Polypropylene electrical properties

Commonly used materials for cable insulation are poly(vinyl chloride) (PVC) compounds, polyamides, polyethylenes, polypropylenes, polyurethanes, and fluoropolymers. PVC compounds possess high dielectric and mechanical strength, flexibiUty, and resistance to flame, water, and abrasion. Polyethylene and polypropylene are used for high speed appHcations that require a low dielectric constant and low loss tangent. At low temperatures, these materials are stiff but bendable without breaking. They are also resistant to moisture, chemical attack, heat, and abrasion. Table 14 gives the mechanical and electrical properties of materials used for cable insulation. 

The electrical properties of polypropylene are very similar to those of high-density polyethylenes. In particular the power factor is critically dependent on the amount of catalyst residues in the polymer. Some typical properties are given in Table 11.3 but it should be noted that these properties are dependent on the antioxidant system employed as well as on the catalyst residues. 

Table 11.3 Some typical electrical properties of a high heat stability grade of polypropylene ...

The mechanical properties (tensile strength, modulus) and electrical properties (resistivity, power factor) of EPDM blends with polypropylene, PP, have been shown to deteriorate during thermal aging [Roy et al., 1990]. Interestingly, cross-linked samples were more susceptible to property loss. 

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... 

The electrical properties, i.e, volume resistivity, dielectric permittivity and dielectric loss factor, as well as thermally stimulated depolarization current, were measured on polypropylene-polycarbonate (PP-PC) blends. The results confirm the existence of some interactions between the non--compatible components of PP-PC blends. 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

Polypropylene materials (PP), because of their electric properties (such as surface resistivity Ps, volume resistivity pv, dielectric loss factor tg8, permittivity e), mechanical properties and resistance to noxious agents (resistance to acids, bases, salts and organic solvents) are used in various industries. Polypropylene materials characterise, also, with the lowest specific density among widely used polymers. Those properties predispose polypropylene to be used as a substrate for composite protective screens shielding people and electric or electronic devices against noxious activity of electromagnetic (EM) fields. Composite shields... 

Lee, S. H., Kim, M. W., BQm, S. H., and Youn, J. R. 2008. Rheological and electrical properties of polypropylene/MWCNT composites prepared with MWCNT masterbatch chips. European Polymer Journal 44 1620-1630. 

TABLE 52.6. Variation in the tensile strength, modulus of elasticity, elongation, and some electrical properties with irradiation dose in polypropylenes. 

Lai CY, Sapuan SM, Ahmad M, Yahya N, Dahlan KZHM (2005) Mechanical and electrical properties of coconut coir fiber-reinforced polypropylene composites. Polym Plast Technol Eng 44 619-632... 

In filled polypropylene cables, low water pickup is important. Increased water pickup leads to a significant deterioration in electrical properties. Often maleated PP is introduced into the compound to improve the mechanical properties of the mineral-filled cable system, but this leads to an increase in the water pickup. The use of silanes in conjunction with maleated PP can markedly improve the mechanical properties... 

The Japanese company Tokuyama has proposed using magnesium hydroxide as an ionic crosslinking agent for polypropylene, rather than adding it as a filler. The product is claimed to have better flammability, flexibility, electrical properties and abrasion resistance than flexible PVC. 

Intumescent systems based on ammonium polyphosphate can produce flame retardant polypropylene. Great Lakes manufactures Reogard 1000, an intumescent phosphorus and nitrogen based, melt blendable flame retardant for polypropylene homopolymers and low ethylene PP copolymers that need V-0 ratings. It is not particularly hygroscopic and gives good electrical properties with improved heat distortion temperature. 

Polypropylene is widely used in both small and large appliances. In small appliances, like electric drip coffee makers, can openers, blenders, and mixers, and in tools, like electric drills, PPs ease of molding, light weight, stiffness, durability, electrical properties, appearance, and cost make it a very attfactive resin choice. Homopolymers and impact copolymers are both used, with an MFR of around 12 g/10 min being the norm. 

A. Soroudi, M. Skrifvars, H. Liu, Polyaniline-polypropylene melt-spun fibre filaments the collaborative effects of blending conditions and fibre draw ratios on the electrical properties of fibre filaments, J. Appl. Polym. Sci. 119 (2011) 558—564. 

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