As directed by the USP and EP, elastomeric closures are made of materials obtained by vulcanization (cross–linking) polymerization, poly-addition, or poly-condensation of macromolecular organic substances (elastomers). Closure formulations contain natural or synthetic elastomers and inorganic and organic additives to aid or control vulcanization, impart physical and chemical properties or color, or stabilize the closure formulation. The testing as outlined applies to closures formulated with natural or synthetic elastomeric substances. Under specific EP test procedures, closures made from silicone elastomer have a separate and distinct test regimen assigned. The tests may be performed on uncoated or non-laminated closures of the same elastomeric compound. The Functionality Tests apply to and are to be performed using the entire laminated or coated elastomeric closure. Biological Tests apply to both the lamination or coating material and to the base elastomer. Biological Tests may be performed on the coating separately from the base elastomer, or on the coated closure itself. For all of the tests in the chapter performed on any closure type, it is important to document the closure being tested, including a full description of the elastomer, and any lubrication, coating, laminations, or treatments applied. This chapter states test limits for Type I and Type II elastomeric closures. Type I closures are those used for aqueous preparations. Type II closures are typically intended for non-aqueous preparations and are those which, having properties optimized for special uses, may not meet all requirements listed for Type I closures because of physical configuration, material of construction, or both. If a closure fails to meet one or more of the Type I test requirements, but still meets the Type II requirements for the test(s), the closure is assigned a final classification of Type II.
Relevant Elastomeric Test Procedures:
USP/NF Section <381> Elastomeric Closures
EP 3.2.9 Rubber Closures (Elastomeric)
EP 3.1.9 Silicone Elastomer – specific to closures made from silicone
Whitehouse Laboratories operates a “Container Testing Center of Excellence”. The entire business unit brings multiple levels of experience to each container testing program. Staff members with specific areas of expertise are always available to consult on your testing needs.