Importance of Booster in Organotin Stabilizer for PVC

Importance of Booster in Organotin Stabilizer for PVC

Polyvinyl Chloride (PVC) is normally exposed to heat during processing. In such processing steps, PVC polymers are compounded with additives such as plasticizers, ultraviolet light stabilizers, and lubricants. These additives are important for extrusion and/or moulding of the polymers to form useful articles. When PVC polymers are exposed to heat for extended periods they tend to decompose by loss of hydrohalide molecules from the polymer chain. Such degradation results in loss of utility.

To overcome the heat instability of PVC polymers, heat stabilizers have been incorporated into the polymers at an early stage during compounding. The stabilizers employed fall into different categories. These are compounds of lead, organic tin compounds, calcium-organic compounds, and mixed metal compounds. PVC has traditionally been co-stabilized with heat stabilizers to prevent discolouration and loss of properties during its processing and/or use. Conventional co-stabilizers include but are not limited to, β-diketones, β-triketones, β-keto-esters, their enamines, dihydropyridines, Tris (2-Hydroxyethyl) isocyanurate (THEIC), and uracil derivatives.This decomposition can be inhibited by organotin stabilizers as an alternative to lead stabilizers.

Two principal functions, first tin reacts with HCl to give organotin chlorides, which do not catalyse the elimination process. Secondly, they substitute the chloride at reactive sites, introducing other groups such as mercaptides, which are not easily eliminated. Liquid organotin stabilizers provide better distribution, better compatibility, and in turn better thermal stability during processing and better transparency to PVC products. They have excellent initial colour hold and work at lower PHR levels than other stabilizers. Tin content varies from 9 – 19% and can be boosted with appropriate compounds. Tin content of more than 1.5% in end products is not allowed in products used for food application.

Platinum Industries Ltd has now developed an unknown class of compounds that can be used to boost organotin stabilizers. The performance of conventional heat and colour stabilizers even when heavy metals and/or Zn are not present. Available grades are Tbooster 916 ZP, Tbooster 917 ZP, and Tbooster 917 ZP. We prepared the sample with and without Tbooster and carried out an oven test. 

Detailed results are in Figure 1. 

Figure-1: Static thermal heat stability test of sample 1 to 7.  Sample1 containing only Methyl Tin Stabilizer and sample 2 to 6 containing Methyl Tin Stabilizer with booster 0.2 and 0.4 PHR respectively.

Based on an internal application study, Tbooster can replace up to 25% of tin stabilizer in existing recipes for customers and their applications.

Benefits of Tbooster:

1. Boost thermal and colour properties

2. Reduce the heavy metal content for compliance requirements

3. Cost-effectiveness

4. Easy to use

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Platinum Industries Ltd., a proud member of the Indian Vinyl Council (IVC)