Textiles membrane properties

Textile membranes are exposed not only to mechanical stresses but also to various environmental influences. The main damaging influences are temperature, humidity, solar irradiation, noxious industrial gases, ozone, dust, salts and micro-organisms. These influences impair the functional properties, performance and life-span of the membranes. DIN EN ISO 4892 standard describes the basics for these tests. It is expected that textile membranes should last for decades without their properties and performance being compromised. However, every year many materials break down due to severe environmental influences and cause damage worth millions of euros. 

Abstract Already many lightweight membrane structures are in existence, and an increasing number of them are planned for the future. In this chapter different materials and coatings for textile membranes are introduced and discussed, which have to fulfil a wide range of properties. The main task of the membranes is to act as a barrier function against water, IR- and UV-radiation and excessive heat, and they should provide, amongst others, mechanical stability, light transmission and resistance to environmental impact. 

PPS fiber has excellent chemical resistance. Only strong oxidising agents cause degradation. As expected from inherent resia properties, PPS fiber is flame-resistant and has an autoignition temperature of 590°C as determined ia tests at the Textile Research Institute. PPS fiber is an excellent electrical iasulator it finds application ia hostile environments such as filter bags for filtration of flue gas from coal-fired furnaces, filter media for gas and liquid filtration, electrolysis membranes, protective clothing, and composites. 

SPMs can now be found in commercial markets and specialty clothing due to their lightweight structure, liquid and aerosol repellent properties, and facilitation of moisture vapor transport. However, for military use, SPMs have limitations (Wilusz 2007). SPMs may act as liquid-repellents but may allow vapors to pass and therefore need an activated carbon layer to add extra protection capabilities. Moreover, military garments experience tremendous stress on a day-to-day basis. SPM-based ensembles are more susceptible to tearing as compared to activated carbon-based textile fabrics (Wilusz 2007). Optimizing the permselectivity of the membrane by surface modification or other such techniques is necessary to achieve a balance between comfort (e.g., moisture vapor transmission) and chemical vapor barrier properties. Furthermore, SPMs or membrane-carbon ensembles must possess acceptable mechanical strength to sustain daily military operations. 

PTFE has a remarkable range of properties. It possesses the simple monomer unit, -(CFj-CE )-, with a molecular weight of 100, an SG of 2.1-2.3 and a degree of polymerisation of 10 000. PTFE is extremely stable and inert, is not soluble in any known liquid solvent and is unaffected by concentrated acids and alkalis. It will not bum in air, is flexible down to -80 °C and dimensionally stable up to 4-250 °C. It has a low coefficient of friction, good abrasion resistance and has excellent liquid repellency properties. It is predominantly available as a thin membrane that is laminated to one or more textile fabrics. PTFE is thus well suited for use against chemicals and liquids in harsh environments. One of the special uses of the membrane is in a shock-expanded microporous form, which confers high liquid barrier properties with high water vapour permeability. In this form laminates are... 

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