forwarded for Steve Williams.
-------- Original Message --------
Subject: Re: RTI on Plastics
List-Post: emc-pstc@listserv.ieee.org
Date: Tue, 2 Oct 2001 10:56:00 -0400
From: steve.willi...@apcc.com
To: tony.reyno...@pb.com
CC: emc-p...@ieee.org, owner-emc-p...@majordomo.ieee.org
Tony, some background
UL sets the world standards on plastic and they look at alot more than
just
flammability. So, the RTI issue is a UL 1950 issue. Now, I took a two
day
seminar to learn all of UL's crazy plastic requirements (very boring but
useful). Here is how RTI ratings work. The actual temperature of the
plastic part in question has to be measured. The RTI has to be greater
than
or equal to the temp measured during test. Now, here is the tough thing.
Your plastic has an RTI of 60. What this means is that it has never been
tested (UL assigns a generic rating of 60C to ABS and my guess is that
you
are using an ABS). What you need to do is ask the lab if you can do an
end
product test. In this case mold stress relief at 85C for 7 hours would
be
appropriate (Max Temp plus 10).
Now, in terms of Ball pressure that only applies if you are using this
plastic piece for direct support of live parts. If you are then the test
needs to be done.
I didn't think that UL1950 looked at things like RTI (I build products
to
UL 1950, 1778, 1449 etc. and I deal with RTI daily but I have never had
to
for UL 1950). My guess is that the test lab will have a hard time
understanding your arguments and you may need to call UL's plastic
division
in Melville, NY USA.
Good Luck
Steve
tony.reyno...@pb.com
Sent by: To:
emc-p...@ieee.org
owner-emc-pstc@majordom
cc:
o.ieee.org Subject: RTI on
Plastics
10/02/2001 08:45
AM
Please respond
to
Tony.Reynolds
All,
I am having some fun with a lab over RTI ratings on plastics. Basically
we
have a plastic moulding with a component mounted directly on it. The
RTI
of the plastic is 60C and the component is getting to around 75C
actual. I
have always looked at the flammability of plastics 5V, V-0, V-1, etc but
never the RTI. Is this a just a UL1950 requirement or is it in EN60950
as
well. We have done the thermal stress at 70C and all is OK. They are
suggesting doing the ball pressure test at 125C, however, I have only
used
this for qualifying mains transformer bobbins, etc.
Regards
Tony Reynolds
Pitney Bowes
+44 (0) 1279 449479
+44 (0) 1279 449118
tony.reyno...@pb.com
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