Degradation of vinyl polymer films upon exposure to chlorinated water: the pronounced effect of a sample's thermal history

Experiments were performed to identify the reactive intermediate(s) involved in the degradation of several vinyl polymers upon exposure to chlorinated water. The potential intermediates of concern are Cl2, HClO, and singlet molecular oxygen, O2(a1Δg), all of which exist in chlorinated water and whose concentration profiles are pH-dependent. The degradation of polystyrene and poly(styrene-co-butadiene) films was monitored in a variety of pH-dependent experiments using FTIR spectroscopy. Data obtained indicate that Cl2 is the principle reactive intermediate that initiates polymer degradation, and that singlet oxygen does not play a significant role under these conditions. Moreover, poly(styrene-co-butadiene) samples were significantly more susceptible to the effects of chlorinated water than were polystyrene samples and, thus, identify olefinic residues as an important reactive functional group under these conditions. Data obtained also indicate that the thermal history of the sample is important. Specifically, upon immersion in chlorinated water, samples that had been exposed to high temperatures during processing and/or that had been annealed for longer periods of time degraded at a much faster rate than did samples that had only minimal exposure to high temperatures. This effect was particularly pronounced with the poly(styrene-co-butadiene) samples. These results are important with respect to the development of polymers that can better resist exposure to water that has been chlorinated to kill bacteria (e.g., drinking water). [Copyright &y& Elsevier]