Nonhalogenated additives, flame retardant material

New Flame Retardant Materials Nonhalogenated Additives from Brominated Starting Materials and Inherently Low-Flammability Polymers... 

WEEE has had a direct affect on flame-retardant use, because flame retardants are used in almost all electrical and electronic equipment to prevent fires from short circuits. This directive lays down rules for disposal and recycling of all electrical and electronic equipment that goes back to the previous incinerator discussion. For flame retardants, this directive affects how the plastic parts, cable jackets, and enclosures are flame retarded. If the plastic cannot be reground and recycled, it must go to the incinerator, in which case it cannot form toxic by-products during incineration. This has led to the rapid deselection of brominated FR additives in European plastics that are used in electronics, or the complete removal of FR additives from plastics used in electronics in Europe. This led, in turn, to increases in electrical fires in Europe, and now customers and fire-safety experts demand low environmental impact and fire safety. However, the existing nonhalogen flame-retardant solutions brought in to replace bromine have their own balance-of-property issues, and so research continues to develop materials that can meet WEEE objectives. 

The next major class of flame retardant additives that are nonhalogenated is the phosphorus-based flame retardants, but even these materials have some regulatory environmental concerns.Other nonhalogenated flame retardants that are not phosphorus-based exist, including mineral fillers (i.e., Al(OH)3, Mg(OH)2), expandable graphite, mela-mine, and polymer nanocomposites combined with other flame retardants.Each of these materials has its own advantages and disadvantages, and effectiveness in one polymer system often does not translate into another system. 

As mentioned earlier, brominated flame retardants are under regulatory scrutiny that may lead to their eventual abandonment as chemicals used in industry. The chemistry of bromination is well understood, and it can yield a variety of different products and structures. In light of this, brominated starting materials, in particular brominated flame retardants, could be a very useful route into new nonhalogenated flame retardants, and the C-Br bond is usually quite reactive to a variety of organic chemical reactions. Work in our laboratory focused on the use of brominated flame retardants as starting materials in flame retardant additive syntheses and their conversion to nonhalogenated FR derivatives. 

The additives business has been at the centre of environmental controversies for many years, and has made strenuous efforts to improve its products. Flame retardants for cable and wire insulation are increasingly made of nonhalogen, low-smoke materials, and there has been increased usage of phosphorus and metal hydroxide flame retardants in recent years. Major changes have also taken place in the heat stabiliser business, with lead compounds being voluntarily phased out over several years. 

For more than a decade potential environmental problems associated with organo-bromine flame retardant systems have motivated the search for non-halogen-based approaches to reduce polymer flammability. Initially, research focused on development of new phosphorus-based flame retardants, and numerous publications and patents have been issued in this area. Similarly motivated research has also produced nonhalogen flame retardant approaches based on other elements, such as boron and sihcon. At the same time, work on the use of additives, or flllers, with nanometer-scale primary particle sizes, produced polymer nanocomposites. These materials exhibit enhancement in a variety of physical properties at one-tenth the loading required when micrometer-size additives are used. ... 

---