I've been doing some 'research' into the membrane situation for a few weeks, working out the situation with membranes...
It turns out they use a plasticiser called DEHP, which is a pthalate. Pthalates are carcinogenic, and they leach out of products. Don't worry, you'd have to suck on a HUGE amount of plastic for a VERY long time for an even measurable amount to be absorbed. Anyway, these pthalates soften the plastic to make it more pliable or rubbery. Membranes need to be a little flexible, but not 'rubbery' so that they eventually distort and take the permanent deformed shape (so keys stick on, etc). Pthalates tend to evapourate. The plastics usually become harder and, if a small amount of pthalates were used the plastic becomes brittle and cracks. Ahah... I am looking at materials and methods to make replacement membranes. If anyone has any knowledge, information, ideas or suggestions, can they please email me? This could include materials, design alternatives, possible sources of materials, manufacturers with short run membrane experience, etc... Thanks... Dave ql.spodmail.com
