Surface modifying additives, such as coupling and wetting agents, can help improve dispersion and adhesion when adding fibres, mineral fillers and nanomaterials to polymers. Glass and other reinforcing fibres are typically used at high levels to improve mechanical properties of compounds. Their effectiveness in this role depends to a considerable extent on how well they are dispersed in the polymer and on the connection between the fibre and the polymer.
Arkema’s Orevac family of maleic anhydride grafted PE and PP resins are used as coupling agents in compounds filled with glass fibre, mineral fillers, or natural fibres. The coupling agents enable the polymer to better coat or wet-out the filler component, which improves the compound properties.
Coupling agents are often used to improve properties in compounds with high loadings of halogen free flame retardant minerals, such as magnesium dihydroxide, or aluminum trihydrate . the modifier acts to create a chemical coupling between the polymer and the mineral, which results in better mechanical properties and flame retardancy. At K2016 Addivant highlighted two MAH grafted LLDPE-based coupling agents for polyethylene halogen free flame retardant wire and cable, targeted at applications that require higher elongation and reduced gel formation- polybond 3249 and 3349. Another new grade is polybond 7200, which is a higher graft-level pp-based grade for filled PP compounds.
Kenrich Petrochemicals produces Ken react titanate, zirconate, and aluminate coupling agents, which can be used with fillers that don’t react with silane coupling agents such as calcium carbonate, carbon black, carbon nanotubes, graphene, boron nitride, and fibres.
Titanate added at low levels (typically 0.2 to 0.6 phr) lower the viscosity of the filled polymer and improve flow and mechanical properties.
Mixing is key for optimizing any coupling agent performance in a compound.