Modification of latex microstructure and adhesive performance using d-Limonene as a chain transfer agent

Core-shell latex-based pressure-sensitive adhesives comprising n-butyl acrylate, styrene and acrylic acid were prepared via two-stage seeded semi-batch emulsion polymerization. d-Limonene (Lim) was used as a renewable chain transfer agent. Adhesive performance was modified by manipulating the microstructure of both the latex particle cores and shells. In the first stage of the polymerization, the concentrations of Lim and divinylbenzene (DVB) crosslinker were varied to alter the core microstructure and thus, the cohesive strength of the adhesive films. The particle shell microstructure was modified in the second stage of the polymerization by varying only the amount of Lim. As a result, a variety of particle microstructures and morphologies were generated. Tack and peel strength decreased with increasing Lim concentration while shear strength showed a maximum at a moderate core Lim concentration of 2 phm. Empirical models were developed using stepwise regression to correlate tack, peel strength and shear strength to Lim concentration in the core/shell and DVB concentration in the core.