Researchers at The University of Warwick have made significant progress in the search for sustainable alternatives to conventional plastics. In response to growing environmental concerns, the move towards a circular economy and changing consumer preferences, the research team has identified that certain mixtures of small organic molecules form interesting glasses and viscous liquids. These so-called organic eutectics are promising candidates for replacing polymers in various products.
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.
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.
A fresh lick of paint breathes new life into a tired looking place. Ever wondered how a thin layer of paint is so effective in hiding what lies underneath from vision? Beside colour pigments, and a binder that makes it stick, paints contain microscopic particles that are great at scattering light and turning that thin layer of paint opaque. The golden standard for these opacifiers are small titanium dioxide particles, of dimensions considerably smaller than one micron. Their use is not without controversy, as they are a big environmental burden, with a large carbon footprint and a questionable impact on human health. The reason why titanium dioxide particles are great at scattering light is that they have a high refractive index compared to the other paint ingredients, so when distributed throughout the dried paint film their hiding power of the underlying surface is fantastic. When no coloured pigments are used, the coated surface appears then whiter than white.
Ideally though, titanium dioxide should be replaced, but the list of safe high refractive materials is very limited. This makes you wonder if there is another handle, beside refractive index? Can we design efficient scattering enhancers from materials of lower refractive index?. Inspiration came from the white Cyphochilus beetle, native to southeast Asia. The scales of the beetle are not made of high refractive index materials, but they thank their white appearance to an intricate anisotropic porous microstructure, resembling the bare branches of a dense bush.
Porous materials that have an interconnected network of pores are an interesting class of materials and have drawn attention in the area of separation science. The ability to fabricate robust so-called open cellular materials with control of the porosity remains a scientific challenge. The ability of regulating the interconnected network determines how a fluid (liquid or gas) can flow through the system. Think for example of how water runs through soil, or how water can be taken up through capillary action into a sponge. In addition, one can foresee that matter which flows through the porous material can temporarily be adhered/adsorbed onto the surface of the porous monolithic structure. The ability to easily control the surface functionality of the walls of the pores therefore is important.
In collaborative work with Chris Desire, a talented PhD student from the group of prof. Emily Hilder at the University of South Australia, we in the BonLab describe in Green Chemistry that we can use polymer latex particles as colloidal building blocks to form robust open cellular porous monolithic materials by simply stacking them onto each other. This assembly process is triggered by colloidal instability of a polymer latex dispersed in water which leads to the formation of a colloidal gel. The structure of the gel can then be made permanent by cross-linking through polymerization.
From developing greener materials and processes to growing more sustainable supply chains, a new £13.6 million research hub, funded by the Engineering and Physical Sciences Research Council (EPSRC), will help researchers at the University of Warwick tackle some of the UK’s biggest manufacturing challenges.
The new Manufacturing Research Hub in Sustainable Engineering Plastics (SEP) will be led by Professor of Polymer Processes, Ton Peijs, at WMG, and has Professor of Polymer and Colloid Chemical Engineering, Stefan Bon, at the Department of Chemistry as one of the co-investigators.