Fluorinated polymers, structure

Multilayer PVC/fluorinated polymer structure for protecting the rear of solar panels. [Data from Bonnet, A, Devisme, S, Ramfel, B, Bizet, S, US Patent US20140044976, Feb. 13,1Q 4, Arkema France.]... 

Modification of alkyd resins with high proportions of silicones considerably reduces rates of attack, but the most spectacular extension of life is shown by fluorinated polymers such as polyvinylidene fluoride where erosion rates can be reduced to 0 -1 /tm/year. If this level of durability can be achieved an initial coating, if firmly adherent and free from any breaks, may often be expected to maintain protection over a metal substrate for the likely life of the structure. The considerably increased first cost, as compared with more conventional coatings, has to be balanced against the probable saving in maintenance costs or consequences of failure. 

Polymers such as polystyrene, poly(vinyl chloride), and poly(methyl methacrylate) show very poor crystallization tendencies. Loss of structural simplicity (compared to polyethylene) results in a marked decrease in the tendency toward crystallization. Fluorocarbon polymers such as poly(vinyl fluoride), poly(vinylidene fluoride), and polytetrafluoroethylene are exceptions. These polymers show considerable crystallinity since the small size of fluorine does not preclude packing into a crystal lattice. Crystallization is also aided by the high secondary attractive forces. High secondary attractive forces coupled with symmetry account for the presence of significant crystallinity in poly(vinylidene chloride). Symmetry alone without significant polarity, as in polyisobutylene, is insufficient for the development of crystallinity. (The effect of stereoregularity of polymer structure on crystallinity is postponed to Sec. 8-2a.)... 

Fluorine is an essential element involved in several enzymatic reactions in various organs, it is present as a trace element in bone mineral, dentine and tooth enamel and is considered as one of the most efficient elements for the prophylaxis and treatment of dental caries. In addition to their direct effect on cell biology, fluoride ions can also modify the physico-chemical properties of materials (solubility, structure and microstructure, surface properties), resulting in indirect biological effects. The biological and physico-chemical roles of fluoride ions are the main reasons for their incorporation in biomaterials, with a pre-eminence for the biological role and often both in conjunction. This chapter focuses on fluoridated bioceramics and related materials, including cements. The specific role of fluorinated polymers and molecules will not be reviewed here. 

Poly (2,2,2-trifl u oroeth y I methacrylate) Fig. 7 Chemical structures of fluorinated polymers... 

Recently several groups have tried to improve the properties of anisotropic gas separation membranes by chemically modifying the surface selective layer. For example, Langsam at Air Products and Paul et al. at the University of Texas, Austin have treated films and membranes with dilute fluorine gas [66-71], In this treatment fluorine chemically reacts with the polymer structure. By careful... 

One of the most attractive and successful attempts in attaining processable aromatic polyimides is the introduction of fluorine atoms in the polymer structure, either as substituents of carbon atoms on the polymer backbone (as mentioned before for perfluoroalkane containing polyimides), or as perfluoromethyl or perfluoroalkyl side substituents. The most popular approach has been the introduction of the hexafluoroisopropylidene group in the main chain as a bulky separator group in the dianhydride monomer or in the diamine one [70]. 

In this paragraph we will examine first the adhesion properties and the structure of aluminum films evaporated i) on oi-axially oriented polymer and ii) on treated (corona and fluorine) polymer samples. Then, an analysis of the influence of some parameters of the metallization such as the thickness of the aluminum film, the evaporation angle and the aluminum deposition by sputtering, will be presented. 

Although the polymer structure varies very little as a function of the plasma parameters, there is a distinct tendency for the polymers formed at the higher discharge power to be a tighter three-dimensional network (more highly cross-linked), as evidenced by a greater amount of CF and carbon that is not directly attached to fluorine (based on the XPS spectrum), as well as a decrease in the overall F/C ratio of the film. 

Polytetrafluoroethylene is a completely fluorinated polymer manufactured by free-radical polymerization of tetrafluoroethylene. With a linear molecular structure of repeating -CF2—CF2- units, PTFE is a crystalline polymer with a melting point of 326.7°C. Its specific gravity is 2.13—2.19. Polytetrafluoroethylene has exceptional resistance to chemicals. Its dielectric constant (2.1) and loss factor are low and stable across a wide range of temperature. It has useful mechanical properties from myogenic temperatures to 260°C. In the United States, PTFE is sold as Halon, Algoflon, Teflon, Fluon, Hostaflon, and Polyflon. ... 

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