Gas barrier coatings play an important role in preserving the quality of products across various fields, including food and pharmaceuticals. To accurately evaluate their performance, it is essential to select an appropriate measurement method. However, there are many types of measurement methods, each with different principles, procedures, and considerations.
This article explains the main types of gas barrier coating measurement methods and introduces how to select the most suitable approach.
Gas Barrier Coating Measurement Methods
Oxygen Transmission Rate (OTR) Measurement
The oxygen transmission rate (OTR) method measures the rate at which oxygen passes through a material. The lower the OTR, the higher the gas barrier performance. Various techniques, such as the differential pressure method and coulometric method, are available. The appropriate method should be selected according to the sample’s shape and the required accuracy. Specialized measurement equipment is necessary, and the precision and maintenance of the equipment can significantly affect the results.
Water Vapor Transmission Rate (WVTR) Measurement
The water vapor transmission rate (WVTR) method measures the rate at which water vapor passes through a material. The lower the WVTR, the higher the moisture barrier performance. Measurement techniques include the cup method and the Karl Fischer method. Strict control of measurement conditions, particularly temperature and humidity, is essential for obtaining accurate results.
Carbon Dioxide Transmission Rate (CO₂TR) Measurement
The carbon dioxide transmission rate method measures the rate at which carbon dioxide passes through a material. The lower the CO₂ transmission rate, the higher the gas barrier performance. Although its principle is similar to that of oxygen transmission measurement, the target gas differs, and therefore the required instruments and conditions also differ.
Helium Leak Test
The helium leak test detects whether helium gas leaks through minute holes or gaps in a material. It is mainly used to evaluate the sealing performance of containers and other products. Because helium has small molecules and diffuses easily, even tiny defects can be detected. For highly sensitive measurements, maintaining a vacuum environment and proper calibration of the equipment are critical.
Selection of Measurement Equipment
The selection of measurement equipment must take into account the measurement purpose, sample properties, required accuracy, cost, and measurement environment. In some cases, highly accurate measurements require expensive equipment, but it is important to balance measurement accuracy with cost. Ease of operation and maintenance of the equipment should also be considered.
Choosing Measurement Methods and Key Considerations
Clarifying the Measurement Purpose
The first step is to clearly define the measurement purpose. The appropriate method will differ depending on whether the goal is to evaluate oxygen barrier performance, water vapor barrier performance, or sealing performance. By clarifying the purpose, it becomes possible to select the right method and conduct measurements more efficiently.
Considering Sample Characteristics
The shape and material of the sample also affect the choice of measurement method. For example, one method may be suitable for film-type samples, while a different method may be better for container-type samples. Understanding the characteristics of the sample is essential for selecting an appropriate method.
Evaluating Measurement Accuracy
Measurement accuracy is another important factor. The required accuracy determines which methods and instruments should be used. When high precision is necessary, expensive equipment or experienced operators may be required.
Cost and Time
Measurements involve costs such as equipment purchase, measurement time, and labor. When selecting a measurement method, it is important to balance cost and time.
Preparing the Measurement Environment
The measurement environment can also affect the results. Conditions such as temperature, humidity, and air pressure need to be properly controlled. By preparing the environment, more accurate and reliable measurement results can be achieved.
Summary
Gas barrier coating measurement methods include oxygen transmission rate (OTR), water vapor transmission rate (WVTR), carbon dioxide transmission rate (CO₂TR), and helium leak testing, among others.
To select the most suitable method, it is necessary to comprehensively consider factors such as measurement purpose, sample characteristics, required accuracy, cost, and measurement environment. By understanding the principles, procedures, and key points of each method, it becomes possible to select an appropriate approach and achieve more accurate and reliable evaluations of gas barrier performance.
We hope this article helps deepen your understanding of gas barrier coating measurement methods.
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