Synthesis and Characterization of Liquid Natural Rubber as Impact Modifier for Epoxy Resin

Abstract

Liquid natural rubber (LNR) with a molecular weight Mn =16×103 was prepared by the depolymerization of deproteinized natural rubber latex (DPNR). The liquid natural rubber (LNR) was characterized by FTIR and H’NMR spectroscopic analysis. LNR was premixed with the epoxy resin (EP) and cured with a diamine curing agent for 1 h at 100 °C and post cured at 110 °C, for 2 h in air oven. The modified EP containing different contents of LNR (5, 10, 15 and 20 phr) were evaluated. Thermal, mechanical and morphology properties were determined. The fracture toughness (KIC) of both unmodified and modified EPs were determined on static loaded single edge notched (SEN-B) specimens at room temperature. The glass transition temperatures (Tg) of the modified EPs were decreased with increasing LNR content. The strengths and modulus of EPs were slightly reduced with the incorporation of LNR. The effect was also reflected in the significant increase in the tensile strain of modified EP. Fracture toughness of the EP was observed to increase with the presence of LNR. The toughening effect became more apparent as the testing speeds were increased from 1 to 500 mm/min. Fracture surface analysis by scanning electron microscopy (SEM) revealed the presence of a two-phase morphology.