Upgrading brewer's spent grain as functional filler in polypropylene matrix

Brewer's spent grain (BSG) is a by-product of the brewing industry that contributes to a large volume of wastes. The lignocellulosic nature of this waste, together with presence of functional components such as antioxidants, represents an attractive for the composite's industry. In this work, BSG has been used as functional filler for polypropylene matrix to give an additional use to this industrial waste. Addition of BSG filler improves the overall environmental efficiency of the polypropylene matrix thus leading to high environmentally friendly materials. BSG can be loaded in the 10–40 wt% range with easy manufacturing, balanced mechanical properties, and additionally, excellent antioxidant properties are achieved with increasing BSG loading due to natural antioxidants that have not been removed during the brewing process. In particular, the onset of the thermo-oxidative degradation of polypropylene is improved by 15–20°C for different compositions. Due to the lignocellulosic nature of BSG, water uptake is a clear drawback of PP–BSG composites but formulations containing 10-30 wt% BSG hold the water uptake at very low values. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers