Instructions

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Akron RTV Silicone Mold Rubber | Packaging | Instructions

Instructions

General

Akron RTV Silicone Mold Rubber is a two part addition cure system exhibiting high tear strength and elongation. You will find it to be well suited to difficult applications where undercuts and thin sections can otherwise be a problem. The firmness of the finished mold will prevent deflection of thin sections during wax injection. Stored at room temperature, unmixed product will retain it's excellent properties for six months or more. Because settling can occur during extended storage, it is recommended that both the resin and catalyst be stirred in their respective containers before use.

Mixing

Weigh the resin (Part A) in a clean container of about four to five times the volume of the resin being weighed. This will allow room for expansion during deairing. Add the appropriate amount of catalyst (Part B). Mix thoroughly by hand or with a low speed mixer under 1000 rpm to prevent heat generation. Two 15 second cycles is sufficient when power mixing. Useful pot life is approximately 90 minutes.

Deairing

Use a vacuum chamber capable of pulling 29 inches of mercury. Most investment units will handle this. Place mixture in vacuum chamber allowing the mixture to expand to about four times it's original volume, crest and recede. Continue under vacuum for 4 to 5 minutes. Although it may appear that there is still air in the mixture, do not continue to vacuum. Stop and allow to sit for 10 minutes, at which time you will note that the mixture is free from trapped air.

Pouring

If you are using glass mold frames, it is recommended that you use teflon mold release spray on the glass surfaces to provide easier release. Pour your mixture carefully down the side of the mold frame, taking care not to introduce new bubbles. See that the mixture flows down the side of the frame and up into undercuts in the model without entrapping air. Further time under vacuum may be appropriate if you introduce air while pouring. Vacuum two to three minutes and allow to rest. With clear RTV, you can see and move stubborn bubbles with a straightened paper clip.

Cure Time

If you are making a mold from a carved wax, you should use the standard 24 hour room temperature cure. If your model is not sensitive to elevated temperatures, you can cure in 30 minutes at 100ºC (212ºF).

Direct Alloy Casting

Akron RTV Silicone is rated for continuous exposure to temperatures up to 500ºF (260ºC). We do not recommend direct alloy casting as it is an unsafe procedure without proper training.

Alternate Catalyst (Softer Molds)

The standard Akron RTV kit includes a catalyst that will produce molds with all of the most important qualities for best reproduction of models or carved waxes. The standard mold is the same hardness as our Akron Jewelry Rubber Flex grade (35 durometer, Shor A). In the case where you have a very delicate wax model to copy, it may be desirable to produce a softer mold to prevent breakage during cutting. For this purpose, you may purchase a bottle of our CAT-5 catalyst. The resultant mold will have a durometer of 25º Shor A. You should recognize that a soft mold is not recommended where you have thin sections that will deflect during wax injection.

Yield

A 1.1 lb. kit will yield 5 to 6 molds from an average mold frame 3/4" x 2" x 3". Actual yield is dependent on model size and other factors within the user's control, such as not filling the mold frame to the top.

How Much?

The approximate amount of mold rubber required is calculated as follows:

(Volume of frame - Volume of model) x 1.1 = total grams of mixture required.

Volume of frame = length x width x thickness (in centimeters)

Volume of model = Specific gravity of alloy or wax model (gms/cu cm) divided by weight of model in grams.

To determine individual weights part A and B:

Weight part A in grams = Total grams of mixture above divided by 1.1

Weight of part B in grams = .1 x weight of part A above.

Please be certain that your units of measure are consistent. The above calculation uses metric units only. To convert final weights to pounds, divide by 454.

1 lb. = 454 grams

1 inch = 2.54 cm

GENERAL PROPERTIES

Color: Translucent Hardness: 35 shor A (durometer)

Pot Life: 1.5 hours Initial Mixed Viscosity: 1000 poise

Tensile Strength: 800 psi Elongation: 300%

Linear Shrinkage: < 0.1% Tear Strength: 125 ppli

Specific Gravity: 1.1 gm/cc


	Zero-D Products, Inc. \| home Akron RTV Silicone Mold Rubber \| Packaging \| Instructions Instructions General Akron RTV Silicone Mold Rubber is a two part addition cure system exhibiting high tear strength and elongation. You will find it to be well suited to difficult applications where undercuts and thin sections can otherwise be a problem. The firmness of the finished mold will prevent deflection of thin sections during wax injection. Stored at room temperature, unmixed product will retain it's excellent properties for six months or more. Because settling can occur during extended storage, it is recommended that both the resin and catalyst be stirred in their respective containers before use. Mixing Weigh the resin (Part A) in a clean container of about four to five times the volume of the resin being weighed. This will allow room for expansion during deairing. Add the appropriate amount of catalyst (Part B). Mix thoroughly by hand or with a low speed mixer under 1000 rpm to prevent heat generation. Two 15 second cycles is sufficient when power mixing. Useful pot life is approximately 90 minutes. Deairing Use a vacuum chamber capable of pulling 29 inches of mercury. Most investment units will handle this. Place mixture in vacuum chamber allowing the mixture to expand to about four times it's original volume, crest and recede. Continue under vacuum for 4 to 5 minutes. Although it may appear that there is still air in the mixture, do not continue to vacuum. Stop and allow to sit for 10 minutes, at which time you will note that the mixture is free from trapped air. Pouring If you are using glass mold frames, it is recommended that you use teflon mold release spray on the glass surfaces to provide easier release. Pour your mixture carefully down the side of the mold frame, taking care not to introduce new bubbles. See that the mixture flows down the side of the frame and up into undercuts in the model without entrapping air. Further time under vacuum may be appropriate if you introduce air while pouring. Vacuum two to three minutes and allow to rest. With clear RTV, you can see and move stubborn bubbles with a straightened paper clip. Cure Time If you are making a mold from a carved wax, you should use the standard 24 hour room temperature cure. If your model is not sensitive to elevated temperatures, you can cure in 30 minutes at 100ºC (212ºF). Direct Alloy Casting Akron RTV Silicone is rated for continuous exposure to temperatures up to 500ºF (260ºC). We do not recommend direct alloy casting as it is an unsafe procedure without proper training. Alternate Catalyst (Softer Molds) The standard Akron RTV kit includes a catalyst that will produce molds with all of the most important qualities for best reproduction of models or carved waxes. The standard mold is the same hardness as our Akron Jewelry Rubber Flex grade (35 durometer, Shor A). In the case where you have a very delicate wax model to copy, it may be desirable to produce a softer mold to prevent breakage during cutting. For this purpose, you may purchase a bottle of our CAT-5 catalyst. The resultant mold will have a durometer of 25º Shor A. You should recognize that a soft mold is not recommended where you have thin sections that will deflect during wax injection. Yield A 1.1 lb. kit will yield 5 to 6 molds from an average mold frame 3/4" x 2" x 3". Actual yield is dependent on model size and other factors within the user's control, such as not filling the mold frame to the top. How Much? The approximate amount of mold rubber required is calculated as follows: (Volume of frame - Volume of model) x 1.1 = total grams of mixture required. Volume of frame = length x width x thickness (in centimeters) Volume of model = Specific gravity of alloy or wax model (gms/cu cm) divided by weight of model in grams. To determine individual weights part A and B: Weight part A in grams = Total grams of mixture above divided by 1.1 Weight of part B in grams = .1 x weight of part A above. Please be certain that your units of measure are consistent. The above calculation uses metric units only. To convert final weights to pounds, divide by 454. 1 lb. = 454 grams 1 inch = 2.54 cm GENERAL PROPERTIES Color: Translucent Hardness: 35 shor A (durometer) Pot Life: 1.5 hours Initial Mixed Viscosity: 1000 poise Tensile Strength: 800 psi Elongation: 300% Linear Shrinkage: < 0.1% Tear Strength: 125 ppli Specific Gravity: 1.1 gm/cc