FTIR is the technique most frequently used to examine the chemical changes that occur in polymers during UV photodegradation. Carbonyl and other indices are used in most studies to quantify the degradation of polymers using FTIR data. These indices have not been correlated with molar mass distribution (MMD) changes as degradation proceeds. This work presents the results of a study that links FTIR index changes to MMD changes in PE, PMMA, and PIB under accelerated weathering conditions at the NIST SPHERE facility. Thin film samples of PE, PMMA, and PIB on CaF2 were irradiated in the NIST SPHERE for 4 weeks at 35 oC and 0 % relative humidity. Three replicates of each polymer were removed each week and analyzed using HPLC-GPC after FTIR spectra of every sample were taken. Each studied polymer degrades through a unique ratio of scission to recombination reactions and through different reaction networks which combined generate unique MMDs. The evolution of those MMDs with UV photodegradation time is compared across polymers and the universalities and differences enumerated. The sensitivity of various FTIR indices to these MMD differences is quantified and the implications of the results are discussed.

How FTIR measurements of polymer UV photodegradation correlate with changes in the molar mass distribution

248th National Meeting (2014)

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