Temperature‐modulated differential scanning calorimetry studies on the origin of double melting peaks in isothermally melt‐crystallized poly(<scp>L</scp>‐lactic acid)

Shieh, Yeong‐Tarng; Liu, Gin-Lung

doi:10.1002/polb.21056

Cited by 64 publications

(55 citation statements)

References 44 publications

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“…When T c C 120°C, only a single endothermic peak is observed and it moves to higher temperatures further with increasing T c . These distinct melting behaviors are analogous with some earlier reports for melt-crystallized PLLA with a slight difference in temperature range [41][42][43][44][45]. Since the melting behavior is greatly dependent on the crystallization behavior, the effect of T c on polymorphous crystallization of PLLA will be further discussed in the following section.…”

Section: Resultssupporting

confidence: 65%

“…According to the conventional and temperature-modulated DSC analysis, this behavior was proposed to originate from the melt-recrystallization mechanism by several research groups [38][39][40][41][42][43][44]. Besides, another possible interpretation was due to the phase transition from a 0 -form crystal to a one and the melting of the as-transformed a crystals.…”

Section: Introductionmentioning

confidence: 95%

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Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Song

Chen

Wei

et al. 2012

J Therm Anal Calorim

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The polymorphous crystallization and multiple melting behavior of poly(L-lactic acid) (PLLA) with an optical purity of 92 % were investigated after isothermally crystallized from the melt state by wide-angle X-ray diffraction and differential scanning calorimetry. Owing to the low optical purity, it was found that the disordered (a 0 ) and ordered (a) crystalline phases of PLLA were formed in the samples crystallized at lower (\95°C) and higher (C95°C) temperatures, respectively. The melting behavior of PLLA is different in three regions of crystallization temperature (T c ) divided into Region I (T c \ 95°C), Region II (95°C B T c \ 120°C), and Region III (T c C 120°C). In Region I, an exothermic peak was observed between the low-temperature and high-temperature endothermic peaks, which results from the solid-solid phase transition of a 0 -form crystal to a one. In Region II, the double-melting peaks can be mainly ascribed to the melting-recrystallization-remelting of less stable a crystals. In Region III, the single endotherm shows that the a crystals formed at higher temperatures are stable enough and melt directly without the recrystallization process during heating.

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Section: Resultssupporting

confidence: 65%

Section: Introductionmentioning

confidence: 95%

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Song

Chen

Wei

et al. 2012

J Therm Anal Calorim

View full text Add to dashboard Cite

show abstract

“…This allows for the resolution of weak or overlapping transions. [24][25][26][27] MDSC data ( Figure 7A) confirmed the existence of two separate melting endotherms in these unsaturated polymers. During the dual annealing experiment, we discovered that the polymers could be conditioned thermally to prefer either of these two different crystalline forms.…”

Section: Polymersupporting

confidence: 53%

Probing the Effects of Hydrophilic Branch Size, Distribution, and Connectivity in Amphiphilic Polyethylene

Berda

Wagener

2008

Macro Chemistry & Physics

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Acyclic diene metathesis (ADMET) polymerization/hydrogenation methodology was used to synthesize a family of amphiphilic polyethylenes (PEs) with precisely placed poly(ethylene glycol) branches. Four structural parameters are varied in this report: size of the hydrophilic pendant group, manner in which the pendant group is connected to the backbone, distance between the pendant moieties along the backbone, and saturation of the polyolefin backbone. Varying the branch size with other parameters held constant results in negligible effects on thermal behavior. However, when either the distribution of branches or manner of connection of the branches is altered, changes in the thermal behavior become clear. These slight structural changes allow tunability of the structural morphology from fully amorphous to semicrystalline materials melting over a range of temperatures above 60 °C.magnified image

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“…T m was shifted to even lower temperatures and split into two peaks under the instrumental conditions used. The presence of double melting peaks was reported for PLA before [70][71][72][73]. Two mechanisms were proposed: melting recrystallization model [74,75] and double lamellar thickness model [76][77][78].…”

Section: Resultsmentioning

confidence: 97%

Use of Nutshells as Fillers in Polymer Composites

et al. 2012

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Nutshells are agricultural waste products that can be procured at relatively low cost. In this work we examined the possibility of using these biodegradable materials as fillers in poly(lactic acid) and low density polyethylene. The nutshells were ground into powder, blended with the polymer, and then injection molded with final weight varying from 10 to 40 weight %. The mechanical and thermal properties of the composites were then studied. In general, the addition of fillers caused reductions in mechanical properties to varying extents, but thermal properties were only slightly affected. The use of maleic anhydride and peroxide with the fillers had a negative effect on poly(lactic acid) but a slightly positive effect on the stiffness of polyethylene. The results suggested that polymer-nutshell composites may be usable in applications where cost is a concern and where some reductions in mechanical properties are acceptable.

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Temperature‐modulated differential scanning calorimetry studies on the origin of double melting peaks in isothermally melt‐crystallized poly(L‐lactic acid)

Cited by 64 publications

References 44 publications

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Calorimetric analysis of the multiple melting behavior of melt-crystallized poly(l-lactic acid) with a low optical purity

Probing the Effects of Hydrophilic Branch Size, Distribution, and Connectivity in Amphiphilic Polyethylene

Use of Nutshells as Fillers in Polymer Composites

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