ISO 15105-2 Plastic Film gas transmission rate test by equal-pressure method

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ISO 15105-2 Equal-Pressure Gas Transmission Rate Tester | UnitedTest

UnitedTest manufactures professional ISO 15105-2 compliant gas transmission rate testers, featuring a precise equal-pressure (isobaric) test setup for measuring gas barrier performance of flexible plastic packaging materials.

ISO 15105-2 Plastics film and sheeting — Determination of gas-transmission rate — Part 2: Equal-pressure method is a global standard that specifies accurate isobaric testing procedures. It is designed to determine the gas transmission rate (GTR) and gas permeability coefficient (P) for a wide range of flexible materials, including plastic films, plastic sheets, multi-layer laminates, co-extruded structures, and plastic-coated flexible materials.

Adopting a stable equal-pressure setup, our ISO 15105-2 test instrument delivers reliable, repeatable gas permeability data for packaging quality control, material research, and industrial compliance certification.

Core Test Principle (Equal-Pressure Isobaric Mechanism)

Unlike differential-pressure methods (ISO 15105-1), both chambers of the transmission cell operate at nearly identical atmospheric pressure. The driving force for gas permeation is partial pressure difference of target test gas, not total pressure difference:

A plastic specimen is sealed between two isolated chambers (Chamber A / Chamber B) inside a transmission cell, forming a complete gas barrier.

Chamber A is continuously fed with pure/mixed test gas (O₂, CO₂, N₂, organic vapours).

Chamber B is swept with inert carrier gas at low flow rates to avoid specimen deformation.

Target gas diffuses through the specimen from Chamber A (high partial pressure) into Chamber B (near-zero partial pressure).

Carrier gas carries permeated test gas to a dedicated sensor for quantitative detection.

After stable steady-state signal is captured, GTR and permeability are calculated via standardized formulas.

Two Specific Mandatory Test Methods

Method A:	Coulometric Sensor Method (Oxygen Only)
Exclusive for measuring Oxygen Transmission Rate (OTR, Jₒ₂ GTR). Working logic: The coulometric electrochemical sensor generates an electric current linearly proportional to oxygen volume flow, following Faraday’s Law. The sensor has intrinsic 95%–98% efficiency and can act as a reference method without frequent calibration, though periodic verification with reference films is required. Suitable for low-to-high oxygen barrier films (food, medical packaging).
Method B:	Gas Chromatography (GC) Detection Method (Multi-Gas Universal)
Universal for all test gases: O₂, CO₂, N₂, organic aromas, hydrocarbon vapours. Working logic: Permeated gas is captured in a sampling loop, automatically injected into a GC column, separated by chromatography, and quantified via detector peak area against pre-built calibration curves. Detector options matched to test gas: TCD (Thermal Conductivity Detector): O₂, CO₂, N₂ inorganic gases FID (Flame Ionization Detector): CO₂ (with methanizer), low-concentration organic vapours Capillary column + FID: High-molecular-weight aroma/odour compounds Critical compensation: Automatic GC injection valves may create backpressure; the system must offset overpressure to prevent specimen stretching or rupture.

Test Specimen Requirements

Size: Larger than the cell’s effective permeation area to ensure full airtight sealing.

Quantity: Minimum 3 replicate specimens unless contract parties agree otherwise.

Test Equipment of ISO 15105-2 Plastic Film gas transmission rate test by equal-pressure method

Core Apparatus

Recommend UnitedTest Oxygen Transmission Rate (OTR) Tester;

Gas transmission cell (dual-chamber A/B):

Effective permeation mask area range: 1 cm² to 150 cm²; removable mask to reduce test area for ultra-high barrier films

Laminar gas flow design on both specimen sides; low-permeability gaskets with negligible gas leakage

Gas conditioning units: Control temperature and relative humidity of test/carrier gas per Table 1 conditions

Multi-way 3-way valves, bypass pipelines, flowmeters (gas flow control: 5–100 mL/min)

Barometer, thermometer, thickness measuring device (compliant with ISO 4593 mechanical scanning thickness test)

Stabilized temperature test chamber (23 °C ±2 °C default)

Leak testing assembly for full pipeline sealing verification.

Coulometric OTR System

(Method A)

Coulometric oxygen sensor

Catalyst bed (removes residual oxygen from carrier nitrogen)

Voltage shunt & signal recorder to capture sensor current output

GC Universal System

(Method B)

Coulometric method gas rules:

Carrier gas: Dry N₂ mixed with 0.5–3 vol% H₂; residual O₂ ≤100 μL/L

Test gas: ≥99.5 vol% pure O₂; air (21% O₂) allowed for high-permeability films

GC method gas rules:

Carrier gas chemically compatible with GC detector

Test gas purity/concentration error ≤±1%; free of interfering impurities

Drying agents (calcium chloride) for specimen pre-conditioning

Standard Test Parameters:

Gas Flow Parameters

Carrier gas & test gas flow rate range: 5–100 mL/min

Low-permeability films: Extended purging with stepped flow (25–50 mL/min first 3–4 min, then 5–25 mL/min for 30 min)

Steady-state stabilization time: 30–60 min for thin high-permeability films; several hours for thick multi-layer high-barrier materials (record stabilization duration in test report).

Standard Humidity Diffusion Conditions

Set	Temperature	Relative Humidity (RH)	Typical Application
1	23 °C	0% RH	Dry packaging, oxygen barrier base test
2	23 °C	50% RH	General food packaging
3	23 °C	60% RH	Standard conditioning reference
4	23 °C	75% RH	Moisture-sensitive food
5	23 °C	85% RH	High-humidity storage products
6	10 °C	85% RH	Cold-chain refrigerated packaging

Full Standard Test Procedure of ISO 15105-2 Plastic Film gas transmission rate test by equal-pressure method

Retrieve fully conditioned specimens from climate/desiccator storage.

Mount specimen into transmission cell, inspect for folding/installation damage, seal all gas pipelines.

Purge both Chamber A and B with carrier gas to eliminate residual target gas inside the cell.

Complete full system leak check; continue purging until sensor signal flatlines (zero baseline signal U₀ recorded).

Switch valve to feed conditioned test gas into Chamber A under set flow, temperature and RH.

Maintain gas circulation until sensor output reaches constant steady-state value U; document stabilization time.

Capture stable signal reading for calculation.

Repeat all steps for remaining replicate specimens.

Post-test: Calculate GTR and permeability coefficient using Annex A/B formulas, compile mandatory test report data.

Industrial Application Fields

ISO 15105-2 equal-pressure testing is the primary barrier performance test for flexible plastic materials across key sectors:

Food & Beverage Packaging (Core Application)

Modified atmosphere packaging (MAP), snack bags, fresh meat/vegetable films, beverage barrier laminates. Test O₂/CO₂ permeability to control oxidation, microbial growth, and extend shelf life.

Pharmaceutical & Medical Packaging

Drug blister packs, sterile medical pouches, IV bag films. Low gas ingress prevents drug oxidation, moisture degradation and contamination.

Cosmetic & Personal Care Packaging

Scented cream sachets, essential oil barrier films; test organic vapour transmission to retain aroma and prevent ingredient degradation.

Electronics & New Energy

Lithium battery pouch films, solar backsheet barrier films, semiconductor chip anti-oxidation packaging; ultra-low gas permeability prevents cell degradation and circuit corrosion.

Flexible Industrial Coated Materials

Agricultural greenhouse films, vacuum insulation laminates, waterproof plastic coated fabrics; custom gas barrier characterization for functional design.

Related Test Standard:

ISO 15105-1	Plastics - Film and sheeting - Determination of gas-transmission rate - Part 1: Differential-pressure methods
ISO 15105-2	Part 2 – Equal-pressure method. adopting carrier gas equal-pressure principle instead of differential vacuum; complementary testing route for gas permeability measurement.
ASTM D3985	Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using a Coulometric Sensor
ASTM F1307	Standard Test Method for Oxygen Transmission Rate Through Dry Packages Using a Coulometric Sensor
ASTM F1927	Standard Test Method for Determination of Oxygen Gas Transmission Rate, Permeability and Permeance at Controlled Relative Humidity Through Barrier Materials Using a Coulometric Detector
JIS K 7126-2	Plastics -- Film and sheeting -- Determination of gas-transmission rate -- Part 2: Equal-pressure method
DIN 53380-3	Testing of plastics - Determination of gas transmission rate - Part 3: Oxygen-specific carrier gas method for testing of plastic films and plastics mouldings
ASTM F2622	Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting Using Various Sensors
GB/T 1038.2	Plastics—Film and sheeting—Determination of gas-transmission rate—Part 2:Equal-pressure methods
GB/T 19789	Packaging material—Test method for oxygen gas permeability characteristics of plastic film and sheeting—Coulometric sensor
GB/T 31354	Determination of oxygen gas transmission rate through dry packages.Coulometric sensor

Keywords: UnitedTest ISO 15105-2 tester, ISO 15105-2 gas transmission rate tester, equal-pressure isobaric gas permeability test machine, plastic film GTR testing equipment, ISO 15105-2 isobaric gas permeability coefficient test, multi-layer laminate and co-extrusion gas barrier tester, flexible plastic coated material gas transmission rate analysis, equal pressure method plastic film sheeting GTR test bench

Adopts advanced electrochemical coulometric detection method for accurate, time-efficient oxygen transmission rate analysis for medium and high barrier packaging materials. Conform with ISO 15105-2, ASTM D3985. Key testing indicators Oxygen Transmission Rate (OTR), oxygen volume passing through.

Gas Permeability Tester is a multi-functional lab instrument dedicated to gas barrier performance testing, gas transmission rate (GTR). Conform to ISO 15105-1, ISO 2556, ASTM D1434, Widely adopted as standard QC testing equipment for flexible packaging, plastic manufacturing and new energy sectors.

Q1. What is the primary difference between ISO 15105-2 and ISO 15105-1?

A1: ISO 15105-2 uses the equal-pressure method, meaning the total pressure on both sides of the film is the same (usually atmospheric pressure). Only the partial pressure of the test gas differs. This prevents the film from stretching or distorting.

ISO 15105-1 uses the differential-pressure method, where a vacuum or high-pressure difference is applied across the film. While faster for some materials, it can cause flexible or thin films to bulge or deform, leading to inaccurate results.

Q2: What are GTR and permeability coefficient P defined in ISO 15105-2?

A2: GTR (Gas Transmission Rate, J₉ₜᵣ): Amount of gas passing through plastic per unit area, per unit time, under unit partial pressure difference across the material. OTR (Oxygen Transmission Rate) is a subtype of GTR when test gas is oxygen.

Permeability coefficient P: Intrinsic material property, calculated as P=JGTR×d (GTR multiplied by specimen average thickness). It eliminates thickness interference to compare barrier performance of different-thickness films directly.

Q3: Can I switch between coulometric and GC methods arbitrarily?

A3: No. Select based on test gas and sensitivity demand:

Only coulometric sensor for dedicated, high-precision oxygen testing;

GC required for CO₂, nitrogen, organic vapours, mixed gas atmospheres.

Both methods follow identical equal-pressure cell setup, specimen conditioning and general test procedure.

Q4: What requirements must test specimens meet per ISO 15105-2?

A4: Free of wrinkles, pinholes, shrinkage defects, uniform thickness;

Specimen size larger than cell effective permeation area for full airtight sealing;

Minimum 3 replicate specimens unless contract parties agree otherwise;

Mark the surface facing test gas to replicate real packaging service orientation;

Measure thickness at ≥5 evenly distributed points, record min/max/average thickness (unit: metre for calculation).

Q5: Why is ISO 15105-2 testing critical for plastic barrier materials?

A5: Quantify core barrier performance: GTR/P values rank material gas-blocking ability; lower GTR means superior protection for packaged goods.

Predict shelf life: Oxygen ingress accelerates food oxidation, vitamin loss and microbial growth; CO₂ permeation breaks modified atmosphere packaging balance. Test data directly calculate maximum storage lifespan for food, pharma and cosmetics.

Guide material R&D: Compare performance of new resins, multi-layer co-extrusion, AlOx/SiOx vacuum coatings to balance cost and barrier functionality.

Global unified quality control: Harmonized ISO test rules eliminate cross-regional measurement deviation for cross-border supply chain incoming inspection and batch release.

Regulatory & contract compliance: Food safety, pharmaceutical packaging global regulations require standardized barrier test records; ISO 15105-2 reports serve as official audit evidence.

Simulate real service environments: Custom T/RH test conditions replicate cold chain, high-humidity storage to avoid unexpected packaging failure in market circulation.

Q6: What errors will invalidate ISO 15105-2 test results?

A6: Unconditioned specimens with residual moisture or surface volatiles;

Leaky cell gaskets or incomplete pipeline purge (residual test gas raises baseline signal);

Incorrect specimen orientation (asymmetric laminates show different barrier on two sides);

Ignoring stabilization time and recording unstable sensor signals;

Mask leakage when reducing effective permeation area for ultra-high barrier films;

Deviation from specified gas flow rate or temperature/humidity diffusion conditions.

Q7: When should I choose ISO 15105-2 instead of differential-pressure ISO 15105-1?

A7: Select ISO 15105-2 if:

Testing thin, fragile, metalized or coated films prone to stretching under pressure difference;

Requiring high sensitivity for ultra-low gas permeability barrier materials (pharmaceutical, battery packaging);

Measuring oxygen transmission rate with coulometric reference method for regulatory certification;

Testing mixed test gases, CO₂ or organic aroma vapours via GC detection;

Needing to simulate atmospheric storage conditions matching real-world packaging service environments.

Q8: What's the key difference of ISO 15105-1 and ISO 15105-2?
A8:

Dimension	ISO 15105-1	ISO 15105-2
Method family	Differential-pressure (vacuum or pressurized on one side)	Equal-pressure (isobaric; total pressure same, partial pressure differs)
Principle	One side evacuated, other side charged with test gas → measure pressure rise on low-pressure side (or GC)	Both sides at atmospheric pressure; carrier gas sweeps one side, test gas the other; permeate measured by coulometric sensor (O₂) or GC
Driving force	Total pressure difference (~0.1 MPa typical)	Partial pressure difference only (no net pressure gradient)
Specimen stress	Pressure load → flexible / thin films can bulge, stretch, wrinkle	No pressure load → film stays flat, no distortion
Detection options	• Pressure sensor (vacuum gauge / electronic diaphragm, min sensitivity 5 Pa) • Gas chromatography	• Annex A: Coulometric sensor (O₂, Faraday-based, "reference method") • Annex B: GC with TCD/FID (O₂, CO₂, N₂, organic vapours, aromas)
Applicable gases	Any gas — O₂, CO₂, N₂, mixed gases, inert gases (method has no gas selectivity)	Primarily O₂ (Annex A); multi-gas / organics via Annex B; but coulometric O₂ is the flagship
Humidity control	Possible, but vacuum side makes RH control tricky; usually run dry	Explicitly defined — Table 1 gives 6 T/RH sets (23 °C 0/50/60/75/85% RH, plus 10 °C/85%), easy to match real packaging
Effective area	10–150 mm diameter (ISO 15105-1:2007, 7.3)	1–150 cm² (mask-reducible, 7.3.5)
Typical unit reported	cm³/(m²·24h·0.1 MPa)	cm³/(m²·d) or cm³/(m²·24h·atm) — volume converted at 273.15 K, 101.3 kPa
Strength	• Gas-agnostic (any permeant gas) • Very high sensitivity at low permeation (vacuum side, low background) • Single-layer & multi-layer OK • Long-established, wide comparator database	• Real-world condition (both sides ~atmospheric, like a pouch on a shelf) • Humidity controllable → essential for PA/EVOH/etc. • No film distortion → better for laminates, co-extrusions, thin flexibles • Coulometric O₂ = intrinsic standard (Faraday)
Weakness	• Vacuum operation = more sealing-critical • Film distortion risk for soft/flexible/laminated specimens • RH control harder • Less "real-use" representative	• Coulometric sensor = O₂ only ( Annex B GC widens this but needs calib.) • Sensor (range) limit — ultra-high-barrier (metal foil composite) may be near or below detection vs. differential-pressure • Equipment cost (coulometric cell + catalyst + H₂-bearing carrier)

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