Besides Ca-Zn stabilizers, Organotin mercaptide based stabilizers are another choice. These are generally available in liquid form, but nowadays powder form is also available with some manufacturers. Organotin stabilizers are very popular for transparent applications and rigid applications in America. They offer outstanding color retention in plasticized and rigid PVC processing. While selecting lubricants with
Tin Stabilizer, stearic acid shall be avoided as it may form highly incompatible alkyl tin stearates and cause spewing in plasticized applications or exudation.
Organotin stabilizers offer excellent thermal performance and therefore, are employed as the most efficient thermal stabilizers. They are more expensive than Leads, but as they are so efficient, processers with top-of-the-line extruders are reported to have come down to 0.3-0.5 PHR with the powerful methyl tins and being competitive to
Lead Stabilizer systems.
Organotin stabilizers are classified as toxic and a few are also classified as toxic for reproduction. Therefore, sufficient precautions have to be taken to avoid ingestion, skin absorption and inhalation. In the case of potable water pipe, tin stabilizers are approved in all Asian, European countries and the USA. However, in Europe, their usage in water pipe has been largely confined to France and Belgium, while it is the dominant stabilizer type used for this application in the USA. Following a risk assessment, risk reduction measures are currently under discussion at the EU level. The industry has already phased out organotin stabilizers in most of the applications.
The other very new and emerging category of heat stabilizers is Organic stabilizers. They are being developed as effective, safer and more eco-friendly additives for PVC processing. The major component acting as primary stabilizer and lubricant is Calcium Stearate. Other than calcium stearate organic stabilizers are based on various organic compounds like alkyl/aryl phosphites, epoxy compounds, beta-diketones, amino crotonates, nitrogen heterocyclic compounds, organosulfur compounds (i.e. ester thiols), hindered phenolics, and polyols (pentaerythritols). These combinations of various ingredients provide a wide processing window. They provide high thermal stability and excellent reprocessability. Organic stabilizers are currently being heavily researched, and their use at the expense of metal-containing stabilizers is expected to grow significantly.
