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Considering the global megatrend that sustainability has become, the adhesive industry had a bit of a head start. After all, natural materials like tree sap were used as the earliest adhesives known to man, and starches have provided renewable options for adhesive formulations in packaging applications for decades.
In addition, hot melts have long represented a significant segment of the adhesive industry; as 100% solids materials, they are inherently quite sustainable. The early shift away from solventborne formulations is another significant example.
“The adhesive industry started to transition from solventborne toward alternative sources like water and hot melt way back in the early 80s, so we were really well ahead of the curve compared to other industries from that perspective,” says Daniel Murad, president of ChemQuest.
Despite the early start and many successes, the adhesive and sealant industry continues to face sustainability-related challenges. The typical “reduce, reuse, recycle” mantra is deceptively simple. In reality, the massive complexity associated with sustainability can create a significant roadblock; with no single clear path forward, directives often falter.
“A major challenge for adhesive companies has been that their customers haven’t defined and decided what they want to do, as far as sustainability is concerned,” says Abe Rezai, ChemQuest senior vice president. “There are so many different options, adhesives go to so many different product lines, and customers in most cases have not really clarified the sustainability direction they have set for themselves.”
The task can seem formidable. However, adhesive and sealant companies have and will continue to support both their own sustainability efforts and those of their customers, along with the desires of end consumers.
End-Use Advancements
Many adhesive and sealant manufacturers have successfully worked to make their operations more environmentally friendly, whether by reducing waste, air emissions, water usage, or other initiatives. While adhesives can also certainly positively influence a finished product’s sustainability, the adhesive generally represents a tiny component of a much larger finished part. Recyclability offers a good example of this issue.
“Part of addressing recyclable content really is completely out of the hands of the adhesive industry,” Murad says. “Adhesives can be enablers, but they’re not the major substrate. Take a diaper, for example. If a diaper is going to be 100% recyclable or compostable, the nonwovens, the Velcro®, the core materials all have to be recyclable and/or compostable. If the adhesive is the only recyclable component, it can’t make a big difference because those other non-recyclable materials are still there.”
One area where adhesives are having a more direct impact is in the transportation sector. Lightweighting initiatives developed in response to increasing automotive emissions regulations have prompted design engineers to increasingly turn to adhesives as replacements for traditional fasteners such as nuts and bolts.
In addition, demand for electric vehicles (EVs), which themselves represent an environmentally friendly alternative to cars and trucks powered by traditional internal combustion engines, continues to rise. Though beset by its own challenges (e.g., lack of charging-related infrastructure), this sector offers numerous exciting opportunities for adhesives.
The global market for EV adhesives was estimated to be $1.4 billion last year; it’s expected to see strong growth at a CAGR of 8% through 2028.1 Primarily liquid adhesives (polyurethanes, epoxies, silicones, and acrylics) are being used throughout EVs to bond body frames, optical components, sensors, radar systems, and more.
Adhesives enable EVs to extend their driving range (the lighter the vehicle, the less battery power required to move it, and the farther it can travel without charging). They also support EV safety through heat management, helping to avoid thermal runaway and protecting the vehicle and its occupants.
Renewable Raw Materials for Adhesives
Many companies—within the adhesive and sealant industry and beyond—seek to improve circularity through the replacement of traditional hydrocarbon-based materials with more renewable alternatives. The chemical sector has embraced this demand and turned to bio-based development with fervor. (Globally, the value of the bio-based chemicals market is expected to reach $181 billion by 2028.[1]) As a result, myriad bio-based alternatives are commercially available for adhesive manufacturers.
Incorporating these bio-based materials in adhesive formulations does not come without challenges, however. The first and biggest of these is cost.
“The problem in every aspect is scale,” Murad explains. “Over the last five, six decades, we’ve refined the synthetic route, which involves oil and/or natural gas at huge-scale crackers that are pushing out a million pounds of material per week at a very low cost. In contrast, a biomass plant is expensive, the capex is expensive, and they don’t achieve the same degree of yield. Scale-wise, they wind up being much more expensive.”
The second challenge is performance. Bio-based materials often struggle to impart the same properties as their synthetic counterparts. While some are essentially equivalent to existing formulations, most bio-based materials tend to be at least somewhat inferior.
The combination of these two factors—higher cost and lower performance—has been difficult to overcome. “Consumers are not willing to pay for bio-based materials at the margins that would make that business viable long term, particularly when they don’t work as well,” Murad says.
Improving the cost efficiency and performance of bio-based materials is not the only avenue open for the exploration of innovative renewable raw materials for adhesives and sealants. Other efforts are focused on investigating chemical recycling processes and their possible contribution toward circularity.
For example, the pyrolysis process involves the use of heat and catalysts to break down polymers into their monomer components. The resulting monomers (e.g., propylene, butylene, butadiene) can then be reused to produce new products instead of adding to the waste stream.
“Many of the large oil companies, which are all motivated to show that they have an ESG philosophy, have put together pilot-scale facilities to demonstrate that this is doable,” says Rezai. “They are now working to understand how the process can be scaled up economically.”
Continuous and Evolutionary Improvement
The adhesive and sealant industry has made great strides in optimizing operations and reducing the carbon footprint, enabling recyclability efforts, expanding into environmentally friendly applications, addressing bio-based and other renewable materials, and so much more. However, continuous long-term improvement remains absolutely necessary.
Some of today’s technology development efforts are focused on alternative energy sources for curing processes, such as radiation, microwave, and ultrasonic. And new applications are being explored for thermoset resins (e.g., two-component polyurethanes and epoxies), which are among the fastest-growing technologies in the adhesive space. As high-solids materials (often 100%), they represent an elevated level of sustainability.
Absent a clear and defined global sustainability standard, companies around the world are focusing on initiatives that align with their portfolios and capabilities. While these various efforts can seem disjointed or fragmented, it is important to keep in mind that, overall, progress is still being made every day.
“Let’s go back to the diaper example. Twenty or even 30 years ago, the industry was talking about diapers being recyclable,” Murad explains. “Are they all 100% recyclable today? Not typically. But think of it in terms of an evolution, starting with 15% of that diaper being recyclable or using recyclable material and evolving over time to 30, 40, 50, 70%. Aren’t we better off continuously improving down that path, as opposed to sticking to an all-or-none philosophy?”
To learn more, contact the author at ssutton@chemquest.com.
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Reference
1. V. Scarborough, “A Heat Map of New Technology in a Post-Pandemic World,” 2023 CoatingsTech Conference, Cleveland, Ohio, June 2023.