Re: More Options for Rub Rail Inserts

Karen Smith

We do not yet know for sure what the old inserts are made of, but EDPM rubber is used uncovered as a membrane for flat roofs, and typically has a warranted life span of 30 years.

Rubber like this is actually only about 25% EDPM plastic.  They are roughly 50% "filler/pigment".  For black rubber, this might be carbon black, for white it would be titanium dioxide, for red it would be a blend of iron oxide.  The rest of the formulation is various "oils" that serve to make it "rubbery" instead of brittle. If the wrong oils are used, they can evaporate over time, and the whole part shrinks.  We will confirm the long term dimensional stability of the extrusion with the manufacturer.  I'm thinking that over 50 feet, shrinkage of 1" is tolerable, leaving just a bit more of a gap at the back of the rail than it started with.  That's about 0.2%, and gives me a number to look for.

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