Organotin mercaptides are not only able to react with hydrogen chloride or annihilate initiating sites by substitution, but also help impede autoxidation. The combination of these two functions gives the organotin mercaptides exceptional thermo -stabilizing properties which are not exceeded by any other class of stabilizers.

Thus it is logical that sulphur-containing organotin stabilizers be used in all types of PVC processing where very high thermo stability is required.

One of the most appreciated properties of the whole group of organotin stabilizers is the absolute crystal clarity of finished articles, an advantage in the manufacture of rigid PVC packaging and overhead-transparency film, bottles and containers. Thiotins are used also in the manufacture of plasticized PVC hoses, profiles, sheets, and transparent top coats of coated articles.

Sulphur-containing organotin stabilizers are not, in general, self-lubricating. Therefore, the high processing temperatures which are necessary for optimum transparency may cause adhesion of the hot melt to metal surfaces of the processing machine, if this is not prevented by the addition of suitable lubricants.

Although organotin stabilizers lower the melt viscosity of rigid PVC, the addition of high-polymeric processing aids based on PMMA is advantageous in order to impart better flow properties and to improve surface quality of finished articles, e.g. in calendaring of films, extrusion of profiles and sheets, blowing of bottles and in the injection molding of fittings.

Organotin stabilizers migrate from rigid PVC only very slightly. This fact, together with favorable toxicological properties is the basis for the worldwide approval of di-n-octyltinbis (isooctylthioglycolate) for use in food packaging and potable water pipes. Certain types of monooctyltin mercaptides specifically designed for calendering have been approved for these uses in some countries.

Butytin mercaptides are utilised as universal stabilizers for the production of article such as films, sheets, injection mouldings, floor tiles and wall coverings. They are also used for pipe extrusion. Transparent and translucent articles for outdoor use can only be stabilized with sulphur-containing organotin stabilizers if used in combination with suitable UV absorbers.

A special field of application for sulphur-containing organotin stabilizers is the production of foamed rigid PVC profiles. Formulations which contain both organotin mercaptides and cadmium or lead-containing stabilizers or pigments may discolour on account of the formation of cadmium or lead sulphide ("sulphur staining").