Surface fluorination polymer applications

Surface fluorination changes the polymer surface drastically, the most commercially significant use of polymer surface direct fluorination is the creation of barriers against hydrocarbon permeation. The effectiveness of such barriers is enormous, with reductions in permeation rates of two orders of magnitude. Applications that exploit the enhanced barrier properties of surface-fluorinated polymers include (1) Polymer containers, e.g., gas tanks in cars and trucks, which are produced mostly from high-density polyethylene, where surface fluorination is used to decrease the permeation of fuel to the atmosphere and perfume bottles. (2) Polymeric membranes, to improve selectivity commercial production of surface-fluorinated membranes has already started.13... 

Many polymer items are designed specifically to make contact with other materials. Where surface contact is concerned, two key properties are coefficient of friction and abrasion resistance. Polymers used in such applications include ultra high molecular weight polyethylene, polyacctal, fluorinated polymers, and natural and synthetic rubbers. Examples that we routinely come across include furniture upholstery, bushings and gears in office equipment, and bicycle tires. Industrial uses include the outer cover of electrical cables, and pipes that convey abrasive liquids such as slurries and powders. 

Surface engineering by means of fluorination is an effective way to change surface properties, and is used for both polymer surfaces and inorganic substrates. Polymer surface fluorination has been around a long time. The first patent we know of dates back to 1938,1 but it was only in the 1970s that the introduction of several major industrial applications led to a rapid acceleration in development. 

However, the fact that industrial applications of polymer surface fluorination employ a fluorine/nitrogen mixture as the fluorinating agent complicates matters because fluorine gas is toxic, may explode when brought into contact with organic substances, and causes severe bums on human tissue. Moreover, the use of fluorine requires highly qualified personnel and special safety systems. 

It is appropriate at this point to recall that XeF2 was originally considered to be exotic and was used only as laboratory chemical in very small quantities. While direct polymer surface fluorination with a gaseous F2/N2 mixture was already in use for several significant commercial applications. 

If solid polymer objects are fluorinated or polymer particles much larger than 100 mesh are used, only surface conversion to fluorocarbon results. Penetration of fluorine and conversion of the hydrocarbon to fluorocarbon to depths of at least 0.1 mm is a result routinely obtained and this assures nearly complete conversion of finely powdered polymers. These fluorocarbon coatings appear to have a number of potentially useful applications ranging from increasing the thermal stability of the surface and increasing the resistance of polymer surfaces to solvents and corrosive chemicals, to improving friction and wear properties of polymer surfaces. It is also possible to fluorinate polymers and polymer surfaces partially to produce a number of unusual surface effects. The fluorination process can be used for the fluorination of natural rubber and other elastomeric surfaces to improve frictional characteristics and increase resistance to chemical attack. 

Fluorinated polymers are considered high value-added materials, due to their outstanding properties which open up various applications [1-9]. Such polymers exhibit high thermostability and chemical inertness, low refractive index and coefficient of friction, good water and oil repellence, low surface energy and valuable electrical properties. In addition, they are non-sticky and resistant to UV, ageing, and to concentrated mineral acids and alkalies. 

The fluorinated polymers exhibit particularly interesting properties which lead to very specific applications in spite of their high prices. Their chemical resistance due to very low molecular interactions, gives them thermostable properties and properties of resistance towards concentrated bases and acids but also excellent surface properties. But, the processing of these polymers is still difficult since several of them are not usually soluble and others are not meltable or exhibit very high melting points. 

Polydimethylsiloxanes have many unique surface applications associated with the lowest surface tension of any non-fluorinated polymer and the high flexibility of the siloxane backbone [14]. 

Despite their potential application, the wetting properties of aqueous surfactant solutions on superhydrophobic (SH) solid surfaces have been rarely investigated. In this work single surfactant solutions and binary mixtures of non-ionic and ionic surfactants have been studied in contact with textured and non-textured surface coatings obtained utilizing nanoparticles and a fluorinated polymer. 

Aso, there will be no change in the bulk physical or mechanical properties of the parts. The plasma treated surface layer is just too thin to affect the bulk properties. While it is not possible to affect the bulk material properties, the major use of plasma is to modify the surface properties of materials. This surface modification makes it possible to get greatly improved bonding to surfaces and can lead to greatly improved composite properties. However, in some applications it is not possible to change the physical properties of the surface to a depth sufficient to be useful. For example, it is possible to fixlly fluorinate some polymers and get a Teflon -like surface. However, this plasma modified surface caimot be used as a low-firiction surface (for most applications) because it is so thin that it is easy to rub off. 

Y. Qinhuan, Z. Tingyou, L. Zhengjun, Characterization and application of low surface energy fluorinated polymer in leather finishing, J. Soc. Leath. Tech. Chemists 94 (3) (2010) 106-110. 

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