Solvent acrylic PSAs are the adhesives of choice for durability and long-term applications; they provide the widest range of expedient performance properties, including better chemical, water and heat resistance over almost all other adhesive types.
The molecular structure of an adhesive determines the way in which it performs in different circumstances. Solvent-based acrylic adhesives feature a number of crosslinking mechanisms, whereas water-based adhesives typically do not. One such effect of crosslinking is an increased resistance to chemicals and other solvents; most water-based adhesives lack this connective ability, resulting in them being more susceptible to poor end-use performance when exposed to solvents.
Through testing and modifications, adhesive technologists are able to use solvent acrylic adhesives to deliver precise polymer performances to meet almost all adhesive needs. This wide breadth of possibility in customisation of solvent acrylic adhesives enables the option of combining positive characteristics with minimal sacrifice to overall performance properties.
Advantages of using formulated/customised solvent acrylic adhesives include:
- Outstanding chemical resistance
Well-suited for use in environments where chemical exposure is a possibility.
- Performance properties retained at a wide range of temperature extremes
This adhesive type performs well at high and low temperature extremes, making it well suited to being used in a diverse scope of locations and conditions.
- Longevity and durability
Solvent acrylic adhesives are usually the best option for an application that requires long-term wear and durability against the elements.
Things To Consider
Tack is the measure of force required to remove an adhesive tape from a substrate immediately after initial application, with very minimal effort. Solvent acrylic PSAs’ tack levels can be manipulated to range from low, to medium, to high tack.
Skin adhesion is measured through testing the bond strength between the adhesive and the substrate. Pressure is applied to the adhesive and is then left to wet-out onto the substrate (adhesive dwell). Adhesion generally continues to increase for a period of time after the initial application, typically 24 hours. For this reason, a peel test, in which adhesion is tested through the force required to ‘peel’ the adhesive from the substrate, is often performed at different periods of time to show any differentiation.
Solvent acrylic PSAs are suitable for use in the medical industry where skin contact is required; many also meet ISO10933 test standards.
Biocompatibility ISO10933 Test
A series of tests designed to provide assurance that the materials used in the manufacture of a medical device are appropriate and safe for use.
The type of testing performed on the material/adhesive is determined by the intended use, duration of contact on the skin and the condition of the intended patient.
The ISO guidance documents for biocompatibility ISO 10993, offer the direction needed to determine which test methods are most appropriate.
The clear appearance of a solvent acrylic PSA is well suited to medical requirements.
Solvent acrylic PSAs can be applied to a variety of substrates, including PU films, polyester films, non-woven carriers, PET & PP scrims, foams and papers.
Moisture vapour transmission rate (MVTR) is a measure of the passage of water vapour through a substance; it is an incredibly important factor to be considered in order to control moisture levels in a wound dressing. The higher the MVTR reading, the more moisture that can pass through the adhesive.
A number of solvent acrylic PSAs have high MVTR ratings, making them ideal adhesives to be used in the construction of a wound dressing as they enable moisture from the wound to escape.
Solvent Acrylic PSAs are both gamma and EtO sterilisation stable:
Gamma sterilisation stable
The substance is exposed to gamma rays as a method of sterilisation or decontamination. The gamma rays are a form of electromagnetic radiation of very short-wave lengths; these rays act as a source of ionising energy that destroys bacteria and pests.
EtO sterilisation stable
Ethylene oxide (EtO) is a gas that acts as a powerful alkylating agent. The sterilisation process disrupts the DNA of microorganisms, preventing them from reproducing, therefore destroying all known viruses, bacteria and fungi and insuring safe, sterile products.
The process of EtO sterilisation consists of four primary variables: gas concentration, humidity, temperature and time. The substance is first brought to the necessary temperature and moisture content, it is then placed in an enclosed chamber where all air is removed and controlled amounts of steam and EtO are introduced. The final stage requires the substance to enter a high velocity aeration room, where gas residuals are lowered to the required levels for a period of at least 48 hours.
The coat weight thickness is dependent on the solid content, viscosity and end use of the solvent acrylic adhesive system; on average coat weights range from 10-100gsm.
Selecting The Right Manufacturer
With customers requesting complex combinations of performance characteristics, it is important that the manufacturer understands the properties of the adhesive and has broad experience of the application of an adhesive onto a substrate.
The manufacturer is also required to have a knowledgeable technical team who have experience in handling solvent acrylic PSAs; understanding where to source the adhesive, how to laminate the construction, how to coat and how to dry. All of the adhesive’s characteristics can be lost if just one step in the process is done incorrectly, highlighting the importance of choosing the right manufacturer to build your construction.
For information on how Raleigh can support you in your solvent acrylic PSA coating requirements, contact our team on 01785 850 357 or email our Business Development Manager, Julian Watkins.