Silicone Dip Molding and Coating
Every silicone dipping project presents a unique set of challenges that require equally unique solutions. Trelleborg Sealing Solutions has over 30 years of silicone dipping experience for medical device applications; during this time, we have developed and optimized specialized processes and equipment to manufacture products to meet our customers’ needs.
In the broadest sense, silicone dipping can be divided into 2 processes; dip molding (sometimes referred to as casting) and dip coating:
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. The dip molding process consists of the following steps:
1. Produce a mandrel in the shape of the final part. The mandrel is typically machined from metal, but can also be fabricated from engineered plastics and ceramics.
2. Immerse the mandrel into the silicone dispersion and then withdraw. The mandrel is now coated with a thin liquid silicone film. The wall thickness of parts can be adjusted by varying the number of dips or adjusting the percent solids concentration of the silicone dispersion.
3. The mandrel with silicone coating is placed in an oven to vulcanize the silicone.
4. Following vulcanization, the silicone rubber is stripped from the mandrel creating the finished product.
Trelleborg Sealing Solutions dipping experts understand and control the many variables that contribute to the quality and reproducibility of each part. Process validations include evaluation of mandrel surface finish, immersion and withdrawal angle and speed, dispersion viscosity and temperature, ambient manufacturing conditions, and vulcanization parameters.
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.