At present, the domestic and foreign use of flame retardants according to the types of flame retardant elements are: halogen flame retardant, phosphorus flame retardant, aluminum magnesium and other inorganic flame retardants, etc.. Effect of halogen containing flame retardants is good, but its combustion smoke volume, corrosive and toxic gas, the environmental pollution caused by, its use has been in the European Union by restrictions and caused widespread concern in the world at present most phosphorus flame retardant of manufacturing using the volatility, toxicity and corrosion of organic solvent, coupled with phosphorus flame retardant agent combustion will release phosphorus oxide, environmental pollution larger; inorganic flame retardant is mainly aluminum hydroxide, magnesium hydroxide, can inhibit the growth of smoke and flame retardant fillers and multiple functions and is widely used.
But aluminum hydroxide and magnesium hydroxide flame retardant used alone when the content in more than 50% when it has good flame retardant effect, such a high filler content and the reduction of the processing and mechanical properties of the material. The development of non halogen, high efficiency, low cost and environmentally friendly polymer flame retardant system has become the key research of flame retardant materials. In recent years, the rise of nano materials promoted the development of the research field of flame retardant polymer materials, nano composite materials due to the nano effect and has excellent mechanical properties, thermal properties and electrical properties, etc.. Therefore, the enhanced role of montmorillonite as the representative of clay polymer nanocomposites has attracted wide attention of scientists in the research of polymer materials.
Polymer nanocomposites are still in the development stage, but according to the prediction, nano composite materials will be developed rapidly. Polymer through melt compounding or in situ polymerization technology using 2%--5% nanofillers reinforced modified, can greatly improve thermal - mechanical properties, gas barrier properties and flame retardant properties of, but also than conventional filler reinforced polymer materials is much higher thermal resistance properties, dimensional stability and conductivity.
In the research and development and commercialization of the main nano fillers are layered silicate nano clay and nano mica, followed by carbon nanotubes and flake graphite. Other nano fillers are also active in the study, such as synthetic clay, polyhedral, and natural nano fillers (flax fiber and hemp fiber). The most extensive and first commercial application of nano clay, can effectively improve the structure and performance of polymer materials, thermal performance, gas barrier properties and flame retardant properties. At present, nano clay is mainly nano montmorillonite.
Due to the unique characteristics of the layered one-dimensional nano structure, the characteristics of the structure, the layer has a design of the reactivity, large specific surface area (750m2/g) and up to more than 200 diameter / thickness ratio. This nano structure and morphological characteristics of different to other 2D and 3D inorganic nanoparticles, thereby giving the montmorillonite composites with excellent mechanical properties, thermal properties, functional properties and other physical properties.
Existing practical results show that the mechanical properties of polymer / montmorillonite nanocomposites were significantly increased, such as tensile strength, bending strength increased by 20-50%, modulus increased by 1-2 times, friction coefficient and wear resistance increased by 1 times. Thermal deformation temperature, crystalline polymer (such as PA) improve 80-90 DEG C, non crystalline polymers improve 10-30 deg.c; thermal expansion coefficient can be reduced about 40%, absorption rate reduced by 50%, dimensional stability improve 2-5 times; water vapor, O2, CO2 UV transmittance decreases to 1 / 2 to 1 / 5; heat release rate was significantly delayed, flame retardant significantly improve, increase the fluidity of molten, molding shrinkage rate is reduced, to improve the processing performance; similar proportion of composite and single polymer, than the conventional inorganic filler modified polymer proportion is reduced by 20 to 30 percent.
The transparency of the material is also improved in different degree. Therefore, polymer montmorillonite nanocomposites have become a new generation of high barrier packaging materials, high strength lightweight engineering materials, high flame retardant insulation electrical materials and anti fatigue high performance elastomer materials. Polymer / montmorillonite nano composite performance improvement degree, decided in the layered montmorillonite in polymer continuous phase of nanoscale dimension peeling, decentralized state, only the layered montmorillonite chip in polymer exfoliated and dispersed, in order to obtain the high performance of the composite material.
The stripping state of montmorillonite in the polymer is directly determined by the quality and the stripping of the montmorillonite, and the dispersed composite treatment method, both of which are indispensable. Quality of montmorillonite for polymer modification, using montmorillonite mineral layer charge density must be moderate, high purity (montmorillonite content at least 95%), the layer expansion agent selection, treatment of organic fully, the montmorillonite and all kinds of polymer with good compatibility, and dissociative. Source: China Packaging Network