Wire and cable formulations

The combination of melamine with hydrated mineral fillers can improve the fire retardancy behavior of PP, eliminating at the same time the afterglow phenomenon associated with these fillers used in isolation.70 Similarly in EVA copolymer, antimony trioxide used in combination with metal hydroxides has been reported to reduce incandescence.56 Chlorinated and brominated flame retardants are sometimes used in combination with metal hydroxides to provide a balance of enhanced fire-retardant efficiency, lower smoke evolution, and lower overall filler levels. For example, in polyolefin wire and cable formulations, magnesium hydroxide in combination with chlorinated additives was reported to show synergism and reduced smoke emission.71... 

Risk reduction is a world wide problem and of course a concern to the field of PVC stabilisers. The replacement of lead stabilisers in wire and cable applications is demonstrated. Newly developed non-lead stabilisers (RUP-series) are shown to offer excellent heat stability, electrical and mechanical properties compared with traditional wire and cable formulations. The overall processability is shown with experimental and actual results. The gradual increase in use of ADKs and other non-lead stabilisers in the USA and Japan demonstrates industry s concern for the public demand in saving the environment without direct laws banning the use of lead. JAPAN... 

Solplus C800 from Lubrizol is a new non-silane organic coupling agent for inorganic fillers such as ATH and calcium carbonate in wire and cable formulations. It is said to form a monolayer coating with a strong ion-pair interaction between the polymer (EVA, LLDPE, ethylene octene copolymer etc.) and the filler surface. This is a useful development, because silanes do not react with calcium carbonate. 

Occidental Chemicals supplies Dechlorane and Dechlorane Plus, a Diels-Alder adduct of hexachlorocyclopentadiene. It has a wide range of processing temperatures, offers the advantage of lower smoke than brominated equivalents on burning, and is useful at the 15%-18% level in PBT and the polyamides. A synergist such as zinc borate, oxide or stannate is advisable as well. Chlorinated FRs can be combined with magnesium hydroxide in polyolefin wire and cable formulations. 

Aromatic amines, normally arylamines, may be more effective than phenolics, but most are staining and discoloring and lack FDA approval for use in contact with food. Amines are commonly used in the rubber industry but also find minor uses in plastics such as black wire and cable formulations and in polyurethane polyols. 

This zinc borate has also been used in some PVC wire and cable formulations. Its application has been limited by its low dehydration temperature (starting at around 190°C). 

Table 2. Wire and Cable Insulation PVC Formulations, Parts by Weight...

The PVC formulations shown in Table 2 represent typical compounds used by the wire and cable industry. PVC compounders have developed new PVC-based formulations with very good fire and smoke properties (can pass the UL 910 Steiner Tunnel test) that compete with the more expensive fluoropolymers. These can be used in fabricating telecommunication cables usable for plenum area applications. 

Other significant uses of PCBs included heat exchangers and hydraulic fluids. Prior to controls PCBs were also used in adhesives, coatings, plasticizers and inks for microencapsulating dyes for carbonless duplicating paper as extenders in pesticide formulations and catalyst carriers in olefin polymerizations to impart hydrophobicity to materials and surfaces in bactericide formulations (combined with insecticides), and in immersion oil for microscopes. Mixed with chloronaphthalenes, PCBs were also used in wire and cable insulation in the mine and shipbuilding industries (ref. 80, p. 455). 

Hydromagnesite (usually found in combination with huntite) has intermediate thermal stability, decomposing between 220°C and 240°C.21 22 Mixtures of these minerals are used in wire and cable applications, due to their higher thermal resistance than ATH and lower cost compared to MH. They have also been considered for use in ethylene-propylene copolymers23 and poly(vinyl chloride) (PVC) formulations, where reduced smoke and acid gas emission are requirements.24... 

The focus of this program was to evaluate the environmental impacts of the current standard material formulations and alternative formulations.95 The partnership used a life-cycle assessment (LCA) approach to examine the impacts of heat stabilizers, polymer systems, and flame-retardants used in insulation and jacketing for selected wire and cable products. The project began in March 2004 and the report was issued in May 2008.96... 

After PVC, polyolefin copolymers, predominantly polyethylene copolymers, are the next most widely used material for FR applications in wire and cable. Polyethylenes have very good dielectric strength, volume resistivity, mechanical strength, low temperature flexibility, and water resistance. In contrast to PVC, polyolefins are not inherently FR and thus are more highly formulated, requiring the addition of FRs to meet market requirements for flame retardancy. For this reason, and because of the steady global trend toward halogen-free materials for wire and cable applications, more space will be devoted to this section on FR polyolefins compared with the above discussion of PVC. 

Wires and cables that are utilized in enclosed spaces are usually required to have fire safety characteristics as described in various codes and standards. The codes and standards governing fire safety of wires and cables are highly complex and diverse, both by application and by geography, and play a critical role in determining selection and formulation of insulation and jacketing materials. Thus, careful review of applicable standards is essential prior to beginning formulation or product development. 

Triorganotin compounds have also been used experimentally in controlled-release formulations to control the infective snail vector in the debilitating tropical disease schistosomiasis (bilharzia) and to control mosquitoes in stagnant ponds (103). As yet, the large-scale use of such methods has little support in the host third world countries where these problems are most severe. Tributyltin chloride has been used to confer rodent-repellent properties on wire and cable coatings (104). 

In some cases cost may be the dominant approval criterial. In applications where color is only an identifying attribute, the customer may be interested in just a close match to target, preferring that the colorist formulate for lowest cost. Examples of such applications could be wire and cable coatings, automotive dunnage applications, pallets, bread trays, and beverage crates. 

Antioxidant for natural and synthetic rubber, tires, automotive and appliance molded goods, polyamides and carbon black filled olefin formulations for use in geomembranes, wire and cable jacketing, and irrigation piping. 

PolvCvinvl chloride). The application of poly(vinyl chloride) as wire and cable insulation occurred after the development of flexible formulations in the mid-1930s. Typical compositions for insulation purposes contain from 50 to 70% poly(vinyl chloride) the remainder is plasticizers, fillers, lubricants, and stabilizers. These formulations provide a combination of attractive features such as good mechanical properties, resistance to oil and moisture, and low flammability. Its main applications are in building wire for connection of outlets and switches with main panels, in equipment and apparatus cables, and in 1ow-temperature electronic applications it is also found in flexible and retractable cords, in telephone wires, and in power cables. 

Polypropylene. Like polyethylene, polypropylene and propylene-ethylene copolymers are used as insulation for telephone wires. Howeyer, polypropylene itself is also used in the fabrication of components for low-yoltage automotive devices such as switches, connectors, and terminal blocks. As will be shown later, polypropylene plays another important role as an insulating material in an application where it is applied as a free film rather than as a formulation for coating or extrusion on wires and cables. 

Initially, two-component, PVC/TPU blends were proposed [B. F. Goodrich Co., 1960], but soon, PVC/TPU blends with a modifier, e.g., ABS [Waugaman et al., 1963] NBR or PA [Kepes, 1959] were disclosed. Blending was also carried out by mixing PVC with polyols and isocyanates then polymerizing these two [Dainichiseika Color Chemicals, 1983]. Commercial PVC/TPU (with NBR) are represented by Duralex . The materials are usually formulated for extrusion, e.g., for wire and cable insulation, hoses and packaging. 

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