Effect of poly(L-lactide-co-ε-caprolactone) macromonomer composition on the properties of hot-melt adhesives with high biomass contents

Recently, an approach was introduced for incorporating renewable biomass into existing commercial acrylic thermoplastic pressure-sensitive adhesive (PSA) polymers in the form of acrylated macromonomers (MM). This was achieved without sacrificing adhesive performance. Here a study is reviewed on the influence of N-hydroxyethyl acrylamide capped poly(L-lactide-co-ε-caprolactone) MM composition on the properties of acrylic hot-melt adhesive. A series of MMs containing a broad range of lactic acid and caprolactone repeat units were synthesized using catalyzed ring-opening polymerization. These MMs were substituted for 2-ethylhexyl acrylate in a commercial formulation to generate adhesive polymers via solution polymerization. Results indicate that the properties and performance of adhesive polymers are strongly dependent on the lactide content in MMs. In general, increasing lactide relative to caprolactone increases polymer hardness enhancing cohesive strength, while reducing it softens the polymer. Optimal adhesion is found to require a balance between these tendencies, as indicated by the existence of a clear maximum in both tack and peel data. The results demonstrate that a broad range of properties is achievable through changes in composition.