Characterization of poly(lactic acid) multifilament yarns. I. The structure and thermal behavior

Abstract

The structure and thermal behavior of poly(lactic acid) (PLA) multifilament yarns were studied by complementary techniques of differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and wide angle X-ray diffraction (WAXD). As for PLA filaments, notable differences in the WAXD patterns, DSC curves, and FTIR spectra were observed. The combination of the WAXD and FTIR results showed that PLA samples with different crystallinity contain a-form crystal structure. The FTIR spectra of the filaments were analyzed to study their crystallinity and crystal structure. The total crystallinity of the PLA filaments was obtained from the percent area loss of the skeletal amorphous band at 955 cm À1. Crystalline fraction from FTIR and DSC were comparable with each other. The C¼ ¼O stretching region, which is sensitive to crystallization and dipole-dipole interactions, was evaluated to provide information about chain conformers and crystallinity of the samples. Depending on the processing conditions, double melting peaks were observed in the DSC curves of the samples. This exhibited the structural reorganization of the crystal phase during heating affected by heating and cooling rate. In the DSC curves of the nearly amorphous multifilament yarn, the exothermic peak observed right above the glass transition temperature (T g ) indicated two relaxed and deformed amorphous regions. However, the multifilament yarn with higher crystallinity showed just endothermic melting peak after its glass transition. V C 2010 Wiley Periodicals, Inc. J Appl

Structure–property relationship for poly(lactic acid) (PLA) filaments: physical, thermomechanical and shape memory characterization

“…The higher average value of the birefringence and the overall orientation function of the J sample confirmed its higher molecular orientation. The partial-crystalline nature of the J sample was confirmed in our previous work on the same samples while the T sample did not indicate any crystallinity [40]. Consequently, the higher birefringence of the J sample is assigned mainly to its crystalline orientation in comparison to the partial orientation of the amorphous T sample.…”

“…3. The observed differences in the dynamic mechanical properties of the two yarn samples are attributed to distinct crystallinity [40] and molecular orientations of the samples, Table 1.…”

“…8. Long-range periodicities as well as the apparent crystal size previously measured by WAXS [40] in the perpendicular Table 2. The Gibbs-Thomson equation correlates mean lamellar thickness, l c , to melting temperature, allowing estimation of the former from melting point measurement [44].…”

Effects of molecular weight and grafted maleic anhydride of functionalized polylactic acid used in reactive compatibilized binary and ternary blends of polylactic acid and thermoplastic cassava starch

“…40 Only 7rPT A had a second T m value slightly higher than PLA, indicating high-regularity crystals. 13,[41][42][43][44] According to Radjabian et al, 45 there are three main mechanisms that can be responsible for the double-melting behavior of PLLA: melt-recrystallization, dual (or multiple) lamellae populations, and dual (or multiple) crystal structures. The double melting peak behavior was also observed in additive-free poly(L-lactide) (PLLA) resin, PLA/ thermoplastic acetylated starch blends, compatibilized blends of PLA/starch, PLA composites, and other structures.…”

Conformational development of polylactide films induced by uniaxial drawing

“…It is possible to change the α ′ form to the α form by increasing the temperature above 120 °C or inducing stress at a temperature close to the glass transition temperature ( T g ) . To date, various groups have studied the crystallinity, orientation and deformation of the α form . Yet, in the commercial fabrication of PLA products, PLA is mostly composed of the α ′ form.…”