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| Silicone
RTV Mold Rubbers |
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Platinum
Silicone 73 Series RTV Silicone Mold Rubbers
Features
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- Very
low viscosity
- Room
temperature cured or heat accelerated
- Easy
release properties
- Very
high tear strength
- Good
chemical resistance
- Low
or zero shrinkage
- 10A:100B
mix ratio
- Range
of hardness A45 to A30
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Benefits
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- Easy
to use, can be cured quickly
- Excellent
detail reproduction. Easy degassing
- Save
on release agents
- Fewer
prematurely torn molds
- Longer
mold life
- Better
dimensional reproduction
- Match
hardness to flexibility required
- Can
be hand or meter mixed with equipment
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Description
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Platinum
Silicone 73 Series RTV silicone rubbers are two-component,
addition-cure, platinum-catalyzed, very high tear strength,
flexible mold compounds. A tough, knotty tear is characteristic
of the 73 Series systems making them especially valuable to
the mold making industry. The 73 Series rubbers are suggested
for assessment as mold supplies for polyester, epoxy, polyurethane
resins, waxes and various other materials. Platinum Silicone
73 Series silicones offer may advantages in curing over tin-catalyzed
systems. They don't shrink, they don't produce alcohol, which
can inhibit urethane castings, and they can be accelerated
with heat to speed the cure.
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MIxing
Instructions
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Weigh
the proper ratios of Part B and Part A into a clean mixing
container. Mix completely, scraping the sides and bottom of
the container. To assure a bubble free mold, deaerate the
liquid rubber under vacuum at 28 to 29 inches of mercury until
the mass of rubber rises and then collapses. Deaerate for
2 additional minutes. Use a mixing container 3 - 4 times larger
than the mass of rubber for vacuum purposes. Do not attempt
to vacuum fast setting 71-10. (Caution, Platinum Silicone
71-10 Part B requires stirring before use.) |
Caution
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Platinum
Silicone 71 Series cure faster at higher temperatures. Temperature
should be above 77°F to obtain full hardness overnight.
At lower temperatures, 48 hours may be required to achieve
full hardness. Curing below 65°F is not recommended. Contamination
from amines, soaps, sulfur, tin compounds or some RTV silicone
rubbers may inhibit surface cure. To test compatibility, pour
a small quantity of catalyzed material on the surface to be
reproduced. Then, allow it to cure and observe for proper
cure and release. Although Platinum Silicones do not shrink
while curing, repeated casting with certain materials may
instigate shrinkage over time. |
Model
Preparation
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In
order to deter penetration of the rubber into the pores of the
material, porous models such as wood or plaster should be sealed.
Acceptable sealers include: wax, petroleum jelly, lacquer, paint
and most other coatings. Materials that will contact the rubber,
such as the sealed or non-porous model, should be sprayed or
coated with a very light coat of release such as a 10% by weight
solution of petroleum jelly warmed and dissolved in mineral
spirits. Inhibition and/or adhesion may occur when silicone-based
release agents, such as Ease 2300 Release Agent, are used on
surfaces that will contact the liquid rubber. Vent porous models
from beneath to prohibit trapped air from producing bubbles
in the rubber. Use a parting agent to prevent liquid silicone
rubbers from bonding to cured silicone rubbers. To determine
complete curing and good release are achieved, a test cure should
be completed on an identical surface in any case where there
is a question about compatibility between the rubber and prepared
model surface. The cure of silicone mold compound may be repressed
by some surfaces, particularly oil based clays including sulfur.
It is strongly suggested to perform a test cure on questionable
surfaces.
Molds may be reinforced with stretchable dacron
cloth or open mesh nylon. The weave of the cloth may show
through to the face of the mold if the fabric is too close
to the mold surface. |
Using
the Mold
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It
is not necessary to use a release agent for casting most materials
in Tin Silicone or Platinum Silicone molds. A barrier coat or
release agent is recommended for longer mold life with epoxy,
polyurethane or polyester resins. Tin Silicone molds can be
stored for more than a year, but as with most tin-catalyzed
silicones, they may ultimately deteriorate and lose elasticity.
Molds constructed with surplus catalyst may degrade upon aging
more rapidly than silicone rubbers cured with less catalyst.
Platinum Silicone 71 & 73 Series rubbers will endure several
years without deterioration.
Alcohol will inhibit the surface cure of polyurethanes.
Tin-cured silicones release alcohol during cure, which must
be allowed to evaporate prior to casting polyurethanes. Exposure
to air for 24 hours in a warm location is often adequate.
To accelerate alcohol evaporation, the mold can be baked for
four hours at 212ºF (100ºC). |
Safety
and Cleanup
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Read
the Material Safety Data Sheets before use. If directions are
followed correctly, Tin Silicone 70 and Platinum Silicone 71
& 73 Series rubbers are safe to use. Irritation may develop
if contact occurs with skin and eyes. Respiratory irritation,
headache and nausea could be caused by overexposure to vapors.
Use only with adequate ventilation. Wipe with disposable paper
towels for most effective method of cleanup. Xylene, toluene,
trichloroethane, naptha and denatured alcohol are suitable solvents,
but should be handled with regard for vapor and flammability
risks.
Thickening for Brush On: For brushing on a
skin mold, all Tin Silicone 70 Series rubbers can be thickened
with Cab-O-Sil. Thickener for Tin Systems, a liquid additive,
may be mixed into the Part B base, as an alternative to Cab-O-Sil,
at levels up to 5%, which yields a non-sag viscosity. A related
product, Thickener for Platinum Systems, is obtainable to
utilize with Platinum Silicone RTV's. |
Physical Properties: |
|
73-29 |
73-45 |
Mix ratio, by weight |
100B to 10A |
100B to 10A |
Hardness, Shore A |
30 |
45 |
Pour time, minimum |
45 min. |
45 min. |
Demold time @ 25oC (77¡F) |
12 hr. |
12 hr. |
Color |
White |
Green |
Viscosity, mixed |
15,000 cps. |
25,000 cps. |
Cu. inches/pound |
25 |
21.3 |
Specific gravity |
1.10 |
1.30 |
Packaging for 71 & 73 Series: |
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Containers |
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Size |
Net lbs. |
Product |
Weight/lbs. |
A |
B |
A |
B |
73-29, 73-45
Mix Ratio 10A to 100B |
1.00 |
4 oz. |
1 pt. |
0.10 |
0.90 |
9.00 |
1 pt. |
1 gal. |
0.90 |
8.10 |
44.00 |
1/2 gal. |
5 gal. |
4.00 |
40.00 |
495.00 |
6 gal. |
55 gal. |
45.00 |
450.00 |
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71-50, 71-40, 71-35, 71-30, 71-10
(71-40)
Mix Ratio 10A to 100B |
1.00 |
4 oz. |
1 pt. |
0.10 |
0.90 |
9.00 |
1 pt. |
1 gal. |
0.90 |
8.10 |
44.00 |
1/2 gal. |
5 gal. |
4.00 |
40.00 |
484.00 |
6 gal. |
55 gal. |
44.00 |
440.00 |
495.00 |
6 gal. |
55 gal. |
45.00 |
450.00 |
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71-20
Gel-10
Mix Ratio 1A to 1B |
2.00 |
1 pt. |
1 pt. |
1.00 |
1.00 |
16.00 |
1 gal. |
1 gal. |
8.00 |
8.00 |
80.00 |
5 gal. |
5 gal. |
40.00 |
40.00 |
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2300
Release Agent: 12
oz. can, Case of 12 cans
2350 Release Agent: 1 qt. (1.5 lb.), 5 gal. (26 lb.)
Silicone Fluid 500 cs or 100 cs grade for thinning
platinum silicone or tin silicone rubbers: 1 qt. (2 lbs.),
1 gal. (8 lbs.), 5 gal. (40 lbs.)
Thickener for Platinum Systems for thickening platinum
silicone:
4 oz. (.25 lb.),1 pt. (1 lb.)
71 & 73X Accelerator for platinum silicone systems:
4 oz. (100g), 1 lb. (454g), 1 gal. (8 lb.)
71 & 73R Retarder for platinum silicone systems:
4 oz. (100g), 1 lb. (454g), 1 gal. (8 lb.), 5 gal. (40 lb.)
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