Photodegradation Study of PVC By New Metal Complexes of Thiourea Derivatives

Abstract

Two series of coordination complexes of Sn(II), Co(II), Ni(II) and Cu(II) metal
with N-diisobutyl-N/-2,4-dichlorobenzoyl thiourea (IBT) and N-diPropyl-N/-2,4-
dichlorobenzoyl thiourea (PBT) as a ligands were prepared and characterized. These
complexes were obtained in high yield from ethanolic solution of both ligand and salt.
The formed complexes results from the salt-ligand interaction with participation of both
salt cation and anion. Information on the coordination chemistry of these complexes was
derived from IR, UV-Visible spectra, elemental analysis and Conductivity study. On
coordination electronic structures of these ligands change as whole, affecting practically
all their vibrational pattern, however, within that complex pattern some vibrations
provide valuable information on the nature of the studied complexes. These thiourea
derivatives behave as neutral ligands, which coordinate the metal ion through the sulfur
and oxygen atoms. Further more; we used the molar ratio method to find the ratio of
coordination between the metal ions and ligands by using THF as a solvent, as it shows
the ratio 2 ligands to 1 metal for all prepared complexes.
The Photostabilization activity of these complexes on Poly (vinyl chloride) film was
investigated. Where the photostabilisation activity of these compounds were determined
by monitoring the carbonyl and polyene indices with irradiation time. The change in
viscosity average molecular weight of PVC were also followed with irradiation time
(using THF solvent)
According to the experimental results obtained we suggest some mechanisms
depending on the structure of the additives. UV absorption, peroxide decomposer and
radical scavenger for photostabilizer additives were suggested.