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1 Department of Micro- and Nanotechnology, Technical University of Denmark 2 Amphiphilic Polymers in Biological Sensing, Department of Micro- and Nanotechnology, Technical University of Denmark 3 Department of Systems Biology, Technical University of Denmark 4 Department of Wind Energy, Technical University of Denmark 5 Composites and Materials Mechanics, Department of Wind Energy, Technical University of Denmark
Biopolymers and natural fibers are receiving wide attention for the potential to have good performance composites with low environmental impact. A current limitation of most biopolymers is however their change in mechanical properties at elevated temperatures. This study investigates the mechanical properties of two biomass-based polymers, polylactic acid (PLA) and cellulose acetate (CA), as a function of ambient temperature in the range from 5 to 80C. Tests were done for neat polymers and for jute fiber/biopolymer composites. Micromechanical models were applied to back-calculate the reinforcement efficiency of the jute fibers. The elastic modulus of neat PLA is constant until a temperature of about 45C, after which it is decreased rapidly. For neat CA, the elastic modulus is almost constant in the whole temperature range. The maximum stress of the neat biopolymers is consistently reduced. For the jute fiber composites, both the elastic modulus and maximum stress are reduced when the temperature is increased. For the elastic modulus, this is shown to be due to a reduction in the reinforcement efficiency of the jute fibers; i.e., a reduction in the back-calculated effective elastic modulus of the fibers. Altogether, the results demonstrate that the thermal sensitivity parameters typically provided for polymers, e.g., the glass transition temperature and the heat deflection temperature, cannot be used as sole parameters for determining the gradual change in mechanical properties of polymers and composites. © 2012 Wiley Periodicals, Inc.
Journal of Applied Polymer Science, 2013, Vol 128, Issue 3, p. 2038-2045
Biopolymers and renewable polymers; Composites; Mechanical properties; Thermal properties
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