Structural characterization, thermal and mechanical properties of polyurethane/CoAl layered double hydroxide nanocomposites prepared via in situ polymerization

Dodecyl sulfate (DS), one kind of sulfate anion, was intercalated in the interlayer space between CoAl layered double hydroxide (CoAl-LDH) layers, and then polyurethane (PU) based nanocomposites were prepared by in situ intercalation polymerization with different amounts of the organo-modified CoAl-LDH. An exfoliated dispersion of CoAl-LDH layers in PU matrix was verified by the disappearance of the (0 0 3) reflection of the XRD results when the LDH loading was less than 2.0 wt%. Tensile testing indicated that excellent mechanical properties of PU/LDH nanocomposites were achieved. The weak alkaline catalysis of DS to polyurethane chains, combined with the dehydration and structural degradation of the LDH below 300 °C, accounted for the process of proceeded degradation as shown in TGA results. The real-time FTIR revealed that the as-prepared nanocomposites had a slower thermo-oxidative rate than neat PU from 160 °C to 340 °C, probably due to the barrier effect of LDH layers. These results suggested potential applications of CoAl-LDH as a promising flame retardant in PUs.     

熔融插层制备聚苯乙烯/蛭石纳米复合材料的结构与性能研究

通过熔融插层法制备了聚苯乙烯(PS)/蛭石纳米复合材料,测试了复合材料的力学性能、燃烧性能和熔体流动速率,并对不同蛭石含量的PS/蛭石纳米复合材料进行了对比。结果表明,当蛭石含量为3%时,与纯PS相比,熔体流动速率只降低了4%,即仍具有良好的加工性能,同时拉伸强度、断裂伸长率和缺口冲击强度分别提高了3.4%、77%和41%。氧指数测试结果表明,蛭石的加入有利于提高材料的阻燃性能。     

聚丙烯/水滑石纳米复合材料的热稳定性

采用未改性水滑石(LDH1)、十二烷基磺酸钠改性水滑石(LDH2)和十二烷基磺酸钠/衣康酸协同改性水滑石(LDH3),通过熔融插层法制备得到了PP/LDH1、PP/LDH2、PP/LDH3三种聚丙烯/水滑石纳米复合材料。用热重分析和燃烧试验法,分析表征了水滑石、PP/LDH1、PP/LDH2、PP/LDH3三种纳米复合材料的热稳定性及空气中的燃烧性能;透射电镜(TEM)分析观察了水滑石在聚丙烯基体中的分散、分布及其形貌。结果表明:LDH3上的羟基起始分解温度最高;不管在有氧条件下还是无氧条件下,LDH3对提高聚丙烯热稳定性效果最好,与聚丙烯基体相容性也好,在基体中分散更为均匀。     

聚马来酸/LDH插层型纳米复合材料的制备与表征

采用离子交换法将马来酸单体插入Mg/Al-Cl-LDH层间,然后通过热或氧化还原引发层间单体链式原位缩聚制备聚马来酸/水滑石(LDH)插层型纳米复合材料。研究了插层组装的条件和引发聚合的方法。采用X射线衍射(XRD)、红外光谱(FT-IR)、热重及差热分析(TG-DTA)和扫描电子显微镜(SEM)等手段对样品进行了表征与测试。结果表明,马来酸插层LDH使层间距由0.767 nm增大至1.19 nm,H2O2引发剂或热引发聚合使层间距由1.19 nm分别减小至1.114 nm和1.085 nm,产物粒径为50 nm~100 nm。聚马来酸分子进入LDH层间形成超分子结构,使其热稳定性提高100℃以上。     

Removal of bacteria and viruses from waters using layered double hydroxide nanocomposites

We have identified synthetic layered double hydroxides (LDH) nanocomposites as an effective group of material for removing bacteria and viruses from water. In this study, LDH nanocomposites were synthesized and tested for removing biological contaminants. LDH was used to remove MS2 and øX174 (indicator viruses), and Escherichia coli (an indicator bacterium) from synthetic groundwater and to remove mixed communities of heterotrophic bacteria from raw river water. Our results indicate that LDH composed of magnesium–aluminium or zinc–aluminium has a viral and bacterial adsorption efficiency ≥99% at viral concentrations between 5.9 × 10⁶ and 9.1 × 10⁶ plaque forming units (pfu)/L and bacterial concentrations between 1.6 × 10¹⁰ and 2.6 × 10¹⁰ colony forming units (cfu)/L when exposed to LDH in a slurry suspension system. Adsorption densities of viruses and bacteria to LDH in suspension ranged from 1.4 10¹⁰ to 2.1 10¹⁰ pfu/kg LDH and 3.2 × 10¹³–5.2 × 10¹³ cfu/kg LDH, respectively. We also tested the efficiency of LDH in removing heterotrophic bacteria from raw river water. While removal efficiencies were still high (87–99%), the adsorption capacities of the two kinds of LDH were 4–5 orders of magnitude lower than when exposed to synthetic groundwater, depending on if the LDH was in suspension or a packed column, respectively.     

Preparation and properties of nitrile rubber/montmorillonite nanocomposites via latex blending

The nitrile rubber (NBR)/unmodified montmorillonite (Na-MMT) clay nanocomposites were prepared by latex blending method followed by melt mixing of compounding ingredients by using two-roll mill. The X-ray diffraction (XRD) studies showed an increase in the basal spacing and broadening of peak corresponding to crystal structure of Na-MMT indicating the formation of intercalated/exfoliated clay layers in the NBR matrix. Increase in clay content of nanocomposite increased the XRD peak height due to the formation of many of clay tactoids at higher loading. The transmission electron microscopy (TEM) strengthened the XRD finding by showing the presence of intercalated/exfoliated morphology of clay platelets having good dispersion. The modulus and tensile properties of the nanocomposites were improved with addition of Na-MMT which is proportional to clay concentration. The retention of tensile properties of aged nanocomposites, with all clay concentration, was superior to either pure NBR and carbon black filled NBR composite. The dynamic mechanical analysis showed proportional increase in storage modulus analogous to Na-MMT loading at all the temperature ranges due to the confinement of polymer chains between the clay layers. Nanocomposites with different proportions of clay showed a decrease in tan δ_max peak height with a shift towards higher temperature indicating the reduction in the segmental mobility of polymer chain. A linear model was proposed to correlate the influence of Na-MMT content on storage modulus of nanocomposites. Differential scanning calorimetry indicated a linear increase in glass transition of nanocomposites which is proportional to clay loading. Thermogravimetric analysis revealed a small improvement in the thermal stability of nitrile rubber/clay nanocomposites.     

Exfoliated poly(methyl methacrylate)/MgFe-layered double hydroxide nanocomposites with small inorganic loading and enhanced properties

The novel exfoliated polymer nanocomposites (PMMA/MgFe(DS)-LDH) were synthesized by in situ polymerization based on poly(methyl methacrylate) (PMMA) and dodecyl sulfate-intercalated MgFe-layered double hydroxide (MgFe(DS)-LDH). The participation of Fe³⁺ ion is found to play an important role in the improvement of thermal stability of nanocomposites with small inorganic loading and well-dispersed inorganic components. The thermal degradation mechanism was discussed.     

Preparation and mechanical properties of exfoliated CoAl layered double hydroxide (LDH)/polyamide 6 nanocomposites by in situ polymerization

Novel exfoliated nanocomposites based on polyamide 6 (PA6)/CoAl layered double hydroxide (CoAl-LDH) have been successfully prepared via in situ polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that the inorganic nanoplatelets of CoAl-LDH were homogeneously dispersed in the PA6 matrix. Mechanical testing (by tensile tests and nanoindentation measurements) shows that, compared with neat PA6, the tensile modulus, the yield strength, and the hardness of the nanocomposites are substantially improved by about 100%, 75%, and 25%, respectively, with incorporating only 1 wt% CoAl-LDH. In addition, tensile fracture morphologies of neat PA6 and its nanocomposites are also compared and discussed.     

多壁碳纳米管/尼龙6复合材料的液相共混法制备及其性能

通过液相共混法制备了多壁碳纳米管/尼龙6(MWCNTs/PA6)复合材料, 研究了不同MWCNTs改性方法及添加量对复合材料热性能和结晶性能的影响。利用场发射扫描电子显微镜(FESEM)、FTIR、DSC、XRD 和 TG对MWCNTs/PA6复合材料进行表征。结果表明: MWCNTs的加入提高了PA6的热稳定性, 且胺功能化的MWCNTs(d-MWCNTs)表现尤为明显; 当d-MWCNTs的质量分数为7.5%时, MWCNTs/PA6复合材料结晶度从48.09%提高到56.62%, 聚合物大分子之间的缠绕度最低。     

POSS/PS复合材料的制备及其热性能

单官能团3-氯丙基笼形倍半硅氧烷(POSS)与官能化的聚苯乙烯(PS)进行缩合反应,得到POSS/PS复合材料,其热性能得到明显改善。单官能团3-氯丙基POSS由顶端封角法制备;PS经过3步处理以引入醇钠基团：Friedel-Crafts酰基化反应将羰基引入到PS的苯基上,羰基被硼氢化钠还原为羟基,金属钠与羟基反应生成醇钠基团;单官能团3-氯丙基 POSS分子上的C—Cl与PS上的醇钠基团缩合从而制备POSS接枝的POSS/PS复合材料。利用1H NMR和FTIR技术表征中间产物和POSS/PS复合材料,结果表明POSS笼上的C—Cl与官能化后PS链上的醇钠官能团之间的缩合反应效率很高。XRD测试表明POSS具有良好的分散性。TGA、DSC分析结果表明,由于POSS的引入,POSS/PS复合材料比纯PS的初始分解温度提高69℃,玻璃化转变温度提高16℃。     

Investigation of in situ prepared polypropylene/clay nanocomposites properties and comparing to melt blending method

The morphological, physical and mechanical properties of polypropylene/clay nanocomposites (PPCNs) were prepared by in situ polymerization are investigated. Non-modified scmectite type clay (e.g. bentonite) was used to prepare bi-supported Ziegler–Natta catalyst of TiCl₄/Mg(OEt)₂/clay. Exfoliated PPCNs were obtained by in situ intercalative polymerization of propylene using produced bi-supported catalyst. X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) micrograph were used to assess the clay morphology and dispersion of clay. The crystalline structures of PPCNs were characterized by differential scanning calorimetry (DSC). The mechanical properties of PPCNs were studied by tensile and impact tests. thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis DMTA were used to characterize the thermal and dynamic mechanical properties, respectively. The thermo-mechanical properties of prepared nanocomposites were considerably improved by introducing small amount of clay, which indicated that the clay most be significantly intercalated or exfoliated in the prepared nanocomposite preparation process. In addition, morphology and some of the mechanical and thermal properties of in situ PPCNs were compared with those of PPCNs prepared by melt blending method in this study and some presented reported results in literatures.     

Synthesis and luminescence properties of YVO4:Eu cobblestone - like microcrystalline phosphors obtained from the mixed solvent - thermal method

The mixed solvent-thermal method has been developed for the synthesis of YVO₄:Eu³⁺ luminescent materials in the N, N-dimethylformamide (DMF)/ de-ionized water (DIW) solution. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electronic microscope (TEM), UV/vis absorption and photoluminescence spectroscopies. The results demonstrate that we have obtained the uniform YVO₄:Eu³⁺ cobblestone - like microcrystalline phosphors in the mixed solution of DMF and DIW, which are different to the as-obtained YVO₄:Eu³⁺ nanoparticles in pure DIW. And the as - prepared YVO₄:Eu³⁺ microcrystalline particles are composed of numerous nanoparticles. The assembling phenomenon of the nanoparticles is strongly affected by the pH value of the solution and the volume ratio of DMF/DIW. Under UV excitation, the samples can emit the bright red light. While, the photoluminescence (PL) intensities of YVO₄:Eu³⁺ show some difference for samples obtained under the different reaction conditions. This is because that different microstructures of samples result in different combinative abilities between the surface and the adsorbed species so as to produce the different quenching abilities to the emission from Eu³⁺ ions.     

海藻酸钙/纳米氢氧化铝纤维的制备与性能研究

用湿法纺丝工艺制备出海藻酸钙纤维和纳米氢氧化铝/海藻酸钙复合纤维.用场发射扫描电镜和红外光谱仪表征了两种纤维的表观形态和微观机制,用热重分析仪测试了两种纤维的热稳定性能.研究表明,纳米氢氧化铝已较好地分散到纤维中,且纳米氢氧化铝与海藻酸钙分子之间产生了新的键合作用.TG和DTG测试结果表明,复合纤维的热稳定性要优于海藻...     

Dispersion,thermal and mechanical properties of polypropylene/magnesium hydroxide nanocomposites compatibilized by SEBS-g-MA

Isotactic polypropylene (PP)/nano-magnesium hydroxide (nano-MH) composites with 10 wt.% maleic anhydride grafted styrene–ethylene-butylene–styrene tri-block copolymer (SEBS-g-MA) as a compatilizer were prepared by melt extrusion compounding and injection molding. The effects of SEBS-g-MA on dispersion of nano-MHs in PP matrix and interfacial adhesion were studied in order to prepare highly filled PP/MH nanocomposites. The results showed that SEBS-g-MA improved both dispersion of nano-MHs and interfacial adhesion in PP/MH nanocomposites with up to 40 wt.% nano-MHs. The elastic moduli of PP/SEBS-g-MA /MH nanocomposites increased marginally and tensile yield strengths were almost invariant with nano-MH loading. Significant impact toughening of these ternary nanocomposites was, however, achieved due to the cavitation of SEBS-g-MA/MH particles and expansion of voids as well as plastic deformation of the PP matrix.     

Syndiotactic polystyrene/multi-walled carbon nanotube nanocomposites: Polymorphism,thermal properties,electrical conductivity,and rheological properties

Syndiotactic polystyrene (sPS)/multi-walled carbon nanotube (MWNT) nanocomposites were prepared using a melt mixing technique. SEM images demonstrated the fine dispersion of MWNTs through the sPS matrix. DSC results illustrated that the MWNTs facilitated the nucleation of sPS (up to ca. 12.2 °C increase), but retarded the subsequent crystals growth. Based on the Avrami analysis, the dimension of sPS crystals growth in the composites decreased because of the effects of extensive nucleation and the formation of a nanoconfined/constrained environment from the MWNTs. XRD data confirmed that the presence of MWNTs facilitated the formation of β-form sPS crystals. The thermal stability of sPS improved to approximately 31 °C at 3 phr of MWNT loading. A rheological percolation threshold between an MWNT loading of 0.5 and 1 phr was determined by measuring the rheological properties of the samples. The incorporation of MWNTs reduced the electrical resistivity of sPS by 10 orders of magnitude.     

碳纳米管/聚苯乙烯复合材料的制备及导电性能研究

用溶液共混的方法将碳纳米管(CNTs)分散在聚乳酸聚己酸内酯(PLLA-PCL)嵌段共聚物中,再采用熔融共混的方法,制备了CNTs/PLLA-PCL/PS复合材料.扫描电镜和高分辨率光学显微镜观察发现,CNTs能够较均匀地分散在PLLA-PCL.电导率的测定表明,CNTs的加入大幅度提高了聚苯乙烯的导电性能,与CNTs//PS复合材料相比,PLLA-PCL的加入对更加有效地分散CNTs.     

氧化石墨烯/密胺树脂复合材料的制备及其热性能研究

首先采用Hummers法制备出氧化石墨烯(GO),然后与三聚氰胺、甲醛进行原位聚合,制备出GO/密胺树脂(MF)复合材料,并用傅里叶红外光谱仪(FT-IR)、原子力显微镜(AFM)、扫描电镜(SEM)分析和观察了氧化石墨烯及复合材料的分子结构及形貌,通过导热系数测试仪、热重分析仪(TG)对复合材料的热性能进行了表征。研究发现,随着氧化石墨烯(GO)添加量的增加,复合材料导热系数增加先快后慢,当GO添加量为0.84%时,复合材料导热系数提高32.0%,GO的添加提高复合材料低温下的热稳定性。     

An intercalated hybrid of polyacrylamide/layered double hydroxide prepared via in situ intercalative polymerization

A new intercalated hybrid of polyacrylamide (PAM)/layered double hydroxide (LDH) prepared via in situ intercalative polymerization procedure is reported. LDH with counterion ion of nitrate or dodecyl sulfate anion was employed for comparison. The obtained PAM/LDH hybrid was characterized by X-ray diffraction, infrared spectra, differential scanning microcalorimetry and X-ray photoelectron spectrum. The results reveal that the LDH modified with dodecyl sulfate anion can be used to obtain an intercalated hybrid, whereas PAM polymer chains can not enter the interlayer space of LDH with nitrate anion as counterion ion.     

聚苯乙烯/CeO2纳米复合微球的粒径及其影响因素

采用原位悬浮聚合法制备了聚苯乙烯/CeO2纳米复合微球。讨论了引发剂浓度、CeO2纳米粒子含量、分散剂聚乙烯醇浓度及复配分散剂等对纳米复合微球粒径及其分布的影响。结果表明,随着引发剂浓度和CeO2纳米粒子含量的增加,纳米复合微球粒径变小,粒径分布变窄;随着复配分散剂中聚甲基丙烯酸钠含量的增加,粒子粒径变小,粒径分别变窄。制得的聚苯乙烯/CeO2纳米复合微球粒径可控。     

功能化纳米氧化石墨烯/POE-g-MAH/聚苯乙烯复合材料的制备与性能

利用硅烷偶联剂(APTES)对氧化石墨烯(GO)进行功能化改性, 在不同的试验条件下制备了3种硅烷偶联剂功能化GO(APTES-g-GO)纳米填料, 并经熔融共混制备了APTES-g-GO填充改性的聚苯乙烯(PS)复合材料。为了改善复合材料的界面作用, 采用马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)为增容剂。分别采用FTIR、XRD、TG、SEM以及拉伸和冲击测试对填料和纳米APTES-g-GO/POE-g-MAH/PS复合材料的结构和性能进行了表征和测试。结果表明:APTES已成功接枝于GO的表面上。接枝过程中, APTES对GO有一定的剥离和还原作用。随着填料含量的增加, 纳米APTES-g-GO/POE-g-MAH/PS复合材料拉伸强度和冲击强度均先上升后下降。当填料与基体质量比为0.75%时, 3种复合材料的拉伸强度和冲击强度都达到最大值, 其中纳米AS-GO/POE-g-MAH/PS复合材料的综合性能最好, 其拉伸强度和冲击强度比POE-g-MAH/PS分别提高了19%和 31%。共混过程中, APTES-g-GO与POE-g-MAH之间的反应改善了纳米APTES-g-GO/POE-g-MAH/PS复合材料的界面相互作用。APTES-g-GO均匀分散于复合材料中, 它的加入提高了复合材料的热稳定性能。添加AS-GO填料的复合材料热稳定性能提高最为明显, 含0.75% AS-GO的纳米AS-GO/POE-g-MAH/PS复合材料的最大失重温度比POE-g-MAH/PS提高了7 ℃。