The feasibility of using ethylene-vinyl acetate/natural rubber (EVA/NR)-based thermoplastic elastomer as filament material in fused deposition modelling (FDM)-3D printing application

A series of ethylene-vinyl acetate/natural rubber (EVA/NR)-based thermoplastic elastomer (TPE) blends were developed for fused deposition modelling (FDM)-3D printing application. Two types of the EVA, namely EVA20 (17–20% vinyl acetate) and EVA24 (24–27% vinyl acetate), were used. The grafted EVA was blended with NR in various ratios using a melt blending approach. The effect of EVA/NR blends ratios were studied for thermal, melt flow index, mechanical and dynamic properties. Differential Scanning Calorimetry (DSC) analysis showed that increasing the NR ratio decreased the crystallinity of EVA/NR blends. Similarly, the melt flow index, hardness and tensile strength also reduced as NR content increased in the EVA blends. Printability study indicated that both EVA20 and EVA24 with their blends experienced buckling problems due to insufficient strength and stiffness for acting as push rods for the filament extrusion. Further investigation revealed that the elastic modulus (E') and loss modulus (E'') of EVA/NR blend was lower indicating lower stiffness and viscous response compared to commercial Thermoplastic Urethane and Nylon filaments. The feasibility study of EVA/NR blend in 3D printing provide fresh insight to develop TPE blends as potential 3D printing materials, especially involving natural rubber.