Clean and effective curing vital for elastomer applications in pharmaceutical packaging

Abstract

Due to their excellent elasticity, penetrability and resiliency performances, elastomers are being used in a wide range of pharmaceutical packaging. Historically the major use of elastomer type in pharmaceutical packaging had transitioned from natural rubber in the early days to regular butyl (isobutylene isoprene rubber, IIR) and then chlorobutyl (CIIR) and bromobutyl (BIIR) polymers. The main driver of the transitions is cleanliness improvement.
With increasing awareness of impact of impurities in drugs on the health of patients, tighter and tighter regulations are being implemented. For example, in recent years the level of extractable and leachable becomes an important parameter for pharmaceutical stoppers to be qualified. The presence of certain impurities can also deactivate the active ingredients or cause changes in certain medicines and therefore drug compatibility of stopper is important.
Cleanliness of pharmaceutical stopper is determined by the manufacturing process and the cleanliness of each ingredient in the composition, i.e., elastomers, fillers, additives, processing aids, curing agents, etc. Elastomer, being a dominant part of stopper composition, plays an important role in cleanliness. Any additive, residue curing agent, antioxidant and other impurities present in the elastomer can potentially become undesirable extractables and leachables. Furthermore, the choice of elastomer will inevitably be associated with certain type of curing systems that could be a major source of harmful extractable. The fact that bromobutyl can be effectively cured via sulfur-free and zinc-free curing systems is a major reason for it to become the number 1 choice worldwide for pharmaceutical stopper and seals applications today.
In this presentation, we will discuss the type of curing systems required for a number of elastomers used in pharmaceutical packaging applications. This includes natural rubber (NR), isoprene rubber (IR), IIR, CIIR, BIIR and BIMSM. BIMSM, brominated isobutylene para-methylene styrene, is a super-clean elastomer for pharmaceutical packaging. We will discuss the clean and effective curing systems that could enable the use of BIIR in pharmaceutical stopper and seal applications. Extractables of BIIR compounds cured with various clean curing systems will also be presented.