Mechanical properties and morphology of poly(lactic acid)/ modified natural rubber blends

Chor. Wayakron Phetphaisit



The blending of poly(lactic acid) (PLLA) with 2 types of modified natural rubber, namely: hydroxyl epoxidized natural rubber (HENR) and hydroxyl natural rubber (ONR), was investigated. The study was carried out using low molecular weight poly(lactic acid)-g- hydroxyl liquid natural rubber (LMW.PLA-g-HLNR) and DL-lactide-g- hydroxyl liquid natural rubber (lactide-g-HLNR) as compatibilizers. The PLLA blends were compounded using an internal mixer and compression moulded into specimens for mechanical testing. Tensile tests and impact tests were performed in order to compare and contrast the mechanical properties of the blends. It was found that the tensile strength and impact strength of the PLLA/HENR blend (70:30) without compatibilizer decreased markedly compared with PLLA, while the elongation at break increased slightly. The addition of 2 wt% LMW.PLA-g-HLNR increased the impact strength and elongation at break but slightly lowered the tensile strength relative to virgin PLLA. In contrast, the PLLA/HNR blends of all compositions did not show any clear improvement of mechanical properties. The effects of the addition of starch and glycerol were also studied from which it was found that the elongation at break increased but the tensile strength decreased compare with PLLA.

Keywords: Poly(lactic acid); Polymer blend; Modified natural rubber; Compatibilizer

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