SES22258/CAT22258-40 and RTV-5240 are both transparent Shore A40 addition-cure silicones for rigid and precision-oriented mold making, but they emphasize different production priorities. SES22258/CAT22258-40 offers a longer 110-minute working window and higher published tensile, tear and elongation values, while RTV-5240 combines transparent A40 performance with low shrinkage, room-temperature curing and published heat resistance up to 250°C.
Addition-Cure Silicone
Platinum-Cure Silicone
SES22258/CAT22258-40 and RTV-5240 are both transparent Shore A40 addition-cure silicones, but they serve different mold-making priorities. SES22258 emphasizes higher published mechanical performance and a longer working window, while RTV-5240 emphasizes low shrinkage, room-temperature curing, transparent precision molds and high published heat resistance.
SES22258/CAT22258-40 and RTV-5240 are both transparent Shore A40 addition-cure silicone systems for relatively firm, dimensionally stable molds. Since their hardness is closely matched, the more useful comparison is how they perform in production: SES22258 emphasizes longer processing time and higher published mechanical performance, while RTV-5240 emphasizes practical room-temperature curing, low shrinkage and transparent precision mold applications.
SES22258/CAT22258-40 is positioned by Shin-Etsu as a high-strength, high-modulus mold-making material with high tensile strength and tear resistance. Its published 110-minute working time is one of its clearest advantages. This gives operators substantially more time for mixing, deaeration, positioning and controlled pouring, which can be valuable for large or complicated molds where a short pot life creates pressure during processing.
RTV-5240 takes a more conventional production approach. It provides a 45-minute working time and an approximately 8–10-hour room-temperature cure, making it more convenient when the goal is to complete a mold within a typical workshop production cycle without relying on heat-assisted curing. This can be particularly attractive for routine transparent molds, precision resin work and smaller production runs.
Both products use a 10:1 mixing system, so mix ratio is not a meaningful selection difference. Accurate catalyst measurement remains important for both systems. Viscosity is relatively high in each case: Shin-Etsu reports approximately 95,000 cP for the SES22258 base and 56,000 cP for the mixed material, while MinghuiLink reports approximately 80,000 mPa·s for Part A of RTV-5240. Because the values are reported at different material states, they should not be treated as a strict numerical comparison. For either product, appropriate mixing, deaeration and controlled pouring can be important when producing bubble-free transparent molds.
The published mechanical data give SES22258/CAT22258-40 a clear advantage. It reports 6.20 MPa tensile strength, 28 N/mm tear strength and 390% elongation, compared with at least 3.5 MPa tensile strength, 14 N/mm tear strength and 300±50% elongation for RTV-5240. These figures indicate a stronger published mechanical profile for SES22258, although different test methods and conditions should be considered when interpreting cross-brand data.
Transparency is an important functional characteristic for both products. A transparent mold allows the operator to see the master more easily, inspect internal detail and determine suitable mold-cut locations. This can be particularly useful for precision molds, complex patterns and applications where accurate mold construction is important. Because both materials are relatively viscous, bubble control remains an important part of transparent mold production.
RTV-5240 has a distinct advantage in room-temperature production and published temperature capability. MinghuiLink lists approximately 8–10 hours curing and heat resistance up to 250°C, together with a published shrinkage of ≤0.1%. SES22258 is instead positioned around high mechanical performance and an extended processing window, with a published standard cure of 24 hours at 23°C.
Overall, SES22258/CAT22258-40 is the stronger fit when longer working time, higher published mechanical performance and more controlled processing are important. RTV-5240 is better aligned with transparent precision molds where room-temperature curing, low shrinkage, shorter production cycles and published high-temperature capability are higher priorities.
| Technical Parameter | Shin-Etsu SES22258/CAT22258-40 | MinghuiLink RTV-5240 |
|---|---|---|
| Silicone Type | Addition-cure silicone | Platinum-cure silicone |
| Color | Transparent | Transparent |
| Specific Gravity | 1.08 g/cm³ | Not publicly listed |
| Mix Ratio | 100:10 by weight | 10:1 |
| Shore Hardness | 40 Shore A | 40±2 Shore A |
| Viscosity | 95,000 cP Base 56,000 cP Mixed |
80,000 mPa·s Part A |
| Working / Pot Life | 110 min | 45 min |
| Cure Time | 24 hours at 23°C | 8-10 hours |
| Tensile Strength | 6.20 MPa | ≥3.5 MPa |
| Tear Strength | 28 N/mm | 14±0.5 N/mm |
| Elongation | 390% | 300±50% |
| Shrinkage | Low shrinkage; numerical value not publicly listed | ≤0.1% |
| Temperature Resistance | Not publicly listed | Up to 250°C / 482°F |
| Technical Data Sources | SES22258/CAT22258-40 | RTV-5240 |
| Key Factor | Shin-Etsu SES22258/CAT22258-40 | MinghuiLink RTV-5240 | What It Means |
|---|---|---|---|
| Mechanical Performance | 6.20 MPa tensile; 28 N/mm tear; 390% elongation | ≥3.5 MPa tensile; 14 N/mm tear; 300±50% elongation | SES22258 reports substantially higher published tensile, tear and elongation values for demanding mold applications. |
| Working Window | 110 min | 45 min | SES22258 provides substantially more processing time for large, complex or carefully controlled mold preparation. |
| Cure Cycle | 24 h at 23°C | 8–10 h at room temperature | RTV-5240 offers the shorter published room-temperature cure for faster workshop production. |
| Dimensional Stability | Low shrinkage; numerical value not publicly listed | ≤0.1% shrinkage | RTV-5240 provides a specific low-shrinkage figure, which can be valuable for precision mold work. |
| Heat Resistance | Not publicly listed | Up to 250°C / 482°F | RTV-5240 has the higher publicly listed temperature specification. |
| Transparency | Transparent | Transparent | Both allow visual access to the master and easier inspection of mold-cut positions and internal detail. |
| Mixing System | 100:10 by weight | 10:1 | Both require accurate catalyst measurement, so mixing ratio is not a meaningful selection difference between them. |
| Published Viscosity | 56,000 cP mixed | 80,000 mPa·s Part A | Both are relatively high-viscosity systems, but the published values are measured at different material states and are not directly like-for-like. |
| Production Positioning | High-strength industrial transparent mold making | Transparent precision molds with practical room-temperature curing | The main choice is between higher published mechanical performance and longer processing time versus shorter curing, low shrinkage and published heat resistance. |
| Application | SES22258/CAT22258-40 | RTV-5240 | Key Consideration |
|---|---|---|---|
| Large Mold Making | Strong candidate | Suitable | SES22258 provides a 110-minute working window, giving operators more time for large mold preparation, deaeration and controlled pouring. |
| Complex / Detailed Transparent Molds | Strong candidate | Strong candidate | Both provide transparent cured silicone. SES22258 offers more processing time, while RTV-5240 offers a shorter room-temperature cure and low published shrinkage. |
| Precision Resin Molds | Strong candidate | Strong candidate | Both provide relatively firm A40 molds for dimensionally stable resin casting. Resin chemistry, shrinkage requirements and production cycle should be considered. |
| Industrial Tooling | Strong candidate | Suitable | SES22258 combines high published tensile and tear strength with high-modulus mold-making positioning for demanding industrial use. |
| Room-Temperature Production | Suitable | Strong candidate | RTV-5240 has a published 8–10-hour room-temperature cure, while SES22258 lists a 24-hour room-temperature cure. |
| High-Temperature Applications | Not publicly specified | Strong candidate | RTV-5240 has a published heat-resistance specification of up to 250°C / 482°F. |
| Rapid Prototyping | Suitable | Strong candidate | RTV-5240 offers the shorter published cure cycle, making it better aligned with faster prototype mold turnaround. |
| Small-Batch Manual Production | Suitable with accurate weighing | Suitable with accurate weighing | Both use a 10:1-type catalyst ratio, so accurate weighing is important. Production choice depends more on cure time and required mechanical performance. |
| 3D-Printed Masters | Suitable with compatibility testing | Suitable with compatibility testing | Resin residues, coatings and other contaminants can inhibit addition-cure silicone. Testing the actual master is recommended before production. |
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Competitor specifications are based on publicly available manufacturer documentation, with links to the original sources where available. Missing values are shown as “Not publicly listed” and are not estimated or inferred. Specifications may change, so always check the latest manufacturer documentation and conduct application-specific testing before production use. Product names and trademarks belong to their respective owners. This comparison is provided for technical and informational purposes only and is not endorsed by the brands mentioned.