As more giant packaging users such as Kraft Foods Inc. are taking sustainable packaging seriously, green packaging issues are reportedly even limiting the demand for virgin polymers (as did the recession), according to a European report – partly because producers are trying to use more recycled plastics and less resin overall in their products.
Meanwhile, the automotive industry is encountering related trends, and its own unique challenges. The industry is facing mandates in the USA for much higher fuel consumption efficiency (+50 miles per gallon) by 2025. Ways for increasing mileage include reducing average vehicle weight, not only by using more plastics and polymer composites instead of metal – but also by trimming mass from current plastic parts.
Minimizing the resin used in products is also a goal of packaging producers, and a couple methods used by the auto industry for doing this can also be applied to packaging. These methods were explained at a new annual conference called “Plastics in Lightweight & Electric Vehicles”, presented this past week in Livonia, Michigan, USA, by the publisher of Plastics News and European Plastics News.
Foaming is one approach for lightweighting. A presenter from Trexel discussed its MuCell process, where a physical foaming agent (nitrogen) is injected as a supercritical fluid into the polymer melt in the plasticating (screw) phase of the molding process. The dissolved gas then triggers the nucleation of foam cells inside the molded product, resulting in a product that’s 20-35% lighter than a corresponding solid product, but still having a solid, aesthetic part surface. MuCell isn’t just for large, thick products; company president Steve Braig said that it has been used in producing a sub-millimeter-thick food packaging part. The process, however, does require some capital investment in processing equipment.
Mass optimization is another method. For example, HyperWorks computer software from Altair Engineering, Inc. is being used to show where and how much plastic can be cut from different areas of a part without it losing key mechanical properties. In using the software, a designer first picks an objective for reducing mass on a part (such as thinner reinforcing ribs) and chooses property constraints (such as how much the part is allowed to deflect under load); the software then provides design options that optimize material use.
At the conference, it was also interesting to hear how automakers’ sustainability goals match those of the plastics packaging sector -- and how they don’t:
- Both sectors seek to reduce material usage and CO2 production using life-cycle studies and other tools, though automotive plastics manufacturers seem relatively unconcerned about the recyclability or biodegradability of their products, at least when compared with packaging makers.
- Companies in both sectors are very careful about the financial risks of making major process or material changes for sustainability.
- And they’re both responsive to consumer demands, though plastics have a relatively negative public image in packaging, compared with the relatively neutral or even positive image of plastics in automotive. (And given growing demand worldwide for personal automobiles – with hundreds of millions of new vehicles produced for India and China over just the next couple of decades – there’s still no sign of bans on automobiles as there are for certain packaging products!)
For more automotive-minded readers, here’s a great blog summary of the broader issues discussed at the conference.
Mike Tolinski is the author of Plastics and Sustainability, published in Oct. 2011 by Wiley-Scrivener, and he is Contributing Editor for Plastics Engineering magazine of the Society of Plastics Engineers in the USA. His views have been shaped by his engineering, university, and journalism experience in the plastics and manufacturing industries over the past 21 years.