Fire-retardant fillers application

Phenol-formaldehyde (PF) resins have been successfully used in FRP materials as inherently fire retardant resins, because they have low flame spread indexes and produce very Utde smoke or toxic fumes without the assistance of other fire retardant fillers. Applications include many fire-sensitive areas such as rocket... 

FIRE RETARDANT FILLERS. The next major fire retardant development resulted from the need for an acceptable fire retardant system for such new thermoplastics as polyethylene, polypropylene and nylon. The plasticizer approach of CP or the use of a reactive monomer were not applicable to these polymers because the crystallinity upon which their desirable properties were dependent were reduced or destroyed in the process of adding the fire retardant. Additionally, most halogen additives, such as CP, were thermally unstable at the high molding temperatures required. The introduction of inert fire retardant fillers in 1965 defined two novel approaches to fire retardant polymers. 

In this chapter, an overview is presented of the principal fire-retardant filler types, including details of their origin, characteristics, and application. Consideration will then be given to their mechanism of action both as flame retardants and as smoke suppressants, and to means for potentially increasing their efficiency using synergists and nanoscale variants. 

This is the second most widely used fire-retardant filler. It is more expensive than aluminum hydroxide, but has a higher decomposition temperature (about 300°C), making it more suitable for use in thermoplastic applications where elevated processing temperatures are encountered. 

Using this concept, it has been shown by cone calorimetry that over a 3 min combustion period, 3 and 6 mm thick laminated structures, made with different fire-retardant skin and unfilled core combinations can give similar resistance to ignition and comparable HRR and smoke extinction area (SEA) results to fully fire-retardant compositions (Table 7.4). Mechanical properties, in particular impact strength, were also found to be greatly enhanced by this approach, since less fire-retardant filler is present in the material. Whereas this approach has been demonstrated to be effective with hydrated fillers, it is applicable to all fire-retardant types. 

Hornsby, P.R. Rothon, R.N. Fire retardant fillers for polymers, in M. Le Bras, C.A. Wilkie, S. Bourbigot, S. Duquesne, andC. Jama, Eds., Fire Retardancy of Polymers New Applications of Mineral Fillers. Royal Society of Chemistry, London, 2005, pp. 19-41. 

Filler surface treatments, such as fatty acids, are very useful for reducing melt viscosities and some fillers would be impossible to use at the loadings needed for certain applications such as fire retardancy without some form of surface treatment. In some cases melt viscosities can be maintained at similar levels to the unfilled polymer, even in highly filled systems, despite the use of high filler loading [9]. 

Many variations of these processes exist with the aim of controlling particle surface area, shape, and purity these characteristics define the fire retarding performance of magnesium hydroxide fillers, especially in more demanding applications where processability and good mechanical properties are also important considerations. In more recent developments, nanosize magnesium hydroxide variants have also been produced. 

Hexagonal BN is stable in inert or reducing atmosphere to about 2700°C and in oxidizing atmosphere to 850°C. It is an excellent thermal conductor and has been frequently quoted as a functional filler for fire-retardant encapsulants for E/E applications. 

The sueeess of graphite in this applications shows that filler with plate like struetures should be considered when intumescent materials are being formulated. Reeent developments in intumescent paints show that performanee ean be improved if a layer of organic material is inserted between the layers of the plate like filler. The degradation of this material in the enclosed space increases the expansion rate and the retention of gas inside the degrading material. Based on this prinei-ple any plate like filler has the potential to be useful in an intumescent applieation. The eomposition of filler is also important. When clay was used as a filler in fire retardant applieations, it was found that some of its components interfere with the action of carbonization catalysts and detract from the overall performance of the system in terms of limiting oxygen index. ... 

The major roles of fillers in these applications is to provide reinforcement, fire retarding properties and to lower the cost. Development work on plastic materials is ongoing and the goal is to develop technology which is inexpensive but can perform under adverse conditions. These studies have intensified recently given the increased worldwide demand for new houses. China is an extreme example. It needs 100,000,000 houses to be built in the next five years. 

R. Borms, R. Wilmer Roland, M. Peled, N. Konberg, R. Mazori, B.Yaakov, J. Schienert and P. Gerolette in Fire Retardancy of Polymers New Applications of Mineral Fillers, Ed., M. LeBras, The Royal Society of Chemistry, Cambridge, UK, 2005, p.399. 

Polymers in their raw state are usually technically unsatisfactory in one respect or another, such as their stability to light or heat, or their processability, or flammability, or colour, or opacity, or antistatic characteristics, etc., and they simply could not be used in commercial applications successfully without the incorporation of one or more additives [2] to modify behaviour. The additives are often present at very low concentrations (0.1-3 parts per hundred of resin, by weight) and are called stabilizers, UV absorbers, viscosity modifiers, lubricants, fire retardants, pigments, etc. Fillers may be present at 50 or even 150 parts per hundred of resin, by weight. Thermosetting resins tend to have fewer additives of the kind... 

Bras ML, Camino G, Bourbigot S, Delobel R (1998) Fire retardancy of polymers the use of intumescence. Royal Society of Chemistry, Cambridge, ISBN 0-85404-738-7 Fina A, Tabuani A, Boccaleri E, Camino G (2005) Fire retardancy of polymers new application of mineral filler. Royal Society of Chemistry, Cambridge Grand AF, Wilkie CA (2000) Fire retardancy of polmeric materials. Marcel Dekker, New York Horrocks AR et al (eds) (2001) Fire retardant materials. CRC Press, Boca Raton, FL Prager FH, Rosteck H (2006) Polyurethane and Fire Fire performance testing under real conditions. Weinheim, Wiley VCH... 

Natural fiber-reinforced polyolefins are commonly apphed to automotive and constmction applications. The most abundantly used additive is fire retardant. Flammability is an important factor that often limits the application of composites to a specified field. Magnesium hydroxide is the most common flame retardant material used in the constmction industry. This filler responds well to surface modifiers and decomposes by an endofliermic reaction that releases water at temperatures close to the polymer degradation temperature as show in Eq. 6.1. Rothon et al. [78] studied the effects of magnesium hydroxide on polypropylene as a flame retarder of 60 % by weight. The smdy found less heat emission at 100 kWm after 6 min of fire exposure compared to filled PP without Mg(OH)2 at 500 kWm. ... 

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