Ozone & Plastics
Ozone Applications are increasing in India. Numerous instances have been noticed that applications are decided without due considerations to the materials of construction of pipes , containers etc .We provide below some information on the use of different type of plastics and Ozone’s effect on them.
Two group of plastics are discussed here ; Plastics termed as Thermoplastic materials and other group of plastics are the Thermosetting Plastics. They find numerous use in Industries and each type of plastics are used for different purposes dependent on the physical & chemical properties of each.
The effects of ozone on each of these materials will depend totally on the configuration of the polymers that make up the plastics. Crossed linked plastics such as poly polypropylene, poly- ethylene , poly- vinyl chloride and silicone or fluorine combined plastics are sufficiently impervious to ozone to enable their use in direct contact.
Most of the packaged water plants all over the world use plastics in some form or the other and the knowledge of each of these will help understand the likely effects with the use of ozone.
From a careful study of different kind of plastics , some forms of polymers are readily attacked by ozone and are not recommended , there are other forms that are quite resistant and take a longer time for effects of ozone. and others attacked immediately and not recommended.
Since most of the packaged water manufacturers prefer residual ozone, and they invariably use PET Bottles, Poly Carbonate Jars, PP Filters, that are all polymer materials , the question of whether they are safe with ozone is frequently asked. The effects of ozone in the long run could unzip some of these polymers to form by- products , Even though they are all dose, concentration and time related , we should never take this risk
For example poly-carbonate has been shown to be very resistant to UV and like water is classified as an universal solvent. Ozone can also be classified as an universal reactant- the only question is how much does it react. Through practical experience, it is very insignificant. For that matter , Ozone is also supposed to be Corrosive to Stainless Steel .But the corrosion is concentration and time related and therefore Stainless steel is regarded safe with the use of Ozone. In fact many ordinary plastics that give out smell (the popular PVC tank) can also be held suspicious, more than ozone which imparts no flavor to the water. The action of ozone on plastics also depends on whether Ozone is used as a gas or solution.. For example Nylon appears to break down faster when in contact with ozone-air mixture than ozone solution
Some care that could be observed while using ozone would include:
- Do not use ozone before cartridge filtration in packaged water process
- Do not store fresh ozonated water in PVC containers ( use ploy carbonate instead)
- Use CPVC /SS pipes preferably if water is being used for drinking.
- Store freshly ozonated drinking water in SS containers instead
- For prospective ozone users check for ozone reactions on MOC of containers/pipes before you use them.
Many of the reported ozone reactions on materials are time concentration related and many of the toxic effects have never been proven .