工艺条件对TPU/CNT体系介电性能的影响

以聚氨酯(TPU)为基体,制备碳纳米管(CNT)含量为0.9％的TPU/CNT复合材料,研究工艺条件对制品的介电性能的影响.分别研究了密炼过程中密炼转速和密炼温度对复合材料介电性能的影响.当密炼温度一定时,随密炼转速增大,密炼时的转矩逐渐增大,从而使基体对填料的剪切应力增大,体系混合得更加均匀,界面增多,界面极化增强,...     

工艺条件对EVA/SCF体系微观形貌及导热性能的影响

以乙烯-醋酸乙烯共聚物(EVA)作为基体树脂,制备短切碳纤维(SCF)含量为10%的EVA/SCF导热复合材料,并对工艺条件进行优化以提升制品的导热性能。分别研究了在密炼过程中,密炼转速和密炼温度对复合材料导热性能的影响。实验结果表明,当密炼转速和密炼温度分别为30 r/min和130℃时,材料的热导率为2.39 W/(m·K)。复合材料内大部分碳纤维的长度较长,在聚合物基体中分布不均,仅能在局部区域形成网络。随着密炼转速的增加,纤维长度逐渐变短,易于在复合材料内的大部分区域形成导热网络。当密炼转速为40 r/min时,制品热导率可达到2.47 W/(m·K)。虽然,继续提升密炼转速能够使碳纤维在聚合物中的分布更加均匀,但由于纤维长度过短不利于导热网络的形成,反而会导致制品热导率下降。经过进一步对密炼温度进行研究发现,在40 r/min的密炼转速下,更高的密炼温度能够有效改善SCF与基体EVA的界面结合效果,使制品的热导率由密炼温度80℃时的1.65 W/(m·K)大幅提升至密炼温度140℃时的2.48 W/(m·K)。     

加工工艺对短切碳纤维/橡胶复合材料性能的影响

采用轿车子午线轮胎胎侧胶配方研究混炼工艺对短切碳纤维/橡胶复合材料性能的影响。结果表明:短切碳纤维使复合材料的硬度和定伸应力提高,拉伸强度、拉断伸长率与撕裂强度降低,压缩生热提高,耐屈挠性能无明显变化;在开炼工艺中,割刀次数多的复合材料压缩生热升高,薄通次数多会破坏复合材料的取向及分散,割刀3次、薄通6次的复合材料综合性能较好;在密炼工艺中,适当提高转子转速,短切碳纤维/橡胶复合材料综合性能较好,延长混炼时间对复合材料的性能没有明显影响,转子转速为100 r·min~(-1),混炼时间为6 min的复合材料综合性能较好。     

低温密炼法制备再生橡胶的影响因素

采用自主研发的新型六棱剪切转子密炼机实现废橡胶在低温条件下的再生,并利用五因子四水平的正交试验考察低温密炼工艺参数对废橡胶再生效果的影响。试验得出的低温密炼法最佳再生工艺参数为:剪切混炼时间12min,转子转速60r·min~(-1),填充因数0. 75～0. 80,压砣压力0. 8 MPa,冷却水温度40℃。在此工艺条件下制得的再生橡胶综合物理性能最佳,再生效果较好。     

密炼工艺对木质素基酚醛树脂纤维性能的影响

木质素具有的酚羟基可以替代苯酚合成木质素热塑性酚醛树脂。使用木质素酚醛树脂为原料制备酚醛树脂纤维,研究了密炼时间、密炼温度、密炼转速对纤维力学性能影响。树脂的密炼时间过长、密炼温度过高、密炼转速过快均会导致树脂搅拌器相互摩擦大量生热,过高的热量使得树脂热解。从而树脂黏度降低,分子量下降,从而影响原丝力学性能。密炼时间15 min、密炼转速45 rad/min、密炼温度135℃为树脂最佳密炼工艺。     

mPE/PE-LD/CB导电复合材料的制备与性能研究

采用在流变仪混炼器中密炼共混的方法制备了茂金属聚乙烯/低密度聚乙烯/炭黑（mPE/PE-LD/CB）导电复合材料,研究了共混温度、转速等工艺因素对mPE/PE-LD/CB复合材料流变性能的影响;并用差示扫描量热仪、扫描电子显微镜对复合材料的结晶性和微观形貌进行分析,同时测试了复合材料的表面电阻、体积电阻和力学性能。结果表明,最佳工艺条件为转速30 r/min、温度180 ℃、共混时间10 min;随着mPE含量的增加,复合材料的结晶度提高、导电性增大,力学性能提高。     

POM/ACR共混物的加工流变性能研究

将聚甲醛(POM)与丙烯酸酯类弹性体(ACR)在转矩流变仪中密炼共混15 min,研究了POM/ACR共混物的加工流变性能。结果表明,随ACR用量的增加,共混物熔体流动速率和最大转矩降低,平衡转矩提高,且塑化时间稍有延长。对于ACR质量分数为16%的共混物,密炼试验表明密炼温度和转速的升高对其平衡转矩、塑化时间及物料温度均有影响,但转速的影响更为突出。在相同的转速下,随着密炼温度的升高,平衡转矩变小、塑化时间缩短而物料温度上升的幅度变大;在同一密炼温度下,随着转速的提高,平衡转矩总体上增大,塑化时间明显变短,物料温度上升的幅度明显变大。转速70~100 r/min、密炼温度175℃是POM/ACR共混物较为合适的加工条件。     

GK190E型密炼机混炼工艺探索

针对新采用的密炼设备GK190E型密炼机进行混炼工艺优化研究,以保证胶料的拉伸强度和断裂伸长率为目标,探讨胶料填充系数β、排胶温度T和转子转速等工艺参数对胶料性能的影响。分别以氯丁橡胶和天然橡胶进行了多方案试制试验,结果表明,对于氯丁橡胶,填充系数0.68～0.7,转子转速30r/min,排胶温度105℃～110℃是较为优选的方案;对于天然橡胶,填充系数和排胶温度范围分别在0.55～0.57、155℃～160℃。     

加工工艺对聚乙烯/乙炔炭黑复合材料中炭黑分散性的影响

采用表面电阻的统计分析、力学性能测试及扫描电镜分析等手段研究了不同工艺方法和工艺条件对聚乙烯/乙炔炭黑复合材料中炭黑分散性的影响。结果表明:与开炼工艺相比,通过密炼工艺制得的试样中炭黑的分散性更好;采用密炼工艺,转速为30 r/min,密炼5 min后出料,裁成小块投入混炼室再密炼5 min,制得的试样中炭黑的分散性最好;高转速、长时间的密炼工艺对炭黑聚集体结构有一定程度的破坏。     

CM/NBR共混胶共混工艺的研究

研究了不同加料顺序及不同工艺参数对CM/NBR共混胶性能的影响。结果表明,先将炭黑、CM和小料制成母炼胶,再将母炼胶与NBR共混可提高炭黑和小料的分散性,制得的共混胶性能较好;采用密炼温度为60℃且转子转速为80r/min的混炼工艺可提高CM/NBR共混胶的共混效果。     

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.