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October  2004

Opening Up

Reader Disagrees with Fiberglass Fact ...
Dear DWM,
I have recently read one of your articles, “Fiberglass Composites: The Holy Grail of Fenestration Materials” by Phil Wake (see August DWM, page 52). I wish to point out an untruth presented by the author as I am very involved in the industry on a national level. In the article he states, “FRP is also a plastic but it is a thermal setting, not a thermoplastic material.” FRP can be a thermoset or a thermoplastic depending on how it’s manufactured. Thermoset implies that it cannot be reformed or recycled as it is not affected by heat or chemicals usually achieved by vinylester and a formaldehyde catalyst. In the cases of the window products listed, they use a polyester resin (absolutely a thermoplastic) so the product can be recycled. 
Michael Lotesto

... and Author Responds to Comment
Your reader is technically correct in saying that polyesters could be thermoplastic or thermosetting. When polymers are cross linked or cured they become thermal setting. We utilize thermosetting polymers which provides fiberglass windows with their strength and dimensional stability over the full temperature spectrum. Most common resins in the pultruded fiberglass window industry are thermosetting polyesters but increasingly thermosetting polyurethanes are being developed.

Fiberglass windows with thermosetting resins are not recyclable in a conventional context but since they retain their original performance characteristics and last indefinitely it is really a moot point. 

Development work is underway to use thermoplastic resins for window applications that would expand the market for pultruded fiberglass windows by permitting post forming to make special shapes.

To use a cooking analogy, chocolate (thermoplastic) can be heated to form a liquid then cooled again to form a solid. The melting cycle can be repeated indefinitely. Now if we take that chocolate, add eggs, butter, sugar, flour then mix and heat them (cross link) we get brownies (thermoset) that are permanently transformed and cannot be melted.

So there is no “untruth” in the article. But I’m not a polymer chemist-just a window salesperson and a late blossoming cook. 
Phil Wake
vice president sales and marketing
Omniglass Ltd., Toronto 

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