AN INFRARED SPECTROSCOPIC STUDY OF THE MIGRATION OF A PLASTICIZER IN POLY(VINYL CHLORIDE) RESINS

Migration of a plasticiser, di-2-ethylhexylphthalate (DOP), in vinyl chloride resins containing stabilisers, di-n-butyl-tin-dilaurate and di-n-butyl-tin-maleate (DBTM) under heat, accelerated weathering (SWM), outdoor exposure or warm water immersion was investigated mainly by depth analysis using Fourier-transform infrared spectroscopy. In the case of heating, the DBTM inhibited the evaporation of DOP from the surface. Electron probe microanalysis and scanning electron microscopy indicated that the concentration of the deteriorated DBTM near the surface formed a barrier layer against the evaporation of DOP. Under the other conditions, migration of the DOP was different from that of heating, and the DBTM did not affect the evaporation of DOP. Under SWM, the evaporation of DOP was observed only from the exposed side, while it was observed from both sides under outdoor exposure. Moreover, the depth profiles of DOP in the samples exposed outdoors were similar to that of the immersed samples, which suggested that the plasticiser was extracted by water such as rainfall and dew, during the outdoor exposure.