Tin-based stabilisers for PVC are in the focus of regulatory bodies – calcium-based stabilisers are a way out

Regulatory activities are one of the dominant drivers for developments. Tin stabilisers for PVC have been in focus of regulatory bodies for years now.

This triggered ongoing developments for Ca-based alternative stabiliser to replace the conventional Tin based chemistry. In many application fields such as plasticised film or rigid compact and foam sheet extrusion Ca-based alternatives have already gained a decent market share proving that the alternatives are workable.

The most relevant applications where tin stabilisers are currently used are rigid, often transparent, calendered film and foamed profiles and sheets.

Conventional Tin stabilisers provide very limited lubrication and provide good transparency which made them an ideal stabiliser for calendering. Good heat stability, low lubricity and high transparency have to be provided by the alternatives. Many foam profile producers are already using Calcium based stabilisers; in fact, a significant amount of the profile in the market is already non-Tin-stabilised, so there’s some know-how existing in that application.

Foam structure, a homogeneous and smooth surface appearance especially in case of large size foamed sheets and good initial colour are the main issues to be addressed.

Latest developments by Baerlocher addressing the issue

For rigid calendered film Baerlocher has now developed various grades such as Baerostab NT 1883 P or Baerostab NT 1929 P-series, which can cope with the demand for high transparency, good initial colour and a stable calendering process due to adjusted low lubricity.

For foam profile and foam sheet formulations used in continental Europe, Calcium-based stabiliser systems are designed in a conventional way as they are used in well-known rigid PVC profile extrusion.

Specific care must be taken when fine-tuning co-stabiliser systems and lubricants for foam extrusion to achieve proper surfaces and colour. Not all aspects are related to stabilisation only, overall formulation adjustments considering all components of a PVC formulation in close communication between Baerlocher and converters is recommended.