Specular reflectance and derivative spectrometric studies of lac-phenol formaldehyde resin blends

Purpose - To investigate changes at molecular level in lac-resole blends, occurring due to the effect of thermal stress at higher temperatures and different intervals of baking time.Design methodology approach - Films of lac-resole blends were applied on tin-panels and baked at 200°C for different time intervals. The baked films were examined by specular reflectance spectroscopy, as they were otherwise difficult to examine through conventional IR techniques, using KBr pellet method. The results obtained were compared and reported.Findings - When lac-resole blends are baked at 200°C, in addition to possible chromic ring structures, esters linkages are formed between lac and resole molecules through cross linkages among different reactive sites of lac and PF resin. Blend of 70 per cent lac: 30 per cent resole, baked at 200°C for 20 min was found to be the best in terms of different physico-chemical properties.Research limitations implications - Lac-synthetic resin blends are structurally complex in nature. Chemical researches on such blends have been typically limited due to lack of modern tools. The present method, to determine molecular level changes in lac-resole blends due to heating effects, using state-of-the-art instrumentation and computational techniques, opens a new field for research and industry.Practical implications - Lac and its blends retain their significance in the surface coatings and food applications, in the formulation of lacquers, varnishes and in the finishing industry. This study could have significant implication for such industries from application point of view.Originality value - As of now, there is no report of specular reflectance data on lac-synthetic resin blends. This paper represents the first attempt to obtain and correlate reflectance data on such blends. It also highlights the convenience of the method and the scope of sophisticated data analysis, including derivative spectrometry.