1. Mixing of the two components
The material can be processed differently according to the version:
- BLUESIL RTV 3720 A&B should only be used by means of a spray or injection equipment with a meter/static mixer, as the pot life is too short to hand-mix and efficiently degas the material.
- BLUESIL RTV 3720 SC A&B
Add 100 parts of BLUESIL RTV 3720 A to 100 parts of BLUESIL RTV 3720 B. The two components may be intimately mixed either by hand or using a low-speed electric or pneumatic mixer to minimize the introduction of air into the mixture.
After mixing parts A&B of BLUESIL RTV 3720 SC it is recommended to degas the product to eliminate the entrapped air introduced in the mixture. The standard (quick-cure) version is usually processed using an automatic dosing machine with a static mixer, and by degassing previously each of the two parts, air is not introduced during the mixing.
BLUESIL RTV 3720 SC can be degassed under a 30 to 50 mbar vacuum. When the vacuum is applied the product expands 3-4 times its initial volume and bubbles form on the surface. Once bubbles disappear, the mixture collapses back to its initial volume. To complete degassing simply wait few minutes before releasing the vacuum. then the product will then be ready to use.
Remark: pull and release the vacuum several times improves the degassing. For easier degassing only fill a recipient only to 1/3 of its height.
Pour the degassed mixed material slowly in a steady stream from one edge of the mold box so that the material flows evenly over the model minimizing the entrapment of air bubbles under the flowing silicone.
3. Cross linking
At room temperature (23°C) BLUESIL RTV 3720 A&B cures in the given demolding time regardless of the mold thickness. For best results the mold should be allowed to fully cure for 24 hours before using it for production.
Room temperature curing assures the lowest possible shrinkage, if accelerated cure of the SC version is desired, mild heat should be preferred. To minimize shrinkage, the elastomer can be cured at temperature of 60°C for 1 hour, higher temperatures might cause higher shrinkage.
Conversely at lower temperature polymerization is much slower: 10°C at the time necessary to complete cross-linking will be almost double the time at 23°C.
Be aware that contact with certain materials can inhibit the curing of this RTV:
In case of doubts it is recommendable to run a quick test with a small quantity of material in order to assess compatibility. Take note that cross contamination due to not well cleaned tools or devices is frequently the main causes of inhibition. The best way is to use only dedicated gear when processing polyaddition RTVs.
- Natural rubbers vulcanized with sulphur
- Polycondensation RTV catalysed with metal salts
- PVC stabilizing agents
- Amine cured epoxies
- Sulphur containing clays.
4. Available tools
Following materials can provide an efficient way to customize the application of BLUESIL RTV 3720 A&B matching the own process needs:
Please refer to the corresponding product datasheet for detailed information about the tools properties and their correct application.
- Retarder Additive to increase working time (for both versions)
- Accelerator Additive to shorten working time (for SC version)
- Thixotropic Additive to adjust the product rheology (for SC version)
- Silicone Adhesive to repair eventual damages
- Silicone Paste to protect sharp mold edges
|BLUESIL RTV 3720 SC A may be stored at a temperature between -5 °C/ 23 °F and 30 °C/ 86 °F for up to 12 months from its date of manufacturing.||Please consult the Safety Data Sheet of this product.||Heavy Metals|
BLUESIL RTV 3720 SC A
The BLUESIL RTV 3720 A&B is a two component silicone elastomer which cures at room temperature by a polyaddition reaction (1:1 ratio).
The material can be applied onto horizontal as well as vertical surfaces thanks to its slight thixotropic behaviour, by means of casting or solventless spraying in both cases a silicone film is obtained.
The product is available in two versions:
- RTV 3720 A&B: fast cure, for spray application
- RTV 3720 SC A&B: slow cure, for casting application
2 Part RTV
- Excellent mechanical properties.
- Low viscosity (easy sprayable) with thixotropic behavior.
- Choice between very fast cure and long open time cure (both room temperature)
- High chemical resistance.
- No release of toxic substances during and after curing.
The BLUESIL RTV 3720 A&B is specifically developed to produce a silicone bag on molds used for the processing of composites applying the "vacuum resin infusion" technology. The material is not limited to this application.
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