Effect of glass fibers on rheology, mechanical properties of recycled thermal and PET

PET-glass fiber composites were prepared by melt mixing of recycled PET with chopped glass fibers (15, 20, and 30 wt%) and their degree of dispersion was assessed by scanning electron microscopy. Rotational rheometry was employed to analyze the interfacial shear strength between the fibers and polymer matrix in the molten state. The composite containing 30 wt% of glass fibers revealed a moderate G' secondary plateau; hence strong fiber-matrix interactions were confirmed. Results of mechanical testing were in a good accordance with structural and rheological measurements. The higher rate of mixing under production-scale conditions resulted in lower fiber-matrix adhesion and in a similar level of fiber dispersion as compared to the same mixture compounded on pilot-plant scale. Thermal characterization of the composites was performed by differential scanning calorimetry and total crystalline fraction was analyzed.