Waterborne acrylic-melamine latexes with controlled film microstructure

Abstract

Crosslinkable latexes aim to improve the physical properties of coalesced latex films, over levels attainable with thermoplastic latexes, which lackthermal, mechanical and solvent resistance. This work investigated the synthesis by miniemulsion polymerization of waterborne acrylic-melamine nanocomposites with the aim of obtaining high solid-content latexes (50%) with controlled crosslinkable capability. Changes in both the acrylic polymer microstructure (i.e., content of hydroxyl groups and molecular weight) and the amount of melamine (a commercial iso-butylated melamine-formaldehyde resin) showed a significant influence on the crosslinking degree, and consequently on the final properties of cured films at high temperature. It was observed that reducing molecular weight of acrylic polymer allowed a good chain inter-diffusion during the course of film preparation, increasing crosslinking occurrence. Also, the content of hydroxyl groups and melamine could promote the enhancement of final film properties.