Recent development of poly (lactic acid) blends with a thermoplastic elastomer compatibilised for fused deposition modelling (FDM) 3D printing

The present study involves the fabrication of Poly (lactic acid) (PLA) blends with natural rubber (NR) or epoxidised natural rubber with 25% and 50% epoxidation levels (ENR 25 and ENR 50) respectively to produce flexible PLA filaments for fumed deposition modelling (FDM) 3D printing. Styrene-ethylene-butylene-styrene-grafted maleic anhydride (SEBS-g-MA) as a compatibiliser was used in the PLA/NR, PLA/ENR 25, and PLA/ENR 50 blends with a fixed blend ratio of 80/20. The effects of SEBS-g-MA content ranging from 5 to 15 parts per hundred polymer (php) in the PLA/NR, PLA/ENR 25 and PLA/ENR 50 blends on the thermal properties, tensile strength, elongation at break, melt flow index (MFI) and morphological analysis were studied. Differential scanning calorimetry (DSC) demonstrated that the glass transition temperature (Tg) and melting point temperature (Tm) of PLA shifted to a higher temperature as the SEBS-g-MA content increased in the PLA blends. Furthermore, a change in the degree of crystallinity was noted as the SEBS-g-MA content increased from 5 to 15 php, directly affecting the elongation at break of the compatibilised PLA blends. Relatively, the PLA/ENR 25/SEBS-g-MA blends have a much lower Tm, enthalpy, and crystallisation degree, indicating higher compatibility than the other compatibilised PLA blends. The results are consistent with the scanning electron microscopy (SEM) analysis, which revealed a possible interaction between the MA moiety, SEBS and rubber component functional groups. The MFI is gradually reduced with the addition of SEBS-g-MA up to 15 php; however, the value is comparable to the commercial PLA filament, which is sufficient for printability study. Overall, the PLA/ENR 25 containing 15 php SEBS-g-MA achieved optimal printability as a flexible PLA filament for 3D printing, as evidenced by a tenfold increase in elongation at break of the 3D-printed parts compared to the commercial filament.