Effect of thermal aging on the mechanical and barrier properties of an e‐PTFE/Nomex® moisture membrane used in firefighters' protective suits

Abstract

Moisture membranes play a key role in high performance protective clothing by preventing outside water to get in while allowing the human body to perspire properly. However, these membranes are confronted to high environmental constraints, in particular within firefighters' protective clothing. The resulting aging effect may lead to modifications of their performances, for example their mechanical or barrier properties. In this study, the thermal aging of an e-PTFE/NomexV R moisture membrane was carried out at five temperatures between 190 and 320 C. The effect of aging on the mechanical performance was assessed by tensile tests and trapezoid tear strength measurements. Variation in the moisture membrane water vapor permeability due to aging was also studied. Large modifications in the membrane mechanical properties as a result of thermal aging were recorded. It was associated in part with a degradation of the NomexV R fibers. The membrane water vapor permeability was observed to decrease with aging time below 220C while values larger than those corresponding to the unaged material were measured above that temperature. This was possibly related to the occurrence of two competing phenomena relative to water vapor permeability: closure of pores in the e-PTFE laminate and creation of cracks and holes. These results show that the aging of the moisture membrane must be considered carefully while estimating the service life of protective clothing.

Butyl Rubber-Based Composite: Thermal Degradation and Prediction of Service Lifetime

“…However, the assumption proposed by Rachid et al [69] in which the material is considered run out when there is a reduction of about 50% of tensile force seems to be acceptable. Here, were calculated the service lifetime for each aging temperature using an empirical regression method proposed by El Aidani et al [16,69]. These lifetime values were exploited from the Arrhenius curve, as shown in Figure 7, by plotting the logarithm of the lifetimes as a function of the inverse of the exposed temperatures.…”

“…This means that at 80 • C the mechanical properties of BRC remained acceptable until 344 days, while it dropped to about 2 days at 120 • C. The definition of the end-used service lifetime of the material is still a subject in question in the literature. However, the assumption proposed by Rachid et al [69] in which the material is considered run out when there is a reduction of about 50% of tensile force seems to be acceptable. Here, were calculated the service lifetime for each aging temperature using an empirical regression method proposed by El Aidani et al [16,69].…”

Determination of critical heat transfer for the prediction of materials damages during a flame engulfment test

“…This is especially true for meltable garments with high thermal resistance, as this requires a higher thermal resistance of the protective layer to prevent material damages. We will investigate in further experiments how the model developed in this study can be used to predict damage to breathable membranes used in multilayer combinations, as they are particularly sensitive to alterations because of heat exposures , or in general the end‐of‐life of materials because of critical heat exposure .…”

Butyl Rubber-Based Composite: Thermal Degradation and Prediction of Service Life Time 

“…K= A exp (-E/RT) Eq.9 The definition of the end-used service lifetime of the material is still a subject in question in the literature. However, the assumption proposed by Rachid et al [67] in which the material is considered run out when there is a reduction of about 50 % of tensile force seems to be acceptable. Here, were calculated the service life time for each aging temperature, using an empirical regression proposed method By El Aidani et al [16,67].…”

“…However, the assumption proposed by Rachid et al [67] in which the material is considered run out when there is a reduction of about 50 % of tensile force seems to be acceptable. Here, were calculated the service life time for each aging temperature, using an empirical regression proposed method By El Aidani et al [16,67]. These lifetime values were exploited from Arrhenius curve, as shown in Figure 7, by plotting the logarithm of the lifetimes as a function of the inverse of the exposed temperatures.…”