Formation and Characterization of Shellac Phthalate Succinate through Organic Solvent-Free Reaction

Abstract

The objective of this study was to synthesize shellac phthalate succinate (SHL-PHT-SUC) through organic solvent-free reaction. Firstly, shellac phthalate (SHL-PHT) was prepared by co-grinding and annealing shellac (SHL) with phthalic anhydride (PHTA). The SHL-PHT was subsequently ground with succinic anhydride (SUCA) and activated by the same process to obtain SHL-PHT-SUC. The formation of all SHL derivatives was investigated by the monitoring acid value, insoluble solid and later confirmed by FTIR spectroscopy. The result indicated that the acid value was increased after annealing SHL-PHT with SUCA, suggesting the addition of succinate moiety at SHL-PHT molecule. The presence of C-O stretching of ester linkage was also observed in the FTIR spectrum. The results suggested the formation of SHL-PHT-SUC by esterification. In addition, the thermal stability was assessed by ageing the SHL derivatives at 100°C for 24 h. The SHL-PHT-SUC demonstrated lower stability as compared to SHL-PHT. The stability of SHL derivatives appeared to be related with the cross-linking of the polymer chain. In the case of SHL-PHT-SUC, succinate group, having more molecular mobility, this might encourage fast and extensive cross-linking as compared to the phthalate group and thus promoted the ageing process.