Measuring the Rate of Carbon Dioxide Production Due to the Effect of Humidity on the Optical Degradation of Polyvinyl Chloride and Polyethylene

The effects of relative humidity on polymer photodegradation were investigated using a closed-loop photoreactor, which allows the measurement of emitted CO۲. Two polymers, PVC and polyethylene, which were expected to have different responses to relative humidity, were investigated. Both polymers contained TiO۲ photoactive pigment. Relative humidity was controlled in the optical reactor using salt solutions and a bypass ring. For both polymers, an initial rate of CO۲ production was observed, which was less dependent on relative humidity. After a short time, the rate of CO۲ production changed to a higher secondary rate that was more sensitive to relative humidity .For polyethylene, the secondary rate increased with increasing relative humidity, although at humidity above ۵۸%, the rate of CO۲ production was constant. This corresponds to the increase in the formation of hydroxyl radicals .Photodegradation of PVC was more complicated; In very low humidity, the production rate of CO۲ was low, but with the increase of humidity to about ۳۵%, it increased significantly and reached its maximum value. At higher relative humidity values, the rate of CO۲ production decreased . This was attributed to the catalytic effect of hydrochloric acid. This explanation was confirmed by investigating the effects of hydrotalcite addition on PVC degradation.Hydrotalcite replaces hydrochloric acid with carbonic acid and reduces the rate of CO۲ production and the effects of humidity. The obtained results clearly show that the CO۲ production method is an effective way to quickly check the effects of humidity.

کلیدواژه ها:

Optical Degradation ، Polyethylene ، PVC ، Humidity ، Hydrotalcite ، CO۲ Production