Contact angle analysis
Before plasma: 79â°
After plasma: 10â°
Without plasma: 420 psi
With plasma: 2600 psi
How to improve adhesion to polyimide?
Surface cleanliness is a critical prerequisite to bonding. Finding a cleaning protocol for your material, however, can be both exhaustive and confusing. Not only is a standard of cleanliness needed for your product, your methods need to comply with restrictions imposed by regulatory bodies such as the EPA and FDA. To add to the complication new limitations are constantly enforced as solvents and chemistries are determined to be user and environmental hazards.
Plasma cleaning is a dry, solvent free technology used to precision clean surfaces. Plasma cleaning removes surface contamination at the molecular level following machining, tooling and wet chemical processing steps. Plasma precision cleaning is a conformal process, not only for substrates of complex geometries but also on textured surfaces with âroughâ topographies. Since plasma cleaning is a dry, gaseous process there are none of the liabilities associated with wet chemistry, such as chemical storage and waste disposal, evolving restrictions on the use of dangerous solvents, solvent absorption into product, etc. Plasma technology is not just a green alternative to wet chemistry, it can also compliment it as a final cleaning step following a gross decontamination using wet processes.
Chemically activating the material surface to work with the adhesive
Polyimide is a thermoplastic that responds well to gas plasma treatment. Its inherently low surface energy and poor polarizability means the surface cannot provide enough energy to bond with adherents such as adhesives and inks. Gas plasma surface treatment solves this problem by increasing Polyimide surface energies. This is achieved by the addition or substitution of polar chemical groups onto the surface. This process is known as plasma activation. It does not weaken, damage or discolor the polymer surface in any way. Plasma is a good alternative to chemical solvent based primer treatments that may be toxic or hazardous, especially for medical devices that come in contact with biological interfaces. The surface activation encourages wetting or wicking of the adhesive over the whole surface.
Selecting the correct adhesive for your requirements
Strength of Bond:
Sometimes strength of bond is the most critical characteristic in choosing an adhesive. Depending on how the load is applied to the bond, the factor to look for in an adhesive is either tensile strength or shear strength.
Stiffness or Flexibility of Bond:
For some applications, a bond needs to be extremely stiff to maintain positioning, or on the other hand, very flexible to withstand strains in operation. For many applications, including strain gauge applications, the level of stiffness required in the adhesive depends on the levels of expected strain. If this characteristic is the primary constraint in the application, look at the Youngâs modulus (E) for the adhesive.
Operating Environment Variables:
Environmental variables can include temperature, moisture, and vibration, among other characteristics. Temperature is often the most critical, especially when extreme temperatures (either hot or cold) are required. Fatigue strength, or the ability to maintain strength characteristics after cyclic loading, can also be a critical constraint.
For adhesive selection contact the following companies:
UV Adhesives, Sealants, Encapsulants and Coatings for general and medical applications: www.emiuv.com
Permabond offers an extensive range of anaerobic adhesives and sealants (threadlockers, retaining compounds, pipe sealants and gasketing adhesives), cyanoacrylate (instant adhesive), epoxy, acrylic and UV-curable adhesives (ideal for glass bonding). www.permabond.com/
Selection of the correct curing parameters
Different types of adhesives require different curing processes. Some can cure at air temperature, while others may require elevated temperatures for a period of time. Others require strong UV light for curing. Some curing methods may not be feasible, especially if the adhesive is used in the field, and outside the controlled environment of a laboratory. Understand the environment in which the adhesive will be applied, and select an adhesive with a curing process that can be used in that environment.
Ultraviolet curing technology offers the following advantages:
UV dryers take up less space, so shops can utilize more revenue-producing equipment
UV uses less energy, therefore significantly cutting operating costs
UV ink goes farther than solvent-based ink (up to 60 percent per gallon)
UV curing can increase throughput four times over solvent-based processes
Clean-up time practically disappears, adding to the time available for production
UV technology doesnât pollute, inside or outside the shop, which means healthier employees, and a healthier, âgreenerâ environment
For UV curing solutions contact the following company:Â www.americanultraviolet.com
How can I increase the bond strength of polyimide?
The bond strength can be increased by chemically activating the surface of polyimide. By doing so, energy becomes readily available at the surface for bonding. The surface of polyimide can be chemically activated by using plasma technology. To find out more information on vacuum plasma systems to chemically activate the surface of polyimide, follow the link provided: http://www.pvateplaamerica.com/im.php. For more information on atmospheric plasma systems to chemically activate the surface of polyimide, follow the link provided: http://www.pvateplaamerica.com/atmospheric/index.php.
What are the methods for improving the adhesion to polyimide?
The first method is critically cleaning the surface of polyimide. This ensures that the surface of polyimide is clean from contamination and organics which interfere in adhesion. The second method is to chemically activate the surface of polyimide, to provide energy for bonding. Both critically cleaning and chemical activation of the surface of polyimide can be achieved using plasma technology. For more information on vacuum plasma systems to improve the adhesion to polyimide, follow the link provided: http://www.pvateplaamerica.com/im.php. For information on atmospheric plasma systems to improve the adhesion to polyimide, follow the link provided: http://www.pvateplaamerica.com/atmospheric/index.php.
How can I improve the bond between polyimide and other materials?
The bond between polyimide and other materials can be improved by ensuring that the surfaces of both materials are critically cleaned and chemically activated before bonding. Critical cleaning and chemical activation of the surface of polyimide can be achieved using plasma technology. For more information on vacuum plasma systems to improve the bond between polyimide and other materials, follow the link provided: http://www.pvateplaamerica.com/im.php. For information on atmospheric plasma systems to improve the bond between polyimide and other materials, follow the link provided: http://www.pvateplaamerica.com/atmospheric/index.php.
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