Impact of Acrylic Polymer Molecular Weight and Groups on Physicochemical Properties and Re-Tanning Effectiveness in Leather Manufacturing

Abstract

Acrylic polymers are widely employed as re-tanning agents in leather manufacturing due to their remarkable re-tanning and filling effectiveness, which is primarily attributed to the careful selection of monomers and control over molecular weight. In this study, a series of acrylic polymer re-tanning agents were characterized for their molecular weight and functional groups, followed by analysis of viscosity, particle size, the ability to form cross-linkage with chromium, penetration properties, and filling properties in chrome-tanned leather. The results demonstrated that the viscosity, particle size, surface charge intensity, and cross-linking ability with chromium increased with the increasing molecular weight of the acrylic acid re-tanning agent. The polymers with lower molecular weight exhibited uneven distribution in leather for the potential “capillary plugging” on the surface of leather. Higher molecular weights corresponded to stronger re-tanning and filling effectiveness, though the absorption was negatively affected. Additionally, non-carboxyl functional groups such as methyl group, ester group, amide group, and cyanide group, exhibited random effects on physicochemical properties and application characteristics of acrylic polymer retanning agents. Greater hydrophobicity of functional groups resulted in higher thickening rates for leather, while enhanced ability to form crosslinks with chromium led to improved compression resistance. This elucidation of the influence of basic structure on typical physical-chemical properties and application characteristics will facilitate the development of novel acrylic polymer re-tanning agents and re-tanning technology