Mold Making

Performance Polymers makes a variety of products to meet the demands of a variety of mold making industries or markets.

Our Silicones are frequently used in following mold making markets:

• Molds for idols, artifacts, figurines and giftware.
• Molds of architectural reproduction - facades, concrete (GRC)
• Molds for plaster-ware – ceilings and covings
• Molds for soaps and designer candles
• Molds for chocolate making, icing sugar and cake decoration
• Prototyping Molds for industrial parts and auto components
• Molds for jewelry production
• Molds for shoe sole manufacturing
• Molds of prototypes for ceramic injection molding

Mold Making Silicone RTVs from Performance Polymers

Our silicone products are much preferred by the market leaders due to their versatility, our dependable technical support and customization capability to meet their needs.

Performance Polymers manufactures several Room Temperature Vulcanizing (RTV) silicone rubber grades having features such as :

• Low viscosity - Good flow characteristics resulting in superb detail reproduction
• Easy mix ratios- Simple to handle
• Room temperature cure
• Excellent mechanical strength – Durable molds
• Good Chemical Resistance – Compatible with most casting materials

Our RTV silicone rubber products are categorized in two different types based on the silicone cure chemistry used to form an elastomeric solid :

• Condensation cure systems which use a tin based catalyst and
• Addition cure systems which use platinum based catalyst

There are some differences between the two systems which have to be considered before choosing the correct material for the intended application. These differences are described below:

Condensation Cure

Most of our Condensation or Tin Cure systems are of 100:5 mix ratio by weight and once mixed usually cure against most mold making media. It takes the moisture from the atmosphere and gives off a alcohol byproduct. The liberation of alcohol results in shrinkage of the end product. Usually the shrinkage is in the range of 0.5%, which is acceptable for most applications.

Salient Features

• No cure inhibition - Can be used with various types of masters – No limitation on master materials
• Lower costs
• Well Suited to fine details and extensive undercuts
• Broader product range
• Less sensitive to exact (A:B) mix ratio
• Cure speed can be adjusted by using different catalysts
• Mixing of grades is possible to achieve desired properties

In condensation cure systems, to adjust the pot life and cure speed it is possible to use different catalyst provided they are recommended for each other, but there are some precautions to be followed. If faster catalysts are used there will be some changes in the long term mechanical properties of the cured rubber and the library life will be shortened. It should be noted that the dosage of the catalyst must be as mentioned in the data sheets. Higher than the recommended dosage will result in deterioration in long term mechanical properties. The catalysts need to be always stored in closed containers to get the recommended shelf life, as they are prone to undergo chemical reaction in contact with atmospheric air and thereby alter the cure speed and final product properties.

Condensation (Tin) Cure Mold Making Systems

Addition Cure

Addition or Platinum Cure Silicone is usually either 10:1 mix or 1:1 mix ratio by weight and follows a chemical reaction with no byproduct or leaving group. This results in negligible or nil shrinkage (0.1% or less) making it a great choice for precision parts. Another distinguishing feature of such type is that the curing of this type of silicone rubber can be accelerated by application of heat. For every 10 degrees above room temperature the cure time gets reduced to half. Prototype designers use it for parts which require a high level of accuracy and parts that need to snap, platinum cure silicone is the best choice and most widely used by the rapid prototyping industry. The silicone is also best for higher temperature applications such as low melt metal alloys. They are highly durable when used with polyester, polyurethane and epoxy resins but are susceptible when mold making subject to surface inhibition caused by substrates like tin, sulfur, amines, oil clay, some adhesives, synthetic rubber etc.

Salient Features

• Excellent mechanical properties
• Cure speed can be accelerated by application of heat
• Low shrinkage, resulting in detailed and honest reproduction of the master
• Sensitive to mixing ratio- Accurate weighing of components is essential
• Sensitive to the type of master material
• Good abrasion resistance
• Glass like transparency for prototyping applications (One can see the master encased within the mold)

Addition cure rubbers use a platinum catalyst and it is necessary to mix to the exact recommended ratio of A:B. Since the properties obtained from the Platinum cured systems are dependent on the A and B component ratio, it is important to adhere to the recommended ratio strictly.

Addition (Platinum ) Cure Mold Making Systems

Molding Applications

Both Tin cure silicone and Platinum cure silicone rubbers are an appropriate choice for several casting resins. The master model, casting resin and the application generally dictates which rubber to use.