Biobased latex adhesives from isobornyl methacrylate and plant-oil-based acrylic monomers

A range of cross-linkable latex copolymers with biobased content of up to 90% was synthesized from isobornyl methacrylate combined with acrylic monomers based on high-oleic soybean oil (HO-SBM) or camelina oil (CMM) through miniemulsion polymerization. By varying the HO-SBM and CMM macromolecular fractions, the cross-linking density of the resulting materials can be altered due to differences in the fatty acid profiles of the plant-oil-based monomers. The glass transition temperature of the synthesized copolymers correlates very well with the calculated Flory–Fox values. A higher cross-linking density of the biobased copolymer films leads to a notable growth in the modulus of the materials, while the elongation at break decreases due to more restricted macromolecular mobility. Remarkably, the copolymer with the highest unsaturation degree in the investigated range (based on CMM) shows an increase in both the modulus and elongation at break, due perhaps to extended entanglements of fatty-acid-based side chains. The adhesion performance of the cross-linked biobased copolymers was evaluated by performing shear and peel strength measurements on steel and polypropylene. Based on the obtained results, the unsaturation degree of CMM and HO-SBM (determined by plant oil composition) can be applied as a criterion for adjusting adhesion by choosing plant-oil-based monomers (or their mixtures) with different unsaturation degrees to achieve properties and performance required for specific applications.