Plasma Polymer Deposition
Plasma processing for polymer deposition has numerous benefits for applications in the medical device, electronics, elastomers and many more industries. Deposition is used to apply thin films uniformly to substrates that render a specific uniquely desirable surface characteristic across a broad range of end use products not naturally occurring in the virgin substrates physical behavior.
Plasma polymerization (or glow discharge polymerization) uses plasma sources to generate a gas discharge that provides energy to activate or fragment gaseous or liquid monomer, often containing a vinyl group, in order to initiate polymerization. Polymers formed from this technique are generally highly branched and highly cross-linked, and adhere to solid surfaces well. The biggest advantage to this process is that polymers can be directly attached to a desired surface while the chains are growing, which reduces steps necessary for other coating processes such as grafting. This is very useful for pinhole-free coatings of a few nanometers to many micrometers thickness with solvent insoluble polymers.
Plasma deposited polymers can exhibit similar properties to those created via standard chemical polymerization techniques.
Proper control of plasma parameters can maintain the characteristics of the monomer resulting in films with desired functional properties. Functional groups such as amines or carboxyls can be very useful when grafting films subsequently onto or as a biologically compatible surface. Plasma polymers are useful to eliminate tack from elastomers and can be used to change surfaces from hydrophobic to hydrophilic or vice versa. Plasma polymers are quite useful as barrier layers when deposited onto other polymers.
Because plasma polymers are deposited directly from the monomer there are no waste streams due to wet chemical synthesis or solvents.
Plasma deposition allows for precise control of the film thickness.
Nordson MARCH offers three system options for plasma deposition, the PD-1000, PD-1500 and PD-Pro systems. The PD series have vapor delivery capabilities added, so that liquid monomer precursors can be heated into a vapor and delivered to the vacuum chamber via a vapor flow controller. Gaseous monomers would be delivered to the chamber via standard mass flow controllers (MFC’s.) After the precursor monomer is delivered to the chamber, the plasma energy is turned on, which excites the monomer, initiating the polymerization process. The polymer forms on all surfaces within the chamber, including the parts to be treated. This results in very uniform film over the treated parts and enables deposition in nooks and crannies that would not be accessible, if using alternative forms of polymer deposition. For more information on the systems and to download the datasheets, visit the PD series page.
Examples of plasma polymer deposition applications:
Catheters - Plasma deposition of polymers using an allyl amine monomers to a medical catheter creates a tie layer for application of a lubricious coating that can withstand the rigors of multiple cycles without losing their lubricious properties.
Rubber, Elastomeric and Silicone Materials - Plasma deposition of materials to surfaces that are traditionally sticky or tacky by nature can be made smooth and slippery (lubricious). This is commonly required for medical devices that use silicone rubbers, so they do not adhere to each other, another material, or even the patient. It is also useful to reduce the stickiness of o-rings and other seals used in industrial applications, where they cannot allow components to stick to each other. Using some sort of siloxane liquid as the precursor to act as the monomer for polymerization and deposition results enables enhanced performance in end uses such as, reduced insertion forces, lower friction forces, enhanced singulation and separation in handling.
Intraluminal Deposition - Plasma Deposition within a tubular structure can be accomplished via the utilization of Nordson MARCH’s Patented Intraluminal Deposition Technology. By placing tubes within a hollow cathode, the plasma is sustained and can allow for material deposition to the ID of a tubular structure. By precisely managing the process pressure and RF frequency and duration cycle, various tube diameters and lengths can achieve reactant diffusion. Nordson MARCH’s application specific gas manifold design is utilized to optimize the deposition uniformity desired.
Electronics and Surface Protection - Plasma polymer deposition is also useful for the deposition of hydrophobic films. These films can be useful as coating on electronics to prevent moisture penetration, as well as barriers to prevent liquid flowing into undesired areas. In addition, plasma can apply precise and thin coatings for anti-microbial, anti-thrombogenic, and corrosion-resistant surfaces.