Additive type flame retardants

There are methods to manipulate the backbones of polymers in several areas that include control of microstructures such as crystallinity, precise control of molecular weight, copolymerization of additives (flame retardants), antioxidants, stabilizers, etc.), and direct attachment of pigments. A major development with all this type action has been to provide significant reduction in the variability of plastic performances, more processes can run at room temperature and atmospheric pressure, and 80% energy cost reductions. 

There are two types of flame retardant - additive flame retardants and reactive flame retardants [1, 4-6, 11]. 

However, most items are actually composites of at least two fabrics (see below) and it is the composite that is subjected to the test. Usually, if a single fabric layer or a multilayer comprising the same fibre type is to be tested and the former passes the test, then so will the latter, and no additional flame retardant is required to enable the standard to be achieved. The use of flame retardants in any case is to be avoided, since not only do they add to cost but also they can increase the levels of toxic gases emitted during burning, although currently levels of these are not required to be assessed. If blends of different fibres or combinations of fabrics comprising different fibres are combined, then it is probable that additional flame retardants may be required to pass the test even if component fabrics alone each pass the test. 

Additive flame-retardants are physically admixed with the polymer in the course of processing. Their main advantage lies in the versatility of their applications, i.e. the processor is free to select the type and amount of the additive according to... 

Polymers, including the various types of epoxy resins, differ in their inherent flammability The types of resins and curing agents selected can impact the fundamental flammability of the resin system and determine how much additional flame-retardant components are needed to achieve the desired flammability rating. For example, polymers with a high concentration of... 

HBCD has been used as an additive flame retardant for more than 20 years. Its main use is in the construction industry, where it is used in polystyrene foams, which are a part of the thermal isolations, and even small concentrations provide sufficient protection against burning. The second major application of HBCD is in the upholstery and textile industries. Products in which the HBCD occurs, for example, include upholstered furniture, various textiles, car seats and upholstery, insulation in trucks and caravans as well as many types of building materials. Unlike other flame retardants, HBCD is not used in electronic circuits. 

Olefin Polymers. The flame resistance of polyethylene can be increased by the addition of either a halogen synergist system or hydrated fillers. Similar flame-retarder packages are used for polypropylene (see Olefin polymers). Typical formulations of the halogen synergist type are shown in Table 15 the fiUer-type formulations are in Table 16. 

Reactive Flame Retardants. Reactive flame retardants become a part of the polymer by either becoming a part of the backbone or by grafting onto the backbone. Choice of reactive flame retardant is more complex than choice of an additive type. The reactive flame retardant can exert an enormous effect on the final properties of the polymer. There are also reactive halogenated compounds used as iatermediates to other flame retardants. Tables 8 and 9 Hst the commercially avaHable reactive flame retardants and iatermediates. 

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

An important use of bromine compounds is in the production of flame retardants (qv). These are of the additive-type, which is physically blended into polymers, and the reactive-type, which chemically reacts during the formation of the polymer. Bromine compounds are also used in fire extinguishers. Brominated polymers are used in flame retardant appHcations and bromine-containing epoxy sealants are used in semiconductor devices (see... 

Reduction in flammability is achieved by the incorporation of flame retardants into the polymer. Two possible approaches to this are available either the use of additives blended into the polymer at processing stage (additive type) or the use of alternative monomers which confer reduced flammability on the final product (reactive type). A number of elements have been found to assist with conferring flame retardancy on polymers, the main ones being bromine, chlorine, nitrogen, and phosphorus. 

A large number of materials, generally inorganic in nature, have been used as additive-type flame retardants, of which hydrated alumina and antimony oxide are among the most important. 

Semimetal that occurs as a tin-type, brittle form and as a yellow, unstable, nonmetallic form. Its main use is in alloys to harden other metals. Without the addition of antimony, lead would have remained the "softy" of the Periodic Table. But with antimony, lead ruled the print world and later found use in the production of rechargeable batteries. It can be found in older ceramic glazing (yellow orange). Everyday encounters antimony sulfide in match heads and red rubber, antimony oxide is used as a flame retardant. Pure antimony is starting to become of interest in the electronics sector. 

A large number of new compounds of this type have been synthesized since 1996. In addition, these types of compounds have found application in catalysis, as pesticides, and in some cases as flame retardants. 

One of the present authors (31) has developed a series of additives which combine the features of both free radical inhibitors and flame retardants of the tetrabromophthalimide or chlorendic imide type with hindered phenol antioxidant structures such as the following compounds ... 

Air Products, a manufacture of latex binders, has completed a comprehensive study of flame retardants for latex binder systems. This study evaluates the inherent flammability of the major polymer types used as nonwovens binders. In addition, 18 of the most common flame retardants from several classes of materials were evaluated on polyester and rayon substrates. Two of the most widely recognized and stringent small scale tests, the NFPA 701 vertical burn test and the MVSS-302 horizontal burn test, are employed to measure flame retardancy of a latex binder-flame retardant system. Quantitative results of the study indicate clear-cut choices of latex binders for flame retardant nonwoven substrates, as well as the most effective binder-flame retardant combinations available. 

Various types of additives are essential to give plastics new or enhanced properties. However, the safety of flame retardants, plasticisers and stabilisers, as regards potential health hazards, is attracting attention. Brome-based flame retardants have been the subject of safety disputes for several years and several substitutes have been developed. The shift to lead-free stabilisers is making further progress. 

Electrolux is the world s largest producer of powered appliances for kitchen, cleaning and outdoors. They have created comprehensive Environmental Product Declarations (EPDs) for many of their product lines. Information within the product profiles details chemicals that have been banned as well as the percentage and types of materials and how they have improved material choices. Forexample, plastic components do not contain cadmium, lead, mercury or their compounds or chlorinated or brominated flame retardants metal components are not coated with cadmium, chromium, or nickel and metal paints do not contain pigments and additives based on heavy metals. Many Electrolux products are also PVC-free. 

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