High Hardness Tin Cured Liquid Silicone Rubber for Mold Making

hard pour-on brush-on 35-40 A condensation tin based

Lead Time

Quantity(kilograms)	1-1000	1000-5000	≥5000
Est. Time(days)	2-3	4-7	To Be Negotiated

Contact for Detailed Quotation
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+86-158 9975 3674

+86-158 9975 3674
+86-158 9975 3674
TDS File

1. Description

This series of condensation-cure (tin-catalyzed) silicone is a high-hardness mold rubber. It consists of a white or translucent Part A base and a transparent to slightly yellowish Part B curing agent. When mixed in a weight ratio of 100A:3B, they cure at room temperature into a high-hardness elastomeric material. This hard silicone rubber exhibits excellent resistance to stress and is well-suited for applications where dimensional stability and rigidity are essential. However, it's important to note that compared to medium-hardness tin-cured silicone, this hard silicone is relatively more brittle.

Based on the properties of tin-catalyzed silicone, it is recommended to work with it within a temperature range of 20 to 30°C (68 to 86°F). Curing becomes challenging below 10°C (50°F), so it is important to maintain suitable temperatures. If you decide to apply heat to accelerate curing, it is not advisable to exceed 45°C (113°F). Additionally, you can adjust the operation time and curing time suitable for your project by adjusting the ratio of part A and part B (100:2-100:4).

2. Feature

High hardness, takes a low compression set.
Withstands temperatures up to 200°C (392°F).
Low shrinkage (≤0.03%).
Excellent mold release, allowing for easy release without sticking.
Simple operation, quick curing at room temperature.

3. Application

This series of silicone rubber has high replication accuracy, dimensional stability, and mechanical strength, making it especially suitable for applications that require high-hardness mold making. It is widely used in rapid prototyping and recommended for prototype mold-making applications in the electronics and automotive industries, such as television sets, home appliances, mobile phones, copiers, console boxes, radiator grills, lamp housings, and more.

Prototype Vacuum Casting

Thin Shell Prototyping

Cement Silicone Mold

Ceramic Silicone Mold

4. Attention

It is recommended to use Part A and Part B of the same model and lot number. If a different model or lot number is used, its suitability should be determined by testing.
Parts A and B should be mixed properly and in the correct proportions. Using too much tin curing agent to accelerate curing may shorten the mold's service life, leading to brittleness and deterioration.
If the tin-cured silicone material appears gummy or uncured after the recommended curing time, it is necessary to investigate the cause, which may include temperature, mixing ratio, whether it was stirred evenly, and whether other substances were added.
Tin-cured silicone molds may exhibit higher shrinkage over time, depending on the material being cast into the mold, mold configuration, and other variables.

5. Safety

When using tin-cured liquid silicone, it is important to ensure adequate ventilation. During curing, the following gases are generated depending on the cure type: acetic acid type (acetic acid), alcohol type (methanol), oxime type (methyl ethyl ketone oxime - MEKO), and acetone type (acetone). If ventilation is inadequate, respiratory protection should be worn. Avoid continuous inhalation of vapors and spray mist, and take precautions to prevent skin and eye contact. Wear safety glasses with side shields and use liquid-tight gloves, such as butyl rubber, neoprene, or PVC, to minimize the risk of contamination. Remember to wash your hands thoroughly after use.
Over time, tin-cured silicone appliances and molds may leach and become brittle due to the catalyst's instability. As a result, these products are intended for industrial use only and should not be used in applications that require a long shelf life or direct contact with the skin. For food contact applications, platinum-cured silicone rubber should be used instead.
Under normal storage and handling conditions, these products are stable in airtight containers at room temperature and will not undergo hazardous reactions.
Please keep these products out of the reach of children.
First Aid Measures:
- Skin Contact: If the product comes into contact with the skin, wash thoroughly with soap and water.
- Eye Contact: In case of contact with the eyes, flush them with plenty of water while lifting the upper and lower eyelids. If irritation persists, seek medical attention.
- Inhalation: Remove the individual from the contaminated area and provide fresh air. If breathing has stopped, administer artificial respiration and seek immediate medical attention.
- Ingestion: If ingested, do not induce vomiting unless instructed by a physician. Never give anything by mouth to an unconscious person.

Please note that these measures are general guidelines. In case of an emergency, always consult a medical professional or seek immediate medical attention.

6. Storage

The shelf life of the product is 12 months from the date of production. Storing the material at higher temperatures can also reduce the available shelf life of unused materials. These products have a limited shelf life and should be used as soon as possible.

Containers that have been opened must be carefully sealed to prevent leakage. Store the material in a cool, dry, well-ventilated place, away from heat, direct sunlight, strong oxidizers, and any incompatible substances such as strong bases and acids.

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Parameter Item	Test Method	RTV-3140 A/B	RTV-3240 A/B
Unvulcanized Physical Properties @ 24 Hrs 25°C/77°F
Physical State	-	Liquid / Fluid	Liquid / Fluid
Form	-	Viscous	Viscous
Odor	-	Slight Odor	Slight Odor
Part A (Base) Color	ASTM E 1767	White	Translucent
Part B (Catalyst) Color	ASTM E 1767	Clear to Light Yellow	Clear to Light Yellow
Part A Viscosity, mPa.s	ASTM D 4287	25,000	25,000
Part B Viscosity, mPa.s	ASTM D 4287	250	250
Part A Specific Gravity, g/cm³	ASTM D 792	1.15-1.18	1.12-1.15
Part B Specific Gravity, g/cm³	ASTM D 792	0.98	0.98
Part A and Part B mixed @ 25°C/77°F
Mix Ratio by Weight (A:B)	-	100:3	100:3
Working Time, Minutes	-	35	35
Curing Time, Hours	-	12	12
Typical Properties of Cured Rubber @ 24 Hrs 25°C/77°F
Hardness, Shore A Durometer	ASTM D 2240	38	37
Tear Strength, N/mm	ASTM D 624 C	19.0	20.0
Tensile Strength, Mpa	ASTM D 412	3.7	3.9
Elongation, %	ASTM D 412	300	330
Shrinkage, %	-	≤0.30	≤0.30
Heat Resistance, °C (°F)	-	200 (392)	200 (392)

Step 1: Preparing the Master Pattern

The master pattern must be clean and dry. If the master models is friable, weak, or porous, one may need to apply a consolidant or sealant, and possibly plug deep holes or crevices.

Step 2: Applying the Release Agent

This series of silicones has excellent mold release properties, and typically does not require a mold release agent for most materials. However, if the master pattern is highly porous or rough, has numerous crevasses and undercuts, or not prone to spalling, it is recommended to apply a thin layer of mold release agent to facilitate mold release and prolong the life of the mold.

The release agent should be applied evenly over the entire master pattern, ensuring that it is distributed into all crevices and undercuts. However, it should only be applied thinly to avoid compromising the surface detail of the master pattern. If a brush is used to apply the agent, any excess should be buffed away afterwards, and any brush strokes erased. Since silicone rubber captures even microscopic details, the surface of the release agent will be recorded rather than the master pattern.

Common mold release agents include acrylic sprays, Vaseline, silicone oil and soapy water, among others.

Step 3: Measuring and Mixing

For the white tin-cured silicone, it is important to note that a small amount of powder may settle over time during storage. Therefore, it is recommended to stir Part A and shake Part B before mixing. The sediments are not reactants, so there is no issue in using them while stirring.

If you are not in a hurry, it is advisable to use the recommended dosage (100A:3B) of the standard catalyst. If you require different colors, you can add the colorant and mix it thoroughly. It is important to ensure that the base and curing agent are thoroughly mixed and stirred evenly to avoid local non-curing.

Never use more than the maximum recommended dose of the catalyst (100A:5B), as doing so may cause the liquid silicone to begin setting up before it can be properly stirred and poured. This will significantly shorten the lifespan of the silicone mold.

Step 4: Vacuum Degassing

After mixing parts A and B, it is recommended to vacuum degas the liquid silicone to eliminate any entrapped air. When subject to a vacuum, the silicone mixture should well up as air pockets rise and burst. You must pay attention to the working time of the silicone and avoid letting the silicone cure before pouring/application.

Vacuum degassing can be carried out either before or after pouring. However, if you choose to vacuum degas after pouring, your vacuum box should have a sufficiently large volume.

Techniques to Reduce Air Bubbles:

One is to apply a thin initial coat of silicone with a fine paintbrush, gently spreading it into all cavities and undercuts (after which more silicone may be poured).
Hold the silicone container high above the master pattern and allow it to flow down slowly in a thin stream. This helps to break up any air bubbles as the silicone flows.
Temporarily incline the master pattern at an angle and pour the liquid silicone onto the higher end, allowing it to flow down over the rest of the pattern. Once the silicone reaches the lower end, lay the pattern flat and/or tilt or rotate it as necessary to achieve even coverage.

These techniques can be used alone or in combination with each other. Additionally, reducing the temperature and decreasing the ratio of curing agent can extend the working time and help to reduce air bubbles.

Step 5: Pouring Silicone

Pour-on Process: The vacuum-degassed liquid silicone is poured carefully over the master pattern, typically covering it to a depth of 0.5-1.5 cm above the highest point. If the layer is too thin, the mold may be prone to tearing. It is also advisable to apply thicker layers of silicone in narrow or intricate sections and along the edges where extra strength is required to prevent tearing.

Brush-on Process: After the first layer of silicone begins to cure, a strip of gauze, cheesecloth, or open-weave cotton cloth can be lightly applied to increase the strength of the mold. If a second batch is applied, it should be applied while the first batch is partly cured but still tacky. Once a layer of silicone is cured completely, it is difficult to make a good bond with a subsequent layer. After the gauze is applied, apply another layer of silicone to thoroughly cover the gauze layer. Typically the finished mold should be at least 3-4mm thick even in the thinnest sections. Be sure not to push the gauze through to the master pattern surface. When selecting gauze, non-elastic types should be used.

Step 6: Demolding the Mold

After the specified curing time has passed, the outer surface of the mold feels hard and dry, and the hardness of the mold does not change after a period of time, and the mold can usually be removed or demolded. When removing the mold, gently peel up all the edges first, and then the middle section. If any portion seems too soft, immediately stop pulling and replace any lifted sections, allowing more time to cure further.

What is the lifespan of the finished mold and how should I store it?
The lifespan of a finished silicone mold is determined by various factors such as the mold type, the material being cast, and the frequency of use. However, there are a few simple things that can be done to extend the life of a silicone mold. You can contact our customer service support to provide you with specific solutions.

Helpful (11) Not Helpful (9) Reply
I was wondering if there is an expiry date once the product package is opened?
There is no expiration date for the product after it has been opened. However, it is important to remember to cover the bottle and store it in a cool place after each use to maintain the quality of the silicone.

Helpful (10) Not Helpful (9) Reply
For a bivalve mold, the hardened part A sticks with part B or need a release agent.
Yes, for making two-part silicone molds, it should be coated with Vaseline release agent to prevent sticking together and difficult to separate.

Helpful (6) Not Helpful (22) Reply
How to understand the amount of liquid silicone to use based on the object to be reproduced? Does anyone have tables, tips etc that they can recommend?
Having built the formwork that contains all the models to be cloned, it will be enough to calculate the area of the formwork to then subtract the area occupied by the model itself. It is recommended that you calculate 5%-10% more loss.

Helpful (7) Not Helpful (87) Reply
Can liquid silicone cure even without a catalyst?
No, this is RTV-2 silicone, so it must be mixed with a catalyst to cure.

Helpful (4) Not Helpful (4) Reply
Is the catalyst included in the price or should it be purchased separately?
The ratio of our tin cure silicone to curing agent is 100:2-100:4, and we will distribute tin curing agent for free. But for a 10:1 ratio of clear silicone, platinum curing agent will count the price.

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