Internal pressure resistance testing is a critical performance evaluation that verifies whether packaging materials and containers can safely withstand internal pressure generated by carbonation, gas evolution, thermal expansion, pasteurization, or altitude changes during filling, storage, and transport. This technical guide explains the test principles, applicable standards such as ISO 7458, GB/T 4546 and ASTM F1140, typical sample types, test methods, acceptance criteria, and industrial applications for glass, plastic, metal and flexible packaging.
Technical Overview
Internal pressure resistance testing, also known as internal pressure strength or burst resistance testing, is a laboratory procedure in which a sealed container or package is subjected to a controlled internal pressure — usually applied hydraulically or pneumatically — in order to evaluate its ability to survive the pressure loads encountered throughout its life cycle without bursting, leaking, or permanently deforming. The test answers a fundamental packaging safety question: how much internal pressure can the container tolerate, and for how long, before failure occurs.
Internal pressure develops in packaging from multiple real-world sources, including:
- Dissolved carbon dioxide in carbonated soft drinks, beer and sparkling wine, which typically generates 0.2–0.5 MPa at ambient temperature and rises steeply during warm storage or tunnel pasteurization
- Thermal expansion of the product and headspace gas during hot filling, retort sterilization, or autoclaving
- Propellant gases in aerosol dispensers, which can approach or exceed 1 MPa at elevated temperatures
- Gas evolution from chemical reactions in household, agricultural and industrial chemical products
- Pressure differentials during air freight and high-altitude ground transport
- Transient pressure spikes caused by drop impact, mishandling, or stacking in distribution
The principal international and national standards governing this testing include ISO 7458 for glass containers, the Chinese national standard GB/T 4546 (technically aligned with ISO 7458), ASTM F1140 and ASTM F2054 for flexible packages, and the hydraulic pressure test specified in Chapter 6.1 of the UN Model Regulations for dangerous goods packagings. Failure modes detected by the test include burst rupture, seal peel or delamination, leakage at closures and finishes, panel deformation, and environmental stress cracking in plastics.
Testing Samples
Glass Bottles and Jars
Glass containers for beer, carbonated beverages, sparkling wine, and pressure-packed foods are the classic application of internal pressure resistance testing. Because glass fails in a brittle manner, even a single burst bottle on a filling line or in a pasteurizer presents a significant safety hazard, so both newly developed designs and routine production lots are evaluated. Typical commercial specifications for returnable beer bottles require resistance to internal pressures of 1.6 MPa or higher, tested in accordance with ISO 7458 or GB/T 4546.
Plastic (PET) Bottles and Containers
PET bottles for carbonated soft drinks must contain sustained CO2 pressure for their entire shelf life. In addition to short-term burst strength, plastic containers are evaluated for creep behavior — slow volumetric expansion and stress-crack initiation under sustained load — as well as base panel performance and ovality. Hot-fill bottles are further assessed for vacuum panel recovery and distortion under combined thermal and pressure loads.
Metal Cans, Pails and Aerosol Containers
Beverage cans are tested for dome reversal and burst pressure, while metal pails, drums and paint cans used for liquid chemicals must pass hydraulic internal pressure requirements before certification. Aerosol dispensers are a high-risk category: under UN transport regulations, metal aerosol containers are commonly required to withstand a hydraulic test pressure of at least 1.5 MPa, or a defined multiple of the equilibrium propellant pressure at 55 °C, whichever is greater.
Drums, Jerricans and IBCs for Dangerous Goods
Rigid packagings intended for liquid dangerous goods must undergo the design-qualification hydraulic pressure test of the UN Model Regulations before a UN certification mark can be issued. Typical minimum test pressures are 100 kPa for Packing Groups II and III and 250 kPa for Packing Group I liquids, held for a defined duration, and testing is performed by accredited third-party laboratories as part of design type approval.
Flexible Pouches and Laminated Packaging
Retort pouches, stand-up pouches, and sterile barrier systems for medical devices are tested by internal air pressurization to quantify seal integrity and seal strength. ASTM F1140 covers burst and creep testing of unrestrained packages, while ASTM F2054 addresses packages restrained between parallel plates; these methods are widely referenced in validation programs conforming to ISO 11607 for terminally sterilized medical device packaging.
Testing Items
Depending on the product standard and the purpose of the evaluation, the following test items are typically performed:
- Pass/fail internal pressure resistance: verification that the container withstands a specified pressure for a specified hold time without breakage or leakage
- Burst pressure (ultimate internal pressure): the maximum pressure at which the container fails, determined by progressive pressurization to destruction
- Pressure creep test: sustained holding at a defined fraction of the burst pressure, or for a fixed duration such as 60 seconds or several minutes, to reveal time-dependent weaknesses
- Volumetric expansion and deformation: measurement of radial and axial growth in plastic containers under pressure
- Pressure cycling and fatigue: repeated pressurization–depressurization cycles for refillable and reusable containers
- Combined temperature–pressure testing: pressurization at elevated temperature (for example 55 °C for aerosol simulation or pasteurization temperatures for beverage bottles)
Testing Methods
Hydraulic Pressurization Method (Pass Test)
The container is filled with water (or another essentially incompressible medium), sealed by clamping the finish or closure area, and pressurized by a plunger-type pump. In the pass test, the pressure is raised at a controlled rate to the specified value and held for a fixed time — commonly 1 second for routine glass bottle testing, with extended holds of 10 seconds or more for referee testing. Because water stores little strain energy, the hydraulic method is the safest way to reach high pressures and is mandatory for dangerous goods packaging qualification, where a 30-minute hold is typical.
Progressive (Incremental) Method to Failure
To determine the burst pressure, the internal pressure is increased in steps — for example 0.1 or 0.2 MPa increments, each held for a short interval — until the container fails. The recorded burst pressure, the failure location (body, shoulder, base, or closure), and the pressure–time curve are reported. This method is used for design development, lightweighting studies, and statistical quality control based on the distribution of failure strengths.
Constant-Pressure Creep Method for Plastic Containers
PET and other plastic bottles are pressurized to a specified level and held while volumetric growth, panel deformation, and stress-crack initiation are monitored. This simulates long-term CO2 containment and shelf-life loading that a simple burst test cannot capture.
Pneumatic Burst Method for Flexible Packages
Flexible pouches are inflated with regulated air through a custom fixture until a seal or material rupture occurs. Testing may be unrestrained per ASTM F1140, which measures the weakest seal route, or constrained between plates per ASTM F2054, which directs stress to the seal area and better simulates stacked distribution. Creep-to-failure (holding a constant pressure until rupture) is often run alongside the burst test.
Equipment, Conditioning and Safety Requirements
Test systems comprise a pressure source, calibrated pressure transducers (typically accurate to within ±1% of reading), clamping fixtures matched to the container finish, a rupture containment enclosure, and data acquisition for the pressure–time curve. Specimens should be conditioned to a standard atmosphere, for example 23 °C and 50% relative humidity per ISO 291 or ASTM D618, before testing. Because compressed gas stores large amounts of energy, pneumatic testing of rigid containers requires robust protective shielding, and only trained operators should perform pressurization-to-failure tests. Reports should identify the sample, the applied standard, the pressurizing medium, ramp rate, hold time, failure pressures, failure modes, and the number of specimens tested.
Applications
Internal pressure resistance testing supports packaging safety and compliance across many industries:
- Beverage industry: design verification and lot release of beer bottles, CSD bottles, and sparkling wine bottles, including pasteurization simulation
- Aerosol and household chemical products: demonstration of container strength against propellant pressure at elevated temperature
- Dangerous goods transport: UN design-type certification of drums, jerricans, and composite packagings for liquids, conducted by accredited third-party laboratories
- Food packaging: qualification of retort pouches, hot-fill containers, and gas-flushed flexible packaging
- Pharmaceutical and medical packaging: validation of sterile barrier seal integrity under internal pressurization as part of ISO 11607 conformity
- Research and quality engineering: lightweighting studies, material comparison, supplier qualification, failure analysis, and statistical process control
- Logistics and e-commerce: assessment of packages subjected to altitude pressure cycles during air freight
FAQ
What is the difference between internal pressure resistance and burst strength?
Internal pressure resistance usually refers to a pass/fail requirement — the container must withstand a specified pressure for a specified time. Burst strength is a destructive measurement of the maximum pressure the container can reach before failure. Both values are complementary: the former verifies conformity to a specification, while the latter characterizes the safety margin above that specification.
What pressure must a typical carbonated beverage bottle withstand?
Carbonated products generate roughly 0.2–0.5 MPa of CO2 pressure at ambient temperature, which can rise substantially during pasteurization or warm distribution. Commercial glass beer bottles are commonly specified at 1.6 MPa or higher, and PET bottle designs are typically qualified with burst pressures several times the nominal product pressure to provide an adequate safety margin.
Why is water used instead of air for rigid container testing?
Water is nearly incompressible, so a hydraulic failure releases very little stored energy, making high-pressure testing far safer than pneumatic testing. Air is used for flexible packages where low burst pressures are expected and where the test must reflect real inflation behavior, always inside protective enclosures.
How does internal pressure testing differ from drop, compression or vibration testing?
Internal pressure testing isolates a single load mode — uniform outward pressure acting on the container walls — whereas distribution simulation tests (drop, stacking compression, vibration) apply external mechanical loads. A complete package validation program combines internal pressure testing with these transport hazard tests, and the relevant methods are often specified together in the same design standard.
How many specimens should be tested?
The number depends on the governing standard and the objective. Design qualification and dangerous goods certification prescribe fixed specimen counts per design type, while statistical lot control may use smaller samples on a sampling plan. Because glass and seal strengths are statistically distributed, testing multiple specimens is essential to characterize variability reliably.
Can internal pressure resistance be improved if failures occur?
Yes. Common corrective actions include increasing wall thickness at high-stress regions, improving glass distribution or annealing quality, adjusting resin selection and orientation conditions in PET bottles, optimizing seal geometry and sealing parameters in flexible packaging, and reviewing closure torque and liner design where leaks originate at the finish.