Phenol-formaldehyde polymers electrical properties

Copolymers of furfural with phenol or phenol-formaldehyde polymers have been available commercially for many years. Since the acid-catalyzed reaction of furfural and phenol has been difficult to control, most industrial applications involve the use of alkaline catalysts. Furfural-phenol resins are used for their alkali resistance, enhanced thermal stability, and good electrical properties compared to phenol-formaldehyde resins. 

The final products of cast phenol-formaldehyde polymers have a number or exceptional properties, including high tensile and compressive strengths, good electrical insulating capabilities, and excellent adhesive qualities. Also, they can be polished and machined. Finally, the presence of very small water droplets in the material gives the surface a superb appearance. 

In Britain, similar experiments were being carried out by a British inventor. Sir James Swinburne, whose search for a material with good electrical properties led him to develop similar materials to Bakelite. His experiments were less complete than those of Baekeland but the two collaborated in the 1920s to develop the Bakelite business in Britain. The success of phenol-formaldehyde mouldings stimulated research into other polymers. 

Both one and two stage polymers are used individually or in combination in applications. The final insoluble and infusible phenol-formaldehyde resins are called Bakelite [1]. Phenol-formaldehyde resins are good electrical insnlators, they are resistant to heat and chemical attack. However, they are brittle and their mechanical properties are not too good. 

Alkanolamines are used as cross-linking and hardener accelerators in epoxy resins applications. Improved thermal and oxidative stability of polyvinyl alcohol, poly(phenylene ether), polystyrene, polypropylene, and polyethylene polymers are achieved by the addition of small amounts of the alkanolamines. Diethanolamine and morpholine act as initiators for the preparation of poly (alkyl methacrylate) in bulk or solution polymerization. The ethanolamines are efficient initiators for the preparation of polyvinyl chloride. Alkanolamines promote cross-linking of styrene copolymers with polystyrene or polyvinyl alcohol. Addition of alkanolamines to phenolic formaldehyde or urea formaldehyde resins affords improved electrical properties and increased water solubility. 

Joseph S, Thomas S. Electrical properties of banana fiber-reinforced phenol formaldehyde composites. J Appl Polym Sci 2008 109 256. 

True synthetic polymers came into use when Bakeland came from Belgium and applied his knowledge of the formation of a moldable plastic from phenol and formaldehyde to give the product named Bakelite. This was about 1914. This product, under heat and pressure, set up to a thermo-setting resin and had useful properties especially as an insulating material for electrical items. 

Membranes which may be used in the removal of alkali metal ions by electrodialysis are those which are impermeable to anions, but which allow the flow therethrough of cations. Such cation-selective membranes should, of course, possess chemical durability, high resistance to oxidation and low electrical resistance in addition to their ion-exchange properties. Homogeneous-type polymeric membranes are preferred, for example, network polymers such as phenol, phenosulfonic acid, formaldehyde condensation polymers and linear polymers such as sulfonated fluoropolymers and copolymers of styrene, vinyl pyridine and divinylbenzene. Such membranes are well known in the art and their selection for use in the method of the invention is well within the skill of the art. 

It is interesting to mention that the first truly synthetic (not based on natural products) polymer material was bakelite obtained in 1907 via polycondensation of phenol and formaldehyde. This material had good dielectric properties and was used mainly as an electrical insulator. The most famous polycondensation polymer is probably nylon belonging to the class of polyamides. Other common classes of polycondensation polymers are polyesters (like polyethylene terephthalate), polysiloxanes, polycarbonates, polysulfides, polyethers and polyimides. 

Commercially successful fully synthetic polymeric materials were produced in the early years of this century, the first example being Bakelite. This was made from phenol and formaldehyde by Leo Bakeland in 1909. Before the end of the 1920s, a large number of other synthetic polymers had been created, including polyvinyl chloride and urea-formaldehyde. Today, there are literally hundreds of synthetic polymers commercially available with ranges of properties making them suitable for applications in many industrial sectors, including the electrical and electronics industries. 

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