When we use the terms "biopolymer" or "bioplastic" are we talking about a plastic material that is bio-based, i.e. based on renewable materials?
Steven Mojo: Some people will say that a biopolymer is a plastic that has a renewable content, and others will say that it is a material that is biodegradable, while others will say it`s a little of each. Many products that are on the market today are combinations of petroleum-based and renewably based materials. "Biopolymer" is one of those terms that comes into the lexicon without being defined very well.
I believe the Japanese have announced that they are going to require a 25 percent renewable content based on weight for many of these materials to be called biopolymers. But in the U.S., I don`t know that we have defined the term biopolymer in any great detail.
Recent announcements in the U.S. and Brazil that some companies can now make traditional polyethylene from the renewable resources of sugar cane and ethanol are exciting new developments in the area of biopolymers. Now you can have a traditional plastic film that`s based solely on renewable resources.
To me, there`s nothing that says that biopolymer materials need to be biodegradable, nor do they need to be 100-percent renewably based. So you could have a blend of synthetic and renewable materials that don`t biodegrade, or polyethylene that`s fully renewable, yet will not biodegrade.
That`s what makes this technology exciting, because you can look at combinations of fiber and renewable materials like PLA [polylactic acid] coatings on paper cups, and you get a fully compostable cup where biopolymers provide added value.
The realm of biopolymers is still coming into fruition, and the term is evolving as technology moves forward. Frankly, I would urge manufacturers to be as specific as possible about claims such as renewable content and biodegradability or compostability.
Can the various types of biopolymer resins on the market today be categorized?
I think what you have to look at is the performance of these materials relative to the applications for which they are being used. For example, PLA resin tends to produce a very stiff, clear material. PLA has a lot of the characteristics of polystyrene and polyethylene terephthalate. On the other hand, a biodegradable material that is made from petroleum, can also be very clear, but it`s a very soft material, and it`s suitable for making films and bags.
Another type of resin is PHA [polyhydroxyalkanoate]. [PHA resins are known as aliphatic polyesters, or a family of polymers that are made biologically by converting sunlight and carbon dioxide from the atmosphere using microbial or plant biofactories.] One example of a PHA is a new corn-sugar-based resin that is said to be a lot like polypropylene as far as its properties and its potential applications are concerned.
From what I`ve seen, "starch-based" can refer to any material that contains starch. Typically these materials are cloudy and translucent, not transparent. But I`ve also heard people talk about PLA as being starch-based. So, I don`t try to categorize the feedstocks, other than renewable versus petroleum-based.
What is most important when discussing the differences between various biopolymers is to understand their properties and their applications. It`s like the differences between PE, PET, PP and PVC. There are many, many different types of resins, and each has benefits in certain types of applications. That`s really the challenge in the market for converters: to understand which of these new resins will perform the way they want them to so they can create value for their customers.