FAQs

• Performance and appearance improvements
• Bulk modification may be too expensive or additives may diminish bulk properties/integrity
• Materials are only required at the surface for attributes such as slip, therapy delivery, color, etc.

Ambient/ Low-Temperature Cure

Does not require high temperatures, which could affect proteins or other heat-sensitive bioactive additives or substrates.

Flammability/Carcinogenicity

Usually not an issue with water-based coatings, which means that they are typically given lower plant insurance rates and are not combustible or have a flash point.

Low/No Odor

Workers love the low odor compared to conventional solvent coatings.

Worker Safety

Water-based coatings are less hazardous to employee health and easier to handle and clean-up.

Energy Requirements

The specific heat of water is higher than most solvents customarily used, but the water will not require the ventilation for cleanrooms required with conventional solvents. This reduces the need for clean, heated/ air-conditioned (humidified) makeup air and the associated costs.

• Line-of-site cure is not an issue.
• Expensive calibration and validation of equipment for curing is not an issue.
• Oxygen inhibition and surface tackiness not an issue.

• Workers appreciate the low odor and easy water wash-up of equipment.
• Easy Disposal—Please consult local and state regulations, but a dry-out/cure will usually allow placement in the trash, as is practiced with latex paints.
• Surface acceptability—No stress crazing on solvent sensitive plastics, such as polycarbonate, acrylic, polyester, urethane, etc.
• Insurance—Because these are non-flammable or non-carcinogenic solvents, lower insurance and facilities costs result.

Your interdisciplinary product development team should produce a project plan describing what features are needed for surface modifications on the device. For many applications that are searching for a second source of coating, there is an existing specification for coating performance describing the test methods and other requirements for the product. In general, these specifications can be described by the categories similar to those that have been shown under our product lines.

If there is no category on our “Products” listing to accommodate your requirements, please contact us. We are able to make these coatings harder or softer, more resilient or less flexible by varying the resins we select.

Proper mixing is key to obtaining a stable solution. Pot life on the Crosslinker A mixes can be several days, but mixes with Crosslinker B may be only 6 to 8 hours depending on the solids of the coating solution. Crosslinker B, which is used with the hydrophilic coating, absorbs water from the air and can become too high in viscosity and eventually gel after repeated opening and closings. Many customers have decided to mix the B concentrate just before use, with a co-solvent such as NMP or MEK. This eliminates the concern for hygroscopic solvents absorbing water upon opening and then reacting with the B functionality. You may opt to specify your orders for Crosslinker B Concentrate, but the premix is included in the coating kit.

More detailed instructions may be found under the Instructions for Use tab.

Mixed coatings may be applied by almost any coating method. Complex geometries and transfer efficiencies often make dipping the preferred method. Flow, spray, brush, and transfer methods— including knife over roll, gravure, and screen—may be employed. Attention to minimizing foam generation is key for many of these methods. There is no defoamer in these formulations, but foam may be suctioned off the top of a bath of coating as needed.

Instructions for Use tab will explain in greater detail.

In most instances we would suggest that you begin your evaluations with small amounts and build experience with the viscosity, handling, pot life, and coating application/cure and performance optimization. These patented coating systems are tougher and more durable with better adhesion, but they should be understood well prior to plant introduction.

If you are doing a rough evaluation of coating utility and can flow coat from an eyedropper or dip the device into (or pull it through) the coating, then the smaller amounts should suffice. You can always order more or in larger quantities. Making the most of the coating can be a continuous improvement project. Consider the pot life of the mixed coating and geometries of the devices to be coated when deciding on mix quantities. The hydrophilic coating with the Crosslinker B added has limited shelf life, and quantities should be optimized early in the development cycle.

If you have a current reservoir that needs filling, we can discuss larger quantities than what is listed on the forms for a better economy of scale. Redesign of the coating process and tanks may be a good option, since pot life should be considered in the process design.

Surface tension is a basic science. If you do not have the surface tension of the coating below that of the surface, the coating will not wet out—never mind stick. Water has a surface tension of 73, and many low- energy surfaces have surface tensions lower than 30. So what can you do? The solution is to either increase the surface tension of the surface with plasma, corona, acid etch, priming, etc., or bring down the surface tension of the coating with the addition of solvents and/or surfactants. (We suggest the solvent route, if possible, since solvent comes out during the drying/curing phase, but the addition of materials that remain in the final coating may alter the biocompatibility test results.) The FDA has been particularly sensitive to the addition of surfactants as an extractable.

If solvent addition does not develop the adhesion, primers and/or corona and plasma are very effective. These methods often produce functional groups at the surface, which can covalently link with the topcoat. Covalent bonding will provide a more robust adhesion and durability.

Most devices are sterilized with ETO. The humidification step may cause adhesion between hydrophilic surfaces, but these will fall apart when hydrated.

The hydrophilic polymer is susceptible to H-abstraction and subsequent addition polymerization, so care should be taken if you are considering E-beam or other high-energy methods.

Typical chemical sterilants and autoclaving are not suggested methods for achieving sterility, but short heat cures may be tolerated.

Experiment with your device and method.

Note: If you are experiencing problems with the application of these products, please contact us for coaching, or consider utilizing our engineering services to prepare initial samples for your evaluation.