Crosslinking of PVC formulations treated with UV light. II. Color formation and viscoelastic properties

Two wire coating PVC formulations stabilized with Ca/Zn systems and one stabilized with a traditional lead compound were prepared. All three formulations contained trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent and Irgacure 819 as a UV photoinitiator. Small specimens of hot-pressed materials with 1.0 and 1.5 mm thicknesses were irradiated with UV light for 10 days, while monitoring changes at different time intervals. The presence of TMPTMA in the samples influenced the coloration of the lead-stabilized formulation, while the others experienced the usual color formation after UV treatment, as seen by Yellowing Index measurements and corroborated by the evaluation of fluorescence spectra. The elastic modulus (E′) determined by DMA was shown to be sensitive to surface changes associated with crosslinking, while the loss modulus (E″) determined by DMA and the complex modulus (E*) obtained by TMA were shown to be sensitive indicators of bulk property changes. J. VINYL ADDIT. TECHNOL., 13:189–194, 2007. © 2007 Society of Plastics Engineers