Study On The Preparation And Flame Retardant Mechanism Of UPR/Clay Nanocomposites With High Flame Retardant Properties

Unsaturated polyester resin(UPR) is widely used in many fields and becomes one of the most application amount thermoset resins because of its excellent performance and simple process. But it's easily flammable. So flame retardant UPR is widely studied. This dissertation studied the preparation of high flame retarsant UPR/clay nanocomposites containing little halogen- antimony additives though adding little clay and nanoparticles. The properties of nanocomposites were characterized by means of XRD, FTIR, TEM, SEM, TG, DSC, limited oxygen index (LOI), vertical burning test and mechanical analysis. The microstructure, formation and flame retardant mechanism have been studied which will provide theory basis for the development of flame retardant materials.In the first time, the monodispersed nano-Sb₂O₃, Sb₄O₅Cl₂ nanobelts, nano-Sb₂O₃/ mica and nano-Sb₄O₅Cl₂/mica composition were prepared with SbCl3 as raw material by alcoholysis, through controling supersaturation of solution and reaction rate, decreasing solide-liquid interfacial tension using surfactants. The growth rule of nanoparticles and how to control the dimensionality, size and morphology of products were discovered. The results show that the mean particle size of monodispersed nano-Sb₂O₃ is about 21nm among them the particle size of 74% particles is less than 15nm. The nanoparticles of Sb₂O₃ have assembled uniformly between mica layers and have a narrow size distribution around 5nm, 95% particles. The drive force comes from the electrostatic attraction force.The distance between the layers limits the growth of particles. The fibers-like structure of Sb₄O₅Cl₂ with 0.3-1.0μm in length and 10-50 nm in diameter were confirmed by TEM. The nano-Sb₄O₅Cl₂ pillared montmorillonite composites were prepared in the first time and the formation mechanism was discussed. The results show that after montmorillonite has been pillared by Sb₄O₅Cl₂, the typical value of d(001) of montmorillonite was increased from 1.2nm to 1.5nm and a diffraction peak appeared in 4nm, the characteristic absorption peak moved. Montmorillonite displayed loose, porous state like honeycomb with Sb₄O₅Cl₂ nanoparticles in it.The kaolinite/propanediol intercalation compounds (K/PD) were prepared quickly by sonochemistry method in the first time. The intercalation mechanism was discussed from the aspect of themodynamics and intercalating force. The results show that dimethylsulfoxide (DMSO) is the better once intercalating agent and the intercalation rate get up to 91%. In UPR polymerization monomers, only K/PD can be prepared by replacing DMSO in K/DMSO composition. The intercalating drive force comes from the stucture of kaolinite, organic intercalating agent, water, energy and so on. Ultrasonic can provide high temperature, high presure and active seed in some area.In the first time, Unsaturated polyester resin/kaolinite intercalation nanocomposites (UPR/K) were prepared by in situ polymerization using K/PD intercalation usher as one of reaction monomers. The change process of composites crystal structures were simulated in dynamic mode by using electron beam bombardment, from which the microstructures and intercalation styles were deduced, and the formation mechanism of UPR/K was analysed. The results show that 5% kaolinite can't effect the properties of resin, the kaolinte layers exfoliated and mixed uniformly in the composites. The energy released from polymerization reaction mostly changes to work resisting attraction force from kaolinite layers, makes distance of layers inlarge in extent, even exfoliate.The high flame retardant nanocomposites were prepared by adding nano-antimony compound into UPR/K using FRP as carrier. The relationship between microstructure and properties of materials and flame retardant mechanism were discussed. The results show that UPR formed net structure when solidifying. There were holes between nets. The flame retardant addtives filled loose in the net, which result in the mechanical properties of materials decreased. The kaolinite intercalating layers dispered uniformly and tightly in the net hole, which increased the stretching intension and flexibility module, limited the movement of UPR molecular and resultes in the improvement of decomposition temperature of resin. This special nanostructure and larger length-radius ratio also conduce diffusing path more zigzag and diffusing time longer of small moleculars in matrix, so the obstruction properties of materials have improved. After adding nano-Sb₄O₅Cl₂ into UPR/nanocomposites, the materials surface got compact. UPR sample with UPR/4% kaolinite preparing by in situ polymerization +6%Sb₄O₅Cl₂+10%CP-70 has best flame retardant properties with 35% LOI. After burning, The nano-kaolinite layers array flat on the materials surface and form hardness char shell, which inhibites effedtively the volatility combustible materials producing by polymer decomposion transfering to burning zone, the quantity of heat diffusing to no-burning zone and entering of oxygen. Polymer forms active radical, and then passes quickly through a chain reaction while burning. Sb₄O₅Cl₂ or Sb₂O₃ decomposes to produce SbCl3 under synergizing with halogen which can capture active radicals in gas, decreases the energy from reaction and finally makes fire extinguish.