Characterization and evaluation of natural copal gum-resin as film forming material

Copal resin (CR) was investigated for its physicochemical properties, which are yellowish cream in colour with acid value 129.82 ± 2.38, saponifi cation value 172.60 ± 4.03, ester value 42.78 ± 3.19, softening point 88-92°C, glass transition temperature (Tg) 85.29°C, refractive index 1.534-1.536 and moisture content (loss on drying) 0.699 ± 0.08% w/w. Th e free fi lms, prepared in alcohol by solvent evaporation technique, were brittle with high tacking property. Addition of 1% w/w propylene glycol improved the mechanical properties (tensile strength, percent elongation and Young’s modulus) of CR fi lms, whereas glyceryl monostearate, sorbitan mono-oleate and sorbitan monolaurate in 15% w/w reduced the tackiness signifi cantly. Water vapour transmission rate of CR fi lm was 2.16 ± 0.31 × 10–5 g cm/cm2 and 4.13 ± 0.18 × 10–5 g cm/cm2 at relative humidity (RH) of 43% and 93%, respectively. CR fi lms show good swelling property in phosphate buff er (pH 7.4). Present investigation proposes the fi lm-forming natural material with its potential as a coating material for sustained release and colon-targeted drug delivery. Key words: Copal resin, fi lm-forming material, fi lms, mechanical property, tackiness, swelling index Abbreviations: Copal resin, Copal resin, WVTR, water vapour transmission rate, LOD, loss on drying, RH, relative humidity