PE-HD复合材料导热性能及力学性能的研究

通过双螺杆挤出机制备了高密度聚乙烯（PE-HD）/石墨/CaCO3增韧母料复合材料,并研究了石墨的表面处理、粒径、含量以及CaCO3增韧母料含量对复合材料导热性能及力学性能的影响。结果表明,偶联剂NDZ201对石墨表面具有较好的处理效果。石墨颗粒直径越小,复合材料的热导率及综合力学性能越高。CaCO3增韧母料能明显提高复合材料的热导率及缺口冲击强度。PE-HD/石墨/增韧母料250B的质量比为45/30/25时,复合材料的热导率可达1.72 W/(m·K),其缺口冲击强度与纯PE-HD相近,拉伸强度和弯曲强度分别比PE-HD提高了52 %和88 %。     

纳米CaCO3填充ABS/PP合金复合物研究

通过熔融共混使纳米CaCO3粒子周围包覆上一层TPE橡胶,制备出纳米CaCO3母料,用其与PP、ABS共混复合制备出ABS/PP合金纳米填料复合物.该复合材料力学性能及熔体流动性能测试结果表明,纳米CaCO3含量在试验用量范围内,ABS纳米CaCO3复合物的拉伸强度随填料含量的增加而增加,当母料含量为17%,母料中纳米CaCO3填料含量为60%左右时有较佳的冲击性能;ABS/PP纳米CaCO3复合物在PP含量9%～10%时有最好的拉伸强度和冲击强度;纳米CaCO3填料含量对复合物的拉伸强度影响不大,随其用量增加对冲击强度有明显的提高;熔体流动性能在PP含量10%左右时达最大,但随填料含量增加而下降.     

PP/POE/CaCO_3复合材料的性能研究

采用熔融共混工艺制备了聚丙烯/聚烯烃弹性体/碳酸钙(PP/POE/CaCO3)复合材料,研究了POE及CaCO3用量对复合材料力学性能、流变性能及热性能的影响。结果表明:随着POE含量的增加,复合材料的冲击强度显著增大,当POE含量为12%时,冲击强度较纯PP增加233%;同时拉伸强度随POE含量的增加缓慢下降。随着CaCO3含量增加,冲击强度先增加后缓慢下降。     

高热导率聚丙烯/石墨复合材料的制备与性能

为了提高聚丙烯(PP)的导热性能,扩大其使用范围,采用价格低廉的商用石墨对PP进行改性,利用转矩流变仪制备了PP/石墨导热复合材料。研究了粒径为2μm和20μm的石墨及其复配对复合材料热导率及力学性能的影响。结果表明,复合材料的热导率随着石墨用量的增加而显著增大,20μm石墨填充的复合材料热导率高于2μm石墨填充的复合材料;由于石墨的各向异性,层内热导率远高于层间热导率;将两种粒径的石墨复配,固定石墨总质量分数为40%,当2μm石墨与20μm石墨质量比为1︰5时,复合材料层间和层内热导率达到最大,分别为1.125 W/(m·K)和2.897 W/(m·K),比相同用量下单一2μm石墨填充PP分别提高了121%和61%,比单一20μm石墨填充PP分别提高了3.6%和20%。随石墨用量增加,单一粒径石墨填充的复合材料拉伸强度和弯曲强度呈现先减小后增大的趋势,随复配填料中20μm石墨用量增加,复配填料填充复合材料的力学性能呈下降趋势,但弯曲强度变化不大,拉伸强度也在10 MPa以上。     

ABS/石墨/NBR导热复合材料性能的研究

采用熔融共混法制备丙烯腈-丁二烯-苯乙烯共聚物(ABS)/石墨/丁腈橡胶(NBR)导热复合材料,通过热常数分析仪、同步热分析仪、扫描电子显微镜、力学性能测试等手段研究了NBR、ABS高胶粉及石墨(G)的添加量对ABS复合材料导热性能及力学性能的影响。结果表明,ABS高胶粉和NBR均能明显提高ABS的热导率和缺口冲击强度,但是丁腈胶粉的改性效果优于高胶粉。以NBR作为ABS复合材料的增韧剂,随着石墨含量的增大,增韧效果下降,ABS复合材料的热导率提高到纯ABS的5倍,热分解温度提高40℃左右,热膨胀系数下降。当ABS/G/NBR复合材料的质量比为60/15/25时,其热导率为纯ABS的2倍,缺口冲击强度达21.8 kJ/m2,明显高于纯ABS(2.6kJ/m2)。     

交联剂和助交联剂对ABS/PP/CaCO3反应性共混的影响

为提高ABS/PP/CaCO3复合材料相容性,采用转矩流变仪观察了ABS/PP/CaCO3三元复合物反应性共混后的扭矩,考察了不同的助交联剂蓖麻油(CO)、异氰脲酸三烯丙酯(TAIC)、松香酯(JS-1)、二甲基丙烯酸乙二醇酯(GD)以及交联剂过氧化二异丙苯(DCP)的用量对共混物的影响.研究结果表明,在交联剂DCP为0.2%(wt)时,助交联剂GD比CO、TAIC、JS-1对ABS/PP/CaCO3体系有更好反应共混效果;反应共混超过2.5 min后,随DCP量增加,复合材料将发生严重的降解.用毛细管流变仪研究了复合材料的流变特性,结果显示用DCP/GD交联体系反应共混的ABS/PP/CaCO3复合材料的剪切黏度,随温度、剪切速率的增加而下降,比较同一剪切速率下的非牛顿指数,说明其流动性能优于纯ABS.力学性能测试数据说明,用DCP/GD交联的ABS/PP/CaCO3复合材料比未交联的有较高的弯曲强度和模量.电镜观察揭示了用DCP/GD动态交联的ABS/PP/CaCO3复合材料有更好的界面相容.     

PP/nano-CaCO_3/POE复合材料性能研究

采用熔融共混法制备了PP/nano-CaCO3/POE复合材料,分别研究了nano-CaCO3和POE的加入量对复合材料力学性能的影响。结果表明:随着nano-CaCO3用量的增加,复合材料的冲击强度和拉伸强度均呈现出先增加后降低的趋势,弯曲模量呈增加趋势;随着POE用量的增加,复合材料的冲击强度先显著增加而后稍有降低,拉伸强度和弯曲模量均呈下降趋势。     

偶联剂NDZ-105用量对PP/CaC03复合材料性能与形态的影响

采用经钛酸酯偶联剂NDZ-105处理的CaCO3与PP在双螺杆挤出机中熔融混合后制备PP/CaCO3复合材料.研究偶联剂NDZ-105用量对PP/CaCO3复合材料力学性能、结晶性能与断面形态的影响.研究结果表明:随着偶联剂NDZ-105用量的增加,PP/CaCO3复合材料的拉伸强度、弯曲强度和结晶温度逐渐下降,而断裂伸长率从65.2%提高到134.5%,冲击强度从6.1 MPa增加到8.8 MPa.     

聚丙烯/碳酸钙复合材料的性能研究

采用反应增容共混法制备聚丙烯(PP)增韧母粒,研究了母料含量、母料中引发剂及马来酸酐(MAH)含量对PP/CaCO3复合体系的力学性能、流变性能及形态结构的影响.结果表明利用反应增容增韧的方法对PP能起到明显的增韧效果.当母料质量含量为10%时,复合体系的冲击强度较纯PP增加了98%.同时保持了体系其它性能的适当水平.     

HDPE/CNTs复合材料的制备及性能研究

以高密度聚乙烯(HDPE)为基体、碳纳米管(CNTs)为导热填料,通过熔融共混法和溶液共混法制备了HDPE/CNTs导热复合材料;研究了CNTs添加量和尺寸对复合材料力学性能、热导率、维卡软化温度和熔体流动速率的影响,并对比了两种制备方法对复合材料力学性能和热导率的影响。结果表明:随着CNTs用量的增加,复合材料的拉伸强度、弯曲强度和热导率均明显提高;直径大的CNTs更有利于复合材料性能的提升;加入10%的CNTs后,复合材料的拉伸强度、弯曲强度和热导率分别提高了33.43%、36.31%和52.59%(测试温度60℃);采用熔融共混法制备的复合材料的性能提高更明显。     

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.