Effect of network morphology on adhesive performance in emulsion blends ofacrylic pressure sensitive adhesives

High-gel containing latices and gel-free latex were blended at various weig ht ratios. The high-gel containing latices was made of poly(2-ethyl hexylac rylate-stat-acrylic acid) and the gel-free latex was made of poly(2-ethyl h exylacrylate-stat-acrylic acid-stat-isobutoxymethyl acrylamide) using semic ontinuous emulsion polymerization. Films were cast at room temperature and dried at 121 degreesC for 10 min. Adhesive performance was evaluated in ter ms of loop tack, peel, and shear holding power. It was found that interlink ing the microgels by the linear polymer due to the isobutoxymethyl acrylami de-acrylic acid reaction in the film when heated gave synergistic effects i n increasing shear. This interlinking could take place only if the molecula r weight between crosslinks (M-c) of the microgels was greater than the ent anglement molecular weight of the linear polymer (M-e), and if the weight a verage molecular weight of the Linear polymer (M-w) was greater than 2 x M- e. (C) 2001 John Wiley & Sons, Inc.