Re: Info on Flexible SLA photopolymer

From: Bronson R. Hokuf 302-328-5635, FAX 302-328-5693 (HOKUFBR@ESVAX-A1.EMAIL.DUPONT.COM)
Date: Thu Feb 27 1997 - 21:05:49 EET


On Feb. 25 Rajeev Garg asked about a flexible material comparable
to the recently introduced DuPont Somos 201 powder being
distributed by DTM for the SLS process:

> Does anyone know about similar polymer for the SLA
> ( i.e., flexible an rubber like)
> Any information is highly appreciated...
> Rajeev Garg

Others have also recently asked:
> My name is Matthias Heger and I'm a Ph.D. student on the German
> Plastics Institute in Darmstadt. My research topic is the
> development of an elastomeric SLA resin for the SLA 250... >
> Matthias Heger

> I was wondering if anyone knew of an SLA resin that will
> directly simulate an elastomer of 40 or 50 durometer. Is
> anyone developing or currently selling something without going
> through a soft tooling process? Thanks for any info.
> Bill Noack

DuPont manufactures a flexible resin for the stereolithography
market. This material is called DuPont Somos(r) 2100 (for Ar+
lasers) or Somos(r) 2110 (for HeCd lasers).

This resin produces parts with a Shore D durometer of 41 and that
can have up to 46% elongation and high impact strength 150 J/m
(2.9 ft-lb/in). At the present time the tear strength for a
typical part is ~33 lbs (~15 kg) as measured on a ASTM D1004 test
sample with a thickness of 0.12 in. (~3mm).

The DuPont Somos group is in the middle of a new study where we
will try to report the range of properties that can be achieved
for this material by varying the post-cure conditions and the
build conditions. I will post these results when they are
available, if there is interest.

Listed below is the information from the Material Properties
Data Sheet. This is (hopefully) ASCII format. If you would like
a nicely printed copy of the information, send me a message with
your address and I'll have one mailed out.

Regards, Bronson
Bronson R. Hokuf USMail: DuPont Company
DuPont Company (NCCC/Penns) 2 Penn's Way, Suite 401
Advanced Material Systems (P&IP) New Castle, DE 19720
Somos(tm) Solid Imaging Materials Tel: 302-328-5635
E-Mail: Fax: 302-328-5693

Material Properties [ASCII Representation, 80 characters wide]

DuPont Somos 2100 Photopolymer Family
Flexible High-Speed Acrylate

Somos 2100 is a low-odor, low-volatility, liquid photopolymer system. It
produces flexible, opaque parts, with smooth surfaces.
(N-vinyl-2-pyrrolidone is not present in this product.)

Somos 2100 is used in the solid imaging (stereolithography) process to build
three-dimensional parts. The resin is intended to be used with layer thickness
in the range of 0.15 mm (0.006 inch) to 0.30 mm (0.012 inch). After part
formation via UV light exposure, including UV Ar+ laser and UV HeCd laser, the
excess resin is removed by wiping and rinsing with a solvent such as isopropyl
alcohol (IPA) or tripropylene glycol monomethyl ether (TPM). The part is
post-cured by heat at 130oC for approximately 30 min depending upon geometry.

Optical Properties:
(Initial Values for Determining Working Curve)
                                             2110 (UV HeCd) 2100 (UV Ar+)
                                             ------------------- ------------------
Dp [slope of cure-depth vs. ln(E)] 0.118 mm (4.65 mil) 0.216 mm (8.5 mil)
Ec [critical exposure] 3.5 mJ/cm2 2.9 mJ/cm2
E-10 [exposure required to produce 30 mJ/cm2 9.4 mJ/cm2
      pane 0.254 mm (10 mils) thick]

Physical Properties: Somos 2100/2110 Liquid
      Appearance Bone white, opaque
      Viscosity 3,500-4,500 cps at 30oC
      Density 1.16 g/cm_ at 25oC

Physical Properties: UV-laser Cured "Green" Part (Typical)
D638M Tensile strength 1.4 MPa 14 Kgf/cm2 206 lb/in2
          Elongation at break 12 %
          0.2% Offset yield 0.47 MPa 4.8 Kgf/cm2 75 lb/in2
          Secant modulus at 1% strain 16 MPa 160 Kgf/cm2 2,300 lb/in2

D790M Flexural strength
        [material did not fail]
          Yield strength at 5% strain 0.49 MPa 5.0 Kgf/cm2 71 lb/in2
          Secant modulus at 1% strain 10 MPa 110 Kgf/cm2 1,500 lb/in2
          Secant modulus at 5% strain 10 MPa 110 Kgf/cm2 1,500 lb/in2

D2240 Hardness (Shore "D" durometer) 32

ISO180 Izod impact (notched) 19 J/m 0.36 ft-lb/in

Physical Properties: Post-cured by Heat (Typical)
D638M Tensile strength 7.1 MPa 73 Kgf/cm2 1,000 lb/in2
          Elongation at break 46 %
          0.2% Offset yield 0.57 MPa 5.8 Kgf/cm2 79 lb/in2
          Secant modulus at 1% strain 37 MPa 380 Kgf/cm2 5,400 lb/in2

D790M Flexural strength
        [material did not fail]
          Yield strength at 5% strain 0.64 MPa 6.5 Kgf/cm2 82 lb/in2
          Secant modulus at 1% strain 15 MPa 160 Kgf/cm2 2,000 lb/in2
          Secant modulus at 5% strain 14 MPa 140 Kgf/cm2 1,800 lb/in2

D2240 Hardness (Shore "D" durometer) 41

ISO180 Izod impact (notched) 150 J/m 2.9 ft-lb/in
(D256A) [Samples did not totally break]

TMA Thermal expansion 150-180 x 10-6um/oC


For more information contact:
DuPont Company
Somos Materials Group
Two Penn's Way, Suite 401
New Castle, DE 19720
TEL: (302) 328-5435 (USA)
FAX: (302) 328-5693 (USA)

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