Fire resistance and mechanical properties of powder-epoxy composites reinforced with recycled glass fiber laminate

In this article the effect of type and content of fractions of recycled glass fiber reinforced plastics (GFRP) on the mechanical properties and flame resistance of epoxy composites (EP) were investigated. For this purpose, post-production waste of glass fabric reinforced laminate with epoxy matrix containing 15 wt % of aluminum diethylphosphinate (AlDPi), 10 wt % of melamine polyphosphate (MPP) and 15 wt % of zinc borate (ZB) was ground and sieved to obtain four fractions of grain size: >1 mm (A), 1-0.5 mm (B), 0.25-0.5 mm (C) and <0.25 mm (D). The two smallest fractions (C, D) were used to prepare epoxy composites containing 10, 15 and 20 wt % of waste. The mechanical properties and fire resistance of obtained composites aimed as structural elements of seat equipment in public transport were determined. Scanning electron microscopy (SEM) was also performed to investigate the morphology of brittle fractures of epoxy composites. It was found that the amount and type of recyclated GFRP fraction affects the functional properties of powder-epoxy resin composites. The best results were obtained for the composite containing 15 wt % of the smallest fraction (D), as all mechanical properties were significantly improved [hardness 147.6 N/mm(2) (+42.5%), impact strength 9.64 kJ/m(2) (+11%), Young's modulus 2.98 GPa (+41.5%), tensile strength 51.5 MPa (+37%) and flexural strength 98.7 MPa (+10.9%)]. On the other hand, significant decrease in mechanical properties was observed for the composite containing 20 wt % of the fractions with grain size 0.5-0.25 mm (C). The analysis of the brittle fractions morphology of composites, indicates the weak dispersion and agglomerates formation in the case of composites with coarse-grained fractions. This also contributed to the flammability results. The highest flame resistance was found in the composite with 20 wt % of the fine-grained fraction: limiting oxygen index LOI = 26.1% instead of 20.6% - EP, peak of heat release rate pHRR = 540.3 kW/m(2) instead of 940.1 kW/m(2) - EP.