Olive pit powder as multifunctional pigment for waterborne paint: influence of the bio-based filler on the aesthetics, durability and mechanical features of the polymer matrix

In this work, olive pit powder has been added into a polyurethane-acrylate top-coat paint, evaluating the effect of four different filler amounts on the aesthetics, durability and mechanical features of the composite coatings. The samples were characterized by electron microscopy and colorimetric analyses to assess the possible change in morphology and appearance introduced by the bio-based additive. The durability of the coatings was evaluated by salt spray chamber and UV-B exposures, which evidenced the water absorption tendency of the lignocellulose based filler and its severe chemical-physical degradation, respectively. Otherwise, the filler based on olive pit causes an increase in the mechanical features of the polymeric matrix, such as abrasion resistance, hardness and static coefficient of friction. Although the coating containing high concentrations of olive pit powder demonstrated poor durability, this study revealed that the bio-based filler can be employed as multifunctional pigment, providing particular aesthetic features, but also improving the mechanical durability performance of polyurethane-acrylate paints.