PVC/改性纳米CaCO3复合材料的制备及性能

合成了纳米CaCO3表面改性剂AP-01,将此改性剂改性的纳米CaCO3用于硬质聚氯乙烯(PVC)抗冲改性.观察PVC/改性纳米CaCO3复合材料的微观结构,并测试其力学性能.结果表明:改性纳米CaCO3以海岛结构分散于PVC基体中.改性纳米CaCO3加入量在10%时,复合材料缺口冲击强度达到18.2 kJ/m2,而复合材料拉伸强度几乎没有改变.对比普通硬脂酸改性纳米CaCO3增韧PVC,其具有明显的性能优势.     

高分子包覆纳米CaCO3的制备及其在PS中的应用

用丙烯酸（AA）与苯乙烯（St）及丙烯酸甲酯（MA）与苯乙烯（St）共聚包覆改性纳米CaCO3，通过红外光谱及透射电镜对改性前后纳米CaCO3的结构和微观形貌进行了表征，利用改性后的纳米CaCO3填充聚苯乙烯（PS），测试了PS／纳米CaCO3复合材料的力学性能。结果表明包覆改性后的纳米CaCO3对，PS有增强增韧作用。经MA与St共聚包覆改性的纳米CaCO3比用AA与St共聚改性的纳米粒子更能提高PS／纳米CaCO3复合材料的力学性能，其拉伸强度及无缺口冲击强度分别比纯PS提高14％和21％。     

聚丙烯/水相法改性纳米碳酸钙复合材料的结构与性能

用三官能团的有机改性剂对纳米碳酸钙进行表面改性，填充到聚丙烯中，制得PP／纳米CaCO3复合材料，同时对复合材料的力学性能、微观形态以及热性能进行研究。结果表明：PP／改性纳米CaCO3复合材料的力学性能及热性能都有较大幅度的改善。改性剂与纳米CaCO3形成化学结合，改性纳米CaCO3对PP有异相成核的作用，能诱导口晶型PP的产生，在提高复合材料强度的同时，使韧性明显提高。     

PP/改性纳米CaCO3复合材料力学性能与断裂形态研究

制备了反应性单体改性纳米CaCO3填充PP复合材料，研究了反应性单体丙烯酸(AA)和苯乙烯(St)在有、无过氧化二异丙苯(DCP)存在下改性纳米CaCO3填充PP复合材料的力学性能，并用扫描电子显微镜(SEM)研究了复合材料弯曲断面的形态。结果表明，PP／改性纳米CaCO3的力学性能优于PP／微米CaCO3的力学性能；在DCP存在下，AA、AA与St混合改性可使PP／纳米CaCO3的拉伸性能和弯曲性能提高，减小拉伸强度随CaCO3含量增加而下降的趋势；并可有效提高纳米CaCO3在基体中的分散性和界面粘结性。     

改性纳米CaCO3/PP动态力学性能的研究

熔融制备了反应性单体改性纳米CaCO3/PP复合材料,用DMA研究了反应性单体对纳米CaCO3/PP复合材料动态力学性能的影响.结果表明纳米CaCO3的加入提高了PP的储存模量E′和损耗模量E″,降低了E″的峰温和β转变温度.丙烯酸AA改性有降低复合材料的E′和E″的作用,但不明显影响转变温度.苯乙烯St或与AA混合改性明显提高复合材料的E′和E″,也明显地降低E″的峰温.不管是否对反应性单体改性,纳米CaCO3加入均使PP的β转变温度移向低温.     

HDPE三单体固相接枝物的制备及其对PA6/UHMWPE的改性研究

通过马来酸酐(MAH)、苯乙烯(St)和丙烯酸丁酯(BA)多单体固相接枝法对高密度聚乙烯(HDPE)进行接枝改性,制得了增容剂HDPE-g-(MAH/St/BA)。研究发现,接枝率与反应时间、温度、HDPE/单体比及引发剂(BPO)用量有关;HDPE-g-(MAH/St/BA)对聚酰胺6/超高摩尔质量聚乙烯(PA6/UHMWPE)共混物有很好的增容作用,加入HDPE-g-(MAH/St/BA)后,复合材料的力学性能和摩擦磨损性能得到改善。     

纳米CaCO3的表面改性及其与聚合物基的复合

分析了影响聚合物/纳米粒子复合材料(NC)力学性能提高的原因,认为良好的分散性是材料增强的第一要素,也是制约复合材料力学性能提高的瓶颈。综述了纳米CaCO3粉体的表面处理方法,表面改性剂的种类和改性机理,指出超分散剂的合成和研究理论的现实意义。同时详述了为达到聚合物/纳米CaCO3复合材料的最佳增韧增强效果,针对不同聚合物体系改性剂的选择和复合工艺,及聚合物/纳米CaCO3复合材料的应用前景和发展趋势。     

一种大分子改性剂对纳米SiO2的改性及其在PU中的应用

采用自制的大分子表面改性剂(MAA)m-(BA)n-NCO对纳米SiO2进行表面改性,对改性前后的纳米SiO2进行FTIR、TGA、粒径分析表征.结果表明,大分子改性剂和纳米SiO2的表面发生化学键合,有效地阻止了纳米SiO2的团聚.用改性后的纳米SiO2制备了纳米SiO2/聚氨酯(PU)复合材料,SEM观察到纳米SiO2颗粒在PU中分散良好,XRD检测表明纳米SiO2阻碍了PU分子硬链段有序排列.力学性能检测显示纳米复合材料的力学性能有明显提高,当SiO2的用量为3％时,复合材料的断裂伸长率和拉伸强度均达到最大值,分别为458％和80.4 MPa.     

纳米CaCO_3表面改性及其对PVC复合材料性能的影响

分别采用十八胺、十二胺和正辛胺对纳米CaCO3进行湿法改性,制备了聚氯乙烯(PVC)/纳米CaCO3复合材料,系统研究了不同改性剂改性的纳米CaCO3对PVC基复合材料力学性能的影响。结果表明:3种改性剂均可以与纳米CaCO3表面结合,形成一有机层,阻止了纳米CaCO3团聚,使改性后的粒子可以均匀分散在PVC基体中;十八胺、十二胺和正辛胺改性后的纳米CaCO3均可显著提高PVC复合材料的缺口冲击强度,并且随着改性剂分子链长度的增加,冲击强度也略有提高;改性纳米CaCO3可以略微提高复合材料的弯曲强度,但材料的拉伸强度略有下降。     

苯乙烯-异戊二烯-苯乙烯嵌段共聚物及其接枝马来酸酐增韧聚苯乙烯/纳米碳酸钙复合材料

以过氧化二异丙苯（DCP）为引发剂,通过单螺杆挤出机熔融挤出,制备了苯乙烯-异戊二烯-苯乙烯接枝马来酸酐（SIS—MAH）,研究了SIS及SIS—MAH对聚苯乙烯（Ps）／纳米碳酸钙（nano—CaCO3）复合材料物理、力学性能的影响,对其结构进行了表征。结果表明,MAH的用量宜为SIS质量分数的3％,DCP的用量应小于MAH质量分数的0．3％;当1份nano—CaCO3加入到PS／SIS（质量比100／2）复合材料3中,SIS与nano—CaCO3产生协同增韧效应,复合材料的无缺口冲击强度可提高到9．83kJ／m^2,但其缺口敏感性增大;SIS—MAH较SIS对PS／nano—CaCO3复合材料具有更好的增韧效果,接枝率为3．08％的SIS—MAH改性PS／CaCO3复合材料（质量比100／5／6）的无缺口冲击强度可提高到11．69kJ／m^2;当SIS用量为6份时,SIS改性复合材料不发生弯曲断裂;当SIS—MAH用量为2份时,SIS—MAH改性复合材料不发生弯曲断裂。     

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.     

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.     

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.     

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.