Preparing A Silicone Rubber/Clay Nanocomposite Powder And Study On Its Application In Flame Retardancy

For a long time, halogenated flame retardants had become the leading role ofthe flame retardant market for its efficiency and low price. But because of theenvironment issue and health concern, Halogen-free has become a tendency offlame retardant. With the combination of nanotechnology and flame retardanttechnology, Nano-sized flame retardants are becoming a research hotspot.Nano-sized flame retardants can not only maximize the effect of the traditional flameretardant, and won’t appear mechanical performance deterioration by adding flameretardant material, and even in some case can produce surprising results. Nano-sizedflame retardants have the biggest problem, however, difficult dispersion, Non-nano-dispersion materials are even poorer than conventional flame retardants material.Dispersion is one of the largest application bottlenecks, as well as is the core ofnanometer materials in the application field.Studies on resin-based nanocomposites have lasted about30years. The mostresearches has focused on studies of organic montmorillonite, few studies hadreported exfoliated montmorillonite, mainly because Exfoliated MMT is moredifficult. In this study, silicone rubber latex and natural sodium montmorilloniteslurry had been mixed and prepared a nanocomposite material containing two nanopowders by spray drying method. In this powder, montmorillonite layers arecompletely exfoliated due to the physical isolation of silicone rubber particles. In thispaper three typical polymers selected as the target materials to study SiliconeRubber/Montmorillonite Nanocomposites powder (SiMT). They are typicalthermosetting plastic—epoxy, typical engineering plastic—nylon6and typicalgeneral plastic polypropylene. Systematic study were done on the dispersion of SiMTnanocomposite powder in three plastic, affect on the mechanical properties of thematerial, and its mechanism of flame retardant, changing the crystal structure ofthermoplastics and processing properties of material.(1) A nanocomposite powder (SiMT) containing exfoliated montmorillonite wasprepared by spray-drying method. The formation mechanism of the compositepowder are isolated from each other due to the rubber particles in the mixture andthe layer of montmorillonite, and the exclusion of moisture after drying, the particles in the initial state will be retained in the mixture. Research shows that the thermalstability of SiMT powder is much higher than traditional organic modifiedmontmorillonite.(2) In the study of flame-retardant epoxy resin, the DOPO was grafted ontobisphenol A diglycidyl ether backbone. A three-roll mill was used to disperse siliconerubber/montmorillonite nanocomposite powder in epoxy resin. XRD and TEManalysis revealed that MMT layers completely exfoliated in the matrix. DOPO alwayscan deteriorate mechanical properties of the epoxy resin material. Siliconerubber/montmorillonite powder can significantly improve the mechanical propertiesof epoxy materials, especially impact strength, and can compensate for reducedmechanical properties of epoxy materials caused by grafting DOPO. Epoxy retardedby DOPO alone have not good flame retardancy. But when the nanocompositepowder was added, epoxy materials will receive excellent flame retardancy. There isa synergistic effect between montmorillonite and phosphorus.(3) Nylon6nanocomposites were prepared with adding siliconerubber/montmorillonite nanocomposite powder and ammonium polyphosphate.X-ray diffraction and transmission electron microscopy analysis showed thatmontmorillonite lamellaes were exfoliated in the nanocomposite powder.Mechanical properties test results show SiMT powder substantially increase impactstrength and heat distortion temperature of nylon6. And there is a enhancement inthe mechanical properties of nylon6retarded by APP. In combustion performance,SiMT nanocomposite powder significantly reduces the peak heat release rate of thematerial. SiMT combined APP not only significantly reduce the maximum heatrelease rate and total heat release. SiMT composite powder can change significantlynylon6crystal behaviors, making α crystalline phase into γ crystalline phase.(4) PP nanocomposites were prepared by SiMT nanocomposite powder andammonium polyphosphate. Affect on the mechanical properties, flame retardancy,thermal stability and rheological properties and other properties by SiMTnanocomposite powder were researched. X-ray diffraction and transmission electronmicroscopy analysis showed that the nanocomposite powder dispersed well.Mechanical properties test results show SiMT nanocomposite powder enhance the impact strength and heat distortion temperature of PP. On combustion performance,SiMT nanocomposite powder significantly reduced the peak heat release rate ofmaterials. SiMT combined APP not only significantly reduce the maximum heatrelease rate and total heat release. TGA studies show that thermal stability of PP hasgreatly improved by adding SiMT nanocomposite powders alone. When PP ismodified by the SiMT composite powder alone, PP prone to crystalline transform.The α crystalline phase is converted into β crystalline phase partly. Research showsthat the rheological behavior, SiMT has good compatibility with the matrix, butoverloading can reduce the compatibility.