GB/T 16929-2025 in English

Background of Standard Revision and Technological Evolution

GB/T 16929-2025 "Test Method for Oil Permeability of Packaging Materials" is the first major revision of the 1997 version of the standard. This revision fully takes into account the development of packaging material technology and changes in actual application needs in the past 30 years, especially the special requirements in the fields of food packaging, pharmaceutical packaging, etc. While maintaining the original test principles, the new standard has comprehensively optimized key links such as term definitions, test equipment, sample processing, and test conditions.

Detailed Explanation of Major Technical Changes

Compared with the 1997 version, the new standard has made the following important adjustments to the technical content:

Standardized term definitions

The new standard clearly defines three key terms: oil permeability, flat specimen and folded specimen for the first time:

Oil permeability refers to the property of a material that allows oil substances to pass through or penetrate its internal structure. This definition accurately describes the oil resistance of packaging materials from the perspective of physical properties. Flat specimens are required to have a smooth, crease-free surface, while folded specimens require a specific folding process to simulate the creases that may occur in packaging materials during actual use. The test principle remains unchanged: the specimen is placed in contact with an oil-soaked cotton pad, and the time it takes for the oil to penetrate the material is measured. However, there are significant updates to the instrument configuration: the base plate must be a single-sided frosted glass measuring 50mm x 50mm x 3mm, and the weight must be a 50g cylinder with a base diameter of 20mm. Of particular note, the new standard replaces the original folding rod with a 5.5kg square metal rod, significantly improving the standardization of the folding process. The thickness measuring instrument must comply with GB/T6672 (plastic film) or GB/T451.3 (paper products) to ensure the accuracy and comparability of thickness measurement results.

Specimen Preparation and Handling Specifications

Specimen Requirements

Specimens should be uniform in thickness and free of defects such as wrinkles, creases, and holes. The new standard has eliminated the existing sampling quantity and procedures, placing greater emphasis on the actual quality requirements of the specimens.

Environmental Conditioning

Specimens must be conditioned in an environment with a temperature of (23±2)°C and a relative humidity of (50±5)% for at least 24 hours. The new standard allows for greater flexibility in selecting appropriate temperature and humidity conditions based on the actual use environment, reflecting the guiding principle of integrating standards with practical applications.

Specimen Size and Quantity

Flat specimens must measure 100mm×100mm, with a minimum of three specimens required; folded specimens must be at least six (three facing up and three facing up). Thickness measurements must be accurate to three significant figures to ensure the accuracy of the test data.

Critical Control Points in Test Procedures

Temperature control during the test is a key factor. The new standard provides three standard temperature levels: 40°C, 60°C, and 100°C, while also allowing the selection of the actual operating temperature to accommodate the application requirements of different packaging materials.

For silicone-oiled paper intended for food contact or materials suitable for high-temperature use, the test temperature can be selected at either 100°C or the actual operating temperature. This provision fully accounts for the unique characteristics of high-temperature applications.

The test oil must be added to allow it to penetrate without flowing. Viscous or solid oils can be melted by heating. Volatile test oil requires regular replenishment. These detailed regulations ensure the stability of test conditions.

Test Result Interpretation and Reporting

The new standard incorporates significant improvements in result interpretation: the oil breakthrough endpoint is observed against a black background, and oil breakthrough is manifested as a decrease in brightness in dotted or patchy areas. Most importantly, the oil breakthrough time is now reported as a time interval, such as '54 min to 60 min.'

For oil breakthrough times exceeding 240 hours, it is recommended that the result be reported as greater than 240 hours. This interval-based reporting method is more scientific and reasonable, avoiding potential misjudgments caused by absolute time values. The test report must include complete information, including laboratory temperature and humidity, test date, specimen type, oil type, test temperature, observations, average specimen thickness, and the maximum and minimum oil penetration range. The new standard requires testing equipment that meets the requirements, specifically a frosted glass bottom plate, a precision drying oven (accuracy ±1°C), and a standard-compliant thickness gauge. The laboratory environment should be able to strictly control temperature and humidity. Operator Training Operators must master key skills such as specimen folding techniques and determining the oil penetration endpoint. In particular, the preparation of folded specimens must strictly follow the standard's procedures to ensure accurate pressure and timing applied by the metal rod.

Quality Control Applications

Manufacturers can use this standard as an important basis for incoming raw material inspection, production process control, and finished product quality inspection. It is recommended to establish a database of oil permeability for different oils and temperatures to provide data support for product development and quality improvement.

Expanded Industry Applications

This standard is not only applicable to traditional packaging materials, but can also be expanded to emerging areas such as medical packaging and electronic product packaging. In practical applications, appropriate test oils and test temperatures can be selected based on the specific product usage conditions to enhance the test results' value.

Standard Implementation Precautions

When implementing the new standard, special attention should be paid to the following points: the test oil should be selected as close as possible to the actual packaging contents; the test temperature should be set to reflect the material's actual usage environment; observing the oil permeability endpoint requires experience, and comparative testing is recommended; test reports must be complete and accurate, especially the determination of the oil permeability time interval must be scientifically and rationally determined.

In addition, for special materials (such as composite materials and coatings), supplementary testing protocols may be necessary to ensure the representativeness and reliability of the test results.