Bio-based solvent identification and evaluation for use in polyurethane resin binders for the roofing industry

Solvents are an important component in roofing coatings; they stabilise formulations and enable the liquid resin to flow into a smooth membrane. Currently, the majority of solvents used in the roofing chemicals industry are petroleum-based. A project led by construction materials specialist Sika Ltd aimed to find more sustainable, bio-based alternatives to help the construction industry transition to a low-carbon economy.

The traditional industrial approach to identifying new materials is to source and test existing ones – a process that incurs high lab-testing costs and long product development times. With funding from the Transforming Foundation Industries Challenge, this innovative project took a new approach that accelerated and de-risked the research.

The team worked with sustainable chemistry consultants Green Rose Chemistry, using their extensive database of bio-based solvents and specialist solvent software to identify potential sustainable alternatives. Crucially, the team also investigated the selected solvents' economics and available supply chains.

"There are a large number of potential bio-based alternatives, but many of these would not be commercially viable, either because they are too expensive or because they are not available in the volumes we need," explains Michelle Round, Technology Centre leader, Sika Ltd.

"This project enabled us to narrow down the options that were technically compatible with our resins but also had the appropriate supply infrastructure in place. It saved time and money because we only conducted the expensive lab testing on the validated options as both scientifically and economically sound."

“[The project] saved time and money because we only conducted the expensive lab testing on the options that were validated as both scientifically and economically sound.”

Dr Anna Zhenova, CEO of Green Rose Chemistry, adds: "Our computational approach to solvent selection lets us screen thousands of solvent candidates instantly, using three-dimensional mapping to identify unconventional options that outperform traditional solvents. In this case, we found a high-performing option, then followed up with economic assessment to ensure it was available and affordable at the scale Sika needed."

The most promising bio-based solvents were tested in Sika Ltd's product development labs to assess their performance and short-term stability. The project identified at least two options that worked in Sika Ltd's polyurethane roofing membrane formulations. As well as improved sustainability, bio-based solvents also have potential health and safety benefits when used by roofing contractors compared with some of the cheaper petroleum-based solvents, including lower odour and reduced volatility due to a higher flash point.

"We are now incorporating the bio-based resins into a number of product developments, including manufacturing small pilot batches, and anticipate we will have a product on the market within the next couple of years," says Michelle Round.

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