Journal
FIBERS AND POLYMERS
Volume 10, Issue 5, Pages 687-693Publisher
KOREAN FIBER SOC
DOI: 10.1007/s12221-010-0687-6
Keywords
Poly(lactic acid); Tensile behavior; Chain orientation; Enthalpy relaxation; Thermal property
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Funding
- Ministry of Education, Science and Technology (MEST)
- Korea Institute for Advancement of Technology (KIAT) through the Human Resource Training Project for Regional Innovation
- National Research Foundation of Korea [M-03-20070202102008] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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A series of amorphous poly(lactic acid) (PLA) monofilaments with various D-isomer contents of 1 similar to 9 mol% have been prepared and then elongated uniaxially at 25 similar to 65 A degrees C in the glass transition region. Both initial modulus and maximum strength of PLA monofilaments are appreciably decreased with increasing the temperature, especially at similar to 50 A degrees C, and they were somewhat lower for the monofilament with higher D-isomer content. Structural evolution, chain orientation, and thermal properties of PLA monofilaments drawn uniaxially with various draw ratios at 65 A degrees C were then investigated by using wide-angle X-ray diffraction, polarized Raman spectroscopy, and differential scanning calorimetry, respectively. X-ray diffraction patterns clearly exhibited the development of chain orientation and stain-induced crystallization of the monofilaments as a function of draw ratio (DR). The dichroic ratio, a measure of the chain orientation, was quantitatively evaluated from the polarized Raman spectra. It was revealed that the dichroic ratios increased up to DR=4 and decreased slightly at DR > 4 owing to the strain-induced crystallization for PLA monofilaments with D-isomer contents of 1 and 4 mol%. The glass transition and cold-crystallization temperatures of PLA monofilaments increased and decreased, respectively, with the increment of DR. The strain-induced enthalpy relaxation endothermic peak appearing in glass transition region became intense with increasing the DR.
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