Thermoplastic Elastomer Bonding Methods for Effective Fluid Sealing
Precision air- and fluid-tight bonds for diagnostic or medical device fluid seals.
Effective fluid sealing with chemical and mechanical TPE bonds
No TPE fluid seal can be fully effective without achieving a good bond with the component it is coupled with. Precision air- and fluid-tight bonds are typically created in one or a combination of the below ways.
Chemical Bonding
Some TPE materials are developed to stick to other rigid plastics. These chemical bonds can eliminate the need for adhesives. Since bonding must occur when the TPE is heated, the process entails injection molding the TPE onto the bonding component, or “overmolding.” Popular examples of rigid plastics used in the life science and biotech industries include the below. Each material has a specific type of TPE that could chemically bond to them:
- Engineering plastics and other rigid plastics: Polycarbonates (PC), polypropylene (PP), polystyrene (PS), and acrylonitrile butadiene styrene (ABS) for cartridges and instruments.
- Clear/transparent plastics: Cyclic olefin copolymers (COC) and cyclic olefin polymers (COP) for microfluidic chips, flow cells, well plates, and microarray slides.
Mechanical Bonding
Mechanical features used to retain the TPE in place can include interlocks, undercuts, or enclosure features in the bonding component. Externally, clamp-like features can be applied. The following may require bonding assistance through mechanical means:
- When material choice is limited to those that have a weak or non-bonding condition.
- When application pressure or aggressive contact between the TPE fluid seal and the docking component require additional assistance, even when chemical bonding is in place.
Achieve Optimal Bonding
The specific requirements of the device or application dictate the choice of materials for the TPE fluid seal and the bonding component. The design must focus on the most reliable and cost-effective measures to ensure that the fluid seal functions properly for every use, maintaining the bond, and minimizing or eliminating leakage. For example, in the following image, the gray TPE fluid seal could be two separate parts, but by designing them as one part with an undercut (red circled area) as mechanical support, the TPE fluid seal is more securely bonded in its place.
