Modified cork/SEBS composites for 3D printed elastomers

Abstract

Three dimensional (3D) printed elastomers is a challenge which can be overcome using fillers. With that in perspective, cork was chemically modified via a two-step reaction, aiming to achieve better compatibility with styrene-ethylene-butylene-styrene (SEBS). In the first step, the OH groups of cork surface were grafted with succinic acid, while in the second step the free acid groups were reacted with a polyol to produce ester moieties. Spectroscopy analysis confirmed the occurrence of the chemical reaction which was supported by contact angle (CA) measurements. The unmodified cork presents a CA of 117.7°, while the modified cork presents a CA of 92.4° which is closer to that of SEBS (102.8°), resulting in better compatibility between the modified filler with the matrix. In fact, the enhancement of compatibility between polymer and filler was observed by inspecting the layer-to-layer bonding and was confirmed by the mechanical properties of the 3D printed composites, since the modified cork-based composite presented higher Young modulus, maximum stress and elongation at break when compared to the untreated counterparts. Additionally, the advantage of the chemical treatment was evaluated by analyzing the processability of composites. The modified filler-based composite, presents lower glass transition temperature (Tg), higher melt flow index (MFI) and higher thermal stability. Overall, in this work, a simple chemical route to modify lignocellulosic biomass and its benefit on the properties of 3D printing objects is discussed. The improved performance and sustainability of the 3D printed objects produced to be used for example in shoe applications was presented