Properties magnesium borate

LijNaBFg doped with Cu and co-doped with P are synthesized by a wet chemical technique and exposed to gamma-rays of Co for their TL properties. The XRD technique shows the crystalline nature of the prepared material. The crystalline form of the materials is characterized by a powder XRD pattern recorded on a Philips P Analytical X Pert Pro diffractometer at room temperature. The XRD pattern of Li2NaBFg is shown in Figure 7.38. This material produced well-defined XRD lines for the powder samples that confirm its crystalline nature. However, for recorded XRD patterns, no matching files are seen in the JCPDS library (limited numbers of files are only available for mixed lithium magnesium borate crystals). The XRD pattern of LijNaBF material did not indicate individual presence of any traces of ammonium fluoride and other likely phases, which is an indirect evidence for the formation of the desired compound. The final product was formed in homogeneous white powder form. 

Table 3.10 Physical and Chemical Properties of Magnesium Borate Whiskers... 

Manufacturers of various fillers continue studies on altemative systems. Most antimony oxide used as a fire retardant can be replaced by a combination of zinc borate without the loss of other properties (in some cases improvements are reported). Another option is to use the same filler systems which are used in polyethylene insulated cables and wires. These are based on magnesium hydroxide and aluminum hydroxide. These systems pcrfoim as flame retardants but require a high filler concentration which affects jacket resistance and mechanical performance. Recently, new coated grades have been developed which can be used at up to 65 wt% without the loss of properties or productivity (extrusion rates 2,500 m/min of cable are possible). ... 

Some industrial minerals possess properties of flame retardaney and ean be used in systems to replace chemically prepared flame retardants. Hydrated alumina, magnesium hydroxide and borates release water endothermically and create dilution in the gaseous phase, as is well-known. 

In the present chapter, we report some of om study on both raw and surface-modified Grewia optiva fiber-reinforced UPE matrix-based composites, which possess enhanced mechanical and physico-chemical properties when compared with UPE matrix. In addition to the effect of flame retardants, i.e., magnesium hydroxide and zinc borate, on flame resistance, the behavior of resulted Grewia optiva fiber-reinforced composites have also been evaluated and was foimd to be improved. A significant discussion on the work of other researcher s work has also been added in the chapter. 

It has been observed from the above discussion that mechanical, physico-chemical and fire retardancy properties of UPE matrix increases considerably on reinforcement with surface-modified natural cellulosic fibers. The benzoylated fibers-reinforced composite materials have been found to have the best mechanical and physico-chemical properties, followed by mercerized and raw Grewia optiva fibers-reinforced composites. From the above data it is also clear that polymer composites reinforced with 30% fibers loading showed the best mechanical properties. Further, benzoylated fibers-reinforced composites were also found to have better fire retardancy properties than mercerized and raw fibers-reinforced polymer composites. Fire retardancy behavior of raw and surface-modified Grewia optiva/GPE composites have been found to increase when fire retardants were used in combination with fibers. This increase in fire retardancy behavior of resulted composites was attributed to the higher thermal stability of magnesium hydroxide/zinc borate. 

Fillers may promote char magnesium hydroxide, zinc borate, antimony oxides require high loadings and can degrade mechanical and other properties. Toxicity of antimony-based retardants is a concern. Can be used with other flame retardants synergistically. 

Commercial chemical fibers are combustible in nature, and improved FR properties must be considered in actual application. Most FR additives contain bromine (Br), chlorine (Cl), phosphorus (P), antimony, or aluminum. Among them, commonly used additives are additive brominated hydrocarbons and reactive brominated hydrocarbons, nonhalogenated phosphate esters, halogenated phosphate esters, trioxide antimony oxide, pentoxide antimony oxide and sodium derivatives, chlorinated hydrocarbons like chlorinated paraffin, and chlorinated cycloaUphatics. Others include chlorinated or brominated compounds, fluorinated compounds, magnesium carbonate, magnesium hydroxide, melamine, molybdenum compounds, silicone polymer, and zinc borate. Sometimes, polymers are chemically modified, and N, P, Cl, fluorine (F), silicon (Si), and Br elements can be introduced into the polymer main chain [49]. 

Zinc borate can also change the oxidative decomposition pathway of halogen-free polymers. It is not completely clear if this is happening because of an inhibition effect of boron oxides toward the oxidation of hydrocarbons or the oxidation of graphite structures in the char, or is due purely to the formation of a protective sintered layer. In combination with ATH, zinc borate creates a porous ceramiclike residue, which has much better insulative properties than those of pure anhydrous alumina. It was shown that zinc borate accelerates dehydration of magnesium hydroxide and creates a ceramiclike structure with dehydrated MgO. 

Papers with fire-resistant properties are used for wallpaper, decoration paper, Chi-nese/Japanese lamps and partition walls. Flame retardants are added either at the wet end or by surface treatment in the paper production process. They either release incombustible gases on heating, which prevent the entry of atmospheric oxygen, or when heated produce a nonflammable melt that surrounds the paper. Chemicals for this purpose include calcium chloride, magnesium chloride, diammonium ethyl phosphate, and mixtures of zinc borates, antimony oxides, and organic haloid salts as well as inorganic bromides and oxybromides. 

Additives that impart smoke-suppressant properties to a composition tend not to be flame retardant. Conventional flame retardant and smoke-suppressant formulations include phosphorus-containing compounds such as a phosphoric acid ester, ammonium poly(phosphate) and red phosphorus, or halogen containing compounds such as tetrabromobisphenol A, decabromodiphenyl oxide and chlorinated polymers, and metal compounds such as magnesium hydroxide, aluminum hydroxide and zinc borate (4). 

There are several fillers that impart flame-retardant properties to mbber compounds. These are magnesium hydroxide, Versamag or Zerogen 50 magnesium carbonate, Elastocarb or Magcarb L zinc borate, Firebrake ZB alumina trihydrate, Micral and antimony oxide, Fireshield H, L, UF or Synpro-Ware R321. These are used primarily with NBR/PVC blends with chlorinated paraffins and/or phosphate ester plasticizers and mineral fillers for flame-resistant applications. 

Flame retardance of ethylene-vinyl acetate copolymer can be achieved using magnesium hydroxide incorporated in the polymeric matrix. The adduct of a small amount of zinc borate as synergistic agent in the formulation increases the fire-proofing properties. Multinuclei solid-state NMR appears as a means to characterise materials before and after combustion. It was shown that endothermic dehydration, water vapour evolved and formation of a glassy coating provided the flame retardancy of interest to the polymer matrix. 12 refs. EUROPEAN COMMUNITY EUROPEAN UNION FRANCE WESTERN EUROPE... 

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