Water
effect in the thermal and molecular dynamics behavior of poly(<Emphasis Type="Italic">L</Emphasis>-lactic
acid) |
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Authors: | Ana Rita Brás María Teresa Viciosa Madalena Dionísio J F Mano |
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Institution: | 1.REQUIMTE/CQFB, Departamento de Química, FCT,Universidade Nova de Lisboa,Caparica,Portugal;2.3B’s Research Group – Biomaterials,
Biodegradables, Biomimetics, Department of Polymer Engineering,University of Minho,Braga,Portugal;3.Department of Polymer Engineering,University of Minho,Guimar?es,Portugal |
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Abstract: | A detailed dielectric characterization
of the relaxation modes found in a poly(L-lactic
acid), PLLA, film containing 0.4 mass% of water is provided. The sub-glass
relaxation process is a superposition of two processes, one highly influenced
by water with activation energy of 50 kJ mol–1,
and another one, with longer relaxation times and lower intensity having activation
energy of 38 kJ mol–1. Dried PLLA exhibits
an abnormally broad secondary β-relaxation that probably corresponds to
the superposition of multiple processes. Upon water sorption the strength
of the more mobile process significantly increases being shifted to lower
temperatures which allows the detection of the underlying process. The glass
transition relaxation process is deviated to higher frequencies almost one
decade due to the water plasticizing effect. The reported results show that
small quantities of water may have a profound impact in the relaxational features
in PLLA, which should be taken in account when considering the properties
and performance of this system. |
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Keywords: | dielectric relaxation polyester thermal treatment water effect |
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