Silicone Dip Molding and Coating
Dip molding uses a mandrel in the shape of the final part. Mandrels are typically machined from metal but can also be fabricated from engineered plastics and ceramics. The mandrel is immersed in silicone and then withdrawn. The mandrel, now coated with a thin liquid silicone film, is then placed in an oven where the silicone is vulcanized. Following vulcanization, the silicone rubber is stripped from the mandrel creating the finished product.
Wall thickness of parts can be adjusted by varying the number of dips or by adjusting the percent solids concentration of the silicone dispersion. Process validations include evaluation of mandrel surface finish, immersion and withdrawal angle and speed, dispersion viscosity and temperature, ambient manufacturing conditions, and vulcanization parameters.
Dip molding provides a cost-effective alternative to silicone molding processes where costly metal molds are often required. This process can be used for rapid prototyping of complex, thin walled shapes or may be scaled for large volume commercial production.
A dipping process can also be used to create silicone coatings on various medical devices. Various types of medical components, including metal, plastic, fabric and glass, can be coated with thin silicone films which are then vulcanized to produce a smooth, durable, and biocompatible finish. For some devices such as needles, cannulas, and syringes, a non-curable film is deposited on the device surface as lubricant to enhance patient comfort.