Tin-Naphthalene Sulfonic Acid Complexes as Photostabilizers for Poly(vinyl chloride)

Angham G. Hadi

Abstract: Poly(vinyl chloride) degrades when exposed to ultraviolet light for long durations; therefore,
the photostability of polymeric materials should be enhanced through the application of additives.
New organotin complexes containing 4-aminonaphthalene-1-sulfonic acid were synthesized
and their role as poly(vinyl chloride) photostabilizers were evaluated. The reaction of 4-amino-3-
hydroxynaphthalene-1-sulfonic acid and appropriate di- or trisubstituted tin chloride (triphenyltin
chloride, tributyltin chloride, dibutyltin dichloride, and dimethyltin dichloride) in methanol under
reflux gave the corresponding tin-naphthalene complexes with yields of 75%–95%. Elemental analyses
and spectroscopic techniques including infrared and nuclear magnetic resonance (proton and
tin) were used to confirm their structures. The tin complexes were added to poly(vinyl chloride) to
produce thin films that irradiated with ultraviolet light. Various parameters were assessed, such as
the weight loss, formation of specific functional groups, changes in the surface due to photoirradiation,
and rate constant of photodegradation, to test the role played by the organotin complexes to
reduce photodegradation in polymeric films. The results proved that organotin complexes acted as
photostabilizers in these circumstances. The weight loss, formation of fragments containing specific
functional groups, and undesirable changes in the surface of polymeric films were limited in the
presence of organotin complexes. Organotin complexes containing three phenyl groups showed the
most desirable stabilization effect. These act as efficient primary and secondary photostabilizers, and
as decomposers for peroxides. In addition, such an additive inhibits the dehydrochlorination process,
which is the main cause of poly(vinyl chloride) photodegradation.

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