Sealing Performance Testing of Packaging – Package Seal Integrity Determination

Sealing performance testing of packaging, also known as package seal integrity determination, verifies that sealed packages reliably prevent leakage of their contents and ingress of external contaminants throughout handling, distribution, and storage. This article explains the technical principles behind packaging seal integrity determination, the applicable standards such as ASTM D3078, ASTM F2096, and GB/T 15171, common test methods, typical sample types, and industry applications.

Technical Overview

Package sealing performance determination is a laboratory evaluation used to confirm that the seals, closures, seams, and overall structure of a package maintain hermeticity under specified conditions. A package seal is considered integral when no continuous leak path exists that could allow the escape of liquid or gaseous contents, or the entry of air, moisture, microorganisms, or particulate contaminants. Seal integrity directly affects product shelf life, sterility assurance, weight or volume consistency, and consumer safety.

Seal failures typically originate from process or material variables, including insufficient sealing temperature, pressure or dwell time, contamination in the seal area, wrinkling or creasing of the film, misaligned sealing jaws, channel leaks along the seal width, and pinholes introduced during forming, filling, or transport. Determination of sealing performance identifies these defects through deterministic or probabilistic leak testing combined, where required, with quantitative seal strength measurement.

The most widely applied standards for this determination include:

• ASTM D3078 – Determination of leaks in flexible packaging by bubble emission under vacuum
• ASTM F2096 – Detecting gross leaks in packaging by internal pressurization (bubble emission)
• ASTM F88 – Seal strength of flexible barrier materials
• ASTM F1929 and ASTM F3039 – Detecting seal leaks by dye penetration in porous and non-porous medical packaging
• ASTM F2338 – Non-destructive detection of package leaks by vacuum decay
• ASTM F2054 – Burst testing of flexible package seals by internal air pressurization
• ASTM D4991 – Leakage testing of empty rigid containers by vacuum method
• ISO 11607 – Packaging for terminally sterilized medical devices
• GB/T 15171 – Test method for leakage of flexible packages
• GB/T 17344 – Evaluation of sealing performance of flexible packages
• JIS Z 0238 – Testing methods for heat-sealable flexible packages

Accredited third-party laboratories routinely perform these determinations to support product development, validation of sealing processes, routine quality control, and regulatory submissions.

Testing Samples

Flexible Packages

Flexible packages include three-side-seal pouches, four-side-seal pouches, stand-up pouches, pillow bags, retort pouches, and vacuum skin packs produced from monolayer or multilayer laminated films. Samples are typically tested in their filled and sealed commercial configuration to reflect actual sealing process conditions, although empty packages may also be evaluated for material-related defects.

Rigid and Semi-Rigid Containers

This category covers plastic bottles, glass jars and bottles, metal cans, drums, and containers sealed with screw caps, snap-on lids, crimp closures, or induction seals. Testing focuses on the closure-to-body interface, gasket or liner performance, and the integrity of welded or seamed joints.

Medical and Pharmaceutical Packaging

Sterile barrier systems such as thermoformed trays with lidding film, Tyvek pouches, blister packs, ampoules, vials with elastomer stoppers, and prefilled syringes require strict microbial barrier integrity in accordance with ISO 11607 and applicable pharmacopoeial expectations. These samples are often tested both after production and after simulated distribution stresses.

Food and Consumer Product Packaging

Vacuum-packaged foods, modified atmosphere packaging (MAP), aseptic cartons, sachets, and cosmetic containers are tested to confirm headspace retention, flavor and aroma protection, and prevention of moisture or oxygen ingress.

In general, samples should be representative of normal production, free from visible pre-test damage, conditioned at standard laboratory atmosphere (typically 23 °C ± 2 °C and 50% ± 5% relative humidity) unless otherwise specified, and supplied in sufficient quantity, commonly five to ten specimens per condition or sampling plan.

Testing Items

The scope of sealing performance determination typically includes the following evaluations:

• Gross leak detection across the entire package, covering seals, body material, and closures
• Micro-leak and channel leak detection along heat seal areas
• Pinhole detection in flexible films and laminates
• Seal strength determination expressed as peak force or average peel force per unit seal width
• Burst pressure resistance of seals under internal pressurization
• Creep resistance, evaluating seal behavior under sustained static pressure
• Closure, gasket, and liner integrity for bottles, jars, and cans
• Integrity verification after simulated transport, altitude, or sterilization conditioning

Testing Methods

Vacuum Bubble Emission Method (ASTM D3078, GB/T 15171)

The specimen is submerged in a transparent liquid, usually water with a surfactant, inside a vacuum chamber. The chamber is evacuated to a defined vacuum level, commonly in the range of 20 to 90 kPa below atmospheric pressure depending on package type and expected sensitivity, and held for a set dwell time, typically 30 seconds or longer. A continuous stream of bubbles escaping from a specific point indicates a leak path. This method is simple, visual, and highly sensitive to gross leaks, and it is the reference technique for many flexible package specifications.

Internal Pressurization Bubble Method (ASTM F2096)

The package is inflated through a probe or dedicated port to a specified internal pressure while fully submerged in water. Continuous bubbling reveals gross leaks anywhere in the package, including seals, corners, and closure interfaces. Because packages can be inflated to pressures exceeding normal handling loads, the method is useful for validating seal robustness and is widely used for medical device packaging in the context of ISO 11607.

Dye Penetration Method (ASTM F1929, ASTM F3039)

A low-surface-tension dye solution is applied to the seal edge or injected into the package. After a defined contact time, the seal is inspected for dye migration through channel defects. ASTM F1929 addresses porous materials such as Tyvek lidding, while ASTM F3039 addresses non-porous packaging. The method can detect very fine channel leaks down to the micrometer scale and precisely locates the defect.

Vacuum Decay Method (ASTM F2338)

The package is placed in a test chamber connected to a vacuum source and a sensitive pressure transducer. The chamber is evacuated to a target pressure, isolated, and the pressure rise due to air escaping from a leaking package is monitored over time. The technique is non-destructive, quantitative, and suitable for 100% inline or offline inspection of pharmaceutical and medical packages, including sterile barrier systems.

Helium Leak Detection (ASTM F2391)

Helium is used as a tracer gas, either flooded into the package or backfilled during production. A mass spectrometer detects helium escaping through leak paths with very high sensitivity, reaching leak rates far below those detectable by bubble or vacuum decay methods. It is applied to highly critical packages such as parenteral vials, prefilled syringes, and implantable device containers.

Seal Strength and Burst Testing (ASTM F88, ASTM F2054, ASTM F1140)

Seal strength is measured by peeling a sealed specimen in a tensile tester and recording the peak or average force. Burst testing pressurizes the whole package until seal failure occurs, providing a measure of the weakest seal. Creep testing holds a reduced pressure for an extended period to assess long-term resistance. These mechanical results complement leak testing by characterizing how robust the seals are rather than simply whether they leak.

Method selection depends on package geometry, required sensitivity, whether the package is porous or non-porous, the criticality of the contained product, and whether destructive or non-destructive results are needed. In many validation programs, a combined protocol applies bubble or vacuum decay testing for leak detection together with seal strength measurement for process capability.

Applications

Sealing performance determination is applied across a broad range of industries:

• Food and beverage: verification of vacuum packs, MAP trays, retort pouches, and aseptic cartons for oxygen and moisture barrier retention
• Pharmaceuticals: container closure integrity of vials, ampoules, blister packs, and prefilled syringes to satisfy regulatory expectations
• Medical devices: validation and routine monitoring of sterile barrier systems under ISO 11607, including after simulated distribution and aging
• Cosmetics and personal care: leak-proof confirmation of sachets, tubes, and pump bottles for liquids and creams
• Industrial and chemical products: integrity of drums, pails, and flexible intermediate containers holding liquids and powders
• Electronics: moisture barrier integrity of barrier bags protecting sensitive components during storage and transit

Beyond lot release, the results support sealing process validation, tooling qualification, material change evaluation, shelf-life studies, failure analysis of field complaints, and regulatory documentation.

FAQ

What is the difference between seal strength and seal integrity?

Seal strength describes the mechanical force required to separate or rupture a seal, measured in newtons per unit width, while seal integrity describes the absence of any leak path through the seal or package. A seal can exhibit acceptable strength yet still contain a channel leak, which is why both evaluations are often performed together.

Is the bubble emission test destructive?

The vacuum bubble method per ASTM D3078 and the internal pressurization method per ASTM F2096 are considered destructive because samples are submerged and often punctured or overstressed. Non-destructive alternatives include vacuum decay (ASTM F2338) and helium leak detection (ASTM F2391).

What vacuum level is used in the vacuum bubble test?

The vacuum level is selected based on the package type and expected defect size, commonly between 20 and 90 kPa below atmospheric pressure, with a hold time of at least 30 seconds. The specific parameters should be defined in the product specification or test protocol.

How many specimens should be tested?

Typical practice involves five to ten specimens per lot, condition, or process setting, though statistical sampling plans or regulatory guidance may require larger sample sizes, particularly during initial process validation.

Which method is best for porous medical packaging such as Tyvek pouches?

Dye penetration per ASTM F1929 is the established method for detecting channel leaks in porous medical packaging, while internal pressurization per ASTM F2096 is commonly used for detecting gross leaks in the complete sterile barrier system.

How sensitive are these methods?

Visual bubble tests generally detect leaks larger than approximately 5 to 20 micrometers depending on conditions, dye penetration can reveal channels in the low micrometer range, vacuum decay reliably detects defects on the order of a few micrometers, and helium leak detection quantifies leak rates at the level of 10 to the power of minus 6 cubic centimeters per second or smaller.