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What is Oxygen Permeability Tester (OTR Tester)?
Release time:
2025-12-05
Oxygen Permeability Tester (OTR Tester)
An Oxygen Permeability Tester, or OTR Tester, is a crucial analytical instrument used to measure the barrier properties of materials against oxygen gas.
1. Introduction
The primary function of the OTR tester is to determine the Oxygen Transmission Rate (OTR) of films, sheets, and packaging containers.
OTR Definition: OTR is the amount of oxygen gas that permeates through a unit area of a barrier material over a unit time under specified conditions of temperature and relative humidity.
Common Units: The results are typically expressed in cubic centimeters per square meter per day (cm3/(m2.day)).
Significance: Oxygen is a key factor in food spoilage (oxidation, rancidity), drug degradation, and the deterioration of oxygen-sensitive electronics (like OLEDs). Accurate OTR measurement is essential for designing packaging and predicting the product shelf life.
2. Working Principles
The industry primarily uses two methods for measuring OTR: the Coulometric Sensor Method (Equal Pressure Method) and the Differential Pressure Method.
A. Coulometric Sensor Method (Equal Pressure Method)
This is the most common method, especially for testing high-barrier materials (standardized by methods like ASTM D3985).
Mechanism: The test sample divides the chamber into two sides.
Test Gas Side: Pure oxygen gas is flowed across one side of the sample.
Carrier Gas Side: An inert carrier gas (usually high-purity nitrogen) is flowed across the other side. The total pressure on both sides is kept equal (isobaric), but an oxygen concentration gradient drives the permeation.
Oxygen molecules permeate through the sample into the nitrogen carrier gas.
Detection: The carrier gas sweeps the permeated oxygen into a highly sensitive Coulometric Sensor.
Sensor Principle: The sensor contains an electrolyte where oxygen is chemically reduced, producing an electrical current. The magnitude of this current is directly proportional to the amount of oxygen that permeated, allowing for precise calculation of the OTR.
B. Differential Pressure Method
This method is based on physical pressure changes, and while it can be used for OTR, it is more commonly used for general gas permeability or for non-ultra-high barrier materials.
Mechanism: The test sample separates a high-pressure chamber (containing oxygen) from a low-pressure chamber (vacuum).
Detection: Oxygen permeates from the high-pressure side into the vacuum side. Highly sensitive pressure transducers measure the rate of pressure rise in the low-pressure chamber over time to determine the OTR.
3. Applications
OTR testing is vital across several high-stakes industries:
| Industry | Application Detail | Why OTR Matters |
|---|---|---|
| Food & Beverage Packaging | Flexible films, rigid plastic bottles (PET), food pouches, modified atmosphere packaging (MAP). | Prevents oxidation, preserves freshness, maintains flavor, and extends the product's shelf life (e.g., controlling oxygen levels in coffee, meat, or beer). |
| Pharmaceuticals | Blister packs, injection vials, IV solution bags. | Ensures drug stability and potency by protecting oxygen-sensitive compounds from degradation. |
| Electronics | OLED displays, flexible electronic devices, solar panels (photovoltaics). | OLED materials are extremely sensitive to oxygen (and moisture). Ultra-high barrier films are required, demanding testers with extremely low detection limits (10-3 to 10 -6 cm3/(m2.day)). |
| Industrial Materials | Rubber, tire inner liners, research into new bio-based films and barrier coatings. | Assessing long-term material integrity and gas retention capabilities. |
Over the past two decades, Labstone's oxygen permeability testers have been running stably for hundreds of clients across various sectors.
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