Paints and coatings from renewable resources

Abstract

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, recent developments in the application of (new) vegetable oils and plant proteins in coating systems are addressed. Regarding vegetable-oil-based binders, current research is focussed on an increased application of oils from conventional as well as new oilseed crops. A very interesting new vegetable oil, for example, 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 tri-ene fatty acid (8t,10t,12c-octadecatrienoic acid or calendic acid), analogous to the major fatty acid in tung oil. Presently, research aims at evaluating film-forming abilities of these oils and of chemical derivatives of these oils, both in solvent-borne and water-based emulsion systems. In research on industrial applications of plant proteins, corn, but particularly wheat gluten has been modified chemically to obtain protein dispersions that have excellent film-forming characteristics and strong adhesion to various surfaces. Especially wheat gluten films have very interesting mechanical properties, such as an extensibility of 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 e.g., varying the degree of cross-linking of the protein binder.