Effects of coupling agent on mechanical and physical properties of spent coffee ground filled with polylactic acid composites

Abstract

This study investigates the feasibility of using polylactic acid and coffee grounds to create environmentally friendly composites. The study applied the design of a statistical experiment to study two factors, namely coffee grounds mixing volume (10, 20 and 30% by weight) and the amount of the reaction substance (0, 1, 3 and 5 parts per hundred). The compositions were mixed by twin screw extruder and formed into specimen for testing the properties by the hot-pressing process. The results of the property testing and statistical analysis show that increasing coffee grounds increased the melting index, hardness, modulus of elasticity, and the percent elongation of the composite. The addition of a coupling agent led to an increase in tensile strength and modulus of elasticity. However, the regression analysis showed that the influence of both factors affected the properties, in which the relationship of factors can be modeled using quadratic polynomial model rather than simple linear model. Morphological analysis shows that coffee grounds should not be mixed more than 20% because it affects the stability and homogeneity of the composite. The results of the research show that 10% coffee grounds should be mixed with 5 parts per hundred, resulting in the properties of composites that are suitable for creating a product with unique color and aroma of coffee grounds.