Sorry to cite my Dad as my authoritative source but he is an organic chemist and materials engineer, so... The following information is from him. Polyethylene is a specific type of plastic, made from a specific and distinct polymer. Polyethylene plastics can be produced in many different forms, such as thin sheets (e.g. many plastic wraps), molded forms (e.g. lots of plastic containers), and foams. Ethafoam, as its name might suggest, is a polyethylene foam (the type manufactured by Dow Chemical). Polypropylene and polystyrene are two other types of plastics, both chemically distinct from polyethylene. Polyethylene and polypropylene are chemically both polymers made of linear molecules, with polypropylene having single-carbon side branches at every third carbon atom in the molecular chain, which makes it a little stronger than polyethylene. Both are somewhat elastic and flexible at the molecular level, which is why the pin-holes in the polyethylene foam tend to close up and the foam doesn't break down. In contrast, the polystyrene polymer has a circular molecular shape with a methyl group sticking out from one of the carbons in the circle. Polystyrene is a more brittle plastic, even at the molecular level, which is why it breaks down with repeated pin insertions. "Memory foam" is probably a mixture of polyurethane with other plasticizers, but he wasn't sure of the details because he never had occasion in his work with polymers to evaluate it or work with it. Anyway, it is definitely soft and 'squidgy' and not at all suitable for lace pillows.
He also told me a lot about relative flammability, resistance to solvents, etc., all of which I don't think is particularly relevant to our questions about Ethafoam lace pillows, but if anyone wants to know... ;-) This link may also be of interest since it is gives lots more information about various types of polyethylene foams: http://cool.conservation-us.org/byauth/williams/foam.html as well as a discussion from a conservator's point of view. The polypropylene foam mentioned, "Strandfoam", might be interesting to try for lace pillows, since it would probably be 'tougher' and maybe firmer to the feel (but also more expensive) than Ethafoam. Hope this clarifies some of the questions about plastics that have been batted about in the last few hours. Nancy, still sweltering in our heat wave in Connecticut. ________________________________ From: "[email protected]" <[email protected]> To: Sherry Naleszkiewicz <[email protected]>; [email protected] Cc: Agnes Boddington <[email protected]>; [email protected] Sent: Sun, July 25, 2010 3:31:53 PM Subject: Re: Re: Re: [lace] Ethafoam ... Google "ethafoam polystyrene" - interesting links. Polyethylene is a generic name for the molecular base for many plastics. On Jul 25, 2010 11:58am, Sherry Naleszkiewicz <[email protected]> wrote: > Actually, ethafoam is ... - To unsubscribe send email to [email protected] containing the line: unsubscribe lace [email protected]. For help, write to [email protected]
