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Further Information - Permeation vs Penetration

Pyrolon CRFR : Permeation Vs Penetration

 

The primary property of Pyrolon CRFR is not its chemical barrier but its FR properties COMBINED with its chemical barrier, so that it can safely be worn OVER a Thermal Protective Garment without damaging thermal protection. The fabric has been tested against a number of chemical to indicate it protective properties, in some cases according to PERMEATION and in some cases PENETRATION. For a full list of chemicals test see the Pyrolon CRFR Product page.

Permeation and Penetration are not the same:-

Penetration                                 The “mechanical” process by which a chemical physically passes through holes or gaps in a non-solid fabric       Deals in larger amounts, the breakthrough being measured at the point at which a “visible” breakthoguh of the chemical is identified.
Permeation


The molecular process by which the chemical molecules pass “between” the molecules of the barrier fabric by a process of absorption into the challenge surface, diffusion through the fabric and desorption from the other surface.

Deals in very small quantities; the measured “Normalised Breakthrough” being the time to achieve a PERMEATION RATE (through the fabric) of 0.1 or 1,0 * µg / minute / cm2. (1 µg or 1 Microgram is 1 millionth of a gram).

 

Permeation testing deals in very small quantities; the measured “Normalised Breakthrough” being the time to achieve a PERMEATION RATE (through the fabric) of 0.1 or 1,0 * µg / minute / cm2. (1 µg or 1 Microgram is 1 millionth of a gram). Penetration testing meanwhile deals in larger amounts, the breakthrough being measured at the point at which a “visible” breakthoguh of the chemical is identified.

In Europe assessment of chemical suits is done by permeation testing (to EN5629) with no penetration test forming part of the certification process. Permeation testing however is limited in several ways, testing is actually subject to variable accuracy, it varies according to temperature (whilst all testing is done at 25oC). Further it is commonly misunderstood. Sole reliance on permeation as part of the garment selection process can be misleading, and consideration of penetration testing may add to the selection process.

For  example:

Benzene: The user needs a chemical suit to protect against benzene in an area where fire is a risk and so the suit needs to be worn OVER a Thermal Protective Garment such as Fyrban.

Benzene         CAS No 71-43-2

  Benzene Hazard Data     

Hazardous in case of eye contact / inhalation / skin contact / ingestion
Carcinogenic Effects: Class 1A - proven for humans
Tosic to blood, bone marrow and cardio-nervous system

Health Hazard                Class 2     - Moderate Hazard - temporary or minor reversible injury may occur
Fire Hazard                     Class 3     - Serious Hazard - will ignite under all temperatures - highly flammable 
Reactivity                         Class 0     - Minimal hazard - normally stable                                           
Protective Clothing        Class H    - Splash goggles / gloves / apron / respirator

(Source: www.sciencelab.com) 

 Chemical Test Data  Permeation  Penetration
ChemMAX 3  >480 Minutes  Not Available
Pyrolon CRFR   Immediate >60 Minutes 

 

Purely on the basis of the permeation testing a user might be forced to select ChemMAX 3 for Benzene protection. However, the MSDS for benzene classifies as a “greater” immediate fire hazard than a health hazard. ChemMAx 3 has no FR properties, may ignite and burn and damage the thermal protection offered by the TPG beneath.

On the other hand, the penetration testing of CRFR shows a breakthrough over 60 minutes, the CRFR has the benefit of excellent FR properties… not only will it not reduce thermal protection it can actually improve it. Further Pyrolon garments have excellent anti-static properties because of the nature of the fabric. This may also be a factor gevin that staic control is vital in flammable areas and around flammable liquids.

Thus despite the poor permeation result offered by Pyrolon CRFR, in this case it may be appropriate to select it as it deals much better with the primary hazard – that of fire – and offers some protection against the chemical. The alternative may offer better protection against the chemical, but results in a greater hazard regarding the fire risk. Other factors may be important – such as the likelihood of fire, the likelihood of chemical contamination, the pressure and volume of possible contamination and the frequency of the task: is it a single one-off task – or is it a regular task done over an extended period?

All of these play a part in the risk analysis, but penetration data, whilst not currently part of the CE certification process, can provide valuable information to assist making the most appropriate decision when factoring the totality of hazards.

 

*Note North Ameircan ASTM F739 testing is measured at 0.1 µg / minute / cm2 whilst the European test EN5629 offers the option of  0.1 µg / minute / cm2 OR 1.0 µg / minute / cm2 . In most cases in Europe 1.0µg is used but often not clearly specified.

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  1. Pyrolon® Plus 2

    Pyrolon® Plus 2

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