BYK-Chemie GmbH (Wesel, Germany) exhibited a range of processing additives and coupling agents for composites processing. On display was a new product, BYK-P 9928, a processing additive for foam-free vinyl esters. Because the primary way to cure vinyl ester resins involves standard curing agents, such as methyl ethyl ketone peroxide (MEKP), which can lead to foam formation, alternatives were investigated but were often toxic. This new additive enables the use of MEKP by slowing the cure slightly and causing the hydrogen peroxide to decompose into radicals that react with the vinyl ester, rather than forming water and oxygen, the culprits behind the foam formation. The additive has no negative influence on the part’s mechanical properties, says the company, and it comes in an easy-to-incorporate liquid form that is said to be stable for at least six months.