Mechanical and flammability properties of poly(lactic acid)/ poly(butylene adipate-co-terephthalate) blends and nanocomposites: effects of compatibilizer and graphene

Poly(lactic acid) (PLA)/polybutylene adipate co-terephthalate (PBAT) blends were prepared by melt blending and compatibilized by glycidyl methacrylate (GMA). The effect of graphene nanoplatelets (GNP) on these compatibilized blends were investigated by incorporating GNP at different content. The formulated blend and nanocomposites were characterized for mechanical, morphological, thermal and flammability properties by using universal testing machine, impact tester, field emission scanning electron microscope (FESEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 respectively. The incorporation of 8 phr GMA into PLA/PBAT (75:25) blend as a compatibilizer results in a significant increase in impact strength (more than 14 times higher) compared to the uncompatibilized blend. Young's modulus and tensile strength of compatibilized PLA/PBAT nanocomposites increased upon addition of GNP and reached maximum values at 4 phr before decreasing slightly. However, impact strength decreased with increasing GNP contents. The thermal stability and the flame retardancy of the GNP reinforced blend nanocomposites were also improved with an increase in nanofiller content and the maximum values for the nanocomposites were achieved at 6 phr. Interestingly, the nanocomposites samples showed a UL-94 rating of V0 at 4 and 6 phr of GNP. Morphological studies using FESEM showed the GNP were evenly distributed and dispersed in the PLA/PBAT nanocomposites. The current methodology to prepare PLA/PBAT blend nanocomposite is an economical way to produce high strength biodegradable polymer which also has good flame retardancy

Mechanical and flammability properties of graphene reinforced compatibilized poly(lactic acid) / poly(butylene adipate-co-terephthalate) nanocomposites

Graphene nanoplatelets (GNP) reinforced, glycidyl methacrylate (GMA) compatibilized blends of PLA/PBAT nanocomposites were prepared by melt extrusion followed by injection molding. GMA act as compatibilizer with contents of 3, 5 and 8 parts per hundred (phr) were added to the base formulation PLA/PBAT (75/25 weight percent). GNP reinforced nanocomposites 2, 4 and 6 phr were prepared and characterized by using universal testing machine, impact tester, field emission scanning electron microscope (FESEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), limiting oxygen index (LOI) and UL-94V. Compatibilization of the blends with 8 phr GMA results in a blend with highest notched Izod impact strength. The impact strength was enhanced more than 10 times compared to the uncompatibilized blend. Tensile and flexural strengths of test specimens were evaluated and the results revealed that with the presence of GNP nanoplatelets, moderate improvement in stiffness and strength of the nanocomposites were observed. The morphological studies from FESEM micrograph showed the GNP nanoplatelets were embedded and reasonably evenly distributed in the polymer matrix. The thermal stability based on TGA results and the flame retardancy of the GNP reinforced nanocomposites were generally improved with increasing nanofillers content with the optimum at 6 phr. The FTIR analysis did not show chemical interaction between GNP nanoplatelets and polymer matrix although the mechanical and thermal properties of the GNP reinforced nanocomposites were moderately improved