Abstract
Poly(ethylene terephthalate)/graphite (PET/G) micro-composites were fabricated by the melt compounding method using a minilab extruder. The carbon fillers were found to act as nucleating agents for the PET matrix and hence accelerated crystallization and increased the degree of crystallinity. TGA showed that carbon fillers improved the resistance to thermal and thermo-oxidative degradation under both air and nitrogen atmospheres. However, a poor agreement was observed at higher loadings of the filler where the composites displayed reduced reinforcement efficiency. The results demonstrate that the addition of graphite at loading >14.5 wt.% made electrically conductive composites. It was calculated that the electric conductivities of PET/graphite micro-composites were enhanced, above the percolation threshold values by two orders of magnitudes compared to the PET matrix. The minimum value of conductivity required to avoid electrostatic charge application of an insulating polymer was achieved, just above the threshold values. The addition of graphite also improved thermal stability of PET, accelerated its crystallization process and increased the degree of crystallinity. Microscopic results exhibit no indication of aggregations at 2 wt.% graphite, whereas more agglomeration and rolling up could be seen as the graphite content was increased in the PET matrix (in particular, above the percolation threshold value). Furthermore, based on the mechanical experimental characterization of the PET/graphite micro-composites, a large deformation-based mathematical model is proposed for material behavior predictions. The model fits well the experimental data and predicts other mechanical data that are not included in the parameter identification.
Highlights
Much research have been focused on preparing polymeric matrix composites (PMC) for high performance applications, using carbon and its allotropes, which include both microand nano-size fillers such as carbon black (CB), graphite, carbon fibers, graphite nanoplateletsPolymers 2019, 11, 1411; doi:10.3390/polym11091411 www.mdpi.com/journal/polymers (GNP), graphene and carbon nanotubes (CNT) [1,2,3,4]
The as-received graphite was examined using the SEM to study their morphology before incorporation into the poly(ethylene terephthalate) (PET) matrix
The graphite flakes appear white in the images and the PET matrix is seen as grey
Summary
Much research have been focused on preparing polymeric matrix composites (PMC) for high performance applications, using carbon and its allotropes, which include both microand nano-size fillers such as carbon black (CB), graphite, carbon fibers, graphite nanoplateletsPolymers 2019, 11, 1411; doi:10.3390/polym11091411 www.mdpi.com/journal/polymers (GNP), graphene and carbon nanotubes (CNT) [1,2,3,4]. Polymers are filled with micro-fillers to improve electrical and mechanical properties. Earlier studies have demonstrated that even low addition levels of nano-fillers can give significant improvements to the electrical, mechanical, and thermal properties of polymers [4,5,6]. Poor interfacial adhesion between the reinforcement and the matrix, inadequate dispersion and non-uniform distribution are parameters of major concern that need to be addressed before reaping the full potentials of particulate conductive nano-fillers. To resolve these issues, sizeable efforts have been applied to the chemical modification of nano-fillers [9]
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