Lactic acid oligomer (OLLA) grafted gum arabic based green adhesive for structural applications

Abstract

L-Lactic acid (LA)-grafted-gum arabic (GA) graft copolymer [OLLA-g-GA] was prepared by using microwave heating in which the hydrophilic GA was grafted with insitu grown lactic acid oligomer. The grafting at OH and NH groups in GA backbone with oligo-(l-lactic acid) (OLLA) chains proved with the help of FTIR and NMR analyses. The grafted GA was dispersed uniformly in OLLA due to the formation of amphiphile GA backbone grafted with OLLA chains, which is supported by XRD, SEM and TEM analyses. This synthesized OLLA-g-GA graft copolymer showed adhesive characteristics with various substrates such as glass and granite. The single lap shear joint of two glass and two granite substrates were fabricated and the adhesive properties of these laminated substrates were tested using Universal Testing Machine. The synthesized biobased adhesive showed excellent shear strength with respect to the present biobased adhesives and substrate failure was observed at optimized conditions during the shear test.