Effect of n-methylolmethacrylamide content on viscoelastic properties of poly(2-ethylhexyl acrylate-co-acrylamide) latexes

The present study investigates effect of internal cross-linker, n-MMAc (n-methylolmethacrylamide) and external cross-linker, HMDI (Hexamethylene diisocyanate) at various amounts on 2-EHA (2-ethylhexyl acrylate)-co-AAm (acrylamide)-based latex designed for determination of viscoelastic properties. n-MMAc was incorporated at 0.50, 1.25, 1.75, 2.50, 3.25% s/m ratio into butyl acrylate-based latex via seeded semi-batch emulsion polymerization procedure. HMDI was added at 0, 1 and 2 wt. % ratio to the latex synthesized in the presence of various n-MMAc ratios. Films of the copolymers were then partially crosslinked through reaction of the isocyanate functions with an amine or a hydroxy group. The study focuses on the effect of cross-linker content on the rheological properties, adhesion strength, and crosslinking density, which was determined using the solvent swelling method. Results showed that increasing the crosslinking density by varying the amounts of n-MMAc and HMDI reduced the adhesion strength, highlighting the correlation between crosslinking density, rheological behavior, and adhesion. This research provides a comprehensive analysis of how crosslinking density influences the viscoelastic properties of the copolymers, which is essential for understanding their overall material behavior.