Flame retardants, additive coloring effects

Red Phosphorus [7723-14-0]. This polymeric form of phosphorus is relatively nontoxic, not spontaneously flammable, and stable up to 450°C. In flnely divided, coated, and stabilized form it is available from Clariant, Rhodia, Ital-match, and Tosoh. It has been found to be a powerful flame-retardant additive (40) effective at relatively low loadings. In Europe, it is used in molded nylon electrical parts in a coated and stabilized form. Handling hazards and color have deterred usage in the United States. The development of masterbatches by Ital-match overcomes the flammable dust problem, but evolution of trace phosphine from reaction with water is still a concern (41). 

This chapter discusses the dynamic mechanical properties of polystyrene, styrene copolymers, rubber-modified polystyrene and rubber-modified styrene copolymers. In polystyrene, the experimental relaxation spectrum and its probable molecular origins are reviewed further the effects on the relaxations caused by polymer structure (e.g. tacticity, molecular weight, substituents and crosslinking) and additives (e.g. plasticizers, antioxidants, UV stabilizers, flame retardants and colorants) are assessed. The main relaxation behaviour of styrene copolymers is presented and some of the effects of random copolymerization on secondary mechanical relaxation processes are illustrated on styrene-co-acrylonitrile and styrene-co-methacrylic acid. Finally, in rubber-modified polystyrene and styrene copolymers, it is shown how dynamic mechanical spectroscopy can help in the characterization of rubber phase morphology through the analysis of its main relaxation loss peak. 

It is generally understood that a suitably flame retarded fabric should retain this property under conditions of wear, wash and weather. Furthermore, the flame retardant component should not effectively alter the fabric characteristics including hand, drape, adsorbency, strength and durability. In addition, this component should not adversely modify other chemicals designed to impart color, size, mildew resistance, water repellency and the like. Finally, the incorporation of a flame retardent treatment in the processing cycle of the fabric should not burden the user with excessive cost. 

A product of given characteristics can be obtained by mixing pellets of different polymers, additives such as colorants, stabilizers, antioxidants, flame-retardants, and so forth. Thermomechanical modifications can be brought about either by silanes or peroxides or by exposure to ionizing radiation. A product of good quality is certainly the result of experience, ability, and good knowledge of the interactions between the different substances, and also characterization of final products with the most effective techniques is of vital importance. Many techniques, collected in Table 1, are available for the characterization of PEX. ... 

Antimony pentoxide is an alternative to antimony trioxide. It finds applications in semi-transparent materials and dark colors because of its low tinting strength. As with antimony trioxide, antimony pentoxide must be used together with halogen-containing compounds to function as a flame retardant (sec discussion under antimony trioxide). The other advantages of antimony pentoxide include its refractive index which is closer to most materials, its very small particle size, its high specific surface area, and its substantially lower density. Because of its small particle size, its is frequently used in the textile industry since its addition has only a small effect on color or on mechanical properties. Production of fine-denier fibers requires a stable dispersion and a small particle size filler. The flame retardancy of laminates is also improved with antimony pentoxide because small particles are easier to incorporate in the interfiber spaces. 

Less than 10% of the polyamide produced is made in a flame retardant version. The best system is composed of a combination of red phosphorus and zinc borate (see table above). The only drawback of this system is its color which is restricted to brick red or black. If other colors are required, ammonium polyphosphate is used either in combination with organic flame retardants or with antimony trioxide. It is possible to manufacture a very wide range of colors in the halogen free system. Some systems make use of the addition of novolac or melamine resins. For intumescent applications, ammonium polyphosphate, in combination with other components, is the most frequently used additive. Figure 13.6 shows that fillers such as calcium carbonate and talc (at certain range of concentrations) improve the effectiveness of ammonium polyphosphate. This is both unusual and important. It is unusual because, in most polymers, the addition of fillers has an opposite influence on the efficiency of ammonium polyphosphate and it is important because ammonium polyphosphate must be used in large concentrations (minimum 20%, typical 30%) in order to perform as a flame retardant. 

The compatibility of a colorant is assessed not only on the basis of the ease with which it can be mixed with the base resin to form a homogeneous mass but also on the requirement that it neither degrades nor is degraded by the resin. In relation to product functional properties, incompatibihty of a colorant can affect mechanical properties, flame retardancy, weatherability, chemical and ultraviolet resistance, and heat stability of a resin through interaction of the colorant with the resin and its additives. Flame retardancy, for example, may impinge directly on the performance of a colorant. Pressure to produce materials with lower levels of toxic combustion products can involve organic fire retardant additives that interact with the colorant either to negate the effect of the additives or affect the color. 

Of the compounding ingredients, fillers and plasticizers are more important in terms of quantities used. Other additives used in smaller quantities are antioxidants, stabilizers, colorants, flame retardants, etc. The ingredients used as antioxidants and light stabilizers, and their effect have been discussed previously. Fillers, plasticizers and flame retardants are described next. 

This cyclic process, along with the fact that HALS are compatible with and relatively nonextractable from the resin, makes them valuable for imparting long-term UV resistance. They effectively delay the degradation of the properties of an exposed polyolefin, and a critical measure of their effectiveness is the speed with which a HALS compound is oxidized into its useful nitroxyl radical form. However, HALS can also react with other stabilizers, flame retardants, or other additives, as discussed in Section 4.4.2. These reactions can lead to color and property changes [1-1, 4-7, 4-12],... 

The effects of BPA-PC molecular weight dominate the properties of blends that contain this material. Modifications are also made by blending with other polymers and the use of additives to achieve specific effects. These additives may be UV stabilizers, thermal stabilizers, flame retardants, mold release agents, fillers, colorants, impact modifiers, etc. Blends are made with... 

Latexes (or latices) are widely used as nonwoven binders because they are versatile, can be easily applied, and are effective adhesives. The chemical composition of the monomer determines stiffness and softness properties, strength, water affinity, elasticity, and durability. The type and nature of functional side groups determine solvent resistance, adhesive characteristics, and cross-linking nature. The type and quantity of surfactant used influence the polymerization process and application method. The ability to incorporate additives such as colorants, water repellents, bacteriastats, flame retardants, wetting agents, and lubricants expands this versatility even further (see Latex Technology). 

Commercial plastics are invariably mixtures of one or more polymers blended with a variety of additives such as colorants, flame-retardants, biocides, etc., all tailored to achieve cost-effective performance for specific applications or processibility requirements. For example, flexible PVC for wire insulation contains one or more plasticizers, and poly (2,6-dimethyl-1,4-phenylene oxide) (PPO), an engineering plastic, is marketed in several grades which may contain varying amounts of lubricants, stabilizers, fillers etc., in addition to the high-impact PS (HIPS) which is added to PPO to modify impact properties and melt viscosity. 

The additives used in PVC in the largest amounts are plasticizers, but one detrimental effect of these additives is an increase in flammability. Rigid PVC, which contains little plasticizer, is quite flame-resistant because of its high chloride content. However, as more plasticizer is added for flexibility, the flammability increases to the point where fire retardants must be added, the most common being antimony(III) oxide (SbiOa). As the PVC is heated, this oxide forms antimony(III) chloride (SbCla), which migrates into the flame, where it inhibits the burning process. Because antimony(III) oxide is a white salt, it cannot be used for transparent or darkly colored PVC. In these cases sodium antimonate (Na3Sb04), a transparent salt, is used. 

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