Advantages of using bio-based plastics

In fairness, plastic has had some positive impact by steadily replacing metal components. Perhaps the best examples here come from the automotive industry. Replacement of both structural and non-structural components has simplified production processes, reduced costs and critically reduced weight. And that has significantly improved fuel consumption and reduced tailpipe emissions. However, plastic materials are on the whole derived from oil, which is by definition unnatural and finite. So, can a plastics company ever really begin taking sustainability seriously? "Sustainability for DSM is extremely important," says Marnix van Gurp, director of research and technology at DSM Engineering Plastics Europe. "It is really in the core of our strategy and we want to focus all of our development on sustainability. The only way a company will last is to think about sustainability in the broader sense and we have to make that work. And in practical terms that is leading us to make materials from renewable sources." Sustainability is one of those buzzwords that everyone in industry seems to be using at the moment. Yet, despite its prolific use, it tends to be misunderstood and is commonly misused. However, for DSM the direction of its sustainable operations are clear and certainly seem to have credibility. Although relatively early days, the company sees its future, long term, in producing bio-derived plastics and view sustainability to be about sustaining the company and keeping it competitive, as much as it does about sustaining the planet. Like many of today's larger plastic manufacturers, it is perhaps less interested in what are commonly described as first-generation bioplastics such as corn-derived Polylactic Acid (PLA), and is instead developing what might be described as engineering bioplastics. DSM has to date made very significant and positive steps towards achieving its goals by cleverly combining diaminobutane with a sebacic acid. In doing so it has made a PA 410 under the brand name EcoPaXX that's suitable for use within the automotive industry. "This allows us to focus on speciality applications in the automotive and other specialist industries," says van Gurp. "We need a material that is both strong and has a high melting point if it is to be used for under-the-bonnet applications. EcoPaXX is a polymer with a melting temperature similar to PA66, which is already well established in the automotive sector, so it is a good fit." The sebacic acid used to make EcoPaXX comes from castor oil, which in turn is derived from the harvest of castor beans. The beans have a number of advantages in terms of how and where they can be grown. In countries like India they can be harvested several times a year and can be grown in poor soil not used to grow crops for human consumption. This potentially removes the beans' production from competing with food crops, a significant criticism of earlier moves toward biofuels and one DSM is mindful to not repeat with bio-plastic production. "The pace that it can be grown at means it has the potential to be a very efficient raw material, with very little environmental impact compared to other possible crops like rape seed oil or corn," says van Gurp. "It produces a very interesting polymer and we can achieve a bio-content of roughly 70% in the EcoPaXX." The move toward making it a suitable automotive plastic relied on DSMs ability to make the melting point of EcoPaXX sufficiently high to enable use within engine compartments. The team has so far been able to push the melting point to 250°C, more than adequate for under-the-bonnet applications. Bioplastics do offer some unique advantages over oil-based ones. Far from simply just replacing oil-derived plastics, they are actually bringing additional advantageous properties to the fore. "As sebacic acid is made up of relatively long monomers, it absorbs much less moisture than standard polyamides," says van Grup. "This makes the material very hydrolytically stable, even more so than PA6 and PA66. So if you have really demanding cooling applications, for example, it's actually a very nice polymer to use." And this is critical for bio-plastics. The material must offer distinct advantages over oil-based plastics in terms of weight, cost and performance. The fact it is bio-based or has less embedded carbon is not enough to convince many engineers and purchasing managers. With tough targets on tailpipe emissions set by the EU on automakers, the focus is on lightweighting and fuel economy, and not bio-based or environmentally friendly materials. "We must sell the material on more than just the fact it's bio-based," says van Gurp. "The material is, however, becoming increasingly valued by the automotive industry because it has excellent properties, but not so much because it is made from renewable sources." In addition, EcoPaXX has a very good surface finish, and while it may be used in the engine compartment the appearance of engine trim has become increasingly important over the last decade to signify quality. However, despite the potential, DSM is cautious of immediate roll-out. "While we see it as a very versatile polymer, the big volumes will not come currently because it is bio-based," says van Grup. "But, going forward, it will become increasingly applied as engineers put more importance in moving away from oil-based polymers." Sustainable future One of the greatest strengths, and weaknesses, of plastics generally is its longevity. There has been much criticism around the throwaway culture that has become part of modern society and the fact that plastics do not simply disappear, but remain in state almost regardless of the environment is a problem. While plastic materials that biodegrade might be one solution, it has been argued that actually is far from an ideal, even if it might answer some our litter problem. "DSM certainly believes in bio-based material rather than biodegradable plastic materials," says van Grup. "In the end, biodegradable materials are not sustainable, as they are designed to be thrown away." DSM has made assessments of both the carbon footprint of oil and bio-based plastics as well as carrying out full life cycle analyses of both materials. Perhaps unsurprisingly, it has shown that at the point of sale EcoPaXX is virtually neutral (cradle to grave) compared compared to an equivalent oil-based plastic. "We feel we have the responsibility of coming up with materials with a carbon neutral status" says van Grup. "But, it is a matter of having these materials in the supply chain and allowing customers easy access to them, and that means they need to accessible from a supply point of view, and an economic one." For the moment, however, EcoPaXX remains a speciality product that can be applied where required. And, currently it is not being marketed as a particularly sustainable product. "A consumer will not buy a Mercedes because it contains EcoPaXX," says van Gurp. "Mercedes market the material as a part of its total sustainability portfolio, but the focus is still on fuel consumption. The volume and big growth will depend on the economic availability and will of course be influence by future legislation."