What are the major differences between tin-cure (condensation cure) and platinum-cure (addition cure) silicone mould making rubbers?
The chemical distinction between tin-cure (condensation cure) and platinum-cure (addition cure) silicone mould making rubbers primarily lies in the metal used for catalysis or curing of the base rubber. Tin is utilised to catalyse or cure tin silicone, while platinum is employed for curing platinum silicone rubber.
Consequently, tin-cure silicone rubbers are generally considerably more cost-effective than their platinum-cure counterparts.
Performance Variations Inhibition All mould making rubbers may be susceptible to cure inhibition due to contaminants on the surface of a model used for mould creation.
Silicone rubber is sensitive to sulphur, which can be present on various surfaces and is found in certain types of modelling clay. Platinum-cure silicone rubbers are extremely sensitive to sulphur and will not cure under any circumstances when exposed to it. Tin-cure silicone can cure over models containing sulphur if the model surface is initially thoroughly sealed with an acrylic spray.
Shrinkage A significant difference between these two systems is the shrinkage of the cured rubber over the short and long term. Tin-cure silicone rubber moulds typically exhibit greater shrinkage over time, depending on the type of mould rubber used, the material being cast into the rubber mould, mould configuration, and other variables.
Shelf Life Tin-cure silicone rubber moulds have a limited shelf life. Depending on the specific tin-cure silicone, the shelf life of a rubber mould can be as short as 12 months, which may be acceptable for short-term projects. Smooth-On's Mold Max™ Series tin-cure silicone rubbers have a relatively extended shelf life, lasting a minimum of 5 years. When a rubber mould reaches the end of its shelf life, it will become prone to tearing and unusable.
Platinum-cure silicone (e.g. Smooth-Sil™ and Mold Star™) has a relatively long shelf life measured in decades. Museums select platinum-cure silicone rubbers for moulding valuable artefacts and works of art. Production Life Which silicone rubber chemistry (tin vs. platinum) will provide the longest lifespan for production casting of wax, gypsum, concrete, resin, etc.? It depends on various variables and is typically specific to the application. To determine the right rubber mould material for your project, get in touch with our technical support team.