Renewable resources in coatings technology: A review

In recent years an increasing interest is observed in the development of more environment friendly paints and coatings. This paper discusses advances in the use of renewable resources in formulations for various types of coatings. In particular, current research on the application of plant proteins and vegetable oils in coatings systems is addressed. In ongoing plant protein research at ATO-DLO corn, but particularly wheat gluten, was modified chemically to obtain aqueous protein dispersions that have excellent film-forming characteristics and strong adhesion to various surfaces. In particular, wheat gluten films have very interesting mechanical properties, such as an extensibility over 600%. Gas and moisture permeabilities were found to be easily adjustable by changing the exact formulation of the protein dispersion. Durability and water resistance of the coatings can be tailored by, for example, varying the degree of crosslinking of the protein binder. Based on the observed characteristics of the modified protein binders the development of novel, organic solvent-free paints and coatings appears to be well within reach. Regarding vegetable oil-based binders, research at ATO-DLO and elsewhere includes the application of oils from conventional as well as new oilseed crops. A very interesting new vegetable oil originates from such crops as Euphorbia lagascae and Vernonia galamensis, which have high contents (> 60%) of an epoxy fatty acid (9c,12,13 epoxy-octadecenoic acid or vernolic acid) that can be used as a reactive diluent. Another interesting new oil is derived from Calendula officinalis, or 'marigold'. This oil contains >63% of a C18 conjugated triene fatty acid (8t,10t,12c-octadecatrienoic acid or calendic acid) like that in tung oil. Current research is focused on the film-forming abilities of these oils and of chemical derivatives of these oils, in particular in emulsion systems.