Chemical Resistance of PVC Pipes
PVC is resistant to many alcohols, fats, oils and aromatic free petrol. It is also resistant to most common corroding agents including inorganic acids, alkalis and salts. However, PVC should not be used with esters, ketones, ethers and aromatic or chlorinated hydrocarbons. PVC will absorb these substances and this will lead to swelling and a reduction in tensile strength.
Considerations for PVC Pipe
For normal water supply work, PVC pipes are totally unaffected by soil and water chemicals. The question of chemical resistance is likely to arise only if they are used in unusual environments or if they are used to convey chemical substances. For applications characterised as food conveyance or storage, health regulations should be observed. Specific advice should be obtained on the use of PVC pipes. Although PVC-O is chemically identical to standard PVC-U, rates of attack may vary and this material is not recommended for use in chemical environments or for chemical conveyance. In most environments, the chemical performance of PVC-M is expected to be similar to standard PVC-U. However, where concentrated chemicals are to be in prolonged contact with PVC-M or elevated temperatures are likely, it is recommended that some preliminary testing be carried out to determine the suitability of the material.
PVC will not be affected by anything that can be normally found in sewerage effluent. However, if some illegal discharge is made then most chemicals are more likely to attack the rubber ring (common to all modern pipe systems) than the PVC pipe. Because of modern pollution controls on sewage discharges PVC can be safely used in any municipal sewerage network including areas accepting industrial effluent.
Chemical Resistance of Joints
When considering the performance of pipe materials in contact with chemical environments, it is important not to overlook the effect of the environment on the jointing materials. In general, solvent cement joints may be used in any environment where PVC pipe is acceptable. However, separate consideration may need to be given to the rubber ring.
Chemical attack on rubbers can occur in two ways. Swelling can occur as a result of absorption of a chemical. This can make it weaker and more susceptible to mechanical damage. On the other hand, it may assist in retaining the sealing force. Alternatively, the chemical attack may result in a degradation or change in the chemical structure of the rubber. Both types of attack are affected by a number of factors such as chemical concentration, temperature, rubber compounding and component dimensions. The surface area exposed to the environment may also influence the severity of the attack.
See Chemical Resistance of Elastomers for guidance on chemical resistance of rubber materials commonly used in pipe seals.
Chemical Resistance Table
The listed data are based on results of immersion tests on specimens, in the absence of any applied stress. In certain circumstances, where the preliminary classification indicates high or limited resistance, it may be necessary to conduct further tests to assess the behaviour of pipes and fittings under internal pressure or other stresses.
Variations in the analysis of the chemical compounds as well as in the operating conditions (pressure and temperature) can significantly modify the actual chemical resistance of the materials in comparison with this chart’s indicated value.
It should be stressed that these ratings are intended only as a guide to be used for initial information on the material to be selected. They may not cover the particular application under consideration and the effects of altered temperatures or concentrations may need to be evaluated by testing under specific conditions. No guarantee can be given in respect of the listed data. Vinidex reserves the right to make any modification whatsoever, based upon further research and experiences.