Water-based pressure sensitive adhesives (PSAs) are typically made by emulsion polymerization using a low glass transition temperature base monomer, such as n-butyl acrylate or 2-ethyl hexylacrylate, together with a range of functional comonomers. Typically these include a high glass transition temperature comonomer, such as styrene or methyl methacrylate and monomers that can promote wetting and undergo secondary interactions such as (meth)acrylic acid.
A golden rule for good adhesive performance is that the polymer latex particles must contain a certain fraction of gel, that is, cross-linked material. This typically is 50-70%. This gel content optimizes the balance between tack and cohesive forces within the adhesive.
Schematic of the branched polymer chain architecture approach to deliver good performance in pressure sensitive adhesives (PSAs).
In our paper, led by PhD researcher Emily Brogden and published in the RSC journal Polymer Chemistry, we challenged this view. Prof. dr. ir. Stefan Bon says: “We designed a range of polymer latexes with low gel content. To balance the adhesive forces, we introduced a branched polymer chain architecture instead. We show that excellent water-based acrylic PSAs can be made using this approach.”
Moreover, the chemical composition of our PSA was designed with sustainability in mind. The base monomer selected was the bio-based 2-octyl acrylate, the high Tg component bio-based 2-isobornyl acrylate. The other monomers and chain transfer agent show promise to be or become fully bio-based.
The paper entitled “Water-Based Polymer Colloids with a Branched Chain Architecture as Low-Gel Pressure-Sensitive Adhesives” has gold open access and can be read here: