When thinking about medical packaging, the first things that typically come to mind are the materials you will use, the sterilization method, and so on. But how often do you stop and think about the adhesive coating on your material? The adhesive coating on your packaging plays an important role in ensuring your sterile barrier remains intact until point of use. In today’s article we are breaking down what an adhesive coating is, how they are made, and the common ingredients you will find in them.
What are adhesive coatings?
Adhesive coatings are applied to substrates acceptable for use in healthcare packaging applications. These coated substrates can be converted into different types of sterile barrier system components, including pouches, lids for thermoformed trays, and lids for FFS (form, fill, seal) blisters. The main role of adhesive coatings is to facilitate the creation of a peelable seal of a sterile barrier system (when processed with heat, pressure, and dwell time), while also providing an effective porosity when applied to porous substrates (such as medical grade Tyvek®).
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How are adhesive coatings made and applied to a substrate?
Adhesive coatings are typically designed, mixed, and applied to substrates in an ISO 13485 based production setting. Typically, air-knife coating is used for overall-coated water-based adhesives. Gravure coating (dot coating) is used for hot melt coatings. Zone coating/pattern coating can be done for both water-based and hot-melt adhesives by alternate methods.
What are the adhesive coatings made of and what properties can be controlled?
Adhesive coatings are proprietary to the company that makes them and therefore can be comprised of several ingredients. Generally, the main ingredients of an adhesive coating are:
- Ethylene vinyl acetate (EVA) copolymers
- Other polymers and copolymers
- Resins
- Waxes
- Dispersants (water-based coatings)
Some of the properties that can be formulated/optimized for include:
- Adhesive strength
- Cohesive strength
- Peel strength
- Adhesive transfer
- Porosity
- Hot tack
- Cold shock
- Anti-Block
What else should I know about adhesive coatings?
Adhesive coatings are generally formulated to peel cohesively (split in the middle). This cohesive split provides visual seal indication (white appearance) of a good seal. Formulators can tailor peel strength by control of an adhesive’s cohesive strength. EVA-based adhesives can be formulated to bond well to a wide variety of materials, including PET/PE, nylon/PE, PETG, PVC, HIPS, C-film (EVA/Ionomer/EVA), polycarbonate, and polypropylene.
Successful aseptic presentation of medical products is crucial when designing your packaging, and adhesive coatings have a significant impact on this. Understanding the basics of adhesive coatings will help you ensure that you are making informed decisions when it comes to your medical packaging.
