Structural, thermal and physico-mechanical properties of polyurethane/brewers' spent grain composite foams modified with ground tire rubber

In this work, brewers' spent grain (BSG) and ground tire rubber (GTR) waste fillers were applied as low-cost reinforcement phase in rigid polyurethane foam (PUR). PUR/BSG/GTR composites were prepared by a single step method, using polyglycerol as partial substitute of commercially available petrochemical polyols. Foaming parameters, chemical structure, dynamic mechanical properties, thermal stability, physico-mechanical properties and morphology of obtained composites were evaluated as function of BSG/GTR ratio (in range: 20/0; 15/5; 10/10; 5/15; 0/20 parts by weight - pbw). Modification of PUR/BSG composite foams with GTR accelerated foaming reactions, which resulted in decrease of rise time and tack free time. Higher content of GTR in PUR/BSG/GTR composites significantly enhanced their physico-mechanical properties and thermal stability. Compressive strength of PUR modified with BSG/GTR in ratio 5/15 pbw was more than 50% higher than for PUR/BSG composite foam without GTR, which correspond to 37% increase of density. Additionally, it was observed that temperatures corresponded to a 2% and 5% weight loss were for 9 °C and 24 °C higher for composite with BSG/GTR hybrid filler than for pure polyurethane matrix. Presented results indicate better compatibility between polyurethane matrix and GTR than with BSG, confirmed also by ATR-FTIR, DMA, swelling behavior and SEM analysis. Conducted investigations showed that performance properties of polyurethane/brewers' spent grain composite foams could be successfully tailored using GTR, which consequently extend their potential industrial applications.