Mg(OH)_2-PMMA复合粒子的制备及表征EI北大核心

为了减小纳米氢氧化镁较严重的团聚问题,通过在氢氧化镁表面接枝大分子聚甲基丙烯酸甲酯(PMMA)来制备氢氧化镁/PMMA纳米复合粒子,以提高纳米复合粒子在有机相中的相容性和分散性。首先,通过油酸对氢氧化镁进行表面修饰,在其表面引入双键烯烃基团,然后以丙烯酸甲酯(MMA)为单体,偶氮二异丁腈(AIBN)为引发剂,聚乙烯吡咯烷酮(PVP)为稳定剂,通过分散聚合的方法在修饰过的氢氧化镁表面接枝有机大分子PMMA。通过XRD、FT-IR、TGA、FESEM、EDS和沉降实验对所得Mg(OH)2/PMMA纳米复合粒子进行了测试表征,结果表明:有机大分子PM-MA成功地接枝在了油酸修饰后的Mg(OH)2表面上,纳米复合粒子在有机相中的分散性和相容性都得到了很大的提高。     

纳米结构氧化镁空心球壳的制备及吸附镍离子性能研究

以Pickering乳液的液滴为模板制备纳米结构MgO空心球壳,用SEM、XRD、BET等对空心球壳进行了表征,探讨了其形成机理,并考察了纳米结构MgO空心球壳对水中Ni2+的吸附性能。结果表明,MgO空心球壳为方镁石结构,比表面积为28m2/g;其平均粒径为63μm,表面由平均宽度为65nm的纳米片层构成。Pickering乳液油水界面的部分MgO通过水化反应转变成Mg(OH)2,复合在未反应的MgO粒子上,形成MgO/Mg(OH)2空心球壳;MgO/Mg(OH)2空心球壳经焙烧后得到纳米结构MgO空心球壳。当纳米结构MgO空心球壳用量为0.4g/L时,溶液(初始浓度25mg/L)中Ni2+的去除率为98.3%。     

油酸钠/Fe纳米粒子的制备及其脱氯性能研究

采用油酸钠作为包覆剂,在液相体系中制备油酸钠/Fe纳米复合粒子,并用TEM、XRD、FT-IR、DSC-TGA对所制得的纳米复合粒子进行结构表征.结果表明,油酸钠/Fe纳米复合粒子呈核壳结构,粒度分布窄,其粒径在90nm左右;T-IR和DSC-TGA分析证明纳米铁与油酸钠之间发生了化学键合,具有空气稳定性,而且憎水亲油;将油酸钠/Fe纳米复合粒子与三氯乙烯(TCE)模拟水样反应,发现油酸钠/Fe纳米复合粒子能够与水相中的三氯乙烯(TCE)有良好的接触性,其脱氯效果优于未修饰的纳米铁粒子.     

壳/核型聚丙烯酸酯乳液的制备及性能

为制备力学性能优异的涂料用有机/无机复合乳液,以硅溶胶、丙烯酸酯类为单体制备壳层乳液和核层乳液,以阴离子型与非阴离子型复配乳化剂,通过半连续种子乳液聚合法制得力学性能良好的聚丙烯酸酯包覆纳米Si O2粒子的壳/核型有机/无机复合乳液,系统地研究了乳化剂配比、核/壳单体质量比及硅溶胶含量对乳液及涂膜性能的影响,并采用透射电镜、红外光谱、粒度仪等测试手段,对乳液的粒径分布及微观结构进行表征。结果表明:在反应温度80℃、乳液滴加时间2~3 h、复合乳化剂SDS/OP-10质量为1∶1、核/壳单体质量比为3∶4(或1∶1)时,制得的乳液及涂膜综合性能最好,乳液为壳/核型包覆的乳胶粒结构,可制备硅溶胶含量高达12%的高性能复合乳液,其涂膜力学性能较纯丙乳液涂膜明显提高。     

液相沉积法制备氢氧化镁包覆碳微球复合阻燃材料

以碳微球(CMSs)、氢氧化钠和氯化镁为原料,采用液相沉积法制备了Mg(OH)_2/CMSs复合阻燃材料,通过场发射扫描电镜(SEM)和X射线衍射仪(XRD)分析了材料的微观形貌和结构;并结合Mg(OH)_2/CMSs复合阻燃材料与聚对苯二甲酸乙二醇酯(PET)共混制备Mg(OH)_2/CMSs/PET复合材料,通过数显氧指数测试仪分析其阻燃性能。结果表明,通过液相沉积法Mg(OH)_2包覆在CMSs表面,且包覆效果较好;Mg(OH)_2/CMSs复合阻燃材料燃烧时分解生成的氧化镁(MgO)、水和残余炭层,使得Mg(OH)_2/CMSs/PET复合材料的极限氧指数由PET的21.0%增加到27.5%,并具有优良的抑烟性和抗熔滴性,提高了PET材料的阻燃性能。     

用于合成纳米苯丙乳液的纳米TiO2表面改性及表征

研究了利用硅烷偶联剂改性纳米TiO2的方法,并通过FTIR、TEM等手段表征化学改性产物的结构和改性后纳米二氧化钛的分散性,结果表明偶联剂与二氧化钛表面发生化学偶联反应,使二氧化钛表面被偶联剂包覆,从而使二氧化钛改性产物在有机物中具有良好的分散性能.通过TEM分析用改性后的纳米TiO2原位合成的纳米TiO2/苯丙乳液复合体系具有以纳米TiO2粒子为核,以聚合物为壳的核壳结构,该乳液涂膜的耐水性达120h不泛白,硬度为H级,明显优于非纳米苯丙乳液,且具有很好的抑菌作用,可用于制备纳米水性涂料.     

梯度核壳结构硅丙乳液的聚合

采用单体浓度梯度加入法合成了具有梯度壳层的核壳结构,可用于木器涂料的硅丙乳液。考察了乳化体系、聚合工艺、有机硅预聚物的引入、软/硬单体比等因素对乳液和漆膜性能的影响,用透射电镜测定了乳胶粒子形态。研究表明:OP-10/SDS/MS-1为最佳乳化体系,有机硅预聚物与其他单体一次性混合引入,软/硬比为1∶2时,所制得乳液的综合性能良好。固含量为45%,成膜温度为48℃,附着力为1级,硬度为2H,乳胶粒子有明显的核壳结构。     

纳米Mg(OH)_2-微胶囊红磷/乙烯-乙酸乙烯酯共聚物阻燃复合材料的性能

以微米Mg(OH)_2(mMg(OH)_2)、纳米Mg(OH)_2(nMg(OH)_2)和微胶囊红磷(MRP)为无卤阻燃剂,乙烯-乙酸乙烯酯共聚物(EVA)为聚合物基体,通过熔融共混方法制备了一系列不同阻燃剂含量的Mg(OH)_2-MRP/EVA阻燃复合材料,采用极限氧指数、垂直燃烧、锥形量热分析、热分析、SEM、拉伸试验、流变学分析等方法研究了复合材料的阻燃、力学和加工性能。结果表明,Mg(OH)_2阻燃剂用量相同时,nMg(OH)_2/EVA复合材料的阻燃和抑烟性能比mMg(OH)_2/EVA复合材料更好,但当Mg(OH)_2用量小于60wt%时,nMg(OH)_2/EVA和mMg(OH)_2/EVA复合材料的垂直燃烧等级都达不到V-0级。Mg(OH)_2本身的阻燃效率较低,nMg(OH)_2和MRP对EVA有非常显著的协同阻燃作用,二者掺杂比例适当时可大幅度降低Mg(OH)_2的用量。与nMg(OH)_2/EVA复合材料相比,nMg(OH)_2-MRP/EVA复合材料燃烧时能够生成连续致密的炭层,覆盖在材料表面形成防火屏障,提高其阻燃性能。nMg(OH)_2的热分解反应对nMg(OH)_2-MRP/EVA复合材料的燃烧性能有极其重要的影响。当nMg(OH)_2热分解后再加入到MRP/EVA体系中时,nMg(OH)_2-MRP/EVA复合材料的阻燃和抑烟性能均急剧降低。当nMg(OH)_2∶MRP∶EVA的质量比为40∶10∶100时,nMg(OH)_2-MRP/EVA复合材料同时具有优异的阻燃性能、力学性能和加工性能,可满足实际应用的需要。     

MgO/Mg（OH）2复合空心球壳的制备及缓释性能的研究

以Pickering乳液液滴为模板,通过液滴表面水合作用制备出MgO/Mg（OH）_2复合空心球壳,通过SEM、XRD等手段进行表征,讨论了空心球壳形成机理,并研究了MgO/Mg（OH）_2复合空心球壳对阿维菌素微胶囊的缓释作用,结果表明,MgO/Mg（OH）_2复合空心球壳形貌完整,粒径分布均匀,平均粒径为62μm。水合过程中部分MgO转变成Mg（OH）_2,并优先复合在未反应的MgO粒子上,形成MgO/Mg（OH）_2复合空心球壳。以MgO/Mg（OH）_2复合空心球壳为壁材的阿维菌素微胶囊具有良好的缓释性能。     

丙烯酸酯类水性超薄膨胀型钢结构防火涂料的研制

以改性丙烯酸酯类乳液为成膜物质,聚磷酸铵、季戊四醇、三聚氰胺为膨胀阻燃体系,并添加可膨胀石墨、硫酸镁晶须进行改性,制备水性超薄膨胀型钢结构防火涂料。采用垂直燃烧法、热重分析(TGA)、扫描电镜(SEM)、X射线衍射(XRD)等方法研究了防火涂层的结构与耐火性能,结果表明,以硅丙乳液和环氧改性丙烯酸酯乳液复配为成膜物质,受火膨胀后防火涂层形成了致密的"蜂窝"状结构,获得较好的防火性能。钛白粉在高温中能转变成焦磷酸钛,对提高防火性能起到积极的作用。添加可膨胀石墨和晶须具有明显的协效阻燃效果。3%可膨胀石墨和3%硫酸镁晶须共同改性的防火涂层在800℃的残余质量为36%。     

Core-shell magnesium hydroxide/polystyrene hybrid nanoparticles prepared by ultrasonic wave-assisted in-situ copolymerization

In this paper, vinylated magnesium hydroxide (MH) nanosheets were prepared with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS) and pristine MH nanosheets, then the MH/polystyrene (PS) hybrid nanoparticles were prepared by ultrasonic wave-assisted in-situ copolymerization of vinylated MH nanosheets and styrene (St). The morphology, thermal stability and chemical structure of the final products were investigated in detail with transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier-transform infrared spectra (FTIR). The TEM and FTIR results showed that the uniformly-dispersed core-shell structure of MH/PS nanocomposites with MH-cores and PS-shell was formed. TGA indicated that the covalent interaction between PS and MH improved the thermal stability of PS. A possible formation mechanism of the MH/PS core-shell nanocomposites was also proposed.     

Magnesium hydroxide sulfate hydrate whisker flame retardant polyethylene/montmorillonite nanocomposites

Flame retardant maleated polyethylene/magnesium hydroxide sulfate hydrate whisker (MAPE/MHSH) composites containing organo-modified montmorillonite (OMT) were prepared by direct melt intercalation. Their morphology, combustion behaviour and thermal stability were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), cone calorimetry and thermogravimetric analyses (TGA). The exfoliation of silicate layers within MAPE has been verified by XRD and TEM images. Cone calorimetry results indicated that a synergistic flame retardant effect on reducing heat release rate (HRR) occurred when MHSH and OMT were both present in nanocomposite. The reduction in HRR improved as the mass fraction of OMT was increased from 2 to 10 wt%, but there was little improvement above 5 wt% OMT loading level. TGA profiles of the nanocomposites revealed that the thermodegradation stability of the nanocomposites decreased as the OMT fraction increased from 2 to 10 wt%.     

Synthesis of silver-iron oxide nanocomposites by thermal decomposition

Silver-iron oxide nanocomposites were synthesized by an easy thermal decomposition method using iron acetyl acetonate and silver acetate as precursors and oleic acid (OA) and oleyl amine (OLA) as the capping agents in a single step. The composite samples were characterized by X-ray diffraction (XRD), infrared spectroscopy, thermal gravimetric analysis (TGA), UV-Visible spectroscopy, scanning electron microscopy (SEM), and magnetic measurements. Powder XRD and UV-Visible spectroscopy results indicate the presence of nanocrystalline silver in the composite and the FT-IR results coupled with TGA results indicate the presence of ligand molecules on surface of the nanocomposites. The FE-SEM images show that the nanocomposite particles are mainly spherical in shape while the energy dispersive X-ray analysis studies indicate the presence of iron and oxygen in the composites. From the magnetic measurements, the composites were found to be superparamagnetic with characteristic blocking temperatures indicating the presence of iron oxide nanoparticles in the nanocomposites.     

Effect of Amino alcohol functionalized polyethylene as compatibilizer for LDPE/EVA/clay/flame-retardant nanocomposites

The synergistic effect of organo-modified montmorillonite (Nanomer I28E and Cloisite 20A) and metal hydroxides (magnesium hydroxide MH and alumina trihydrate ATH) as flame retardants in LDPE/EVA nanocomposites compatibilized with amino alcohol grafted polyethylene (PEgDMAE) was studied. Morphological characterization of nanocomposites was carried out by means of X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Flame-retardant properties of nanocomposites were evaluated by the UL-94 horizontal burning and cone calorimeter tests and limiting oxygen index (LOI). Thermal degradation behavior was analyzed with a Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR). The XRD analysis showed a displacement of the d₀₀₁ plane characteristic peak of clay to lower angles, which indicates an intercalated–exfoliated morphology. From STEM images it was observed a good dispersion of flame retardants (MH and ATH) throughout the polymer matrix which was reflected in flame-retardant properties. TG-FTIR showed a better thermal stability of nanocomposites and the gases evolved during combustion showed an important reduction. Based on thermal stability and thermal degradation results, the flame-retardant mechanism of LDPE/PEgDMAE/EVA/Clay/MH nanocomposites was proposed.     

Self-assembly directed synthesis of poly(ortho-toluidine)-metal(gold and palladium) composite nanospheres

Poly(ortho-toluidine) (POT)-gold (Au) and palladium (Pd) composite nanospheres were successfully synthesized by the reaction of o-toluidine with the corresponding metal (Au or Pd) colloidal solution through self-assembly process in the presence of dodecylbenzenesulfonic acid (DBSA), which acts as both a dopant and surfactant, and ammonium peroxydisulfate as an oxidizing agent. The composites (POT-DBSA/Au or Pd) were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, UV-Visible (UV-Vis) spectroscopy, and electrical conductivity measurements. TEM images of the nanocomposites reveal that metal (Au or Pd) nanoparticles were well dispersed on POT spheres. TGA and XRD results show that the composites exhibit high thermal stability and are more crystalline compared with pristine POT. It was found that the electrical conductivity of the POT-DBSA/Au or Pd composites is 2 orders of magnitude higher than that of pristine polymer. Also, the POT-DBSA/Pd composite exhibits magnetic property. The formation mechanism of the POT-DBSA/Au or Pd composite nanosphere is discussed.     

使用硅油-水体系制备纳米氢氧化镁

以硫酸镁和氢氧化钠为主要原料,用化学沉淀法在硅油-水体系中制备氢氧化镁阻燃剂,用X射线衍射(XRD)、透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)和热重分析仪(TGA)对产物的形貌、粒径、晶型结构和热稳定性进行表征,研究了反应时间、温度、搅拌速度、盐和碱溶液浓度、加料方式等因素对氢氧化镁形貌和分解温度的影响.结果表明:当反应时间为6 h、反应温度为60℃、搅拌速度为1500 r/min时,制得质量和性能较好的纳米氢氧化镁.     

油酸包覆针状氢氧化镁纳米粉体的制备

采用一种新工艺来合成油酸包覆的氢氧化镁针状纳米粒子,其合成过程是在一种常温下具有特殊结构、能产生复合剪切力的反应器内进行,出料后经过特殊的搅拌、陈化、水洗、干燥工艺,可以大量合成短轴为3～4nm、长轴为50～60nm的油酸包覆的针状氢氧化镁纳米粉体,并提出可能的反应机理。用透射电镜、X射线衍射、红外光谱和热重分析等方法进行检测。结果表明:油酸包覆的氢氧化镁纳米粒子结晶度、包覆效果、分散效果、热稳定性能优异,可有效地防止纳米粒子在干燥过程中的团聚现象。     

表面改性剂对聚丙烯/氢氧化镁复合材料燃烧性能和热稳定性及结晶行为的影响

研究了硅油对聚丙烯(PP)/氢氧化镁(MH)复合材料性能的影响。通过极限氧指数(LOI)、热失重分析仪(TGA)、差示扫描量热仪(DSC)和偏光显微镜(POM)对PP及阻燃PP的性能进行了研究。结果表明,阻燃PP比纯PP有较高的残留量,热稳定性得到改善。其LOI达到难燃塑料的要求,有良好的阻燃性。未经改性的MH对PP基体有异相成核作用,使结晶峰温度向高温方向偏移,而硅油削弱填料对PP基体的异相成核作用。POM分析表明,MH粒子在基体中的分散性对PP的晶粒形貌和尺寸起着十分重要的作用。     

Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites

Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (ε) and magnetic permeability (μ) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.     

In-situ polymerization approach for preparation of rare earth fluoride phosphors coated with PAA

Up-conversion nanoparticles (UCNPs), which can convert a radiation from a longer wavelength to a shorter wavelength, have great potential uses as bio-labels in biological detection. However, these NPs usually cannot be used directly unless their surfaces are further modified. In this paper, NaYF4:Yb, Er nanoparticles (NPs) were coated with poly(acrylic acid) (PAA) by in situ polymerization for the first time. Accordingly, NaYF4:Yb, Er/NaYF4 NPs were synthesized before PAA coating to avoid the decay of optical intensity. The resulting UCNPs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and up-conversion photoluminescence spectrometry. The XRD results indicated that the resultant UCNPs exhibited a pure hexagonal phase. The FT-IR spectra and TGA curves revealed that these NPs were coated successfully with PAA. Meanwhile, the TEM results showed that well-dispersed UCNPs with the best morphology and an average size of about 90 nm were obtained with 8.0 wt% acrylic acid content (the content percentage in the whole reaction system) at 0 degrees C within 130 min. Fluorescence tests showed that the UCNPs had a strong UC fluorescence intensity. Settlement tests revealed that PAA-coated NaYF4 UCNPs had more favorable dispersion stability than uncoated UCNPs in an aqueous system. These functionalized nanocomposites could be used for further bio-conjugation.