Requirements for Styrene Block Copolymers

Following the previously published Ph. Eur drafts for COC / COP, a new Ph. Eur. chapter 3.1.18. Styrene block copolymers for containers and closures for parenteral preparations and ophthalmic preparations has been proposed in Pharmeuropa 34.2. The comment deadline is 30 June 2022.

Definition

The general chapter defines styrene block copolymers (SBCs) as thermoplastic elastomers (TPEs) which consist of styrene, butadiene, isoprene and isobutylene monomers in different ratios. They may contain additives and can be mixed, blended or alloyed with other polymers. The microstructure of SBCs is characterized by hard polystyrene domains that link polydiene or polyisobutylene elastomeric chains.

Additives & Tests on Extractable Elements

SBCs may contain additives (e.g. antioxidants, lubricants or antiblocking agents) to optimize their processing or their chemical, physical or mechanical behaviour. The additives which can be used (unless otherwise justified and authorized) are provided in the proposed Ph. Eur. chapter together with a maximum permitted content. Moreover, catalysts may be added to facilitate production. These substances can be extracted and therefore need to be tested (i.e., aluminium, titanium, zinc, nickel, cobalt and lithium). The content of these extractable elemental impurities (maximum 1 µg/g of sample) is determined using a validated analytical procedure according to the principles defined in general Ph. Eur. chapter 2.4.20 Determination of elemental impurities . Other extractable elements are limited according to the (draft) general Ph. Eur. chapter 2.4.35. Extractable elements in plastic materials for pharmaceutical use. Tests on e.g. antioxidants, stearates, are carried out only if required by the stated composition of the material (supplementary tests).

The supplier of the material must be able to demonstrate that the qualitative and quantitative composition of each production batch complies with that of the type sample (‘type sample’ according to Ph. Eur. general chapter 3.2.2. Plastic containers and closures for pharmaceutical use).

More information can be found after registration on the Pharmeuropa website.