Residual Seal Force Measurement of Parenteral Vials. I. Methodology

Abstract

A quantitative method for measuring the force a closure exerts against a vial finish after sealing is demonstrated using an Instron Constant Rate of Strain Testing Machine. By exerting a slow, constant rate of strain on the sealed vial, a stress vs. time curve is generated which can be correlated to the closure's “residual seal force.” A linear relationship is demonstrated to exist between residual seal force, as measured using the Instron, and the degree of closure compression exerted upon vial sealing. The Instron method is shown to be applicable to a variety of closure sizes and shapes. Residual seal forces for molded, tubing, and standard flat finish vials are compared. This new Instron technique is compared to a method of residual seal force measurement using the commercially available West Seal Force Tester.