RE: Humidity's Effects on Cured Photopolymer Resin Epoxy TensileS trength

From: Jim Burt (
Date: Tue Oct 14 1997 - 00:34:59 EEST

Scott, have you considered using the SLA to produce an aluminum
investment casting or to create a silicon mold to make urethane or epoxy
parts with better physical properties? SLA are useful tools for creating
even more useful tools. I use several prototyping processes every day,
many of which originate as SLA's. Hope this helps.
Jim Burt
Manager, Product Design Services
Voice: 503) 685-8543
FAX: 503) 685-8544

        -----Original Message-----
        From: Scott Ostrem []
        Sent: Monday, October 13, 1997 11:17 AM
        Subject: Humidity's Effects on Cured Photopolymer Resin
Epoxy TensileStrength

        Does anyone have ANY data or experience(s) related to how
different humidity
        levels affect the tensile strength of Ciba-Geigy's Cibatool
SL5180 Photopolymer
        resin epoxy after it has cured? How about information related
to similar
        resin epoxies? 3D Systems was able to provide limited data
related to
        the tensile modulus versus the humidity environment, but they
had no data
        relating humidity and the tensile strength of the cured epoxy.
A second
        question - are there any sealants, paints, etc... that anyone
would recommend
        applying to the cured part to protect the part from the outside
        humidity. (The facility we test in has side doors that stay
open and allow
        outside air in.) Is it true that Thompson's water seal may
work? A third
        question if anyone knows the answer - what is the bearing
strength of the
        cured SL5180 epoxy? I ask this question from the standpoint
of, "What
        kind of torque can be applied to tension fasteners that hold
our SLA part

        A little background: As a design engineer, I am currently
designing a
        10 inch inside diameter air flow control valve that we (Boeing
        plans to build and test in a cold flow propulsion test lab in
St. Louis,
        Missouri. Using an SLA part instead of a metal part will save
a lot of
        money, but the unknowns associated with pressurizing a
        part in a fairly humid environment have many engineers worried.
We plan
        to make the valve out of Ciba-Geigy's Cibatool SL5180 due to
its published
        tensile strength and toughness, and we plan on using a large
safety factor.
          What we don't know is how is the documented tensile strength
of 6,000
        to 6,300 psi affected by various humidity levels and exposure
         Any information would be helpful.

        Thank you.

        Scott Ostrem
        Boeing Corporation
        MC S064-1225, Bldg 65, L3
        P.O. Box 516
        St. Louis, MO 63166-0516
        (314) 233-5846
        (314) 232-6054 (fax)

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