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Silicon rubber plasma processor surface treatment

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Published on:

20 Nov,2020

Silicon rubber plasma processor surface treatment:

 

Polymethyl methacrylate has been used as a contact lens material since the 1940s. PMMA is still widely used because of its high refractive index, suitable hardness and good bioaffinity. However, PMMA has poor hydrophilicity, which can cause long-term pannus closure and discomfort to the wearer. At the same time, its oxygen permeability is poor, serious can lead to complications. If the above shortcomings of PMMA can be overcome, its efficiency can be greatly improved. Plasma polymer of acetylene, nitrogen and water was used to coat PMMA lens surface, which can improve the hydrophilicity of material and reduce adhesion of corneal epithelial cells. The addition of organosiloxane to the polymer sandwich can improve the permeability of the material, but due to its inherent hydrophobic nature, siloxane will reduce its moisture retention. The surface hydrophobic problem of silicon-containing polymer can be treated by glow discharge generated by vacuum plasma cleaner. PMMA through vacuum plasma cleaning machine and polysiloxane binding material surface treatment, can reduce the surface carbon content, increase the oxygen content of PMMA, improve its moisture.

 

Contact lenses made of silicone rubber are called "soft" lenses. Silicone rubber has good permeability, soft texture, good mechanical elasticity, durability and other characteristics. Its disadvantages are too large viscosity, hydrophobic, liquid easy to permeate. Coating the silicone rubber with a layer of methane film can improve its moisture retention, reduce viscosity, reduce the permeability of liquid, and maintain its air permeability.

 

PMMA is a material commonly used for intraocular lens transplantation, but its contact with corneal epithelial cells can lead to damage of corneal epithelial cells. Hydrophilic monomers, such as hydroxyethyl isobutenate or N-vinyl pyrrolidone, can be deposited on the PMMA surface by grafting or irradiation with a vacuum plasma cleaning machine. Static "contact tests" between the cornea and lens of rabbits showed that PMMA surfaces without plasma treatment could cause 10-30% cell damage, while PMMA/HEMA composite surfaces could cause about 10% cell damage, and PMMA/NVP composite surfaces could cause less than 10% cell damage. Plasma deposition on C3F8, HEMA and NVP all significantly reduced corneal cell damage. In addition, adhesion ability of NVP membrane on PMMA surface was significantly lower than that of PMMA.

 

Plasma treatment is usually a plasma reaction that causes changes in the molecular structure of the surface or substitutions of the surface atoms. Even in the inert environment of oxygen and nitrogen, plasma treatment can produce high active groups at low temperature. In the process, the plasma also emits high-energy ultraviolet light and produces fast-moving ions and electrons that break the polymer's bonds and generate the energy needed for chemical reactions on the surface. The bulk properties of the polymer remain unchanged only if a few atomic layers are involved in the chemical process on the surface of the material. In addition, the possibility of thermal damage and deformation is avoided due to the low temperature of plasma treatment. Selecting appropriate reaction gas and process parameters can promote some specific reactions and form special polymer attachments and structures.

Silicon rubber plasma processor surface treatment

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