原位增容PA6/POE/EVOH共混物的流变性能研究

采用熔融共混法制备了聚酰胺6/乙烯-1-辛烯共聚物/乙烯-乙烯醇共聚物(PA6/POE/EVOH)共混物,利用毛细管流变仪对共混物的流变行为进行了研究。结果表明:PA6/POE/EVOH共混物为假塑性流体,呈现出切力变稀的现象;EVOH的加入增大了PA6/POE/EVOH共混物的表观黏度和黏流活化能,说明共混物对温度的依赖性较强。     

PA6/PBT合金的制备与性能

将乙烯–辛烯共聚物接枝马来酸酐(POE-g-MAH)和乙烯–辛烯共聚物接枝甲基丙烯酸缩水甘油酯(POEg-GMA)复配作为增容剂,采用熔融共混的方法制备尼龙(PA)6/聚对苯二甲酸丁二酯(PBT)合金。通过扫描电子显微镜、力学性能和吸湿性研究了PA6/PBT配比和增容剂用量对合金性能的影响。研究表明,增容剂的加入能改善PA6/PBT合金的相容性,PBT和增容剂的加入能有效地抑制PA6的吸水率。添加15份增容剂可使合金的缺口冲击强度达到15.5 k J/m~2,相比未加入增容剂提高385.9%。     

聚烯烃弹性体对剑麻纤维增强聚丙烯复合材料性能的影响

为提高剑麻(SF)增强聚丙烯(PP)复合材料的韧性,分别采取乙烯-辛烯共聚物(POE)和马来酸酐接枝POE(POE-g-MAH)二种弹性体对其进行增韧改性;研究了弹性体和纤维用量的变化对SF/PP/弹性体三元复合体系力学性能的影响及其内在原因。结果表明:POE和POE-g-MAH对剑麻增强聚丙烯复合材料均有良好的增韧效果;仅从增韧效果而言,在弹性体用量较低阶段POE优于POE-g-MAH,但当弹性体增至30%以后,POE-g-MAH则好于POE;在拉伸强度、拉伸模量、弯曲强度及弯曲模量方面,POE-g-MAH均比POE效果更好。     

POE-g-MAH反应性增容HDPE/PA66共混合金性能研究

以乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)作为高密度聚乙烯(HDPE)/尼龙66(PA66)共混合金的反应性增容剂,采用熔融挤出法制备了HDPE/PA66/POE-g-MAH共混合金。研究了POE-g-MAH用量对共混合金形态结构、力学性能、流变性能和热致形状记忆性能的影响。结果表明:通过POE-g-MAH的反应性增容作用,改善了HDPE/PA66合金的界面黏结,促进了分散相粒子的细化,显著提高了合金的力学和热致形状记忆性能,并缩短了塑化时间。     

DB-AO对POE/POE-g-MAH复合材料性能的影响

采用熔融共混方法制备乙烯-辛烯共聚物(POE)/马来酸酐接枝POE(POE-g-MAH)/十溴二苯醚-三氧化二锑(DB-AO)复合材料,研究DB-AO对POE/POE-g-MAH复合材料性能的影响。结果表明:DB-AO延缓基体的分解,复合材料表观热稳定性降低;DB-AO质量分数为15%时,复合材料阻燃级别达到FV-0级;随着DB-AO含量的增加,复合材料的热释放速率和质量损失速率有不同程度的下降;合适的DB-AO加入量有利于复合材料力学性能的提高。     

PP/M-HOS/POE三元复合材料的界面改性与力学性能

采用马来酸酐接枝聚丙烯(PP-g-MAH)及马来酸酐接枝乙烯-1-辛烯共聚物(POE-g-MAH)为界面相容剂，利用熔融共混法制备PP／镁盐晶须(M—HOS)／POE三元复合材料，研究了PP-g-MAH及POE-g-MAH的用量及配比、M-HOS和POE的用量对三元复合材料力学性能的影响。结果表明：当PP／M-HOS／POE的质量比为100／10／20时，PP-g-MAH的最佳用量为3份；利用PP-g-MAH及POE-g-MAH作为复合相容剂可同时改善M-HOS与PP和POE的界面相容性，促进POE、M-HOS对PP的增韧补强作用，使三元复合材料的力学性能得到了明显的改善。     

PA6／POE-g-MAH体系的结构与性能研究

以动态硫化及非动态硫化方法制备了马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)增韧的聚酰胺6(PA6) 共混物,研究了PA6／POE-g-MAH体系的力学性能以及POE-g-MAH在PA6中的分散状况。结果表明动态硫化 PA6／POE-g-MAH共混物的屈服强度、冲击强度、断裂伸长率及弯曲模量均高于非动态硫化方法制备的PA6／POE-g- MAH共混物,动态硫化的PA6／POE-g-MAH共混物可以在材料的刚性与韧性之间达到良好的平衡。扫描电子显微镜图像的统计分析表明,非动态硫化PA6／POE-g-MAH共混物中分散的橡胶相数均颗粒尺寸随组成中POE-g-MAH 的含量增大而不断增大,动态硫化的PA6／POE-g-MAH共混物中分散的橡胶相数均颗粒尺寸随POE-g-MAH含量的增大变化不大。     

投料方式对动态硫化POE／PP性能影响

采用动态硫化法制备了POE/PP(乙烯-辛烯共聚物/聚丙烯)共混型热塑性弹性体,考察了不同投料方式对POE/PP体系的加工流变性、力学性能、交联程度等的影响.结果表明,优化投料顺序能有效抑制PP的降解作用,使体系性能得到改善,投料方式对POE/PP体系的相容性影响显著.当POE相尺寸较小且分布均匀时,体系的力学性能提高.     

PA66/POE/POE-g-MAH的分散相形态与力学性能研究

以(乙烯/辛烯)共聚物(POE)和马来酸酐接枝POE(POE-g-MAH)并用,制备了尼龙(PA)66/POE/POE-g-MAH合金,研究了POE-g-MAH用量对合金形态结构、力学性能的影响.结果表明,随着POE-g-MAH含量的增加,PA66/POE/POE-g-MAH合金的形态结构得到明显改善,弹性体分散相粒径细化且分布均匀,冲击强度显著提高;分散相粒径越小,粒径分布越均匀,POE-g-MAH较好增韧PA66的粒径范围是0.1～0.3μm;弹性体含量一定时,合金的缺口冲击强度随弹性体的细化而增大,但拉伸屈服强度和拉伸弹性模量不受影响.     

PA6/CaCO3/POE-g-MAH分散相态与性能研究

分别使用超细碳酸钙(ufCaCO3)和纳米碳酸钙(nano-CaCO3)与尼龙6(PA6)熔融共混后,再与马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)熔融共混,制备了不同碳酸钙含量的PA6/CaCO3/POE-g-MAH复合材料,通过扫描电子显微镜(SEM)观察其分散相态的变化,并测试了材料的力学性能.结果表明:在PA6/ufCaCO3/POEg-MAH复合材料中,当ufCaCO3含量较少时(PA6/CaCO3/POE-g-MAH质量比为99/1/25和95/5/23.8),碳酸钙粒子全部存在于弹性体相中;在PA6/nano-CaCO3/POE-g-MAH复合材料中,在nano-CaCO3含量很少时(PA6/nano-CaCO3/POE-g-MAH质量比为99/1/25),碳酸钙粒子才全部存在于弹性体相中;当nano-CaCO3含量增加后,碳酸钙粒子同时存在于弹性体相和基体相中;无论ufCaCO3还是nano-CaCO3,当其进入到弹性体相中都降低复合材料的弹性模量,当其分散于基体相中则提高复合材料的弹性模量;随着碳酸钙的增加,复合材料发生脆-韧转变所需的弹性体量增加;在脆-韧转变区后,碳酸钙和POE-g-MAH对PA6的增韧有显著的协同作用,其因为可能是碳酸钙粒子进入弹性体相所形成的壳-核结构中的填料粒子"滚珠"作用使断裂应变增加.     

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.