With the increasing production of synthetic polymers, waste management has become a global issue, posing an enormous threat to the natural environment [1]. Cellulose diacetate, a modified natural polymer, serves as an excellent alternative to synthetic plastics. By incorporating plasticizers, such as polyethylene glycol, triacetin and triethyl citrate, this polymer can withstand extrusion parameters and be formed into various products [2]. Additionally, agriculture and food production waste can be utilised as fillers to adjust product mechanical, thermal and/or hydrophobicity properties and reduce manufacturing cost. Thus, in this study, compositions of thermoplastic cellulose diacetate were obtained using ecofriendly plasticizer – triacetin and coffee silverskin filler which is by-product of food industry. Additionally, incorporating waste materials—such as agricultural or food industry waste—into compositions helps address waste utilization challenges while reducing production costs. By varying the particle size and amounts of filler, a set of thermoplastic mixtures was prepared and thermally processed using twin-screw extrusion. By the means of injection moulding and 3D printing the samples of novel bioplastics were obtained to investigate their properties. The properties of the resulting composites were evaluated by determining the melt flow index, hardness, mechanical properties, and contact angle.
It has been found that increasing particle size and concentration of coffee silverskin in composition decreases melt flow index. Hardness values increased with higher coffee silverskin content, while particle size had minimal influence on hardness. Mechanical properties analysis revealed that tensile strength and elongation at break decreased with increasing coffee silverskin content and particle size. The tensile modulus increased with higher coffee silverskin content but decreased when using larger size particles. The influence of coffee silverskin content and particle size on the hydrophobicity of the composites was minimal.