Lead is an abundant metal which has been exploited since mining began in ancient historical times.
Lead has the longest history as a stabiliser for PVC. Lead compounds are a cost-effective stabiliser for PVC. Their stabilising effects are excellent and used for PVC products with long service life and required to endure longer fabrication (heating) hours. Use has been decreasing as a result of the Vinyl 2010 substitution commitment;, they now represent only about of total stabilizers used in PVC applications. A number of different lead compounds are used in PVC formulations in order to provide optimum performance in a particular application. The main compounds used are shown in the table.
Types of Lead Stabilisers
|Tetra-basic lead sulphate||85%|
|Tri-basic lead sulphate||82%|
|Di-basic lead phosphite||82%|
|Di-basic lead phthalate||75%|
|Di-basic lead stearate||51%|
|Normal lead stearate||28%|
Concerns have been expressed about possible adverse effects of lead on health and the environment. Independent experts completed a full Risk Assessment on lead in 2004 and the results have been passed on to the European Union authorities. Under the terms of the PVC Industry Voluntary Commitment, sales of lead stabilisers will be reduced in stages and ended by 2015. The use of lead stabilisers for potable water piping has been voluntarily discontinued end 2005 by the pipe producers members of the European association TEPPFA, which is a partner of Vinyl 2010.
Properties and Applications
The major properties of PVC compounds incorporating lead stabilisers include:
Excellent heat and light stability.
Good electrical properties.
Excellent short and long-term mechanical properties.
Low water absorption.
Wide processing range.
Good cost/performance ratio.