Conjugated Linoleic Acid/Styrene/Butyl Acrylate Bulk and Emulsion Polymerization for Adhesive Applications

Abstract

Summary The incorporation of conjugated linoleic acid (CLA) into pressure sensitive adhesive (PSA) formulations was evaluated. First, a series of free radical bulk copolymerizations of CLA/styrene (Sty) and CLA/butyl acrylate (BA) were run for reactivity ratio estimation. This was followed by CLA/Sty/BA bulk terpolymerizations. Pseudo‐kinetic models were developed and validated with the copolymerization data and extended and validated for the CLA/Sty/BA terpolymerization case. The pseudo‐kinetic models incorporated the electron trapping effect of oleic acid, a common impurity found in CLA. A series of emulsion terpolymerizations of CLA/Sty/BA were then designed to investigate the influence of terpolymer composition, molecular weight, chain transfer agent concentration, cross‐linker concentration, latex viscosity and particle size on PSA performance (tack, peel strength and shear strength). Empirical PSA performance models were developed and expressed as 3D response surfaces for optimization of the PSA formulation. All experiments were performed at 80°C and monitored with attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy both off‐line (bulk experiments) and in‐line (emulsion experiments). Ultimately, the incorporation of 30 wt.% CLA into a practical PSA application suitable for removable adhesives was achieved.