently cooling-induced contraction differences in different directions were invalid or not sufficient to address the complex cracking behavior in PLLA. In addition for PLLA-11k with a substantially high crystallinity cracks were so prone to occur that even cover constraint imposed another factor in determining the crack and ring-band patterns. More plausible mechanisms and correlations between the cracks MW crystallinityspherulite size and spherulite lamellar patterns of PLLA were analyzed in detail and proposed in this study.



Keywordscrystallization; morphology; polyesters, spherulites; thin films
 
Subject:  Crystalline materials
Date Create: 28/05/2013
Type: Text
Format: PDF
Language: English
Identifier: ITS-Article-23105130000670
Collection ID: 23105130000670
Call Number: 541.39 Nur e


Source
article of journal of Applied Polymer Science, Vol. 122, 19761985 (2011)

Coverage
ITS Community

Rights
@ 2011 Wiley Periodicals, Inc.




[ Download - Summary ]

ITS-Article-23105130000670-25276.pdf



[ Link of Contents]
  1. EFFECTS OF CRYSTALLINITY AND MOLECULAR WEIGHT ON CRACK BEHAVIOR IN CRYSTALLINE OF POLY(L-LACTIC ACID)
    http://onlinelibrary.wiley.com/doi/10.1002/app.34021/abstract;jsessionid=5E05D478D451FE41D5B13C072D97C51D.d04t04?



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