MATERIALS | COMPATIBILISERS
T S
R
effect of fillers and impurities on end-product properties, which requires a high degree of expensive sorting, separating and cleaning. Another barrier is the melt processing of polymers causes chain scissoring resulting in recycle and regrind materials having inferior properties compared to virgin. Current compatibilisers offered to recyclers are based on co-polymers or maleic anhydride modified polymers (MAH). Co-polymer compatibilisers require extensive sorting to match up the polarities of the recycled materials and MAH depolymerises condensation polymers such as PET and polyamide, preventing their use in post-consumer recycling. Monte says MAH technology claims to be a coupling agent, which is true for rebuilding molecular weight, but not when applied to coupling filler and organic interfaces. Kenrich uses either a monoalkoxy or neoalkoxy titanate in combina- tion with aluminium silicate mixed metal catalyst in powder and pellet forms for in-situ macromolecular repolymeri- sation and copolymerisation in the melt. Monte says this facilitates polymer compati- bilisation and the neoalkoxy titanate proton coordinates with inorganic fillers and
organic particulates to couple/ compatibilise the dissimilar interfaces at the nano-atomic level, reducing the need for expensive sorting of materials in recycled plastics. Also, many
Above: BYK has developed a number of compatibilisers and coupling agents for deal- ing with mixed recycled polymers
compounders are familiar with silane coupling agents, which limit filler and organic interface coupling to hydroxyl bearing materials such as silica and fibreglass. This categorises fillers such as calcium carbonate, barium sulphate, carbon black and organics such as oils, as contaminants. In addition, silane use requires knowledge of hydroly- sis mechanisms and techniques usually outside the realm of melt recycling compounders. Nano-titani- um technology applied at the interface of dissimi- lar materials is the Holy Grail of plastics recycling, claims Monte. The Compound Company emphasises the
importance of mechanical recycling for the plastics industry. “We need to make our industry more circular and mechanical recycling of thermoplastics constitutes a large piece of that,” says Wouter van den Berg, Commercial Director. “In addition, unless the recycle stream is extremely pure, compatibilis- ers and stabilisers are required to optimise the
18 PLASTICS RECYCLING WORLD | May/June 2023
quality of the regranulate. Current legislation and directives, on national and European levels, push for recycled content of all plastic articles. There is no choice but to make our products recycle-ready and to develop technologies for recycling further. While mechanical recycling has the advantage of the lowest energy consumption, there is also the need for other forms of recycling, such as chemical and dissolution.” Miscibility of different polymers can be improved
quite efficiently with thermoplastic compatibilisers, says van den Berg. “For example, film waste of multilayer barrier film – with PA or EVOH as barrier polymer – can be recycled well into a high quality granulate,” he says. “However, a mix of PE and PP, the two most abundant polymers which seem rather similar, proves quite difficult to recycle mechani- cally. The challenge is to be able to deal with the many combinations of polymers that are found in recyclate streams, or polymer-filler combinations.”
Multiple materials The Compound Company says that in the Yparex- Exxelor product portfolios it has added grades that can handle combinations of polymers including polyolefins, PMMA, polycarbonate and polystyrene. The company has also developed a coupling agent for glass-filled PP that has an extremely low volatile content. In addition, there are chain extender additives for the mechanical recycling of PET, where viscosity control is particularly important. There are also chain extenders for PLA. The EcoForte chain extenders are an easy-to-dose masterbatch. They react with broken polymer chains and control molecular weight. This is important in using PET and PLA in high viscosity applications such as blow moulding or extrusion. A new development is a tie resin for multilayer film, based on mechanically recycled polymers. The recycling and regeneration of post-consum- er and post-industrial material flows faces two major obstacles, according to BYK. “Firstly, a basic polymer rarely meets the full required property profile, meaning that compounds of different materials are frequently used,” says Jörg Garlinsky, Head of Global End Use Thermoplastics – Industrial Applications. “These can take the form of a blend, for example PC/ABS, or a combination of unmixed polymers such as multi-layer films. Secondly, separation of pure materials cannot always be ensured by mechanical means, particularly in these multi-material systems.” However, there is also the desire of brand owners and OEMs to use more recycled material without compromising on the properties of virgin
www.plasticsrecyclingworld.com
M I
A
E G
S
:
U
H
K T T
C
O E
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58
