Thermal annealing assisted 3D printing: Enhancement of the mechanical and thermal properties of a SiC reinforced PET polymer in the FDM process

Polyethylene terephthalate (PET) is an odourless, relatively easy to produce, low cost and biodegradable material. However, its low mechanical and thermal properties limit its use. In this study, silicon carbide (SiC) was reinforced into the PET matrix to improve the mechanical and thermal properties of virgin PET. The manufacture of the objects was carried out at four different reinforcement ratios (3–6–9–12%) by mass. The composites were manufactured into objects using fused deposition moulding (FDM), which is an additive manufacturing process. A thermal annealing process was applied to enhance the properties of the samples. A tensile test, impact strength test, and surface hardness test were applied to investigate the mechanical properties of the produced samples. In addition, thermal characterisation by a thermal conductivity test and internal structure characterisation by XRD and SEM analyses were carried out. It was determined that the tensile strength, impact strength and surface hardness of the samples increased by 8.95%, 24.44% and 7.70%, respectively, with SiC reinforcement. As a result of the thermal annealing process, the mechanical properties of the samples were enhanced. The annealed specimens have 8.57% higher tensile strength, 11.17% higher impact strength and 1.46% higher surface hardness than unannealed specimens. XRD analyses indicated that the annealed samples have higher crystallinity. SEM analysis showed that SiC nanoparticles were homogeneously dispersed in the PET matrix. Also, SEM analysis showed that micro-voids were not formed in virgin PET but micro-voids were formed in SiC reinforced composites and the presence of these voids increased with an increase in SiC reinforcement. Thermal annealing and SiC reinforcement were found to increase the thermal conductivity.