Swelling phenomenon in rubber weatherstrip manufacturing under real process conditions imposed in a commercial extrusion line

Abstract

We investigated the swelling under different process and boundary conditions in a commercial weatherstrip extrusion line. For the experimental investigations, we used two extrusion-dies and three compounds. An in-situ laser optical measurement set-up was used immediately after the die-exit to measure die-swelling. The traditional projection-based measurement method was used at the end of the line to measure the swelling of the cured extrudate. A dimensionless number, namely Extrudate Speed Number (ESN) was defined as the ratio of the average speed of extrudate at the die exit to the puller speed. We used ESN to analyze die-swelling. Two extrusion-dies were designed to extrude strips with axisymmetric and rectangular cross-sections with low and high aspect ratios. We tested solid and sponge compounds for their swelling behavior. Independent of the die shape and compound, it is found that dimensionless swelling tends to increase with the increase of ESN and vice versa. However, the gradient of the dimensionless swelling with respect to ESN can differ depending on the compound, extrudate shape, and the direction for which swelling is measured.