COMPATIBILISERS | ADDITIVES
Developments in compatibilising and coupling technology aim to enhance the performance of plastic compounds while expanding opportunities for recycled materials, writes Mark Holmes
Making polymers more compatible
Compatibilisers and coupling agents have long played a key role in the compounding sector for their ability to improve the performance of virgin polymer compounds containing fillers. However, today they are also increasingly being used to help upgrade recycled materials — carefully selected compatibilisers can allow the successful combina- tion of dissimilar polymers, overcoming unwanted negative effects on mechanical and physical properties. Compatibilisers fall into three general catego-
ries, according to Salvatore Monte, President of Kenrich Petrochemicals, which manufactures the Ken-React range of coupling agents and compati- bilisers, as well as plasticisers and other speciality chemicals. “Malleated polymers can couple polymers, but not fillers and non-polymeric materials found in recycled plastics,” he says. “In recylates, they work best on sorted materials, particularly addition polymers such as olefins. However, they may cause depolymerisation of
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condensation polymers such as PET and polyam- ides. Secondly, there are bi-polar polymers. These additives contain both polar and non-polar chemical structures to link polymers that would otherwise be incompatible, and work well with post-industrial recyclates. Finally, organometallic coupling agents can repolymerise polymers and couple fillers. They require reactive compounding in an extruder polymer melt and are synergistic with other compatibilisers.” Kenrich has developed compatibilisers and coupling agents for a wide range of applications. For virgin polymers, Ken-React CAPS L 12/L is a titan- ate coupling agent in a masterbatch pellet form. Coupling agents provide molecular bridges at the interface between two substrates, says the company, usually but not limited to an inorganic filler/fibre and an organic polymer matrix. Titanium-derived coupling agents react with free protons at the inorganic interface resulting in the formation of organic titanium monomolecular layers on the
Main image: Compatibilisers play a key role in lifting the performance of a range of virgin and recycled polymers,
including TPEs
May 2023 | COMPOUNDING WORLD 41
IMAGE: KRATON CORPORATION
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