Effect of temperature on removal torque of discontinuous-thread plastic closures.

摘要

This thesis investigates the effect of high and low temperature extremes on the removal torque characteristics of a linerless plastic closure. An initial torque of 12 in-lbs was applied to polypropylene (PP) and cross-linked high density polyethylene (HDPE) closures of the same design. After exposure to temperatures ranging from 60°C (140°F) to -18°C (0°F), the closures were removed from the bottles while removal torque was recorded, and percent torque reduction was calculated.; A significant (p .01) torque reduction was observed in the control group, varying from 44.6% to 57.5%. Exposure to high temperature had a noticeable effect on removal torque; the highest torque reduction was 79.4%, found on the PP closures exposed to 60°C. The lowest torque reduction was 35.4%, found on the cross-linked HDPE closure exposed to -18°C. The data indicate that removal torque is greatly affected by exposure to different temperatures, and that closure material is also an important factor.