Chemical Resistance Of Basecloths

Basecloths

1. Polyester
2. Nylon
3. Polyvinyl Alcohol
4. Aramid
5. Viton
6. Teflon

1. Polyester

   Polyester has high resistance to a wide range of chemicals, especially for short term exposure at ambient temperatures. Long term exposure, particularly at elevated temperatures, may result in fibre damage and so individual tests are necessary.

   Chemical degredation of polyester occurs particularly in steam and in alkaline and strong acid conditions. Strength declines as either temperature, concentration or exposure time is increased.

   Even if polyester does not dissolve, it may swell and change over a period of time. Some chlorinated hydrocarbons such as methylene chloride, tetrachloroethane and trichloroethelynecause swelling at room temperature. Such swelling results in a loss of strength of the fibre.

   Effect of inorganic salts

   At ambient temperatures Polyester is generally very resistant, some exceptions being ammonium sulphide and other alkaline salts. At higher temperatures, especially over 60°C, resistance decreases.

   Effect of acids

   At ambient temperatures Polyester has good resistance to organic acids (e.g. acetic acid) and dilute inorganic acids (e.g. hydrochloric acid). It is fairly resistant to battery acid (38% sulphuric acid) but is destroyed by more concentrated inorganic (or mineral) acids at room temperature.

   Effect of alkalis

   In contrast to its acid resistance, polyester has very limited resistance to alkalis. It is particurly sensitive to ammonia conditions and to caustic soda and caustic potash at relatively low concentration (< 5%). Resistance at elevated temperatures is particularly poor.

   Effect of organic chemicals including solvents

   Polyester is resistant to many organic chemicals, exceptions being some amines (e.g. Chloramine) and solvents such as benzyl alcohol and tetrachlorethane at ambient temperatures. With increasong temperature resistance decreases.

   Effects of fuels and fertilisers

   Polyester is very resistant to fuels, but is attacked by most fertilisers as these are usually slightly acid or alkaline and frequently contain ammonium salts.

   Effect of other chemicals

   Polyester is resistant to plasticisers (fortunately) and to bitumen. It is however degraded by concrete, especially in damp conditions with attendant alkalinity. Resistance in soil burial conditions is problematic due to possible alkalinity in the soil. Polyester is fairly resistant to bleaching conditions.

   Effect of gasses

   Polyester is very resistant to dry chlorine, hydrogen chloride, sulphur dioxide and ammonia.

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2. Nylon

   Effect of acids

   Mineral and oxidising acids such as hyrochloric, sulphuric and nitric acid, cause degredation.
   Organis acids such as benzoic and oxalic will cause loss of strength dependant on time, temperature and concentration.

   Effect of alkalis

   Nylon is substantially inert to alkalis except hot concentrated caustics.

   Organic solvents

   Nylon is generally insoluable except in some phenolic compounds and concentrated formic acid.

   Effect of other chemicals

   Nylon is generally resistant to other chemicals including oils, petrol, benzene and ammonia chemicals.

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3. Polyvinyl Alcohol

   PVAL is generally very resistant to acids and alkalis and for instance is a good sewing thread to use when both are likely to be encountered.

    

4. Aramid

   This speciality high strength, high melting point, expensive fibre/basecloth is generally very chemical resistant. It is unaffected by most acids, except for some strength loss after long exposure to hydrochloric, hydrobromic, nitric and sulphuric. Generally good resistance to alkalis and solvents.

    

5. Viton

   This florinated fibre/cloth is very chemically resistant and finds use in protective clothing.

    

6. Teflon

   Extremely chemical resistant and mostly used as a coating resin, but sometimes as a sewing thread and in special fabrics such as Gore-Tex.

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