Poly methyl electrical properties

Electrical Properties. Poly(methyl methacrylate) has specific electrical properties that make it unique (Table 4). The surface resistivity of poly(methyl methacrylate) is higher than that of most plastic materials. Weathering and moisture affect poly(methyl methacrylate) only to a minor degree. High resistance and nontracking characteristics have resulted in its use in high voltage appHcations, and its excellent weather resistance has promoted the use of poly(methyl methacrylates) for outdoor electrical appHcations (22). 

Table 4. Electrical Properties of 6.35-mm Thick Poly(methyl methacrylate) Sheet ...

The important features of rigidity and transparency make the material competitive with polystyrene, cellulose acetate and poly(methyl methacrylate) for a number of applications. In general the copolymer is cheaper than poly(methyl methacrylate) and cellulose acetate, tougher than poly(methyl methacrylate) and polystyrene and superior in chemical and most physical properties to polystyrene and cellulose acetate. It does not have such a high transparency or such food weathering properties as poly(methyl methacrylate). As a result of these considerations the styrene-acrylonitrile copolymers have found applications for dials, knobs and covers for domestic appliances, electrical equipment and car equipment, for picnic ware and housewares, and a number of other industrial and domestic applications with requirements somewhat more stringent than can be met by polystyrene. 

Siloxane containing interpenetrating networks (IPN) have also been synthesized and some properties were reported 59,354 356>. However, they have not received much attention. Preparation and characterization of IPNs based on PDMS-polystyrene 354), PDMS-poly(methyl methacrylate) 354), polysiloxane-epoxy systems 355) and PDMS-polyurethane 356) were described. These materials all displayed two-phase morphologies, but only minor improvements were obtained over the physical and mechanical properties of the parent materials. This may be due to the difficulties encountered in controlling the structure and morphology of these IPN systems. Siloxane modified polyamide, polyester, polyolefin and various polyurethane based IPN materials are commercially available 59). Incorporation of siloxanes into these systems was reported to increase the hydrolytic stability, surface release, electrical properties of the base polymers and also to reduce the surface wear and friction due to the lubricating action of PDMS chains 59). 

Table III lists some of the physical properties of polymers which contain ethylenebis [tris (2-cyanoethyl) phosphonium bromide]. This additive caused an increase in the dissipation factor and dielectric constant and lowered the dielectric strengths of polyethylene and poly (methyl methacrylate). The effects on mechanical properties were mixed. Obviously, lower concentrations of phosphonium halides would have less effect on mechanical and electrical properties. At levels of 1-3% very little change in properties would be expected. It was surprising that the phosphonium salts were compatible with such a range of polymers. We did not observe any tendency for the phosphonium salts to plate out of or exude from the polymer. In all cases homogeneous blends were obtained.

Poly (methyl methacrylate) is characterized by crystal-clear hght transparency, unexcelled weatherability, and good chemical resistance and electrical and thermal properties. It has a useful combination of stiffness, density, and moderate toughness. PMMA has a moderate Tg of 105°C, a heat deflection temperature in the range of 74 to 100°C, and a service temperature of about 93°C. However, on pyrolysis, it is almost completely depolymerized to its monomer. The outstanding optical properties of PMMA combined with its excellent environmental resistance recommend it for applications requiring light transmission and outdoor exposure. Poly (methyl methacrylate) is used for specialized apphcations such as hard contact lenses. The hydroxyethyl ester of methaciyhc acid is the monomer of choice for the manufacture of soft contact lenses. Typical applications of poly(methyl methacrylate are shown in Table 15.6. 

The wide assortment of polymer systans (polypropylene, poly(methyl methacrylate) [PMMA], polyepoxide, polystyrol, PC, etc.) is used as a polymeric matrix for nanocomposites production (Ray and Okamoto 2003). The most well-known fillers of polymeric matrix are nanoparticles (silica, metal, and other organic and inorganic particles), layered materials (graphite, layered aluminosilicates, and other layered minerals), and fibrous materials (nanofibers and nanotubes) (Thostenson et al. 2005). Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific combination of physical and electric properties (Rozenberg and Tenne 2008, Zezin et al. 2010). Nanocomposites on the base of layered materials... 

Figure 4.23 (a) Typical electrical responses of PANI/PMMA composite nanofibers to TEA vapors of different concentrations (doping acid TSA). (b) Sensing magnitude of PANI/PMMA composite nanofibers with different diameters as a function of the concentration of TEA vapor. Concentration ofelectrospun PMMA solution (a) 0.32 g ml and (b) 0.18 g ml (Reprinted with permission from Sensors and Actuators B., Gas sensing properties of a composite composed ofelectrospun poly(methyl methacrylate) nanofibers and in situ polymerized polyaniline byS.Ji, Y. Li and M. Yang, 133, 644-649. Copyright (2008) Elsevier Ltd)... 

Another commercially produced polyolefin is isotactic poly(4-methyl pentene-1). The polymer carries a trade name of TPX. This material is known for high transparency, good electrical properties, and heat resistance. PoIy(4-methyI pentene-1) has a density of 0.83 g/cm. This polyolefin exhibits poor load-bearing properties and is susceptible to UV degradation. It is also a poor barrier to moisture and gases and scratches readily. This limits its use in many applications. 

Introducing derivatives and copolymers of PANI also results in different ER effect because of different molecular structure and electrical properties, e.g., poly(o-anisidine), poly(anihne-co-o-ethoxy aniline), poly(o-tolu-idine) (POT), substituted PANI (with long alkyl pendants, PDOA), poly(N-methyl aniline) (PNMAn), poly(N-ethyl aniline) (PNEAn), and poly(2-ethyl anihne) (P2EAn) with reduced conductivity [36,37]. 

Electrical properties such as conductivity, resistivity, I (current)-V (voltage) characteristics of vegetable oil-based polyurethane nanocomposites are sometimes influenced by nanocomposite formation with a suitable nanomaterial. BaTiOs superfine fibre-filled castor oil-modified polyure-thane/poly(methyl methacrylate) interpenetrating polymer network nanocomposites exhibit an increase in conductivity between insulator and semiconductor with an increase in nanofibre loading. ... 

Dicyclohexyl phthalate (DCHP) n. C6H4 (COOC6Hii)2. a plasticizer for PVC and many other resins. It imparts good electrical properties, low volatility, low water and oil absorption, and resistance to extraction by hexane and gasoline. In vinyls DCHP is usually combined with other plasticizers. In cellulose nitrate, polystyrene, poly-methyl methacrylate, and ethyl cellulose it serves as a primary plasticizer. 

Another strategy that allows the combination of electronic, electrical and optical properties of ICP with tunable properties of the matrix has also been explored. Nanostructure materials with an ICP core and an insulating polymer shell have also been reported [79-81]. Highly transparent conductive coatings with core-shell nanoparticles have been reported by Jang et al. [82]. Poly(methyl methacrylate)... 

---