Coupling agents play a key role in modifying and enhancing the mechanical properties of the filled polymer compounds. Coupling agents and other surface treatments can be added directly to the filler or fiber, or incorporated during the compounding process. In recent years the trend has been to pre-treated fillers and reinforcements in order to optimize economics and control VOC emissions. Generally they are incorporated at levels of 1% to 5% by weight of the filler/fiber. The benefits of using these additives in filled or reinforced compound include higher flexural strength, improved impact strength, better moisture resistance and surface finish/gloss, reduced shrinkage, improved weatherability, better dispersion of the filler/fiber. Much of the use of coupling agents has focused on polyethylene, polypropylene, and nylon due to the non-polar properties of these polymers. New applications for these polymers in specialty packaging films, wood-plastic composites, appliances, and transportation related components have driven much of the growth in modified minerals/fibers. All of these applications have a growth potential of over 10% pa, and for some the growth forecast exceeds 20% pa. PVC also incorporates modified fillers/reinforcements. The requirements of compounders for performance enhancement, higher through-put rates, and better economics has encouraged new and improved chemical additives.

Typically the coupling agent should have two functions: an ability to interact strongly with surface of the filler particles and an ability to interact with or chemically bond with polymer matrix.

Solplus C800, a new oligomer having bifunctional properties has the capability of interacting with filler surface via an ionic bond and can also graft on to the polymer matrix via a reactive double bond. This new coupling agent can anchor on to filler surface by acidic groups and thus behave like malieinized polymers. It does not require hydroxyl group on the surface. This new class of coupling agent was evaluated in EVA based cable compound containing higher dosage of ATH filler. When this new additive was incorporated in place of Vinyl Silane, it provided an improved balance of tensile strength and elongation.

Solplus C800, when incorporated in PP formulation containing Magnesium hydroxide also showed an improvement in mechanical properties. Solplus C800 can also be used in the composition containing stearic acid coated calcium carbonate PP filled composition. It can enhance tensile strength dramatically by almost 50% as well as impact strength. Noveon Performance Coatings has extended its product range with the introduction of Solplus C825, a powder-supported form of its novel coupling agent Solplus C800. This new coupling technology has been developed for use with basic and amphoteric fillers, and is particularly effective in increasing the mechanical properties of highly filled calcium carbonate/polypropylene composites. In a 60% filled magnesium hydroxide/polypropylene homopolymer system, both tensile strength and impact strength are increased by over 50%, whilst elongation at break is increased even more dramatically. Both are extremely cost effective, delivering an improved performance at a cost increase of just US$40/ton of composite. They show major benefits in LSFOH cabling systems, and FR composites for stadium seating and electrical trunking.