Rubber Storage

From: Bill Henderson <billh0231_at_yahoo.ca>
Date: Sat, 01 Nov 2008 19:54:25 -0000

My name has been mentioned in connection with this subject and so I
decided I should surface and post the advice I used to give friends
that had an interest in indoor flying.
The problem with plastic storage bags is that they are made from many
different plastics depending on the country they are made in and/or
the intended end use. Many plastics outgas or contain platicizers
that cause rapid deterioration of indoor rubber. The worst amomg
these are the laminated films that have a layer of plasicized PVC.
The best films, that are inert as far as rubber is concerned, are
those made from Polyethylene. There are two types used; Low Density
Polyethylene (LDPE) and High Density Polyethylene (HDPE) the only
difference between the two is the length of the side chains attached
to the main polymer chain. LDPE has longer sidechains and could trap
unwanted molecules in the spaces beteen the chains, but this is very
unlikely due to the very high-pressures and high temperatures used in
its production.
How do you know if the bags you are using are PE?
The basic test is the flotation test, where the bag is filled with
water and then lowered into a bath of water. PE bags will float all
others will sink.
If you still have some doubts then you put a corner of a bag into a
gas flame. If the flame is blue with no smoke then it is PE. (PE is
just a sophisticated wax) If the flame is yellow or smokey the bag is
not PE and should not be used for rubber storage.
Paper bags have been suggested, but paper is usually acidic and will
cause rapid deterioration of the rubber. Acid free envelopes are
available, but are expensive, because they are of archival quality.
Hope this clarifies the discussion on this subject.
Bill Henderson
Received on Sat Nov 01 2008 - 12:54:31 CET