The influence of formulation and processing parameters on the thermal properties of a chitosan-epoxy prepolymer system

Waterborne epoxy dispersions have been employed effectively for many years in response to environmental regulations aimed at reducing solvent levels in coatings. Very few non-toxic bio-based polyamines have been reported in the literature as curing agents for epoxy-functional waterborne dispersions. Currently to our knowledge the only bio-based amino hardener used to cure a waterborne epoxy prepolymer is ϵ-polylysine. Being one of the rare primary amine-containing polymers of natural origin, chitosan is produced commercially by the deacetylation of chitin. In the work reported here, chitosan and oligochitosan were evaluated as curing agents for diepoxy prepolymers. A solvent-free prepolymer (Epotec) and a waterborne prepolymer dispersion (Epirez) were both used. A crosslinked network was obtained when the reaction was performed with the waterborne epoxy dispersion. The influence of the hardener-to-epoxy prepolymer ratio on the crosslinking density was investigated. The thermal properties of networks were measured using differential scanning calorimetry and thermogravimetric analysis. © 2013 Society of Chemical Industry