Low‐temperature UV irradiation induced the color change kinetics and the corresponding structure development of PVC film

Abstract

The low-temperature ultraviolet (UV) irradiation equipment, developed in our Lab, was used to study the photo-aging of poly (vinyl chloride) (PVC) films at low temperature. The color change kinetics and corresponding structure development of PVC film during low-temperature UV aging were studied through L*a*b* coordinates Commission International d' Eclau-age (CIE 1976 color space) and Ultraviolet spectrophotometer (UVvis) and Fourier transform infrared spectroscopy (FTIR). It was found that the yellowness difference (~b*) and color difference (~E*) of the PVC film increased almost linearly with the aging time. Their values had a slower change at lower temperature. The kinetic study showed that the relationship between the velocity of coloration of the PVC film and the temperature agreed well with Arrhenius equation at low temperature. The activation energy of coloration of the PVC film was calculated. The FTIR spectra indicated that photo-dehydrochloration, resulting in the generation of conjugated carbon-carbon double bonds, was the main reaction for PVC during photo-aging at low temperature. Meanwhile, the photooxidation was also obvious and could not be neglected. It clearly confirmed that the absorption peaks of conjugated carbon-carbon double bond increased and shifted to longer wavelength during photo-aging in the UV-abs analysis.

Electron and gamma irradiation‐induced effects in poly(ethylene‐co‐tetrafluoroethylene) films

“…This is because their low absorptivity (bands around 200-300 nm) can be neglected comparing with the predominant absorptions of the conjugated C C bonds. 82,88,89 In the irradiation doses of 50-400 kGy, the linear relations are clearly observed for the peak areas with irradiation doses as presented in Figure 4c. However, in the higher dose range of 400-800 kGy, these linear behaviors vanish even the appearance of intense absorbances.…”

“…Note that the CO bonds are not included in the fitting models despite the presence of carbonyl bonds in the irradiated films as revealed by the FTIR spectra. This is because their low absorptivity (bands around 200–300 nm) can be neglected comparing with the predominant absorptions of the conjugated CC bonds 82,88,89 . In the irradiation doses of 50–400 kGy, the linear relations are clearly observed for the peak areas with irradiation doses as presented in Figure 4c.…”

The Design, Synthesis and Application of Nitrogen Heteropolycyclic Compounds with UV Resistance Properties

“…To visualize the interactions present in the designed molecules, The degradation of PVC films and four PVC/TTT films at different aging times are depicted in the pictures presented in Tables 1 and S5. Based on the power of the UV aging chamber and the distance between the samples and the light source, 1 h of accelerated UV irradiation in the aging chamber is equivalent to 100 h of outdoor exposure under normal conditions [38,39]. The pure PVC film showed a burnt yellow color after 48 h, followed by turning into dark brown after 96 h and exhibiting a large area of fracture, while the color became dark after 144 h. The aging degree of the PVC/TTTB film was better than that of the pure PVC film, but this effect was not significant.…”

The influence of two‐stage variable temperature suspension polymerization on polyvinyl chloride resin: The molecular chain segment structure and thermal stability

“…Allyl chloride and the tertiary chlorine structure, termed unstable chlorine, were characterized as the main unstable sites. The removal of hydrogen chloride gas during degradation produces a large amount of conjugated polyene structures, changes the color of the PVC resin to yellow , and generates a serious decline in the transparency of the PVC product.…”