Properties of Lignocellulosic Composites of Coffee Husk Filled Polypropylene

Ground coffee husk has been incorporated into polypropylene (PP) at 20, 30 and 40 wt%, along with a PP maleated compatibilizer at 10 wt% relative to the coffee husk, by means of a co-rotating twin-screw extruder and subsequent injection molding into test specimens. In relation to neat PP, the 40 wt% composite showed an increase in flexural strength, flexural modulus, tensile modulus and heat distortion temperature of about 35, 90, 75 and 45%, respectively. However, strain at break, impact and tensile strength decreased by around 95, 40 and 20%, respectively. The presence of coffee husk practically did not affect PP melt temperature, but increased both composite's degree of crystallinity, measured by DSC, and temperature at maximum degradation rate, measured by TGA.