"Seng, Dave" wrote: > > > -----Original Message----- > > From: PGevanthor_at_aol.com [mailto:PGevanthor_at_aol.com] > > What do readers of the list know about the high > > performance thermoplastic used by Prijon vs. the standard plastic used by > > Necky and most of the other plastic boats? Thanks foe any help. > > In my layman's understanding - Prijon uses a blowmolding process that > utilizes a cross-linked polyethylene. Most other poly boat makers use a > roto-molding process - linear polyethylene. The long polyethylene molecules > in a cross-linked plastic are "linked" to each other thus forming a stronger > bond and the result is a stiffer plastic. Linear plastics have the same > long poly molecules all laying side by side - but without the crosslinks > between molecules. Good description, Dave. X-linked PE is stiffer, also, which may reduce the oil-canning problem some PE designs have. There are other differences between the two ways of making PE boats. Some may significantly affect boat lifetime. In rotomoulding, the PE is measured into the cold mold as a passel of small (pea-size) lumps. Then the mold is warmed, and rotated along at least two perpendicular axes, so as to distribute the PE "uniformly." Then the mold is cooled, and separated, releasing a yak body, ready for trimming and outfitting. Naturally, the skill of the operator/software who/which controls the rotation process affects the result. In blow-moulding, my understanding is that the "bubble" thins as it expands into the mold, and the main deficiency is that the PE layer can get too thin as it stretches over bumps in the mold surface. I have not seen many blow-moulded boats, but before I bought one, I'd look for this flaw at places where the shape changes rapidly. Not knocking PE boats -- I owned a roto-moulded "Blem" made by Perception for several years which performed well -- and it was strong. But, it pays to check over the specific boat you buy. -- Dave Kruger Astoria, OR chemist *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Wed May 31 2000 - 21:44:05 PDT
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