Antistatic Coating

Another antistatic composition comprises a 10 90 blend of PHT and polystyrene [778] or polyheteroaromatic compounds, e.g. PBT, and polymeric sulfate [671], or an electrically non-conductive polymer matrix and POT [779]. Silver halide photographic materials containing electrically conductive polymers, e.g. PT, PMT, PET, poly(3-methoxythiophene), poly(3-cyanothiophene), poly(3-fluorothiophene), poly(3-nitrothiophene), poly(3-bromothiophene), poly-(3,4-dibromothiophene), poly(3,4-dimethylthiophene), are claimed to have improved antistatic properties [780-783]. 

A p-n-heterojunction type device can be fabricated on the basis of the junction formed between poly(pyrrole) and PT derivatives (e.g. PT or PMT) [784]. A PODT/Cfio junction device with a photo-induced charge transfer between PODT and Cgo is shown in Fig. 22 [449]. Rectifying bilayer electrodes with sequential bilayer structures are prepared from any pair of PBT/poly(pyrrole) and poly(3-bromothiophene)/poIy(pyrrole) by anodic electropolymerization on platinum electrodes [785]. 

PEDOTiPSS was first introduced in an industrial product as a roll-to-roll deposited antistatic layer on biaxially oriented poly(ethylene terephthalate) (PET) during photographic film production in order to avoid unwanted, stray electrostatic discharges within the photoactive layers during film processing. The use of PEDOTiPSS as the conductive ingredient in the antistatic layer proved particularly advantageous because 

In a second commercial antistatic application, PEDOTiPSS was used as the conductive ingredient in an outer surface antistatic layer on cathode ray tubes (CRTs) to avoid dust contamination during manufacture and use. In addition to the same advantages as described above, the PEDOT PSS layer was found to enhance optical contrast in the displays. 

The other potential uses of PEDOTiPSS for antistatic layers are numerous and include antistatic gloves [99], carrier tapes, displays and video display panels [100-102], textiles [103], antistatic release films [104, 105], protective films [106], recording tapes [107] and polarizers [108], 

100 S cm can be reached and increased up to 1100 S cm by stretching these films [51-57]. Via poly[2,5-thiophenediyl(l-methoxyethylene)] as a soluble precursor polymer, oriented PTV films with up to 1000Scm can be prepared following two routes the more common simultaneous tensile deformation and conversion method to PTV and - more effective - the sequential conversion and drawing method to form PTV [57]. 

A copolymer having 20 to 230Scm can be synthesized electrochemically with the electrolyte salt tetraethylammonium perchlorate in propylene carbonate starting from thiophene and l,2-di(2-thienyl)ethylene forming a polymer with 2,2 -bithio-phenediyl vinylene units [58], 

PEDT is used for antistatic coatings. The 1997 production of this product was in the order of about 1000 kg per annum. As a transparent polymer it substitutes the classical materials carbon black for compoundings, ionic compounds as layers on different materials or metallic layers on the surfaces of such materials with a very high electrical resistivity. 

PEDT is also used in electronic technology (DMS-E process) for the production of electrically conductive layers of conductive plates. The first conductive layer in this process is prepared from EDT forming PEDT with a lower resistivity than usual in the present normally used technical process. This new process yields in electrically conductive layers of higher quality than by the other used technical processes in shorter time combined with easier handling [63]. PEDT has qualified itself especially as an excellent material that can be used for through-hole electroplating by electroless deposition. 

Under special conditions it is possible to prepare PEDT films of more than 20 m length [64]. For such films suitable polyanions, e.g. sulfated poly(/3-hydroxyether)s or poly(hydroxyether)s bearing trifluoromethyl groups and sulfated poly(buta-diene)s are necessary. The preparation can be achieved on cylindrical electrodes of a computer controlled system. The electrical conductivity of such PEDT materials with the above mentioned polyanions composites exceed 150Scm , and reaches as high as 400Scm if the polyester with trifluoromethyl groups is used. Such films are used for the production of batteries (see section 10.5) [64]. 

There is no reliable method to predict whether a combination of two materials will generate electrostatic charges. It will therefore always be necessary to take actions to control electrostatic charges. 

A common measure to control electrostatic charges is the use of antistatic agents either in the bulk or as surface coating. Common antistatic agents are 

Salt-like and nonionic surfactants have the disadvantage that the mechanism to conduct charges is based on moisture that is absorbed from the surrounding atmosphere. Therefore the surface resistance of protected parts will change with humidity. In dry atmospheres the surface resistance may increase to an unacceptable value and a reliable discharge of electrostatic charges will not be possible. However, in many cases salt-like and nonionic surfactants are readily available at a low price and are therefore widely used for the majority of less critical applications. 

Another common antistatic agent is carbon black, a form of amorphous carbon with intrinsic conductivity. The conductivity of carbon black, therefore, does not change with humidity. Carbon black is used in coating formulations and as a conductive filler in polymeric materials, especially in the electronics industry. The main drawback of carbon black is its intrinsic black color and the tendency to generate particles that dissipate in the clean room air and may cause undesired shorts. 

The aqueous dispersion of PEDOTiPSS has a surface tension of approximately 65 to 71 mN/m depending on the ratio of PEDOT to PSS. Such a surface tension is too high to wet hydrophobic surfaces such as plastic substrates like polyethylene terephthalate (PET), polycarbonate (PC), or polyethylene (PE) with aqueous PEDOT PSS dispersion. 

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Antistatic coatings Antistatic finishes Antistatic yarns Antistatin D Antisterility vitamin Antistick agents Antistick applications Anti-Stokes lines... 

CS derivatives/salts have found limited use as detergents (25), antistatic coatings for photographic film (26), oil drilling fluids (25), thickeners in food, cosmetics, and pharmaceuticals (27). They have been recommended for use as cation exchangers (28,29). Also, sulfated polysaccharides have recendy shown interesting antiviral activity (30). 

These coatings are used to prevent the transmission of radio frequency interference from sources such as television or computer displays, as antistatic coatings, and to absorb or reflect microwaves. 

Polymers of N, N, N, A-diallyldimethylammonium chloride (DADMAC) (and its copolymers with acrylamide) are allyl resins in terms of the monomers used but are very different in properties since they are not crosslinked. Cyclopolymerization is the mode of reaction (Sec. 6-6b) and the polymers are water-soluble. Applications include potable and wastewater treatment (flocculation aid) and paper and textile industries (antistatic coating, reinforcement, color removal). 

Film coatings (antistatic coatings, antiscratch coating on phone and other cards)... 

Antistatic coatings -conductive polymers in [ELECTRICALLY CONDUCTIVE POLYMERS] (Vol 9)... 

It is expected that the intermacromolecular complexes display entirely new physical and chemical characteristics different from those of the individual polymer components. So the following applications are, for example, considered membranes for dialysis, ultrafiltration, fuel cells and battery separators, wearing apparel, electrically conductive and antistatic coatings for textiles, medical and surgical prosthetic materials, environmental sensors or chemical detectors, and electrodes modified with specific polymers. 

Baytron P) has been extensively used as antistatic coating. See also conducting polymers. 

Antistatic coating Backing layers -Anticurl layer... 

Sotzing [2] prepared intrinsically conducting water-borne dispersions of poly (thieno[3,4-b]thiophene) homopolymer, (II), and copolymers of thieno[3,4-b] thiophene and 3,4-ethylenedioxythiophene, (111), for electroactive applications including electrochromic displays, optically transparent electrodes, and antistatic coatings. 

In this section we shall consistently refer to resistivity, rather than to its reciprocal, conductivity. The choice is arbitrary, and commercial instruments are sometimes calibrated in units of resistance and sometimes in units of conductance.1 Unless otherwise stated, when we refer to resistivity we shall mean volume resistivity pv (Am), the resistance between opposite faces of a unit cube. A surface resistivity ps is often used to characterise current flow over a surface, as with an antistatic coating, and is defined as the resistance between opposite edges of a unit square. We note first that the resistance across a square is independent of the size of the square and that the unit of surface resistivity is simply the ohm (Q), occasionally written rather superfluously as ohm per square. Secondly, a conducting surface must in reality be a layer with a finite thickness t, and we have only an effective surface resistivity, which is related to the true volume resistivity of the layer by... 

Special applications of bright electro-conductive pigments based on metal-oxide-coated mica are conductive plastic surfaces and antistatic coatings [5.122, 5.148]. 

Optical quality thin films of metallic polymers are useful, therefore, as transparent electrodes [68]. For example, polyaniline [69], polypyrrole [70] and PEDOT [71] have been used as transparent hole-injecting electrodes in polymer LEDs (the initial demonstration of mechanically flexible polymer LEDs utilized PANl as the anode [69]). Transparent conducting films can be used for a variety of purposes for example, as antistatic coatings on CRT screens, as electrodes in liquid crystal display cells, or for fabricating electrochromic windows. 

Figure 17.16 shows the electric charge decay characteristics on the CRT surface. The CRT with the antireflective/antistatic coating has excellent antistatic performance. Photoirradiation promotes the densification and purification of the film. The film is purified by photoirradiation because ozone generated by photoirradiation decomposes organic residues on the film. Heat treatment during photoirradiation contributes to increasing the adhesion between the film and substrate. 

Tin oxide Coatings for solar cells, antistatic coatings, coatings for plate glass and light bulbs. 

Evonik has developed an ITO nanopowder, VP AdNano ITO (Figure 2.8), and has formulated this nanopowder into dispersions for antistatic coatings. Both the nanopowder and the dispersion are commercially available. Current-... 

Antistatic Coating 1412. [Coating Systems] External antistat fw plastics. 

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