Due to the COVID-19 pandemic, a company which previously had its products manufactured overseas was facing difficulties to continue having their products manufactured with the COVID-19 standard of procedures that have been set in place. The company had contacted us asking us to manufacture pencil cases targeted at children. They already had a mold from their previous manufacturer which had only 1 cavity. From referencing that previous mold we designed a new mold with 2 cavities, this allowed more products to be produced within a period therefore reducing time and cost.

When it came to the material selection part of the production process, we had initially suggested using Ethylene-vinyl acetate (EVA). EVA is an elastomeric polymer and would produce materials that are rubber-like in softness and flexibility. We thought this material would be suitable as the pencil case was to look and feel like a child’s shoe. There were 2 types of EVA which were food grade and non food grade. The customer then requested that we use food grade EVA as the product was to be used by kids. Aside from that, the material has good clarity and gloss, low-temperature toughness, stress-crack resistance and waterproof properties. However, upon fabricating the part using the food grade EVA it was discovered that the material was too sticky and would not release itself from the mold.

Since the mold had already been made we didn’t give up and tried using Thermoplastic Elastomers (TPE) instead. TPE is a class of copolymers or a blend of 2 or more polymers with both thermoplastic and elastomeric properties, typically a rubber and a plastic. We used over 20 grades of TPE attempting to find a suitable material. To avoid facing the previous problem of the material of not being able to be released from the mold we tried using material with a higher shore hardness. But materials with higher shore hardness had a low shine and when we tried to use material with lower shore hardness the material got too sticky and soft. We were struggling to find a perfect balance between the shore hardness and the shininess of the material.

Finally, because of our sheer determination we found a special formulation of TPE that managed to give us a perfect balance between the shore hardness and shine. The part was then tested by our competent Quality Assurance (QA) team where they determined the part was compliant to the customer’s Certificate of Analysis (COA).