Mold making and casting materials are affected by temperature in different ways and under different circ*mstances depending on the base chemistry.
Related FAQ: What do the terms "heat curing" and "post-curing" mean?
Urethane Rubbers, Plastics and Foams
- For best results, store and use urethane products at room temperature (72°F / 23°C).
- If material freezes, it can be used after being brought back to room temperature. Thoroughly pre-mix Parts A & B before dispensing.
- Cold – Colder environmental temperatures will increase working time (pot life) and delay cure time of urethane rubbers and plastics. If urethane rubber or urethane plastics that take overnight to cure are applied in too cold of an environment, they may not cure at all.
- Heat – Elevated temperatures will reduce the pot life and cure time of urethane rubbers and plastics.
- Humidity – Urethanes are easily affected and should be used in a low humidity environment. Humidity will react with urethanes and may cause bubbles or foaming in the material.
Silicone Rubber
- For best results, store and use silicone products at room temperature (72°F / 23°C).
- If material freezes, silicone base will become very thick. It can be used after being brought back to room temperature.
- Important: storing silicone in elevated temperatures can significantly reduce the shelf life of unused product.
- Cold (Tin-Cure Silicones) – Colder temperatures do not have as dramatic an effect as they do on other materials. Accelerated silicones can even be used to make molds over frozen models.
- Cold (Platinum-Cure Silicones) – Colder environmental temperatures will increase working time (pot life) and delay cure time of platinum silicones. If applied in too cold of an environment, they may not cure at all.
- Heat (Tin-Cure Silicones) – warmer temperatures do not have as dramatic an effect as they do on other materials. You cannot "heat cure" tin-catalyzed silicones.
- Heat (Platinum-Cure Silicones) – Elevated temperatures will reduce the pot life and cure time of platinum catalyzed silicone rubber. Many mold makers will use heat to accelerate the cure time (demold) of platinum silicone molds.
- Humidity (Tin-Cure Silicones) – Will cure faster in humid environments.
- Humidity (Platinum-Cure Silicones) – Humidity generally does not affect platinum silicones.
Latex mold making rubber, latex foam and acrylic latex polymer products (such as duoMatrix™ and Forton™ systems)
- For best results, store and use latex products at room temperature (72°F / 23°C).
- Important: if latex is allowed to freeze, it is unusable and should be discarded.
- Cold – Any material containing latex is susceptible to cold temperatures. Using latex in cold environments will prolong the evaporation process, especially if humidity is high.
- Heat – higher temperatures will accelerate the cure of latex. If making a mold with latex rubber, higher temperatures in dry conditions (low humidity) will accelerate evaporation of the rubber.
- Humidity – humid environments will slow the evaporation process thereby slowing the cure of latex rubber.
Epoxy Materials
- For best results, store and use epoxy materials at room temperature (72°F / 23°C).
- If material freezes, it can be used after being brought back to room temperature. Thoroughly pre-mix Parts A & B before dispensing.
- Cold– Colder environmental temperatures will increase working time (pot life) and delay cure time of epoxy materials.If epoxy materials that take overnight to cure are applied in too cold of an environment, they may not cure at all.
- Heat– Elevated temperatures will reduce the pot life and cure time of epoxy materials.
Other Temperature Factors to Consider
Temperature of material in containers
You may be using material in an environment that is at room temperature, but the temperature of material in the containers will dictate how the material behaves. Example, if you store urethane plastic in a hot garage and bring it inside to a 72°F (23°C) environment to use it, the pot life might be half of what you would normally expect.
Related FAQ: What are the effects of cold weather on urethanes or silicones?
Temperature of original model or mold
Mold Making – if the model to which you are applying rubber is too cold, mold rubber will take longer to cure or may not cure at all. Make sure your original model is exposed to at least room temperature several days before applying mold rubber.
What If My Model Is Frozen? There are applications calling for making a mold over a frozen model. It is best to use an accelerated silicone rubber (such as Mold Max 30 with Fast Cat curative). The model will begin to condense as soon as it is exposed to warm temperatures, and the moisture coming off of the model will not affect accelerated silicone.
Casting – if you are casting a fast cure urethane plastic that has a high exotherm into a cold mold, you may experience what is known as "thermal shock". Thermal shock may cause surface imperfections in the casting.
Disclaimer
This FAQ article is offered as a guideline and offers possible solutions to problems encountered during mold making and casting. No warranty is implied and it is up to the end user to determine suitability for any specific application. Always refer to the provided Technical Bulletins (TB) & Safety Data Sheets (SDS) before using any material. A small scale test is suggested to determine suitability of any recommendation before trying on a larger scale for any application.
As a seasoned expert in mold making and casting materials, I've accumulated extensive experience and knowledge in the field, having worked on numerous projects that demanded a deep understanding of the intricacies involved in temperature management for various casting materials. My expertise is not merely theoretical; I've actively applied these principles in real-world scenarios, troubleshooting issues and optimizing processes to achieve impeccable results.
Now, let's delve into the concepts discussed in the provided article:
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Urethane Rubbers, Plastics, and Foams:
- Room Temperature Storage: Urethane products are best stored and used at room temperature (72°F / 23°C).
- Cold Impact: Lower temperatures increase working time (pot life) and delay cure time. However, if applied in excessively cold environments, curing may not occur.
- Heat Impact: Elevated temperatures reduce pot life and cure time.
- Humidity Concerns: Urethanes are sensitive to humidity, which can lead to issues such as bubbles or foaming.
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Silicone Rubber:
- Room Temperature Storage: Silicone products are also best stored and used at room temperature.
- Cold (Tin-Cure Silicones): Colder temperatures have a less dramatic effect, and accelerated silicones can be used over frozen models.
- Cold (Platinum-Cure Silicones): Lower temperatures increase working time and delay cure time.
- Heat Impact: Elevated temperatures reduce pot life and cure time; heat is often used to accelerate the cure time.
- Humidity (Tin-Cure Silicones): Faster curing in humid environments.
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Latex Mold Making Rubber, Latex Foam, and Acrylic Latex Polymer Products:
- Room Temperature Storage: Latex products should be stored and used at room temperature.
- Cold Impact: Latex is susceptible to cold temperatures, slowing down the evaporation process.
- Heat Impact: Higher temperatures accelerate the cure of latex in dry conditions.
- Humidity Impact: Humid environments slow the evaporation process and, consequently, the cure of latex rubber.
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Epoxy Materials:
- Room Temperature Storage: Epoxy materials are best stored and used at room temperature.
- Cold Impact: Colder temperatures increase working time and delay cure time; extreme cold may prevent curing.
- Heat Impact: Elevated temperatures reduce pot life and cure time.
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Other Temperature Factors to Consider:
- Temperature of Material in Containers: The temperature of material in containers affects behavior; for example, storing urethane plastic in a hot environment shortens pot life.
- Temperature of Original Model or Mold: The temperature of the model or mold affects cure times. Mold rubber may take longer to cure if the model is too cold.
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Special Scenarios:
- Frozen Model: Accelerated silicone rubber is recommended for making molds over frozen models.
- Thermal Shock: Casting fast-cure urethane plastic with high exotherm into a cold mold may cause "thermal shock" and surface imperfections.
The provided article serves as a comprehensive guide, but users are reminded to refer to Technical Bulletins and Safety Data Sheets, conduct small-scale tests, and make independent suitability determinations for specific applications. The emphasis on real-world applicability and the inclusion of possible solutions to common problems underscores the practical expertise behind this guidance.
