Permeation Rate
Quantitative measurements of the amount of oxygen gas that passes through a flat substance over a specific period define the protective capacity of a barrier layer. This otr is typically expressed in cubic centimetres per square metre per day. It is a necessary metric for packaging sensitive items that are prone to oxidation or spoilage.
Testing Protocol
Environmental conditions such as relative humidity and temperature significantly affect the measured values for many polymer films. Standardized tests for otr often utilize coulometric sensors that detect oxygen molecules in a carrier gas after they have diffused through the sample. One side of the material is exposed to a known concentration of oxygen while the other is purged with an inert gas like nitrogen.
Keeping the pressure balanced across the film prevents mechanical stress from skewing the results.
Barrier Selection
Shelf life extension for nuts and snacks depends on maintaining a low rate of gas ingress to prevent rancidity. When designers choose a coating or a laminate, they compare the otr of different materials to find the most cost-effective solution for the required protection. High-performance barriers like metallized films or ethylene vinyl alcohol layers are used when extremely low transmission is necessary.
Understanding how this value changes after the material has been flexed or creased is essential for predicting real-world performance.
