Fire retardant polymers electrical properties

Key mechanical and electrical properties of intrinsically fire retardant polymers (i.e., LOI > 30%) are listed in Tables 6.10 and 6.11, respectively. 

The principle uses of the zinc borate Zn[B304(0H)3] are as a polymer additive and preservative for wood composites, such as oriented strand board (OSB). As a polymer additive it functions as a fire retardant synergist and modifier of electrical and optical properties. Its function as a fire retardant additive is discussed further below. A substantial amount of Zn[B304(0H)3] is used to improve the tracking index, which is an important performance criterion for polymers, such as polyamides (nylon) and polybutyl teraphtha-lates (PBT), used in electrical applications. 

Examples of fluoroplastics include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), ethylene—chlorotrifluoroethylene (ECTFE), ethylene—tetrafluoroethylene (ETFE), poly(vinylidene fluoride) (PVDF), etc (see Fluorine compounds, organic). These polymers have outstanding electrical properties, such as low power loss and dielectric constant, coupled with very good flame resistance and low smoke emission during fire. Therefore, in spite of their relatively high price, they are used extensively in telecommunication wires, especially for production of plenum cables. Plenum areas provide a convenient, economical way to run electrical wires and cables and to interconnect them throughout nonresidential buildings (14). Development of special flame-retardant low smoke compounds, some based on PVC, have provided lower cost competition to the fluoroplastics for indoors application such as plenum cable, Riser Cables, etc. 

Continued commercial interest in poly(phosphazenes) is demonstrated by extensive patent activity and related applications oriented publications (some of which have been noted above). Fire retardency is an ongoing theme in cyclo-and linear phosphazene applications (see section 3). Aryloxy phosphazenes, including a commercial product, Eypel A, have been utilized for components for fire resistance in foam cushioning, rocket motor insulation and electrical wire coating . Alkoxy phosphazene polymers and copolymers impart antistatic properties to silver halide based... 

Nylon, beside its important utility as premium fiber in the textile industry, also serves as an engineering polymer due to its unique properties of rigidity and toughness, low friction coefficient (including self lubrication), high resistance to abrasion and fatigue, supreme chemical resistance (including fire retardancy), as well as excellent thermal and electrical performance. 

In some cases the incorporation of a fire retardant can affect mechanical, electrical and thermal properties of polymers. 

In general, when compared with the conventional polymer composites, polymer nanocomposites exhibit significant improvements in different properties at relatively much lower concentration of filler. The efficiency of various additives in polymer composites can be increased manyfold when dispersed in the nanoscale. This becomes more noteworthy when the additive is used to address any specific property of the final composite such as mechanical properties, conductivity, fire retardancy, thermal stability, etc. In case of polyolefin/LDH nanocomposites, similar improvements are also observed in many occasions. For example, the thermal properties of PE/LDH showed that even a small amount of LDH improves the thermal stability and onset decomposition temperature in comparison with the unfilled PE [22] its mechanical properties revealed increasing LDH concentration brought about steady increase in modulus and also a sharp decrease in the elongation at break [25]. While in this section, fire-retardant properties and electric properties of polyolefin/LDH nanocomposite were described in detail. 

Based on the size, fillers can be broadly classified into two categories, micro and nano sized fillers. Lighter, thinner, stronger and cheaper structures are the goals of material science and engineering applications today. Nanoparticles satisfy these requirements. The use of nanofillers improves mechanical and physical polymer properties. The added cost of the nanofilled matrix can be low due to the small amounts of filler necessary for a significant improvement. Nanofillers can significantly improve or adjust the properties of the materials into which they are incorporated, such as optical, electrical, mechanical, thermal or fire-retardant properties. 

Unmodified polyarylates exhibit sufficient fire-retardant characteristics for many applications, whereas more stringent combustion requirements can be achieved with the proper selection of additives. The electrical properties of polyarylate polymers are reasonably constant over a broad temperature range and present a competitive profile for high performance electrical applications. 

In many applications of engineering polymers, there is a requirement for fire retardant properties. This will occur in appliances of polymers used in situations were excessive heat or long periods of time may occur or the plastic part is used in a region where there is risk of ignition and fire. This might be particularly so in electrical applications of reinforced polymers. 

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