Polyvinyl chloride pipe degradation studies in natural environments

PVC pipes are generally stabilized with lead, tin, or calcium‐zinc based additives. The performance of PVC products in outdoor applications is highly dependent on the types of stabilizers used and environmental factors such as UV radiation, temperature, humidity, rain, dust, etc. This study involves two‐year exposure of a lead‐stabilized and titanium dioxide‐pigmented PVC pipe at Dhahran (Saudi Arabia) and Miami, Florida. The white pigmented PVC pipes are mostly used outdoor for low pressure potable water services, irrigation in greenhouses, and electrical conduits in Saudi Arabia. The PVC pipe formulation stabilized with Pb‐stabilizer provides good light stability and is also widely used for potable water pipes. The pipes are exposed not only to the natural environment during outdoor usage but also to high UV doses, and to high temperatures during transportation, installation, and long‐term storage. Changes in the exposed pipe were monitored using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetery (DSC), and mechanical properties testing. The data show that the PVC pipe lost 50 percent of its elongation at break within 12 to 16 months at Dhahran and more than 24 months in Florida during outdoor exposure. The growth of carbonyl groups and the lowering of the glass transition temperature (T_g) was also observed during this exposure period. The extents of degradation of the PVC pipe exposed at the Dhahran and Florida sites were compared.