MATERIALS | COMPATIBILISERS
ExxonMobil says its compatibilisers enable the
Above: Mixed packaging waste bales usually
comprise both PP and PE containers
compound that is not under control. It is necessary to know if off-spec resins are being added as it is no longer 100% recycled resin and the off-spec nature of the resin is giving variability from lot to lot. Some of these plastomers are also not as easy to mix into the recycled resin stream and the more energy that is put into the compounding step could be causing more degradation, which results in low molecular weight species or crosslinking when mixing polyethylenes that result in gels or lower melt flow rates.”
It is also necessary to know how the compound- er has mixed in the compatibiliser. “It is found in many cases that single screw extruders are used before repelletisation,” adds Cadile. “If a compati- biliser is added, this single screw may not fully disperse the additive and properly mix it, which may result in pellet to pellet inconsistency. Twin screw extruders help to ensure compatibilisers are mixed thoroughly and convertors do not see as much variation when they process.” Brand owners are making changes to facilitate
increased use of recycled materials. But some consumers are concerned that not all of the plastics they are collecting is being recycled but instead is going into landfills, adds Cadile. In order to address these issues being faced by
recyclers and end users currently, ExxonMobil has introduced a number of products for use in recycled content streams — Exact plastomers, Exxelor polymers and Vistamaxx performance polymers. The choice of product depends on what needs to be achieved, and with Vistamaxx it is possible to compound with less shear and lower processing temperatures. It is amorphous so it can incorporate the low molecular weight species that are produced after working the material multiple times and is compatible with polyethylene and polypropylene.
40 PLASTICS RECYCLING WORLD | May/June 2020
use of lower quality, lower cost recycled content sources. Vistamaxx polymers effectively compatibi- lise at low loading levels, increase process consist- ency and better overcome variability in melt flow characteristics. The melt flow of the recycled content stream can be tailored to the process requirements of the end-use application. Incorpo- rating recycled content materials often reduces the toughness of a product, but adding small amounts of Vistamaxx restores toughness. Vistamaxx 6102, Vistamaxx 6202 and Vistamaxx 6502 have been developed for customers with mixed polyolefin recycling streams. The company says that by adding 5-10% of Vistamaxx polymers to a blow moulded PCR HDPE the environmental stress cracking resistance of bottles containing recycled content can be improved. The addition of 10% Vistamaxx 6102 to PCR HDPE contaminated with around 20% PP delivers 250% higher impact strength. The addition of 5% Vistamaxx 6202 to PCR PP contaminated with around 30% PE delivers 50% higher impact strength and approaches virgin ICP impact performance. Adding 5% Vistamaxx 6102 to a film structure based on PCR PE contami- nated with around 15% PP delivers 40% higher dart impact and 20% higher tear resistance. ExxonMobil was recently involved with Chilean company Atando Cabos to turn discarded fishing ropes into high-quality end products in a project that brought environmental, social and financial benefits. Atando Cabos wanted to recycle these ropes contaminating the delicate ecosystem of Patagonia, but found they were made of incompat- ible plastics that could not be separated. Vistamaxx
Above: ExxonMobil says the use of its Vistamaxx products enables conversion of PE and PP waste into durable products such as these crates produced by Atando Cabos
www.plasticsrecyclingworld.com
IMAGE: SHUTTERSTOCK
IMAGE: EXXONMOBIL
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