Mechanical properties of thermoplastic elastomer blends with reduced warpage and recyclability potential for fused deposition modelling 3D printing

Abstract

Fused Deposition Modelling (FDM) presents some challenges when printing with polypropylene (PP)-based materials because they shrink and warp, making it difficult for the materials to adhere to 3D printer build plate/platform. A combination of appropriate thermoplastic elastomers (TPEs), additives, and an optimised material formulation results in significantly improved warpage behaviour of PP-based 3D-printed parts. Two series of experiments were conducted in which PP/maleic anhydride-grafted ethylene vinyl acetate copolymer (EVA-M) with and without the addition of an external compatibiliser was tested. An evaluation of the mechanical and thermal behaviour and 3D printability of TPE based on PP/EVA blend compounds at various ratios was performed. Both compatibilised and non-compatibilised PP/EVA-M compounds were successfully prepared and demonstrated to be viable for 3D printing using the FDM method, except for a 30/70 blend ratio for PP/EVA-M and a 30/60/10 blend ratio for the PP/EVA-M/compatibiliser compound. Analysis of the thermal behaviour of selected PP/EVA-M compared to that of virgin PP was conducted to study the relationship between warping and the crystallinity of the blends. The differential scanning calorimeter results revealed that lower crystallisation in TPE blends than in PP compounds reduced warping issues. Furthermore, the 3D printer processing parameters were adjusted to improve adhesion to the 3D printer platform. In terms of enhancing the mechanical properties, the addition of an external compatibiliser improved the mechanical properties of TPE at a specific blend ratio. This paper also demonstrated the feasibility of reusing waste thermoplastic elastomer materials through multiple reprocessing cycles.