In the field of pharmaceutical packaging, the interlayer bonding strength of high barrier composite packaging materials (such as cold-formed aluminum, polyester/aluminum/polyethylene composite film, etc.) is the basis for their protective function.peel strengthAs the core physical indicator for quantitatively evaluating this binding force, it directly determines whether packaging will fail due to delamination during molding, filling, transportation, and other processes, thereby affecting the sealing and shelf life stability of drugs.General Rule 4004 of the Chinese Pharmacopoeia 2025 EditionThe plastic peel strength determination method provides a precise standard testing method, which is a scientific basis for drug packaging material manufacturers and pharmaceutical companies to conduct raw material acceptance, process validation, and finished product quality control.

Standard Overview: Definition and Application Scope

according toPharmacopoeia 4004 standardPeel strength is defined as the ability to test a specimen of a specified width at a specific speedT-shaped peelingWhen measuring the distance between the composite layer and the substrateaverage peel forceThe unit is expressed in N/15mm. This standard is applicable to various soft and hard plastic composite materials on substrates such as plastic, aluminum foil, or paper, and is a key means of evaluating their adhesive properties and composite process quality.

Analysis of the core points of testing methods

Accurate sample preparation is a prerequisite
The standard requires uniformly cutting the width along the longitudinal and transverse directions of the sample15.0mm±0.1mmFive samples with a length of not less than 200mm each. To ensure that the peeling starts from the interface, a separation layer of no less than 50mm needs to be manually pre peeled at one end. For samples that are difficult to manually peel off, solvents (such as ethyl acetate) are allowed for local treatment, which requires the operator to have extensive experience to avoid damaging the material itself. If it still cannot be peeled off after processing, it can be directly judged as "unable to peel off", which is also an important quality conclusion in itself.

Strict environmental and equipment control are the foundation
All samples must be in23 ℃± 2 ℃, relative humidity 50% ± 5%Adjust the state under standard temperature and humidity environment for at least 4 hours, and test under the same conditions to eliminate the influence of environmental factors on the viscoelasticity of polymer materials. The accuracy required for testing isIndication error within ± 1%The material testing machine (such as high-precision intelligent electronic tensile testing machine) is the hardware cornerstone to ensure data comparability.

Standardized T-peel testing process
During testing, clamp the two layers of the pre peeled end of the sample separately onto the upper and lower fixtures of the testing machine to form a T-shape. with300mm/minThe speed for uniform peeling should not be less than 100mm, and the effective peeling distance should not be less than 100mm. The key is to ensure that the force value curve is stable during the peeling process, and the instrument needs to record the complete data in real timePeel force curveInstead of just reading a peak value.

Data interpretation and industry application value

Scientific curve analysis and result judgment
The standard requires taking values based on three typical peel force curves and calculating the average peel force. This not only requires high-precision equipment, but also requires operators to have a deep understanding of the curve shape to determine the stability of the peeling process (such as whether there is stick slip phenomenon). The final result is reported as the arithmetic mean of the vertical and horizontal dimensions, providing a comprehensive evaluation of the materialanisotropyIf the composite layer breaks during the peeling process instead of interlayer separation, it is also considered qualified, indicating that the bonding strength has exceeded the strength of the material itself.

The value of quality control throughout the industrial chain
Implementing this standard has multiple implications for the industry: forPharmaceutical packaging material manufacturing enterprisesIt is a "ruler" for optimizing composite process parameters such as temperature, pressure, and adhesive selection; Forpharmaceutical companyIt is responsible for auditing packaging material suppliers and conducting incoming material inspectionsCore Quality Control (QC)basis; For research and development institutions, it can provide key data for the development of new high barrier packaging structures. Compliant and stable peel strength ensures the integrity of drug packaging throughout its entire lifecycleKey performance guaranteeEffectively avoiding the risk of decreased barrier properties caused by packaging layering.

Frequently Asked Questions (Q&A)

Q1: What is the difference between peel strength testing and heat sealing strength testing?
A1: Both are tests for evaluating the bonding performance of materials, but the objects and mechanisms are different.heat seal strengthThe main evaluation is the strength of the sealing edge formed through hot pressing processes (such as heat sealing), with a focus on melt bonding.peel strengthIt is used to evaluate products made through processes such as adhesives and extrusion compositesMulti layer composite materialsThe interlayer adhesion force. The former concerns the local sealing of the packaging, while the latter concerns the overall structural integrity of the packaging.

Q2: What impact does it have on the results if there is significant damage to the composite layer or substrate during pre stripping of the sample? How should it be handled?
A2: The damage caused by pre stripping will seriously interfere with the test results, resulting in the measured peel strength valueAbnormally high or increased data dispersionBecause peeling may start from the damaged defect rather than a uniform adhesive interface. The standard clearly requires that 'the peeled off part must not have obvious damage'. The processing method isDiscard the sample and prepare a new one by cutting itProficient and patient manual operation and the use of appropriate auxiliary tools (such as flat tweezers) are key.

Q3: What does the severe oscillation (stick slip phenomenon) in the peeling force curve in the test report indicate?
A3: Severe oscillation of the curve usually indicates the presence of an adhesive interfacenon-uniformityPossible reasons include uneven application of adhesive, pressure or temperature fluctuations in composite processes, inconsistent surface treatment effects on substrates, etc. This oscillation phenomenon itself is important quality information, indicating that there may be stability issues in the production process that need to be investigated and improved from the production end, rather than just focusing on the average force value.

Q4: How to sample and test the peel strength of irregularly shaped composite packaging bags?
A4: For irregular bags that are not flat or have insufficient width, the standard provides flexible solutions. The sample can be cut as wide as possible according to standard methods. If the unfolded length is less than 100mm,Allow the use of adhesive tape to bond materials of the same material for overlappingTo construct a test segment that meets the length requirements. This ensures that even for complex packaging, the composite quality of its key parts can be evaluated, reflecting the adaptability of the standard in practical applications.

DisclaimersThis article is based on public standard documents such as General Rule 4004 of the Chinese Pharmacopoeia 2025 edition for technical interpretation, aiming to provide information reference and industry knowledge sharing. The details of the testing methods described in the text should be based on the officially issued standard text. The selection and application of instruments should be based on specific product specifications and laboratory certification requirements. If you have any questions or find any omissions, please feel free to communicate with us for correction.