Composites of Recycled PET Reinforced with Short Glass Fiber

Composites of recycled poly(ethylene terephthalate) (PET) and short glass fibers (GFs) in different compositions (0, 20, 30, and 40 wt% of GFs) with optimized microstructures and high mechanical performance were obtained through melt processing. Composites showed appropriate dispersion and distribution and suitable bonding of the GF throughout the PET matrix, using either recycled bottle-grade PET in its degraded form or in a solid-state polymerized (SSP) form and GFs treated with either aminosilane or epoxysilane coupling agents. The high level of reinforcement of these PET/GF composites was confirmed by comparison of the experimental elastic modulus values of PET/GF composites with theoretical ones obtained using the Halpin-Tsai model. An important aspect highlighted by this study is that although it has been stated in the literature that this is only possible with the use of twin-screw extruders, these PET/GF composites with optimized microstructure and with high mechanical performance were compounded using a single-screw extruder with a double-flight barrier screw. In general, slightly better mechanical strengths were achieved for the composites based on the SSP recycled PET, which may be associated with its highly entangled amorphous phase arising from its higher molecular weight.