Tony Walsh, Managing Director of Freefoam Plastics, a fast growing supplier of roofline products, sets the record straight on 'Pinking'

THE PINKING ISSUE
Readers of trade magazine Glass & Glazing Products will have seen an article by Swish about 'Pinking', the term used to describe discolouration of PVC sometime after installation.

It's not a common problem by any means, but the issue or the threat of pinking in PVC-UE cellular foam or PVC-U window profile is a key concern to stockists, installers and specifiers for obvious reasons. It was much talked about in the early 1990s when there was a spate of problems, but discussion of the causes have rumbled on. Recently the British Plastics Federation presented three reports on the phenomenon that aimed to provide objective evidence of the causes and set the record straight. At this time the reports are not available to non BPF members, anti-PVC bodies such as Greenpeace or the public.

In the article Swish say that 'It is difficult to be definitive about the actual facts, because 'experts' disagree on the detail'. But they then go on to say that 'what they do agree on' is 'the only 100% sure way of protecting a PVC formulation against pinking seems to be to take a lead-free stance.' They also 'urge fabricators and installers of PVC-U products to ask their manufacturers for assurance that their products do not contain lead.' Swish go on to propose use of tin stabiliser for cellular foam, and to Calcium Zinc for window profile 'as soon as the market allows'.

I believe this interpretation of the report's conclusions differs significantly from the BPF's by laying the blame for pinking squarely on lead. I also believe that bringing this debate out of the technical and into the commercial arena in this way plays into the hands of the anti-PVC environmentalists and runs the risk of damaging the industry as a whole, something Swish claim to be warning us against.

Swish warned about lead in both window and cellular foam profiles. Freefoam Plastics don't manufacture PVC-U window system profiles and therefore don't comment on them, although I believe the arguments are similar. However I believe Freefoam may be unique in that our PVC-UE Cellular Foam products are completely lead free. The cellular foam core is tin stabilised and the PVC-U skin is Calcium Zinc stabilised.

On this basis you might expect us to side with Swish. As Swish propose, our products are ideal being based on tin and calcium zinc, and you might therefore expect us to welcome their argument. Certainly we are unaffected by the debate and can take an objective view of the issue.

Freefoam have never suffered from pinking, or indeed any other form of discolouration when we used lead. However we changed very early on, first to tin for the cellular foam core, and then eighteen months ago to calcium zinc for the PVC skin. This change had nothing to do with pinking but purely to gain production efficiencies and better product characteristics.

A combination of tin for the foamed core and calcium zinc for the skin is more expensive than using a lead formulation it's true. But although it's more expensive the finish is better. Consistency is improved and stability is better for coloured profiles. We also find that less waste is produced in the production process. An additional benefit is that the end product is lighter, more flexible and forgiving in use. This is important to us because for some time our aim has been to produce what we call a more fitter friendly product.

A more objective reading of the findings of the three BPF reports, which I believe are not in the public domain as Swish asserts, might be that it is not lead itself which is to blame for pinking problems but poor formulations which include a mismatch of lead and pigment. A better, more careful formulation of the right pigment and the right lead would not be affected. Indeed as I understand it in Germany, where they have used, and are still using lead formulations they have been totally free of pinking problems.

The arguments raised in the Swish article about lead and the environment in the context of PVC manufacture are specious and raising them and creating an issue where there is none certainly does provide fuel for anti-PVC groups such as Greenpeace. But it is Swish who are creating the issue and bringing it into the public domain. We believe that if manufactured using the correct formulation lead based product contains no threat to the end user, consumer interests or the environment.