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Visualizing the drying and film formation of polymer latexes

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Visualizing the drying and film formation of polymer latexes

Polymer latex particles, typically 50-600 nm in diameter, are used in many applications, such as paper manufacturing, water-based adhesives, printing, and coatings. Commonly, a water-based formulation that contains these polymer colloids is used, often together with other components, such as pigments for opacity and color, fillers, and rheology modifiers. Each of the polymer latex particles consists of many individual polymer chains. These water-based dispersions are applied onto a substrate as a droplet or a film, after which these systems are dried. Upon evaporation of water, the individual components will pack closely. When little water remains in between, a so-called capillary under-pressure facilitates tight packing, and if the polymer latex particles are soft, it deforms them. The last stage of the film formation process is when polymer chains from one latex particle now diffuse into a neighboring latex particle and the other way around. This process ensures that the dried film has good adhesive and mechanical properties.

Visualizing this drying and film formation process in real time would greatly help in understanding how the properties of a dried film come about. In our paper, published in the American Chemical Society’s journal Langmuir, we used TeraHertz Time-Domain Spectroscopy (THz-TDS) to map the water content spatially in real-time during the drying process.

Water-Based Acrylic Latexes are excellent Pressure Sensitive Adhesives when Branched

Water-Based Acrylic Latexes are excellent Pressure Sensitive Adhesives when Branched

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.

BonLab designs a stick-on-demand adhesive for linerless labels

BonLab designs a stick-on-demand adhesive for linerless labels

Labels are big business. A typical label has multiple layers: a topcoat for protection, the face stock, which contains the message in the form of text and/or images, a pressure-sensitive adhesive, and a release liner, which often has a release coating. The release liner and coating are only there to protect the label from sticking to things you do not wish it would stick to. You remove the liner when you wish to apply the label onto your substrate of choice, for example, a bottle containing a drink.

Imagine a label without a release liner and coating, imagine a label that could be activated at the moment you want it to stick to a substrate, a stick-on-demand linerless label.

BonLab has designed and developed a concept and prototype for a sustainable solution: a mesh reinforced pressure-sensitive adhesive for linerless label design. The idea was worked out by Emily Brogden and prof. dr. ir. Stefan Bon, in collaboration with UPM Raflatac Oy, a global supplier of label materials for branding and promotion, information and functional labelling (patent application: WO2023105120A1). The complete study, which was done at the University of Warwick, is now published in the new journal RSC Applied Polymers.