Improving fire retardancy

Phosphate Esters. The principal advantage of phosphate esters is the improved fire retardancy relative to phthalates. The fire performance of PVC itself, relative to other polymeric materials, is very good due to its high halogen content, but the addition of plasticizers reduces this. Consequendy there is a need, in certain demanding appHcations, to improve the fire-retardant behavior of dexible PVC. 

As weU as imparting improved fire retardancy these materials may also result ia volume cost savings if they can be purchased for a lower price than the commodity phthalate. Precise knowledge of the compatibiHty between standard plasticizers and chlotinated paraffins is requited because some mixtures become iacompatible with each other and the PVC resias ia use at certain temperatures. Phthalate—chlotinated paraffin compatibiHty decreases as the molecular mass of the phthalate and the plasticizer content of the PVC formulation iacrease. Many compatibiHty graphs are available (1). 

Most research on chemical modification of lignocellulosic materials has focused on improving either the dimensional stability or the biological resistance of wood. This paper reviews the research on these properties for wood and other lignocellulosic composites and describes opportunities to improve fire retardancy and resistance to ultraviolet degradation. 

Romenesko DJ, Buch RR (1995) Silicone resin powder for improving fire retardancy of organic resins. US Patent 5391594... 

Improved Fire-Retardant Treatments for Panel Products. Fire-retardant treatment for panel products is also an area where research efforts need to be concentrated. Currently, there is only one commercially available fire-retardant-treated particle board that qualifies for use in commercial and institutional buildings. Ex-... 

The Naval Ammunition Depot (NAD) at Crane, Indiana has developed improved fire-retardant phenolic foams containing blends of boric/oxalic acids as catalysts, as described above. The resultant foams were found to be extremely efficient fire barriers due to their high heat absorptivity, the amount of carbon and/or coke produced during pyrolysis, and the adhesion of the char to the burned materials. Other advantages of the foam during flaming and nonflaming pyrolysis are its low smoke emissions and lack of toxic fumes other than carbon monoxide. It takes one hour to reach 230°F (110°C) when a 13 Ib/tf (208 kg/m ) phenolic foam specimen 2.9 inches (7.4 cm) is exposed to a fully developed fire (41). 

In fire tests it was recognized that the ability of fire endurance of a wooden door depended on the thickness of materials. In order to improve fire endurance of a panel-stile constructed door, it was proper to improve thinner portion of door, named panels. So laminated boards with improved fire retardance at the surface were used for a wooden fire door and it has been authorized by the Ministry of Construction. 

In all these processes the key ingredients are the elements from group III (B and Al) of the periodic table. Now, at the end of the 20th century, with so much of research activity for better fire retardants, the most effective elements are still found in groups III (B and Al), V (N, P and Sb) and VII (Cl and Br). Research efforts to find new and improved fire-retardant agents for synthetic... 

Acrylic fibers are polymers with greater than 85% aerylonitrile content, while those containing 35 to 85% acrylonitrile are known as modaeryhe. Aeryhe fibers eontain minor amounts of other comonomers, usually methyl acrylate, but also methyl methaerylate and vinyl aeetate. These comonomers along with ionic monomers such as sodium styrene sulfonate are ineorporated to enhance dyeability with conventional textile dyes. Modaeryhes usually eontain 20% or more vinyl chloride (or vinylidene chloride) to improve fire retardancy. 

Fibers prepared from straight polyacrylonitrile are difficult to dye. To improve dyeabiUty, manufacturers invariably add to monomer feed minor amounts of one or two comonomers, such as methyl acrylate, methyl methacrylate, vinyl acetate, and 2-vinyl-pyridine. Small amounts of ionic monomers (sodium styrene sulfonate) are often included for better dyeability. ModacryKc fibers are composed of 35-85% acrylonitrile and contain comonomers, such as vinyl chloride, to improve fire retardancy. 

Oswith, S. Improved fire-retardant unsaturated polyester resins. Reinforced Plastics 15, No. 5, 127 (1974)... 

Improved fire retardancy can be conferred to most resins by the incorporation of other materials. These materials may be specifically formulated for chemical incorporation into the resin during cure or exist as particulates in physical contact with the resin. Most organic phosphate esters and halogenated hydrocarbons, as well as antimony trioxide, are physically combined with the resin, and some halogen compounds are combined chemically. High concentrations of aluminium tri-hydrate (ATH) act as both filler and an effective low smoke/toxicity additive by releasing water of hydration at the flame temperature. 

The situation is different for LOI criteria Al(OH)j and Mg(OH)2 are the most effective and talc and kaolin (which only act as a diluent) still show a very little effect. Increased fillers concentration improves fire retardance but also impairs physico-mechanical properties. Therefore there is interest in the minimum loading conferring the minimum fire-retardance level acceptable for a general-purpose application (such as LOI 25 UL 94 V-0). Melamine improves UL 94 rating of PP compared with the mineral filler alone. 

Currently, nano-clays are of most interest as admixtures with flame retardant fillers such as ATH, rather than as primary flame-retardants. Beyer [57] has reported that replacement of a small amount of ATH can significantly improve fire retardancy and increase char integrity at the normal filler loadings used. Alternatively, the overall filler loading can be significantly reduced, while maintaining the existing level of fire retardancy. 

There are several limitations associated with the conventional composites, although they have higher mechanical and other properties. To overcome the limitations, the concept of nanocomposite arises. Nano-dimensional particles-based WPC are reported to improve fire retardancy, moisture barrier, UV protection, etc.. 

Tang, T. Chen, X.C. Chen, H. Meng, X.Y. Jiang, Z.W. Bi, W.G. Catalyzing carbonization of polypropylene itself by supported nickel catalyst during combustion of polypropylene/clay nanocomposite for improving fire retardancy. Chem. Mater. 2005, 17(11), 2799. 

Addition of bromine to allylsuccinic anhydride 1 gives rise to the dibromo derivative 75. Inclusion of such material in polyesters has been claimed to improve fire retardancy of the product. The resin made with 75 was described as having self-extinguishing properties. " " Bis-(2-hydroxyalkyl)-esters of 75 has been converted to flame-retardant urethanes. ... 

In addition to the already mentioned effects in terms of attaining both flexible and rigid PU foams with improved mechanical performance, enhanced electrical conductivity, or even improved fire retardancy or sound damping, depending on the type of... 

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