有机改性蒙脱土／木粉／PVC复合材料的阻燃性研究

将有机改性蒙脱土（OMMT）加入PVC木塑体系，制备了有机蒙脱土／木粉／聚氯乙烯（OMMT／WF／PVC）纳米复合材料。采用锥形扫描量热测试法研究了OMMT用量对WF／PVC复合材料阻燃性能的影响。结果表明，添加OMMT可明显降低木塑的初始热失重率，但使快速热分解的开始时间提前，大大提高样品的燃烧残余率，显著延迟木塑的点燃时间和燃烧热峰值产生时间，OMMT起到了有效的阻燃作用。OMMT的加入还降低了总燃烧热，但燃烧热峰值有所增加，并使发烟量有所增加，CO和CO2产率也随之提高，增加了木塑燃烧的烟气危害性。     

熔融插层法制备聚乳酸/有机蒙脱土纳米复合材料及其性能研究

以新疆地产蒙脱土和聚乳酸为原料,通过熔融插层的方法制备了聚乳酸(PLA)/有机蒙脱土（OMMT）纳米复合材料。分别采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、热重分析仪等对复合材料的微观结构、形貌及热稳定性进行了表征和分析。研究表明,PLA大分子链已经插入OMMT片层间,层间距明显增大,形成PLA/OMMT纳米复合材料,体系的相容性良好。PLA/OMMT纳米复合材料的热失重曲线移向高温端,其热分解温度提高。PLA/OMMT纳米复合材料的熔点、维卡软化点、冲击强度、拉伸强度、热稳定性均比PLA基体有明显的提高。PLA/OMMT纳米复合材料的降解性初步研究表明其是一种良好的生物可降解环保塑料。     

CPE对PVC/木粉复合材料动态力学性能及耐热性能的影响

为了增强聚氯乙烯(PVC)基木塑复合材料的动态力学性能,加入氯化聚乙烯(CPE)对复合材料进行改性,并探究CPE对PVC基木塑复合材料性能的影响。采用动态力学分析仪(DMA)和维卡软化温度测试仪,对加入CPE的PVC/木粉复合材料进行测试,分析CPE对PVC/木粉复合材料动态力学性能及耐热性能的影响。结果表明:CPE的加入会对PVC/木粉复合材料的动态力学性能产生重要的影响,且CPE含量约为5份时,复合材料的动态力学性能最佳;但维卡软化温度、热变形温度测试结果显示,CPE的加入降低了PVC/木粉复合材料的耐热性,且随着CPE含量的增加,复合材料的耐热性逐渐减弱。     

聚丙烯/蒙脱土复合材料的热重分析

利用热重分析技术对聚丙烯和含4%蒙脱土的聚丙烯蒙脱土(PP/OMMT)复合材料的热分解行为进行了研究。运用Qzawa法计算了PP和PP/OMMT复合材料的热分解动力学参数,并用Coats-Redfem法研究了热分解动力学机理。结果表明,PP和PP/OMMT复合材料的热分解一步完成;OMMT的加人,使得PP的初始失重温度较高;失重22%以前,复合材料的活化能大于纯PP,失重率大于22%后,复合材料的活化能低于PP。失重率在30%一80%时,PP和PP/OMMT热分解反应的机理函数分别为Valensi方程(n=1/2)和Mampel Po~法则,对应机理为二维扩散和幂函数法则。     

相容剂对UHMW-PE/OMMT复合材料耐热性的影响

在填料有机纳米蒙脱土(OMMT)含量不变的条件下,采用挤出成型的方式,制备了UHMW-PE/OMMT复合材料。分析了不同含量的马来酸酐接枝聚乙烯(HDPE-g-MAH)作为相容剂对复合材料耐热性的影响,并通过多元共聚反应型SW600相容剂和偶联剂KH560处理填料,分析了其对复合材料耐热性的影响。实验结果表明,在OMMT添加量一定的条件下,随着HDPE-g-MAH含量的增加,复合材料的热变形温度、维卡软化温度均呈先增大后减小的趋势,当HDPE-g-MAH含量达到3%时,复合材料的热变形温度与维卡软化温度达到最大,分别为133.1℃与135.2℃。使用SW600相容剂或偶联剂KH560处理填料虽然也能够提高复合材料的热变形温度与维卡软化温度。但是,HDPEg-MAH作为相容剂,能够有效提升复合材料的耐热性。     

PVC／OMMT／WF纳米复合材料性能研究

对蒙脱土进行有机改性制得有机蒙脱土（OMMT），并制备了聚氯乙烯侑机蒙脱土／木粉（PVC／OMMT／WF）纳米复合材料。采用硅烷偶联剂对木粉表面进行改性，有效提高了聚氯乙烯／木粉（PVC／WF）复合材料的力学性能，其中加入1．5％（质量含量，下同）硅烷偶联剂可使复合材料的冲击强度和拉伸强度分别提高14．8％和18．5％。研究了OMMT的加入对木粉改性前后的PVC／WF复合材料力学性能、耐热性能及阻燃性能的影响，结果表明，木粉未经改性时，OMMT加入无助于PVC／OMMT／WF复合材料力学性能的提高；木粉用硅烷偶联剂改性后，添加少量的OMMT，可使PVC／OMMT／WF复合材料的冲击强度和拉伸强度明显提高。研究表明，添加OMMT可显著延迟复合材料的点燃时间，燃烧残余率也明显增加，OMMT是PVC／WF复合材料的高效阻燃剂。     

环氧树脂/环氧液晶/蒙脱土纳米复合材料研究

采用液晶环氧预聚物(PHQEP)与有机蒙脱土(OMMT)共混改性环氧树脂制备三元共混体系的环氧基复合材料。用X射线衍射法(XRD)测试了有机化蒙脱土在被插层前后片层间距的变化,通过DSC、TGA及SEM等对PHQEP/OMMT增韧改性环氧树脂固化体系的力学性能,热性能及微观相态结构进行了研究。结果表明:当PHQEP质量分数为5%,添加1.5%的有机蒙脱土可以使环氧树脂的冲击强度达到最大值23.43 kJ/m2,比纯环氧树脂提高2倍左右,玻璃化转变温度及5%热分解温度比纯环氧树脂分别高出15℃和27℃。PHQEP与OMMT的加入使纳米复合材料的力学性能和热性能得到明显提高。     

聚氯乙烯/蒙脱土纳米复合材料性能的研究

利用低聚有机蒙脱土(OMMT)与聚氯乙烯(PVC)基质通过熔融共混法制备(PVC/OMMT)纳米复合材料。通过X射线衍射(XRD)、透射电子显微镜(TEM)表征了两种复合材料的微观结构和形貌,通过热重分析测试和热变形温度测试探讨了材料的热性能,并对材料的力学性能进行了测试和讨论。结果表明:PVC分子链段插入了OMMT层间;在OMMT质量分数为0.5%时,耐热性提高了7℃;热变形温度提高了约3℃;拉伸强度增加了9.9%;断裂伸长率提高了17.0%。     

聚丙烯/蒙脱土纳米复合材料的制备与性能

合成了TiCl4/MgCl2/MMT插层催化剂,通过原位聚合制备了聚丙烯/蒙脱土纳米复合材料。X射线衍射结果表明:蒙脱土在聚丙烯基质中达到了纳米级分散。与纯聚丙烯(PP5004)相比,聚丙烯/蒙脱土纳米复合材料的力学性能、维卡软化点、热变形温度以及热分解温度都有所提高。     

MAH/MMA共接枝PEW/有机蒙脱土复合材料的制备与耐热性研究

用熔融接枝法对有机蒙脱土(OMMT)/聚乙烯蜡(PEW)进行马来酸酐(MAH)、甲基丙烯酸甲酯(MMA)双单体共接枝改性,考察了MAH含量、MMA含量、OMMT含量等因素对PEW的接枝率的影响.结果表明:当MAH、MMA、OMMT质量含量分别为5%、3%、10%时,得到PEW的接枝率为3.5%左右.热重分析(TGA)、差示扫描量热(DSC)的结果表明改性PEW/有机蒙脱土复合材料的熔融温度和热分解温度比PEW分别高7.7℃和23.4℃,热重与红外联用(TGA-FTIR)分析表明在183.24℃时,改性PEW/有机蒙脱土复合材料开始分解.制得的改性PEW/有机蒙脱土复合材料具有较好的耐黄变性能,在220℃下挤出加工不变色.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Sintering of Si3N4-Y2O3-Al2O3

Sintering kinetics of the system Si₃N4-Y2O₃-Al₂O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si₃N₄ were studied with additions of 4 to 17 wt% Y₂O₃ and 4 wt% A1₂O₃. Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si₃N₄ and glass or β '-Si₃N₄, α '-Si₃N₄, and glass. The compositions and amounts of the residual glassy phases are estimated.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.