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Improvement of the thermal stability of branched poly(lactic acid) obtained by reactive extrusion
Carrasco Alonso, Félix Ángel; Cailloux, Jonathan; Sanchez Jimenez, P.E.; Maspoch Rulduà, Mª Lluïsa
Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica; Universitat Politècnica de Catalunya. POLYCOM - Polimers i compòsits: tecnologia
One-step reactive extrusion-calendering process (REX-calendering) has been used in order to obtain sheets of 1 mm from poly(lactic acid) modified with a styrene-acrylic multifunctional oligomeric agent. In a preliminary internal mixer study, torque versus time has been monitored in order to ascertain chain extender ratios and reaction time. Once all the parameters were optimized, reactive extrusion experiments have been performed. An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of PLA sheets manufactured by reactive extrusion. This improvement has consisted of replacing the n-order conversion function by a modified form of the Sestak-Berggren equation f(alpha) = c (1 - alpha)(n) alpha(m) that led to a better adjustment of experimental data and also adequately represented the conventional mechanisms for solid-state processes. The kinetic parameters so obtained have been compared to those determined by conventional differential methods and n-order reaction kinetics. Given that the thermal degradation of PLA has been argued to be caused by random chain scission reactions of ester groups, the conversion function f(alpha) = 2 (alpha(1/2) - alpha), corresponding to a random scission mechanism for L = 2 (as well as other functions for L values up to 8), has been tested. Once optimized the kinetic model, the thermal degradation kinetics of sheets obtained by REX-calendering process was compared to that of conventional sheets and polymer matrix. (C) 2014 Elsevier Ltd. All rights reserved.
Peer Reviewed
Àrees temàtiques de la UPC::Enginyeria dels materials
Polymers--Deterioration
Branched poly(lactic acid)
Kinetics
Thermal degradation
Enhanced general analytical equation
Random scission
Reactive extrusion
COMBINED KINETIC-ANALYSIS
EVA CROSS-LINKING
MECHANICAL-PROPERTIES
THERMOGRAVIMETRIC DATA
POLY(L-LACTIC ACID)
ACTIVATION-ENERGY
DEGRADATION
PARAMETERS
MODEL
EPOXY
Polímers -- Deterioració
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
info:eu-repo/semantics/publishedVersion
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