磷酸酯改性纳米氢氧化镁的研究

以六水硝酸镁和氢氧化钠为原料,磷酸酯为改性剂,采用直接沉淀法一步合成改性纳米氢氧化镁,通过沉降体积实验,确定改性剂的较佳用量为1.0%,并用红外光谱(FHR)、X射线衍射(XRD)、透射电镜(TEM)、堆密度对改性前后的样品进行表征.结果表明,该方法可以使磷酸酯吸附在氢氧化镁颗粒表面,改变氢氧化镁的表面性质,从而提高在有机介质中的分散稳定性,与未改性的氧氧化镁样品相比,改性后纳米氢氧化镁XRD衍射峰主峰强度提高,团聚程度和堆密度减少.     

氢氧化镁的表面处理研究

为了解决氢氧化镁与聚合物相容性不好等问题，表面改性是有效的途径之一。分别采用稀土偶联剂、硬脂酸钙偶联剂，以及其联合偶联剂，以干法和湿法对4种不同的氢氧化镁进行了表面包覆工作。包覆后的氢氧化镁真密度都有下降，而表观密度和灼烧失重都有所增加。通过对比得出了以稀土为偶联剂，采用干法对氢氧化镁进行处理得到的效果最好。     

纳米氢氧化镁材料的制备与应用

对制备纳米氢氧化镁材料的直接沉淀法、均匀沉淀法、金属镁水化法、均质流体法、液一固电弧放电、沉淀一共沸蒸馏法、全返混均质乳化法进行了详细的评述。简要介绍了纳米氢氧化镁材料制备过程中的分散与表面改性问题，以及纳米氢氧化镁材料的应用状况。最后，对纳米氢氧化镁材料的应用前景进行了展望，并对纳米氢氧化镁材料研究存在的问题进行了简要的讨论。     

氢氧化镁阻燃剂在聚合物材料中的应用

氢氧化镁是近几年广泛应用的环境友好的新型无机阻燃剂,综述了氢氧化镁阻燃剂的阻燃机理、应用现状、改性技术和发展趋势。指出了今后氢氧化镁阻燃剂的研究发展方向。     

Stearic acid surface modifying Mg(OH)2: Mechanism and its effect on properties of ethylene vinyl acetate/Mg(OH)2 composites

In this article, FTIR spectra and ESEM images were employed to evaluate the effect of stearic acid surface modification of Mg(OH)₂. As a result, the absorbing peak intensity of organic group on Mg(OH)₂ increased with the coating amount of stearic acid increasing and there was no so‐called surface saturation as expected. The results indicated stearic acid surface treatment of Mg(OH)₂ belonged to the acid–base reaction between stearic acid and Mg(OH)₂, and it would not stop until Mg(OH)₂ was reacted completely. In addition, stearic acid surface treatment of Mg(OH)₂ had remarkable influence on the properties of ethylene vinyl acetate/Mg(OH)₂ composites. With the increasing coating amount of stearic acid, the composites had decreased tensile strength, increased elongation at break, and deteriorated flame retardancy, compared with the composites filled with the uncoated Mg(OH)₂. However, stearic acid surface treatment of Mg(OH)₂ benefited processing ability of composites, and the composites had better processing ability as the coating amount of stearic acid increased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氢氧化镁的固相制备及其表面改性

采用固相法合成了纯度较高的Mg(OH)2,并利用XRD、SEM等进行了表征.以硬脂酸钠、油酸对其进行表面处理得到改性Mg(OH)2,沉降实验表明其与液体石蜡中有较好的相容性,而且油酸改性Mg(OH)2显示出更好的效果.     

Interfacial modification of high impact polystyrene magnesium hydroxide composites effects on flame retardancy properties

High impact polystyrene (HIPS)/magnesium hydroxide (MH) composites were prepared by melt‐blending. Two kinds of interfacial modifiers were used in this research, maleinated poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS‐g‐MA) triblock copolymer and PS. The effects of the use levels of SEBS‐g‐MA on the flame retardancy of HIPS/elastomer/MH based on unmodified and PS‐modified surface were investigated by TEM, FTIR, and combustion tests (horizontal burning test and cone calorimetry). The combustion results showed that comparing composites containing unmodified MH, the flame retarding properties of composites containing PS‐modified MH were obviously improved. The increased performance can be explained that the PS covered on the surface of MH could further improve dispersion of the filler in matrix. Furthermore, there existed a critical thickness of interfacial boundary for optimum flame‐retarding properties in both ternary composites based MH and PS‐modified MH. When the interfacial boundary relative thickness is less than 0.53, the introduction of SEBS‐g‐MA can improve the dispersion degree, leading the improvement of flame retardancy properties. However, with the increase of interfacial boundary thickness, the SEBS‐g‐MA coating around MH acted as a heat and mass transfer barrier, leading to the reduction of flame retardancy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure and properties of polypropylene composites filled with magnesium hydroxide

Silane and silicone oil modified superfine magnesium hydroxide (MH) was filled into polypropylene (PP) as a flame retardant. The PP and flame‐retarded PP composites were studied for their mechanical properties and rheological behaviors by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), limiting oxygen index (LOI), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the addition of MH improved flame retardancy of PP/MH composites, but seriously deteriorated mechanical properties of the composites. Surface treatment of MH could significantly improve tensile and impact strength of PP/MH composite because of its enhanced interfacial adhesion between MH and PP matrix. DSC results showed that MH had heterogeneous nucleation effect on PP. Surface treatment of MH weakened its heterogeneous nucleation effect. POM results showed that the dispersion of MH particles played an important role in the crystalline morphology and spherulite size of PP crystals. TGA indicated that MH greatly enhanced the thermal stability of PP. The introduction of treatment agent further improved the thermal oxidative stability of the composite. According to LOI, silane‐treated MH greatly enhanced flame retardancy of PP/MH composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4943–4951, 2006     

Preparation of thermally stable and flame-retardant sugarcane bagasse-ammonium dihydrogen phosphate/epoxy composites and their performance

Epoxy resin was often applied in fiber-reinforced composite materials, adhesives, and encapsulation materials. However, epoxy was easily flammable and limited its usage in certain applications. The study recycled and reused agricultural waste sugarcane bagasse to prepare a halogen-free bio-based intumescent flame retardant and then mixed with epoxy resin to prepare a composite containing polymer with improved thermal properties and flame retardancy of the materials. The work followed the concept of circular economy and sustainability. Bagasse-ammonium dihydrogen phosphate (ADP) flame retardant was added to an epoxy resin to prepare epoxy/bagasse-ADP composites, an effective flame-retarding composite material through hydrothermal method. Adding bagasse-ADP increased the thermal stability and flame retardancy of the composite materials compared with that of pure epoxy. For the material with 30 wt% added bagasse-ADP, the char yield was 32.3 wt%, which was 18.2 wt% higher than that of pure epoxy (14.1 wt%) through thermogravimetric analysis. In addition, the limiting oxygen index increased from 21% to 30%, and the UL-94 classification improved from “Fail” to “V-0.” This performance was attributed to the nitrogen, phosphorus, and silicon content of the flame retardant.     

A simple and green strategy for preparing poly(vinyl alcohol)/phosphate cellulose aerogel with enhanced flame-retardant properties

Phosphorylated celluloses (PCFs) were obtained via reaction of microcrystalline cellulose with phosphorous acid in molten urea. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the chemical structure and microstate of the PCFs. A flame retardant glutaraldehyde cross-linked poly (vinyl alcohol)/PCF aerogel was fabricated using a melt cross-link and freeze-dried method. The results of thermogravimetric analysis confirmed that the thermal stability of the poly(vinyl alcohol) (PVA) aerogels incorporating PCF is more outstanding. The peak of heat release rate (PHRR) and the total heat release (THR) values of the PCA/PCF₁₀ aerogel deceased obviously by 33.8 and 64%, respectively, compared to the corresponding values for the pure PVA aerogel; these changes confirm that the PCA/PCF aerogel had better flame-retardant properties than the pure PVA aerogel. Moreover, the fire performance index and fire growth index indicate that the introduction of PCF would diminish the occurrence of fire.     

氢氧化镁阻燃剂的表面改性及其在聚丙烯中的应用

采用不同改性剂对氢氧化镁进行表面改性处理，通过实验发现采用4％的硬脂酸钠处理后的氢氧化镁阻燃剂在聚丙烯体系中分散均匀，当氢氧化镁在聚丙烯体系中的添加量达65％时，达到了理想的阻燃效果。     

Effect of particle size on the flame retardancy of poly(butylene succinate)/Mg(OH)2 composites

Poly(butylene succinate)/magnesium hydroxide (PBS/Mg(OH)₂) composites were prepared by melt compounding to investigate the effect of particle size on the flame retardancy of PBS. Their flammability properties were investigated by limiting oxygen index, UL‐94, and cone calorimeter tests, which suggested that the medium‐sized Mg(OH)₂‐5 µm displayed the best flame retardancy. The residual char structure were analyzed and indicated that Mg(OH)₂‐5 µm could form a better protective layer than other sized particles, leading to the better flame retardancy to PBS. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal stability of poly(vinyl chloride)/layered double hydroxide nanocomposites

Effects of nanoscale dispersed layered double hydroxides (LDHs) on thermal stability of poly(vinyl chloride) (PVC) in thermal and thermooxidative degradation processes are investigated by dynamic and isothermal thermogravimetric analysis (TGA), discoloration test, fourier transform infrared (FTIR), and ultraviolet‐visible (UV‐vis) spectroscopic techniques. During both stages of thermal degradation, the degradation temperatures, including onset degradation temperature and temperature of the maximum degradation rate, increase, and the final residue yield of the PVC/LDH nanocomposites reaches 14.7 wt %, more than double that for neat PVC. The thermooxidative degradation process is more complex. During the first two stages, the presence of nanoscale dispersed LDH particles enhances the thermal stability, whereas in the last stage accelerates the thermal degradation possibly due to the accumulation of heat released. Additionally, the studies of the isothermal thermooxidative degradation process by FTIR and UV‐vis spectra indicate that both polyene backbone formation and some carbonyl groups are simultaneously developed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

超细氢氧化镁的制备及应用

对平均粒径为100nm左右的氢氧化镁超细粉体进行了表面改性处理，通过对聚氯乙烯材料的力学性能测试，筛选出钛酸酯偶联剂做为氢氧化镁的最佳改性剂，并确定了氢氧化镁在聚氯乙烯型材中的最佳添加份数。     

Behavior of flexible poly(vinyl chloride)/poly(hydroxybutyrate valerate) blends

Blends of flexible poly(vinyl chloride) (PVC) and a poly(hydroxybutyrate valerate) (PHBV) copolymer were prepared and characterized with different techniques. The tensile strength of PVC did not show a marked reduction at PHBV concentrations up to 50 phr, despite a lack of miscibility between the two polymers. The crystallization of the PHBV copolymer was markedly hindered by the presence of PVC, as calorimetric results revealed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of water erosion on flame retardancy of high-impact polystyrene/magnesium hydroxide composite and its mode of action

High-impact polystyrene (HIPS) flame retarded by magnesium hydroxide (MH) was treated in water at different conditions. The effect of water erosion on flame retardancy of the HIPS/MH composite and its mode of action was investigated by various means. The results indicate that both limiting oxygen index value and UL-94 rating of the HIPS/MH composite decrease observably after water erosion. The average heat release rate, average mass loss rate, total heat release, and total smoke release of the composite all increase remarkably after water erosion. The MH content in the surface layer of the HIPS/MH composite reduces, and the surface of this composite becomes rough and porous after erosion. The water-eroded composite shows a loose and discrete surface morphology after subjected to fire, which favors heat transfer and mass exchange between flame area and the underlying polymers. Consequently, both flame retardancy and smoke suppression of the polymer composite decrease significantly. The decrease in flame retardancy occurs in condensed phase. The result of this work has provided a basis for further investigations to prevent this detrimental effect induced by water erosion.     

Poly(trimethylene terephthalate)/magnesium hydroxide composites with on‐demand thickening at high temperatures

Magnesium hydroxide, when melt extruded with poly(trimethylene terephthalate) (PTT) at low concentrations (1–3 wt.%), can be melt processed during extrusion and injection molding. When the polymer is heated in the melt to 295°C, the viscosity of the composite behaves similarly to control samples and the viscosity decreases as a function of temperature. When the temperature of the composite is raised above 295°C (above the normal processing conditions for PTT), a significant change in the melt rheology of the composite is observed relative to unfilled compositions. This change in melt rheology coincides with the decomposition temperature of magnesium hydroxide and formation of magnesium oxide, a common thickening agent employed in unsaturated polyester resins. Lower processing temperature polyesters, including PTT, enable processing of the polymer in the presence of magnesium hydroxide under normal conditions. The viscosity modifier ‘turns on’ when the composite sees elevated temperature where magnesium oxide is known to form. The magnesium oxide is hypothesized to interact with PTT carboxyl end groups, providing the observed increase in viscosity. The rheological response observed in the composites is dependent on the concentration of magnesium hydroxide. During burning, the viscosity modifier results in a non‐dripping formulation of PTT. Copyright © 2012 John Wiley & Sons, Ltd.     

氢氧化镁改性技术及阻燃效果研究进展

在环保型的无机阻燃剂中,氢氧化镁有阻燃、抑烟、填充的三重功能和热稳定性好、分解温度高、无腐蚀性、无毒、无味等特点,因而成为有机高分子材料阻燃添加剂的首要选择。综述了氢氧化镁作为阻燃剂时,其表面有机化改性过程中改性剂种类和改性条件的研究进展。总结了不同改性剂改性后的氢氧化镁填充到不同的高分子聚合物中,其对复合材料的阻燃性能和机械力学性能的影响。     

表面改性剂在超细氢氧化镁过滤中的应用

以氯化镁为原料,氨水为沉淀剂,采用直接沉淀法制备了超细氢氧化镁,但超细氢氧化镁料浆的过滤性能差一直是制约氢氧化镁工业化生产的关键性问题之一。采用硬脂酸钠与水溶性钛磷酸脂偶联剂对超细氢氧化镁进行湿式改性实验,在改善超细氢氧化镁的表面性能的同时二者都能显著提高过滤性能。实验结果表明：采用固含率为15%的超细氢氧化镁悬浮液为原料,表面改性剂的最佳添加量为氢氧化镁粉体质量的2.00%。并以54框的BM70-800/25的板框式压滤机为例,对操作及生产能力进行了讨论。     

氢氧化镁的制备及其表面接枝改性

以硫酸镁、氢氧化钠溶液、丙烯酸及接枝单体和引发剂为原料，采用微乳液聚合方法，一步制备了表面接枝聚合物改性的纳米氢氧化镁颗粒。试验表明先在1mol／L的硫酸镁溶液中逐滴加入2mol／L的氢氧化钠溶液，在80℃下反应3h，得到热分解温度为384℃的六方片状结构的氢氧化镁粉体。当在上述合成过程中加入接枝单体和引发剂，生成了聚合物包覆改性的氢氧化镁粉体，并且不改变氢氧化镁的热分解温度，而能改善粉体的吸湿性和与液体石蜡的相容性；TEM结果表明接枝产物粒径分布均匀，约为80～100nm。