ADDITIVES | COMPATIBILISERS
Right: Coupling agents can improve adhesion in PA/TPE
overmoulding applications, according to Polyscope
between PA substrate and the over-moulded material, leading to an excellent adhesion and a high quality final part,” he says. Doelen cites the example of one PolyScope customer that was using a PP-g-MA type polymer to increase the adhesion between TPE and PA, explaining that by using Xibond180 at a 5% addition even better adhesion was achieved.
Bio branches out Also branching out into new areas is Yparex, previously part of DSM and now part of the Dutch holding The Compound Company. It has been known for some considerable time for its extrud- able adhesives (polyolefins modified with maleic anhydride), which are used for multilayer barrier food packaging as well as multilayer pipes. For the last few years, however, the company has also been offering polyolefin-based coupling agents and compatibilisers with extremely low amounts of residual maleic anhydride. “A high level of residual maleic anhydride causes worries for the injection moulders regard- ing the surface quality of the moulds,” says Frank Huijnen, Business Development Manager at Yparex. “In addition, the trend towards more sustainable compatibilisers is noticeable. Yparex was the first to offer bio-based products. We expect to also have biodegradable compatibilisers available within a few months. Furthermore, there is a trend towards compatibilisers for new material combinations like PE-PC.”
Below: Properties of WPCs can be enhanced significantly using Clariant’s functionalised Licocene waxes
WPC options Clariant has developed a range of maleic anhydride (MAH)-grafted metallocene waxes, branded Licocene, and one target application is polyolefin- based wood-plastic composites (WPCs). The maleic anhydride is grafted onto an olefin backbone. The MAH-grafted moiety is free to react, or couple with, the cellulose (wood), while the long chain end of the
wax entangles itself with the olefin base polymer (be it LDPE, LLDPE, HDPE or PP) of the WPC. AS a result, the strength of the composite is improved and, as the two materials now flow as one, the flow is more lamellar and the flow rate increased. Extrudates are also said to have a smoother surface and show improved water repellency. Clariant says common structural reinforcers and
fillers like calcium carbonates, glass, talc and chalk are also better coupled to the host polymer when using MAH-grafted Licocene waxes. “Of course, with glass fibres and certain mineral fillers, the bonding is more centred around coupling with the surface treatments, such as the amino group of aminosilanes often used with glass fibres, or the organic acid treatment of certain minerals,” says Frank Neuber, Regional Technical Segment Manager, Clariant Plastics and Coatings, Business Line Advanced Surface Solutions. “The new interfacial boundary is now more
complex and deeper than just a surface bond, which improves adhesion and can augment impact results, as the [now] more complex and deeper interface dissipates force better. This can be seen in structural profiles, 3D printing stock and injection moulded heavy-duty articles.” Laboratory data has confirmed that the coupling
effect seen with the high percentage (6-7% MAH) grafted PE-MAH and PP-MAH Licocene waxes greatly improves the tensile strength, E-modulus and impact strength of the filled olefin compounds, so allowing more durable products which replace traditional wood or metal applications.
Melt blending US-based PolyGroup, a marketer of specialty thermoplastic polymer products, points to two grades made by Two H Chem in Korea. Novacom and Novacom-P are specifically designed to provide compatibility and to act as coupling agents
50 PLASTICS RECYCLING WORLD | May/June 2018
www.plasticsrecyclingworld.com
PHOTO: CLARIANT
PHOTO: SHUTTERSTOCK
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