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Improving coating properties of shellac–epoxidised-novolac blends with melamine formaldehyde resin

Mohammad Fahim Ansari (Department of Processing and Product Development, Indian Institute of Natural Resins and Gums, Ranchi, India)
Gautam Sarkhel (Department of Chemical and Polymer Engineering, Birla Institute of Technology, Ranchi, India)

Pigment & Resin Technology

ISSN: 0369-9420

Article publication date: 6 March 2017

148

Abstract

Purpose

The purpose of this study is to improve the coating properties of shellac–epoxidised novolac blends by treatment with melamine formaldehyde resin (MF) at ambient temperature for its use as a coating material.

Design/methodology/approach

Epoxidised-novolac resin was synthesised by epoxidation of novolac resin with epichlorohydrin. Novolac resin was synthesised by reaction of phenol with formaldehyde in acidic medium. Shellac was blended with the epoxidised-novolac resin in solution in varying ratios and treated the blends with MF resin in fixed ratio. Coating properties of the treated compositions were studied using a standard procedure. The compositions were characterised with Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopic (SEM) spectroscopy.

Findings

Treatment of shellac–epoxidised-novolac blends with MF resin improved water and alkali resistance of the blends, besides enhancing gloss. Gloss in all the blends was uniformly increased on treatment with MF resin. Water resistance of the blends tremendously improved after treatment with MF resin. Contact angle of the blends against water increased while decreased against ethylene glycol and dioxane. The compositions were more resistant to polar solvent than non-polar ones, suggesting that the compositions shifted to hydrophobic (lipophilic) nature on treatment with the MF resin.

Research limitations/implications

A specified concentration of MF resin was used in the study. Different concentrations of the MF resin can also be tried for treatment of shellac–epoxidised-novolac blends to see the effect of the resin on the blends.

Practical implications

Treatment of shellac–epoxidised-novolac blend with MF resin improved the coating properties of the blends. The formulation SeNB-64 is the best with high gloss, good impact, scratch hardness and water resistance, and hence can be used as coating material for metal surfaces.

Originality/value

Blending of shellac with epoxidised-novolac resin and treatment of the blends with the MF resin was done for the first time. The formulation SeNB-64 can be used as coating material for metal surfaces.

Keywords

Citation

Ansari, M.F. and Sarkhel, G. (2017), "Improving coating properties of shellac–epoxidised-novolac blends with melamine formaldehyde resin", Pigment & Resin Technology, Vol. 46 No. 2, pp. 92-99. https://doi.org/10.1108/PRT-02-2016-0022

Publisher

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Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited

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