Effect of reprocessing on the service life properties of glass fiber-reinforced in-house polypropylene waste composites

Reprocessing of synthetic fiber-reinforced thermoplastics for reuse in the design of structural components applications is important owing to their non-biodegradability. This study evaluates the effect of reprocessing on the service life properties of in-house polypropylene wastes reinforced with E-glass fiber. Composite materials containing 10 mm length glass fiber (GF) and recycled polypropylene were manufactured with 10 wt% GF and subjected to five reprocessing cycles via extrusion and compression molding under similar conditions. Properties such as mechanical, melt flow index (MFI), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis were used to analyze the effect of reprocessing on the composites. The results obtained revealed that the composites' properties diminished with successive reprocessing. The thermal study showed reductions in the thermal stabilities with a drop in onset degradation temperature from 338.07 to 245.15 degrees C after five runs, indicating an increase in the polymer chain molecular movement and less rigidity due to shorter chains provided by X-ray diffraction analysis with reduced peak intensities, average crystallite sizes, and degree of crystallinities but no destruction of the main functional groups was observed with the spectral studies. An increase in the MFI (6 g/10-17.88 g/10 min) indicated the possible loss of complex viscosity and damage in molecular weight for the reprocessed matrix. Reinforced in-house PP plastics can, therefore, be reprocessed twice only for the same product except with the addition of either virgin PP or other materials to compensate for the lost properties and help manufacturers save costs.

Automated summary

The aim of this study was to evaluate the effect of reprocessing on the service life properties of polypropylene wastes reinforced with E-glass fiber. The results showed that the properties of the composites decreased with successive reprocessing, including reduced thermal stability, crystallinity, molecular weight, and complex viscosity. Therefore, reinforced in-house PP plastics can only be reprocessed twice, unless virgin PP or other materials are added to compensate for the lost properties.