26 April 2013 12:52 [Source: ICB]
Innovation must address performance and cost issues as well as ecological concerns. Work is focused on bio-feedstocks and replacing harmful intermediates
Green chemistry is revolutionising industry and academia alike. Environmentally-friendly products are appearing across many diverse end-use markets, including adhesives and sealants.
Copyright: Rex Features
For John Warner, who developed the 12 Principles of Green Chemistry with Paul Anastas, sustainability is a competitive and performance issue. Warner, president of the Warner Babcock Institute for Green Chemistry in the US, says: "Everyone is looking at sustainability, but, unfortunately, in this business climate, cost and performance cannot be sacrificed for the environment."
According to Warner, new products should address all three areas of performance, cost and environment. If a company goes to market with a product that performs exactly like its predecessor, but with a greener profile, then it is unlikely to be successful, he warns. The first rule to be observed on sustainability, is a product's success in the market. He says: "No matter how wonderful it is for the environment, if that product sits on the shelf, it is not helping the environment."
Developments to date have concentrated on producing adhesives from bio-resources such as starch, soy and vegetable oil. For example, polyols from an agricultural feedstock such as soybeans can be used in polyurethane (PU) adhesives and sealants. Gecko lizards, and their natural van der Waal interaction which allows them to stick to vertical surfaces, have provided inspiration for tapes and other adhesives.
SHIFT FROM SOLVENT BASE
Much interest is being shown too in fermentation product malonic acid and vinyl malonate compounds, which is an area of focus for BioFormix. The US-based firm is developing sustainable polymer platforms that polymerise with little or no energy at high speeds, with the ability to outperform current products.
The industry has worked hard to shift from solvent-based feedstocks and the majority of sealants and coatings are now water-based. However, there remain certain applications, such as bonding wood products, where it is more difficult to move away from solvent coatings and it will take some time, says David Constable, director of the American Chemical Society's (ACS) Green Chemistry Institute. "There will continue to be challenges but it is about investing in new chemistries and being smart with innovation," he says.
Removing volatile organic compounds (VOCs) remains the largest challenge for adhesives and sealants manufacturers. Constable says that the main problem here is in the curing step, where a lot of VOCs are present.
Another area seeing a tremendous amount of development work is in alternatives for urea-formaldehyde (UF) and isocyanate/PU systems. UF has been largely used in the wood panel industry because of its high reactivity, good performance and low cost, but studies have shown it to be an irritant and potential carcinogen. Constable says customers are concerned about exposure to UF and want to move to safer alternatives.
BPA IS THE NO. 1 ISSUE
Many PU adhesives used for wood and flooring contain polyisocyanate compounds, and epoxy resins used in flooring commonly contain bisphenol A (BPA), which is currently the subject of environmental and health toxicity concerns.
Warner says that BPA used in coatings is the number one issue for manufacturers at the moment. BPA has infiltrated into so many products, that there is not one single replacement. A principal alternative is bisphenol S (BPS) but Constable says there are early indications that it has the same issues as BPA. "The industry is pulling its hair out to find a replacement," he comments.
Becoming more innovative to meet society's needs is Warner's key message. He says there is a perception that sustainable solutions exist and that industry is choosing not to use them. His belief is that these solutions have not been invented yet and no viable alternatives exist. "We are going to have problematic compounds for decades. There is no magic switch to turn green tomorrow, so we are going to have to invent," he states.
Constable believes the markets that will see the most innovation and largest changes are specialities and high, value-added products, rather than commodities where barriers to entry are higher for an entrepreneur.
A product's life cycle is gaining more attention with increasing consideration being given from start to end: from raw materials, through synthesis and formulation, process and application, to the consumer and ultimately, end of use.
End of life needs to be considered in design, otherwise opportunities will be missed, Constable asserts. Researchers are identifying materials that can return to their original state and are more readily biodegradable and products are being designed for dematerialisation, deconstruction and reuse.
The primary issues for Warner surrounding green chemistry are misperception and education. He says that people hear green, and see red, believing that the concept of turning to greener solutions results in being more expensive. But greener technology can save money by lowering environmental, health and safety costs, and reducing the number of synthetic steps in a process, leading to shorter production times.
Industry has historically manufactured everything at high pressure and high temperature, notes Warner. "Nature outperforms us, by pre-assembling molecules that react at ambient pressure and temperature. Bio-mimicry at the molecular level can influence green chemistry," he says.
He is working hard to promote the addition of green chemistry to curricula in schools and universities through his non-profit organisation, Beyond Benign, which is dedicated to sustainability and green chemistry education. "People can do green chemistry, it is common sense," he says.
The ACS Green Chemistry Institute is also encouraging smart, green chemistry-inspired innovations, by hosting a business plan workshop for entrepreneurs and working with established businesses to catalyse and enable industry-specific solutions.
The shift to a more sustainable product portfolio is providing strong growth opportunities for adhesives and sealants manufacturers who are constantly investing in new and improved products. Providing the irresistible combination of superior performance and cost, as well as ecological benefits, will ensure that people beat a path to your door, summarises Warner.
ECO-TECHNOLOGY SET TO TRANSFORM HOT MELT
A unique, corn-soy based, eco-friendly technology is under development that could transform the market for hot melt adhesives. Based on polylactic acid (PLA), PLATech is being developed jointly under a research and development agreement between Sagamore Adams Laboratories (S/A Labs), based in Lafayette, Indiana, and Chicago, Illinois, and the Metastable Fluids and Advanced Research Laboratory (MFARL) at Purdue University in West Lafayette, Indiana.
Commercialisation of the technology is already underway in select applications such as hot melt gun and spray-based uses. Alexander Bakken, a graduate researcher at MFARL, says PLATech offers the ability to tailor bond strength for a customer's application, and can exceed bond levels of standard epoxies. "Only up to about 2,000 psi (pounds per square inch), can be reached for standard epoxies, but our tests for PLATech have shown over 6,000 psi," says Bakken.
Other advantages over conventional, petroleum-based adhesives include the ability to gain full functionality and use of the bonded materials within seconds to minutes after application; being able to use existing applicators such as hot glue guns; joining substrates without the need for surface preparation or the use of pressurisation, and the ability to join an exceptionally wide range of substrates as well as sealing holes or crevices.
Bakken says Purdue University and S/A Labs are exploring other application areas for PLATech. He says there are no commercial adhesives made from PLA on the market currently, and the majority of hot melt adhesives are manufactured from polyamides, urethanes and ethylene vinyl acetate (EVA).
"The industry is looking for eco-friendly options going forward. Our PLA product is 100% based on renewable feedstocks and is biodegradable. This is a big difference," states Bakken, adding that although many new technologies are appearing, they are not solely based on eco-friendly sources.
The hot melt adhesive sector accounted for 20% of North American adhesives demand, valued at $1.7bn, in 2011, when the ASC released its last market study. This global survey of adhesives and sealants markets is due to be updated in June this year, with projections on a three-year horizon.
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