Thermoplastic elastomers, or TPEs, deserve a post of their own, as they are an interesting polymeric family that is not very well known. You can find a good introduction in Wikipedia. If you are not familiar with Wikipedia, give it a go, you’ll be surprise how thorough it can be considering is free. Just be careful to check the facts elsewhere afterwards, as anyone can edit an entry and some are almost like corporative pages.
Coming back to the initial issue, TPEs have rubber and thermoplastic properties. This combination of properties is achieved by blends of elastomers and thermoplastics or by using copolymers. Usually elastomers are thermosets and the crosslinking is by a covalent created during vulcanisation. TPEs crosslinked thanks to weaker bonds or by bonds being created in only one of TPE’s phases.
In the previous table you can see types of TPEs commercialised, some companies that produced them and their trade name. Links are at the bottom of the post. Arkema and DuPont have already announced the launching of renewable versions of their elastomers. DuPont is clearly shifting its strategy, focusing on sustainability. Its moto for its renewable materials range is:
Dupont Renewable Sourced Materials – an idea whose time has come
And no doubt its time has come, because DuPont has forged an alliance with Tate & Lyle, one of the biggest sugar producers in the world, to commercialise Bio-PDO. This diol is sourced from corn and DuPont is already using it in other materials, like Sorona. Bio-PDO can be transformed into a poliol, called Cerenol, replacing the oil based poliol used in the production of Hytrel’s, DuPont’s TPE. Hytrel‘s renewable content, when synthesised with Cerenol, can range from 20 to 60%.
Arkema counts on a different natural resource: castor oil. Thanks to it Arkema produces Rilsan 11, a totally renewable polyamide. Arkema also commercialises Pebax, a traditional TPE, in this case a polyamide copolymer. By mixing Rilsan 11 and Pebax, Arkema can provide the market with Pemax Rnew, a partially renewable TPE, .
In June 2008 I joined a teleconference organised by Omnexus. On it, Merquinsa presented its new product, Pearlthane Eco, a thermopolyurethane (TPU) from renewable sources. Merquinsa, like DuPont and Arkema, is a traditional chemical company, but unlike them is focused on especialised TPUs. Merquinsa has certified its new renewable TPU range by using the ASTM-D6866, which has proved their TPUs have between 30 and 90% of renewable content. I haven’t found out yet the renewable source used by Merquinsa, so if anyone out there knows, do let me know.
These are just a few examples on how chemical companies substitute oil based products by natural compounds, generally using just one source, like corn, sugar cane or castor oil. This limitation is due to the resources or know-how that needs to be acquired by petrochemical companies in such a new area as biorefineries. Those companies investing time and money now in this area are working in the long term diversity of their portfolio.
Obviously this is not the only advantage of these materials. They are also added value products, always needed in a healthy range of products. Some of TPEs applications are high range anyway; this should ease the introduction of a new product. Similarity in properties between renewable products and oil based ones should also help, as processes do not need to be modified.
I personally agree with DuPont’s slogan, the time has come.