Unfortunately, the mold has significant undercuts, making it difficult to remove plugs from the mold without tearing them and leaving pieces stuck in the mold. And the mold’s surface would get so dirty with silicone, the mold had to be removed every two weeks for 8 hr of cleaning.
To avoid an expensive redesign of the tool, the company used the KE2004-20 Series of silicones from Shin-Etsu Silicones of America, Akron, Ohio, which are said to have the highest tear strength of any silicone on the market. The new silicone also has good release properties, so earplugs could be removed from the mold without tearing and still have a soft feel. Other benefits include less maintenance on the mold tool and a 60% drop in scrap, which explains a 100% improvement in productivity.
McKeon invented silicone earplugs for swimmers in 1962. Mack’s Pillow Soft silicone earplugs have been a top seller ever since.