The Role of Components in Waterbased Microsphere Acrylic Psa Adhesive Properties

In this paper the batch suspension copolymerization of ethyl acrylate/2 ethyl hexylacrylate (EA/2-EHA) for production of suspension-based microsphere acrylic pressure sensitive adhesives (PSA) is presented. The effects on the adhesion properties of PSA different process (reaction temperature and stirrer speed) as well as chemical parameters (amount of EA, initiator concentration) are discussed. The conversion was monitored in-line using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and the results were compared with the standard gravimetrical method. The glass transition temperatures (T_g) of the PSAs were measured using differential scanning calorimetry (DSC) technique, while molecular weight distribution (MWD) was determined by gel permeation chromatography (GPC). The adhesion properties of PSAs were characterized via the measurements of tack, peel adhesion and peel strength. The results of the experiments have shown that the kinetics of the suspension polymerization for production of PSAs is significantly affected by temperature of polymerization and the initiator concentration, but are shown to be relatively independent of the EA amount and the stirrer speed. The tack, peel and shear strength depend on the mean particle size and particle size (PS) distribution (PSD) and T_g. The mean particle size and PSD depend primarily on the stirrer speed during the PSA synthesis process, while the T_g is most affected by amount of EA used for the synthesis. The results have also shown a rather unexpected relationship between MWD of the PSAs and the applicative properties: tack, peel and shear are seen to be increasing to the decreasing values of weight average MWD, which is the exact opposite of the previously published research. The most likely explanation for this relationship is the formation of a gel during the synthesis of PSA.