• Exceptional chemical resistance supported by comprehensive test data

• Long-term durability

• Good mechanical properties and environmental stress crack resistance

• Good welded seam peel and shear performance

• Flexible to accommodate undulating ground contours

• High-visibility yellow on upper surface for easy recognition during excavations

Please Register to download Design & Installation Guide and Product Technical Data Sheets. 

Chemical Resistance test data and other technical documents are available on request by emailing our Puraflex Technical Department or telephoning +44 (0)1347 825221

Typical applications - covered installations

Civil Engineering & Construction

Basement linings, brown-field developments, building foundations, tanking, tunnel linings

Environmental protection

Containment cells, contaminated land, groundwater protection, remediation, separation

Gas Barrier

Gas barrier membrane, landfill capping

Industrial

Chemical waste containment, retention ponds, secondary containment liners & basins, sludge desiccation basins, tank floors

Mining

Evaporation and brine basins, cut-off trenches, leachate pond liners, mining heap leach pads

Waste

Landfill containment and capping, waste disposal & storage sites

Water & Water Treatment

Effluent treatment, fluid barrier, reedbeds, groundwater protection reservoir and potable water lining, water storage & treatment

EN 14414: Chemical Resistance to leachates and aggressive chemicals

EN 14415: Resistance to leaching

EN 13361: Construction of reservoirs & dams

EN 13362: Construction of canals

EN 13491: Construction of tunnels and underground structures

EN 13492: Construction of liquid waste disposal sites, secondary containment

EN 13493: Construction of solid waste storage and disposal sites

Test data to ASTM, BS, EN international standards

Given a known level of contaminants in a soil, how effective will a barrier membrane be in keeping the soil on the “clean” side safe from the contaminants?

Reporting on over 200 hydrocarbons and toxic chemicals, Puraflex Permeation Modeller is a powerful and effective software program that calculates site-specific permeation rates for soil contaminants. 

Following a contaminated soil test analysis, contaminant concentrations are uploaded into the Puraflex program.  Key variables directly influencing contaminant permeation rates (temperature, soil moisture etc.) are entered and the software then calculates the project-specific permeation rates which can be imported directly into environmental risk assessment modelling software.

Interestingly, soil moisture content has a significant influence on the Effective Concentration levels at the face of a geosynthetic membrane.  As soil moisture increases, the more a hydrocarbon will partition away from the moisture-laden soil and congregate on the surface of the membrane thus increasing its Effective Concentration which, for some hydrocarbons, could be over 60 times higher in an environment with only 10% moisture.

Puraflex Permeation Modeller is provided free of charge to qualified environmental and geotechnical consultants. The Standard version reports on Liquid Migration and the Professional upgrade includes Vapour Migration. Registration is required for licence keys.

Permeation data comparisons of different geosynthetic membrane polymers.  Please note that Puraflex performance is compared with 1.5mm thick membrane materials, whereas Puraflex is 450 microns.  Permeation based on soil temperature of 20 deg C and challenge chemicals at 100 mg/kg concentration.  Units mg/sqm/yr.

These results ignore soil moisture partition coefficients.  Moisture in soils have a significant effect on the permeation rates of hydrocarbons through HDPE and other monolithic membranes.  Puraflex Permeation Modeller software provides the option to use Soil Moisture Partition Coefficients.

Soil Moisture has a significant effect on the permeation rates of hydrocarbons through HDPE and other monolithic membranes. 

The higher the soil moisture, the more a hydrocarbon will partition away from the moisture resulting in a higher concentration (Effective Concentration) on the surface of the membrane.  The effect of this is quite dramatic.

By way of example, the effect of 10% Soil Moisture on 100 mg/kg Toluene contamination (determined by soil analysis) will increase the Effective Concentration to 100,000 mg/kg on the surface of the membrane.  Inevitably, this has a significant effect on permeation.

Puraflex Permeation Modeller software provides the option to use Soil Moisture Partition Coefficients and thus provide more accurate predictions and Risk Assessments. 

The unique Puraflex Permeation Modeller (PPM) software program enables you to:

1. Upload Soil Analysis chemical concentration values - the programme recognises chemical names, synonyms and/or CAS No.
2. Enter project-specific variables:  Soil Temperatures, Partition coefficients, Soil Densities etc.
3. Export results to Excel for incorporating directly into risk assessment software models (e.g. CLEA)

Puraflex Permeation Modeller is provided free of charge to qualified environmental scientists and design engineers.  The Standard version reports on Liquid Migration and the Professional upgrade includes Vapour Migration.  A software licence is required for extended use.

Please Register to download an evaluation copy of Puraflex Permeation Modeller.  Alternatively, you can request the software by email or on disk by Email from Puraflex Technical Department or by Telephone +44 (0)1347 825221.

Puraflex Permeation Modeller screenshot

Permeation is a natural phenomenon that occurs with all membranes.  It is a process by which a chemical passes through the membrane by molecular diffusion.  This occurs when the membrane absorbs the chemical until the membrane is saturated; the chemical then diffuses from the opposite side. 

Typically a soil analysis will report on concentrations of some 60 hydrocarbons and toxic chemical contaminants.  This data is used in Risk Assessments to ensure that unacceptable risk is removed and to make a site suitable for its intended use and to protect the wider environment, particularly surface water and groundwater.

Therefore to ensure accuracy and maintain the integrity of any risk assessment model, permeation data of the separating geosynthetic membrane is essential to the modelling predictions of the migration of contaminants from the Source, through the membrane and into the Pathway to the Receptor.

Puraflex Permeation Modeller is a powerful software program that calculates permeation rates for site-specific hydrocarbon contaminants.  Reporting on over 200 hydrocarbons, it is provided free of charge to qualified environmental consultants and design engineers.

It is important to make a distinction between a material's Durability and its Performance.  To correctly interpret manufacturers’ claims and test results, it is necessary to have an understanding of the appropriate test methods.

Material selection should therefore evaluate both Chemical Resistance (Durability) test data and Permeation (Performance) test data.

Chemical Resistance tests provide a measure of a material's Durability, in other words the membrane's ability to withstand chemical attack after exposure to a challenge chemical.  Such tests provide a measure of changes to the physical properties of the membrane.  Though not a measure of Barrier Performance, they are useful ‘gatekeepers’ and quickly eliminate unsuitable materials in the first round of material selection.

For Durability, as a minimum, the material should pass EN 14414 Method A (Acids) and Method C (Organics).

Next, Barrier Performance should be evaluated by studying Permeation test data.  Permeation tests for geosynthetic materials commonly used are:

ISO 6179:2010  Rubber, vulcanized or thermoplastic -- Rubber sheets and rubber-coated fabrics -- Determination of transmission rate of volatile liquids (gravimetric technique).

This test method is inaccurate and obsolete since it gravimetric (by weighing) and is restricted to materials with transmission rates of more than 0.1 g/m²/h.  This extrapolates to 2,400 mg/m²/hr or 864,000 mg/m²/yr as a minimum.  A barrier with these permeation rates would surely not be fit for purpose.

ISO 15105-2 :  Plastics - Film and sheeting - Determination of gas-transmission rate - Part 2: Equal-pressure method.

This mass spectroscopy test that provides highly accurate permeation test data.  Puraflex is tested to ISO 15105-2.

Most membrane materials commonly sold as 'Hydrocarbon Resistant' are merely HDPE. 

This chart summarises the Barrier Performance of Puraflex vs HDPE.

Puraflex chemical resistance data and permeation rates for the following hydrocarbons and other environmental contaminants is available to Geotechnical Engineers and Environmental Consultants.  

It is important to make a distinction between a material's Durability and its Performance.  To correctly interpret manufacturers’ claims and test results, it is necessary to have an understanding of the appropriate test methods.

Chemical Resistance tests provide a measure of a material's Durability, in other words the membrane's ability to withstand chemical attack after exposure to a challenge chemical.  Such tests provide a measure of changes to the physical properties of the membrane.  Though not a measure of Barrier Performance, they are useful ‘gatekeepers’ and quickly eliminate unsuitable materials in the first round of material selection.

Chemical Resistance test methods are immersion tests, also known as Accelerated Life Testing (ALT).  They are designed to stress a membrane at a higher level of chemical concentration and temperature than it would experience in normal use.

The ASTM D5322 immersion test method is the basis for EPA Method 9090, ASTM D5747,EN 14414 and EN 14415 chemical resistance tests .  It is normally performed at a 100% concentration and typically the sample is immersed in the challenge chemical and maintained at a raised temperature for a specified period, 50 ºC for 56 days.  As a rule of thumb, chemical reactivity doubles with a temperature increase of 10°C.  Therefore testing at 50 ºC simulates an eight-fold increase in chemical reactivity, compared with tests at an ambient 20 ºC.

The test measures changes in weight, volume and tensile strength to provide a measure of the material’s durability.  These measurements are then compared with a control sample and the extent of the variation is indicative of the extent of chemical attack.  Residual tensile strength and elongation must be greater than 75%.

For Durability, as a minimum, the material should pass EN 14414 Method A (Acids) and Method C (Organics).

Puraflex has been tested to the following EN Chemical Resistance Standards.  Note that ASTM D5322 is a widely recognised test method for chemical resistance and it is incorporated within the EPA Method 9090 and ASTM D5747.  Both EN 14414 and EN 14415 incorporate the ASTM D5322 test procedures.

Limitations of EN 14414 and EN 14415

The scope of industry standard test in EN 14414 and EN 14415 is limited to but a few hydrocarbons.  Test data is limited to changes is weight and thickness and residual tensile strength and elongation.  Whilst these immersion test methods provide a measure of of the membrane's resiliance to durability, there is no permeation data for measuring the effectiveness of the membrane against specific challenge chemicals as identified in environmental risk assessments.

It is important to make the distinction between a membrane being resilient to a hydrocarbon and a membrane being effective as a barrier to permeation.

Current Industry test methods for chemical resistance are limited in terms of scope and value.  Permeation rates for hydrocarbons and chemical contaminants are essential for determining the suitability of barrier membranes for site-specific installations.