Case Studies

Case Study: Food Storage Container Housing Gasket Seal

School lunch box with sandwich, vegetables, juice and almonds on table. Healthy eating habits concept.

A coworker recently gave me a plastic food storage container to evaluate. Apparently, his daughter filled the container with watermelon and took it along to school.  At lunch, she found that the watermelon juice had leaked inside of her backpack. This came as a surprise since the clear plastic lid had a visible blue o-ring housing gasket seal.

The Problem

The storage container was made of quality clear plastic with two hinged snaps to securely fasten the lid to the container. The lid had what looked like a molded o-ring gasket pressed into a channel. As for the container, a nice flat flange could be seen around the perimeter for the housing gasket to seal against.  

Food container 1

I tested the sample containers by filling them with water and securely fastening the lid with the two snap features. When turned on its side, the water leaked freely from the container.

Our Discovery

An FTIR test indicated that the gasket material was a TPE (thermoplastic elastomer).  The hardness of the o-ring housing gasket was in the 65 Shore-A range. There was an obvious gate mark on the molded parting line of the gasket.  Ejector pins with significant flash could also be seen on the sealing surfaces of the gasket. 

food container 2

After measuring and comparing the housing gasket cross-section to the gland depth of the plastic lid, there was minimal squeeze or interference on the sealing component. Apple Rubber recommends a compression range between 10% and 30%

After researching the seal, it’s clear that the plastic food container is not a watertight device. However, it’s important to note that the manufacturer of this product promotes it as a food storage container, not a sealed liquid-tight container. Just because there is a nice colored o-ring housing gasket in the lid does not ensure that it’s designed to be a functional sealing component. 

Unfortunately, the o-ring housing gasket appears to be more for marketing than performance.  If you are looking for a sealed food container, be sure to read the detailed description to ensure it is designed for that purpose.