Physical properties of films

Table 4.Physical properties of film prepared from irradi—... 

Large differences in permeability, absorption and solubility were reported for the films of untreated alkaU-refined oil and heat-treated oils. However, it is not possible to make a direct comparison between the physical and chemical characteristics of a series of oils and the physical properties of films made from these oils, as there are a large number of variables involved. 

It has been more than forty years since Devaux (1) first studied the physical properties of films of proteins spread on water. There were, however, few papers on such films until Gorter began his investigations in the nineteen twenties. Interest in spread protein films appears to have reached a high point in the late nineteen thirties. Coinciding with the war years there has been a considerable decline in the number of papers on spread films of proteins, and the present, therefore, is an appropriate time to summarize and to consolidate our position. 

Many workers in the field of water transport have concentrated on the physical properties of film, such as capillary structure, or composition of the electrolytes. The work of Kumins and London has shown that the chemical composition of the polymer is equally important In particular, the concentration of fixed anions in the polymer film is aitical. They found that if the concentration of salt in the electrolyte was below the film s fixed-anion concentration, the passage of anions through the film was very restricted. If the electrolyte s conceutration was above the polymer s fixed-anion concentration, anions could permeate much more freely through the film [30],... 

Nakamura T, Tachibana H, Yumara M, Matsumoto M and Tagaki W 1993 Structure and physical properties of Langmuir-Blodgett films of Cgg with amphiphilic matrix molecules Synth. Met. 55 3131-6... 

Thin films (qv) of lithium metal are opaque to visible light but are transparent to uv radiation. Lithium is the hardest of all the alkaH metals and has a Mohs scale hardness of 0.6. Its ductiHty is about the same as that of lead. Lithium has a bcc crystalline stmcture which is stable from about —195 to — 180°C. Two allotropic transformations exist at low temperatures bcc to fee at — 133°C and bcc to hexagonal close-packed at — 199°C (36). Physical properties of lithium are Hsted ia Table 3. 

Table 3. Typical Physical Properties of Poly(Ethylene Oxide) Film...

Table 17. Physical Properties of a Multilayer Barrier Film and a Polyethylene Film ...

The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. The polymer is an excellent adhesive and possesses solvent-, oil-, and grease-resistant properties matched by few other polymers. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which, under dry conditions, are superior to those of any other known polymer. The polymer s low surface tension provides for excellent emulsification and protective coUoid properties. 

These conclusions are further suppo] ted by expected physical properties of dried film of chlorosulfonated polyethylene from the different types of ... 

Electrochemical polymeriza tion of heterocycles is useful in the preparation of conducting composite materials. One technique employed involves the electro-polymerization of pyrrole into a swollen polymer previously deposited on the electrode surface (148—153). This method allows variation of the physical properties of the material by control of the amount of conducting polymer incorporated into the matrix film. If the matrix polymer is an ionomer such as Nation (154—158) it contributes the dopant ion for the oxidized conducting polymer and acts as an effective medium for ion transport during electrochemical switching of the material. 

The physical properties of the liquid, rather than those of the vapor, are used For determining the film coefficient for condensation. Nus-selt [2. Ver. Dt.sch. Ing., 60, 541, 569 (1916)] derived theoretical relationships for predicting the film coefficient of heat transfer for condensation of a pure saturated vapor. A number of simplifying assumptions were used in the derivation. 

Mass-transfer theory indicates that for trays of a given design the factors most hkely to inflnence E in absorption and stripping towers are the physical properties of the flnids and the dimensionless ratio Systems in which the mass transfer is gas-film-controlled may be expected to have plate efficiencies as high as 50 to 100 percent, whereas plate efficiencies as low as 1 percent have been reported for the absorption of gases of low sohibility (large m) into solvents of relatively high viscosity. 

The energy densities of laser beams which are conventionally used in the production of thin films is about 10 — 10 Jcm s and a typical subsU ate in the semiconductor industry is a material having a low drermal conductivity, and drerefore dre radiation which is absorbed by dre substrate is retained near to dre surface. Table 2.8 shows dre relevant physical properties of some typical substrate materials, which can be used in dre solution of Fourier s equation given above as a first approximation to dre real situation. 

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