The Preparation, Properties Of Fire Retardant Form-Stable Phase Change Material And Styrene-acrylonitrile Series Polymer/Clay Nanocomposites

Polymer materials mainly consist of carbon and hydrogen. Therefore, they have easily combustion and will lead to many fire accidents. It is necessary to deal the polymer materials with flame retardant technologies in order to reducing the loss of fire and improving the level of safety of human existence. It is one of the important research aspects in improving the flame retardant properties of polymer materials. Based on the recent literatures, the latest progresses are reviewed in this dissertation in the fields of the from-stable phase change materials (PCM) and styrene-acrylonitrile series polymer/clay nanocomposites. In this thesis, the preparation and properties of the flame retardant form-stable PCM and styrene-acrylonitrile series polymer/clay nanocomposites are studied. The contents mainly include five aspects of two parts in this dissertation.The first part: Study on flame retardant form-stable PCMThe influences of three kinds of different flame retardant systems on structure, thermal stability, flammability and latent heat properties of the form-stable PCM are studied. In order to further improving the flame retardant property, the flame retardant form-stable PCM are prepared combining with the OMT and IFR. The structure, thermal and flame retardancy properties are investigated. The synergistic flame retardant effects are discussed. The form-stable phase change nanocomposites are prepared from considering the design of materials and combining the principles and technologies of nanocomposite with halogen-free flame retardancy. The thermal stability property has notably increases. And then the flame retardant form-stable phase change nanocomposites are prepared. The thermal stability, heat storage and flammability properties are studied. The flame retardant mechanism is discussed.1. The form-stable PCM consists of phase change material (paraffin) and supporting material (HDPE). The paraffin disperses in the formed three-dimensional net structure of HDPE. The CONE results show that three kinds of flame retardant systems have notable effects on flammability of the form-stable PCM and the peak value of heat release rate (PHRR) has remarkably decrease. The flame retardant mechanisms of MPP-PER, BPBE-AO and MCA are respectively happened in condensed phase, gas phase and condensed phase. For full considerations, IFR has been taken as the outstanding flame retardant systems. The TGA results show that the loadings of flame retardant decrease the decomposition temperature of the form-stable PCM, but increase the final char residue. The DSC analyses show that the latent heat of the flame retardant form-stable PCM has no notable changes.2. The flame retardant form-stable PCM by combining the OMT with IFR has been prepared. The synergistic flame retardant effects are also studied. The CONE experiment indicates that the PHRR, total smoke released (TSR), specific extinction area (SEA), release of carbon monoxide (CO) and carbon dioxide (CO₂) of the flame retardant form-stable PCM have remarkably decreases. The results show that the OMT can react with IFR to form a compact char structure and create a physical protective barrier on the surface of the materials, and thus limit oxygen diffusion and retard the volatilization of the flammable gas. Meanwhile, the increase of fire propagation index (FPI) and the decrease of fire growth index (FGI) indicate the OMT is propitious to improve the fire safety of the form-stable PCM. The TGA results show that the char residue of the flame retardant form-stable PCM increase, although the onset decomposition temperature advances slightly. The DSC analyses indicate that the loadings of IFR and OMT have hardly influences on the latent heat of the form-stable PCM.3. The supporting materials based on HDPE-EVA alloy/OMT nanocomposites are prepared by twin-screw extruder technique. And then the form-stable phase change nanocomposites based on HDPE-EVA alloy/OMT nanocomposites and paraffin compounds are prepared. The XRD and SEM indicate the paraffin disperses well in the formed three-dimensional net structure by HDPE-EVA/OMT nanocomposites, and the paraffin intercalates partly into the silicate layers. Dynamic FTIR, TGA and DSC results show that the form-stable phase change nanocomposites have low thermo-oxidation degradation rate, enhanced thermal stability and slightly low latent heat. Based on the intumescent flame retardant principle, the flame retardant form-stable phase change nanocomposites are prepared. The thermal stability, latent heat, combustion properties and flame retardant mechanism of the flame retardant form-stable phase change nanocomposites are studied. The TGA results indicate that the flame retardant form-stable PCM produce a larger amount of char residue at 800°C than that of the HDPE-EVA alloy/paraffin compound, although the onset of weight loss occurs at a lower temperature. The DSC results show there are hardly any changes of the latent heat in the form-stable PCM. The studies of flame retardant mechanisms show that the multicellular char residue are formed in condensed phase and an ablative reassembling of the silicate layers may occur and create a physical protective barrier on the surface of the material. The alumino-phosphate char structure, which MMT reacting with APP, play also an important role. The physical protective barrier on the surface of the materials limit oxygen diffusion and retard the volatilization of the flammable gas.The second part: Study on the styrene-acrylonitrile series polymer/clay nanocompositesThe poly (styrene-acrylonitrile) (SAN)/clay nanocomposites are prepared by melt-mixing methods. The relations between the structure and properties are studied. To simplify the tedious process of technics, the SAN nanocomposites are prepared by an improved "one-step" methods. The influences of the structures of different reactive compatibilizer (RC) and the proportion of RC relative to MMT on the morphology and properties of SAN nanocomposites are investigated. The intercalation mechanism is also discussed. Combining the principles and technologies of catalyzing carbonization, halogen-free flame retardancy and nanocomposite, the catalyzing carbonization effects between Lewis acid (ferric chloride, FeCl₃) and OMT on the acrylonitrile-butadiene-styrene copolymer (ABS) are studied. The catalyzing carbonization mechanism is explored. Meanwhile, the catalyzing flame retardant synergism function among the rare compounds (lanthanum trioxide, La₂O₃), OMT and magnesium hydroxide (MH)/red phosphorus (RP) in ABS are discussed.4. The organic-modified MMT with hexadecyl triphenyl phosphonium (P16) and cetyl pyridinium chloride (CPC) are prepared according to the cation exchange capacity (CEC) of MMT. The TGA results show that the OMT-P16 and OMT-CPC have higher thermal stability than that of the OMT-C16 (hexadecyl trimethyl ammonium bromide). The SAN/OMT nanocomposites are prepared by melt-mixing technique. The results of XRD, TEM and HREM experiments show the OMT disperses well in SAN matrix. The TGA and DMA tests show the structure of the nano-dispersed silicate clay improves the thermal stability, storage modulus and glass transition temperature of the SAN. To simplify the process, SAN/MMT/RC nanocomposites have been prepared by an improved "one-step" melt intercalation method directly from MMT, using C16 and P16 as the polymer/clay reactive compatibilizers. The XRD, TEM, HREM and TGA results show that such appropriate proportion as 1wt% RC to 5wt% MMT induces well clay dispersed in SAN matrix and better thermal stability properties. At last the intercalation mechanism of the technology is discussed.5. Based on the principles and technologies of catalyzing carbonization, halogen-free flame retardancy and nanocomposite, the ABS/OMT nanocomposites containing FeCl₃ are prepared by melt intercalation. The XRD, TEM and HREM results show that the OMT disperses well in ABS matrix. The TGA results indicate that the loadings of FeCl₃ decrease the onset temperature of weight loss, but increase the charred residue. The structure and morphology of the char residue are studied by XRD, HREM and laser Raman spectra. The results indicate the presence of graphite sheets with polycrystalline structure. The catalyzing carbon mechanisms between FeCl₃ and OMT in ABS are discussed. At the same time, the influences of La₂O₃ on the thermal properties of ABS/OMT nanocomposites are also studied. The structure and morphology of the char residue show that the graphite sheets enhance the thermal stability of ABS. The results of UL-94 combustion tests indicate that the V-0 rating can be achieved and flame retardant property has been improved, contributing to the synergistic catalyzing flame retardant effect among the La₂O₃, OMT and MH/RP.