Development of silane grafted halloysite nanotube reinforced polylactide nanocomposites for the enhancement of mechanical, thermal and dynamic-mechanical properties

Abstract In this investigation, halloysite (Hal) nanotubes were surface modified with 3-aminopropyltriethoxysilane (APTES) to enhance the surface interaction of Hal nanotubes with polylactide or poly (lactic acid) (PLA) and to achieve good dispersion of Hal nanotubes across the PLA matrix. Unmodified and silane modified Hal nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), Nitrogen adsorption-desorption analysis, Thermogravimetric analysis (TGA) and Field emission scanning electron microscopy (FE-SEM) with Energy-dispersive x-ray spectroscopy (EDX) analysis. Nitrogen adsorption-desorption, FTIR and TGA analysis results were confirmed the successful modification of Hal nanotubes surface with APTES. The different wt% of unmodified and APTES modified Hal nanotubes reinforced PLA polymer composites were prepared by using a laboratory scale melt mixer. The resultant Hal-PLA nanocomposites were characterized for their morphology, thermal, mechanical and dynamic-mechanical properties. Tensile strength increased to 62.6 MPa with the addition of 4 wt% of APTES modified Hal-PLA nanocomposites which is 26.5% higher than pure PLA and 15% higher than unmodified (4 wt%) Hal-PLA nanocomposites. Impact strength of 4 wt% APTES modified Hal-PLA nanocomposites was 29.8 MPa, which is 20% higher than the unmodified Hal-PLA nanocomposites and 40% higher than pure PLA. Thermal stability also increased by 17 °C with the addition of 4 wt% of APTES modified Hal nanotubes and 10 °C for the unmodified Hal nanotubes onto PLA. Storage modulus increased > 10% with the addition of 4 wt% of APTES modified Hal nanotubes as compared to pure PLA and tan delta values were decreased for the modified Hal nanotubes due to an increase in the compatibilisation between filler and matrix phase. Based on these results, APTES is one of the best choices for the functionalisation of inorganic surface such as Hal nanotubes. The mechanical and thermal properties significantly improved with the addition of a small quantity (4 wt%) of APTES modified Hal nanotubes.