Mold Making Systems
Low Viscosity Platinum RTV (R-2138 R-2157)
R-2138 A/B, R-2157 A/B are a two-part, Platinum Based Silicone rubbers designed for mold making, embedding, electrical applications, and thermal expanding tools. The controlled coefficient of thermal expansion makes these RTV ‘s ideal for casting pressure pads and for use as an advanced composite tooling rubber. These low viscosity systems require a scale measurement for accurate mix ratio.
Physical Properties (TYPICAL VALUES): 24 hrs. @ 77F (25C)
| R-2138 A/B | R-2157 A/B | |
| Color: | Pinkish | Light Green |
| Mixed Viscosity@ R.T.: | 30,000 CPS | 30,000 CPS |
| Specific Gravity: | 1.25 | 1.25 |
| Mix Ratio A/B: | 10/1 | 10/1 |
| Durometer A Shore: | 42 | 50 |
| Tensile Strength (PSI): | 750 | 650 |
| Elongation %: | 350 | 300 |
| Tear Strength (PSI): | 125 | 102 |
| Shelf Life | 6 months | 6 months |
Mixing Instructions: **(Scale Measurement Required)
The base and curing agent are mixed just before using. Mix 10 parts base to 1 part curing agent by weight. Automatic mixing equipment or manual mixing may be used to combine base and curing agent. Immediately after mixing, place the material in a vacuum chamber to remove entrapped air. As vacuum is drawn, the material will expand as much as four times its original volume. Remove from vacuum chamber and pour very gently, so as not to incorporate air into the material.
Inhibition:
Certain materials will cause inhibition or neutralizing of the curing agent: sulfur and organo-metallic salt containing compounds found in organic rubbers, and many condensation cure RTV, chloride solvents, and amines-epoxy. Inhibition may easily be determined by brushing a small quantity of these materials over a localized area of the part to be reproduced. If the material remains gummy or uncured after the curing time, then the part’s surface is acting as an inhibitor. **See Addition Cure Technical Data Sheet for inhibiting
| TEMPERATURE | POT LIFE | CURE TIME |
| 100 F | 30 MIN | 2 HOURS |
| 150 F | 10 MIN | 30 MIN |
| 300 F | ---- | 5 MIN |
The information and data contained herein are based on information we believe reliable. Each user of the material should thoroughly test any application and independently conclude satisfactory performance before commercializing. Suggestions of uses should not be taken as inducements to infringe on any particular patent.