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P - Series Platinum cure silicones


P series RTV silicones rubbers are two component addition reaction platinum catalyzed systems that cure at room temperature. The systems are designed to produce flexible mold making materials with exceptionally high tear resistance, easy release properties and minimum shrinkage. The catalyzed rubbers offer long working times, good flow characteristics and the curing rate can be accelerated with heat. The materials offer a wide service temperature range of -50 to 400F, have excellent chemical resistance and will not undergo reversion. The systems will cure evenly in any thickness, producing a mold with excellent detail reproduction and very low shrinkage allowing the mold maker to hold more exact tolerances.

The P series rubbers will exhibit a slight amount of thickening during storage. This thickening is reversible with simple shear, such as mixing with a spatula or mechanical mixer. If the normal consistency of the rubber is too thick for a specific application, additions of up to 10% RTV diluent (silicone thinner) can be made which reduces the viscosity to allow flow into very intricate models. The addition of diluent will slightly reduce the physical properties.
The uncatalyzed shelf life of P series rubber when stored in the original unopened containers at or below room temperatures is six months from the date of shipment.


The P series rubbers are mixed 10 parts of base to one part of activator by weight. Deviations from ratio will cause changes in the physical properties.
Choose a container with a volume that is three to four times greater than that of the rubber. Weight the components carefully and mix thoroughly by hand or in a mechanical mixer. After the color is evenly mixed into the base, scrape the sides and bottom of the container to insure that there is no unmixed portion. Place the container in a vacuum chamber and deaerate at 28 to 29 inches of mercury vacuum until the mass of rubber rises and then collapses. Continue to deaerate for an additional two to three minutes. Remove the mixed rubber and carefully pour over a well-released master.

P series rubbers can be used on most meter mixer dispensers.


Vulcanization of the P-series rubber takes place in 18 - 24 hours after mixing at room temperature conditions. Heat can be used to accelerate the cure rate. Care must be taken to ensure that the master doesn't gas or give off vapors ar the temperature used, since this can cause severe distortion of the mold surface. Some woods give off moisture and gas at relatively low temperatures, causing failure in the mold making attempt.

Averge cure times for 1/2" thick samples are:
75F - 18 to 24 hours
125F - 1.5 hours
150F - 45 minutes
200F - 25 minutes
250F - 15 minutes
300F - 10 minutes


P series RTV Rubbers show some tendency to have their cure inhibited at the interface. Models that have come in contact with tin catalyzed rubbers may show cure inhibition at the face of the mold. This can usually be prevented by thoroughly cleaning the model with naptha or methylene chloride, releasing and checking the area by brushing on a small amount of catalyzed P series rubber. After 24 hours this film must be cured and non-sticky. In the event that contamination still exists, the model should be cleaned again and a thin film of acyrlic or nitrocellulose lacquer or base coat should be applied. This should serve as a barrier coat and allow a completely cured mold to be prepared. Other substrates such as clays containing sulphur or any other sulphur, amine or tin containing materials will cause surface inhibition and in all cases a test should be run as outlined above to determine compability.

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