The structure of organotin mercaptoesters

This paper describes the structural differences existing among various organotin mercaptoesters of the general formula R_nSn[S(CH₂)_1–2COOR′]_4–n. Infrared and Mössbauer spectroscopies were the methods of choice to investigate such differences and they have revealed that thioglycolate and 3-mercaptopropionate esters adopt cyclic cis- or trans-trigonal bipyramidal as well as trans-octahedral configurations, according to the composition of the organotin compounds and their mode of preparation. Structural relationship among organotin mercaptides and thioacetates are also discussed.     

Antioxidative stabilization of poly(vinyl chloride)

Halogenated resins such as poly(vinyl)chloride undergo rapid degradation when exposed to heat. Such degradation is significantly increased by oxygen, and it is believed that the induction of the process of decomposition is caused by autoxidation of the polymer, followed by extensive dehydrohalogenation. Sulfur-containing peroxide decomposers allow primary stabilization of PVC with organic compounds which are not HCl acceptors but prevent free radical cross-linking of the polymer. This implies a discolored polymer melt (due to loss of HCl and formation of polyenes) which nonetheless exhibits good long term stability (no cross-linking). The stabilization of labile chlorine atoms results from the oxidation of various chain irregularities, and thus the elimination of the early discoloration can be achieved by the use of small quantities of monohydrocarbyltin co-stabilizers. The relative performance of various antioxidant systems are reported and possible stabilization mechanisms are discussed.