COMPATIBILISERS | MATERIALS
Various specialist additives companies have developed solutions for getting immiscible polymers to work together in recycled
compounds.Peter Mapleston takes a look at the differing approaches
Making the most of the mix
Sorting technologies for plastics waste are getting better all the time, but the idea of multiple 100% pure streams of individual polymer types in post-consumer recycling operations remains rather Utopian. The picture is better when it comes to post-industrial waste, but it is not perfect. Separat- ing polyethylenes from polypropylenes is far from easy, and untying multilayer barrier films is close to impossible. Many of the mixes that have to be recycled contain polymers that are incompatible with each other, so there is a strong need for additive systems that can hold them together – compatibilisers. They come in many forms and, fortunately, they too are getting better all the time. Here is a run-through of a few of the latest developments from around the world.
Intermix Performance Materials is a startup based on technology developed in the lab of Prof. Geoffrey Coates of Cornell University in Ithaca, New York, USA (this technology was first described in Plastics Recycling World May/June 2019.) Coates says Intermix is commercialising a suite of polypro-
www.plasticsrecyclingworld.com
pylene/polyethylene block copolymers, which “provide non-covalent compatibilisation of PE and PP via entanglement and co-crystallisation. Unlike current commercial compatibilisers for PE and PP, these block copolymers function with as little as 0.5% compatibiliser, allowing the economically- viable development of superior performance polymer alloys comprised of PE and PP.” Intermix is also developing a range of related compatibilisers for other commodity plastics. At Nexam Chemical in Lund, Sweden, CMO Lars Öhrn says the company has been working on improving properties in recycled PP. “When studying different streams of recycled PP, we see that they often contain other polymers and most often PE,” he says. “One question often raised by customers is how they can get the processing performance their process demands to be as efficient and reliable as with virgin PP. We have products, like Nexamite R202, that can help increase MFR [melt flow rate] in recycled PP to fit the process.” He says: “To lower MFR in a recycled PP has
Main image: There is an increasing role for compatibi- lisers to play in plastics recycling
May/June 2021 | PLASTICS RECYCLING WORLD 41
IMAGE: SHUTTERSTOCK
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