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 variou s types of coatings. In particular, current research on the applicatio n of plant proteins and vegetable oils in coatings systems is addresse d. In ongoing plant protein research at ATO-DLO corn, but particularly wheat gluten, was modified chemically to obtain aqueous protein dispe rsions that have excellent film-forming characteristics and strong adh esion 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 b y 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 th e observed characteristics of the modified protein binders the develop ment 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 convention al as well as new oilseed crops. A very interesting new vegetable oil originates from such crops as Euphorbia lagascae and Vernonia galamens is, 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 reacti ve diluent. Another interesting new oil is derived from Calendula offi cinalis, or 'marigold'. This oil contains >63% of a C18 conjugated tri ene fatty acid (8t,10t,12c-octadecatrienoic acid or calendic acid) lik e that in tung oil. Current research is focused on the film-forming ab ilities of these oils and of chemical derivatives of these oils, in pa rticular in emulsion systems.