Modification and Characterization of Shellac Through Hydrolysis and Polyesterification as Biocomposite Nanik Dwi Nurhayati
Faculty of Teaching and Education, Sebelas Maret University, Surakarta
Abstract
The aim of this study was to improve shellac properties through modification of the hydrolysis and polyesterification processes. The process of hydrolysis by extraction uses NaOH. The process of polyesterification with the addition of phthalic anhydride in the varied concentration of 5%, 10%, 15%, 20% and 25% w/w.
The analysis results showed an absorption in the intensity shellac hydrolyzed and shellac polyesterification caused to the hydrolysis process which resulted in the break of natural shellac polyester groups into carboxylic monomers (-COOH) as evidenced by a strongly the absorption of the hydroxyl group at 3425,58 cm-1 indicates the hydroxyl group is not hydrogen bond and the reduced CO absorption at 1300-1000 cm-1 is a characteristic of the ester group. Shellac polyesterification with phthalic anhydride showed absorption at 2931,75 cm-1 the presence of an alkane group (-CH). Absorption at 1450,47 cm-1 presence of methylene group and absorption at 740,67 cm-1 the presence of a benzene ring phthalic anhydride supported by the absorption of the carbonyl group 1249,87cm-1. Analysis the value acid of natural shellac was increased after the hydrolysis process to 6,79 because the ester shellac bonds (C=O) were broken into carboxyl groups (-COOH) and the number of hydroxyl groups (-OH) increased. The polyesterification process caused the acid value is decrease because added shellac with phthalic anhydride to acidic properties and releases H+ so that shellac becomes acidic than addition-crosslinking between the -OH group in shellac so the number of C=O groups increases and the OH group decreases cause in increased acidity. Analysis intrinsic viscosity shellac of 36,77mL/g and hydrolysis shellac 29,44 mL/g. The optimum modification of polyesterification of shellac-phthalic anhydride of 48,36 mL/g indicated a reaction between shellac with phthalic anhydride so that the polymer chain formed the longer occurs in the straight-chain -OH group.
