Crystallization kinetics of virgin and processed poly(lactic acid)

Poly(lactic acid) (PLA) is an emerging material mainly because it can be synthesized from renewable resources and is thus environmentally and ecologically safe. The mechanical properties, above all the thermal resistance of PLA are determined by the crystalline content: the heat deflection temperatu...

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Bibliographic Details
Published in:Polymer degradation and stability 2010-07, Vol.95 (7), p.1148-1159
Main Authors: Pantani, R., De Santis, F., Sorrentino, A., De Maio, F., Titomanlio, G.
Format: Article
Language:English
Subjects:
Applied sciences
Calorimetry
Cold crystallization
Crystal structure
Crystallization
Crystallization kinetics
Ecology
Exact sciences and technology
Extrusion
Extrusion moulding
Heating
Injection molding
Injection moulding
Machinery and processing
Mechanical properties
Moulding
Plastics
Poly(lactic acid)
Polymer industry, paints, wood
PVT
Technology of polymers
Thermal resistance
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Summary:Poly(lactic acid) (PLA) is an emerging material mainly because it can be synthesized from renewable resources and is thus environmentally and ecologically safe. The mechanical properties, above all the thermal resistance of PLA are determined by the crystalline content: the heat deflection temperature of crystalline PLA can reach 100 °C, whereas amorphous PLA loses mechanical properties at temperatures slightly higher than 60 °C. However, PLA has a low crystallization rate, so that after processing it remains mostly amorphous. This characteristic heavily limits the use of PLA for commercial applications. Many studies have been recently published on the crystallization kinetics of PLA. The effect of processing on this feature is however often neglected. In this work, the significance of processing on the crystallization kinetics of a commercial PLA was investigated. Two processing methods were explored: extrusion and injection moulding. The obtained materials, and the starting pellets of virgin polymer, were analyzed by calorimetry in order to obtain the crystallization kinetics. Two protocols were adopted to determine the crystallization rates during cooling from the melt or heating from the solid. The parameters of a kinetic equation were determined for all the materials and protocols adopted and it was thus possible to describe the evolution of crystallinity during heating and during cooling.
ISSN:0141-3910
1873-2321
DOI:10.1016/j.polymdegradstab.2010.04.018