The influence of processing conditions on the mechanical properties and structure of poly(ethylene terephthalate) self-reinforced composites

The self-reinforced composites based on poly(ethylene terephthalate) (PET) are relatively new materials, competitive to composites based on polymers from the group of polyolefins. The use of PET as a base material should be another step forward for this technology, taking into account the properties, price, and the recycling possibility of proposed composites. In this research work, the main subject was to assess the impact of processing conditions on the final properties of the PET self-reinforced composites (srPET). The examined samples were prepared by hot-compaction technique under variable thermal conditions. The input material was composed of PET resin and low-melting copolymer (LPET). The high tenacity PET fibers were used as reinforcement for PET copolymer matrix. Initially both materials were in the form of continuous fiber; they were woven into a hybrid yarn wherein the proportion of PET and LPET fibers was 50/50. The properties of this hybrid yarn were investigated by differential scanning calorimetry (DSC) analysis, where the hot-compaction process conditions were simulated. Composite samples were investigated using the dynamic mechanical analysis (DMA) and static tension tests. The structure of the composite was observed using the optical microscope. The obtained mechanical properties of such a composite are not comparable to commercially made composite sheets, in which overall properties are mostly higher.