滑石粉-玻纤协同增强尼龙复合材料

采用熔融共混法制备了玻纤(GF)/尼龙6(PA6)复合材料,考察了GF含量对GF/PA6复合材料力学性能的影响。实验结果表明,在玻纤含量较低时,拉伸强度、弯曲强度和冲击强度伴随着玻纤含量的增加而提高。当GF质量分数为30%时,复合材料的力学性能和熔体流动速率处于最佳平衡状态。在GF增强的基础上,采用滑石粉(Talc)与GF复合增强体系,制备了系列增强尼龙复合材料。考察了Talc含量对PA6/Talc/GF复合材料力学性能的影响,Talc含量为5%时,复合材料的力学性能最好,片层状Talc与纤维状GF发挥了良好的协同作用。     

高韧高强聚酮/聚酰胺66共混物的制备与性能研究

采用熔融共混法制备了聚酮（PK）/聚酰胺66（PA66）共混物,通过扫描电子显微镜、差示扫描量热仪、冲击试验机和电子万能试验机等研究了PK/PA66共混物的形态结构、结晶与力学性能。结果表明,当PA66含量较低时,PA66分散相粒径较小,且分布较均匀,PK/PA66（质量比为80/20）共混物的干态冲击强度达到29.5 kJ/m2,湿态下冲击强度为纯PK的4倍,同时共混物拉伸强度及弯曲模量也明显提高;但当PA66含量较高时,PA66相区尺寸明显增大,PK/PA66共混物的冲击强度呈下降的趋势;PA66的引入会显著降低PK的结晶度。     

PA6/SMA/N-PMI共混物的制备及其性能研究

采用熔融共混法制备了尼龙6/苯乙烯-马来酸酐共聚物/N-苯基马来酰亚胺共混物(PA6/SMA/N-PMI),并利用DSC、TGA及力学性能测试等手段研究了SMA用量对PA6/SMA/N-PMI共混物熔融结晶行为、热学性能以及力学性能的影响。结果表明,共混物的最大分解温度较纯PA6有较大提高;SMA用量的增加,共混物的结晶温度、结晶度以及熔融焓均先降低再升高;当SMA用量为5份时,共混物的弯曲强度、弯曲模量以及热变形温度均达到最大值,分别为113.8、3 053 MPa及61.3℃,较纯PA6分别提高了25.1%、28.0%及19.0%;拉伸强度在SMA用量为7.5份时达到最大值81.4 MPa,较纯PA6提高了17.1%。     

PPS/PA66/GF复合材料的制备及性能研究

在聚苯硫醚（PPS）树脂基体中引入聚酰胺66（PA66）,随着PA66含量增加,PPS/PA66共混物的拉伸强度和弯曲强度逐渐下降,结合PPS/PA66共混物的相形貌分析,提出了通过玻璃纤维（GF）的引入,制备具有互锁结构的PPS/PA66/GF三元体系复合材料,达到同时提高复合材料的强度、刚度及韧性的目的。分别考察了短玻璃纤维（SGF）和中长玻璃纤维（LGF）增强PPS/PA66的综合性能。结果表明,GF的引入显著提高了共混物的力学性能,同时,PPS/PA66/SGF和PPS/PA66/LGF复合材料的扫描电子显微镜和动态力学性能分析都表明共混物内部形成了一个高度互锁的结构。     

加料方式对PA6/CaCl_2/GF复合材料性能的影响

制备了不同含量玻纤增强的PA6/CaCl2/GF(聚酰胺6/氯化钙/玻璃纤维)复合材料。通过差示扫描量热仪(DSC)、动态力学分析(DMA),研究了不同加料顺序下玻纤含量对复合材料结晶性能、动态力学性能和维卡软化温度的影响。结果表明:先加入玻纤再加入CaCl2的加料方式下,复合材料的结晶度、储能模量、玻璃化转变温度、拉伸强度和弯曲强度更高;不同加料方式下,随着玻纤含量的增加,PA6/CaCl2/GF复合材料的缺口冲击强度和维卡软化温度都大幅度增加。     

PA6/SMA共混物的热性能及力学性能

采用熔融共挤制备了尼龙6(PA6)/苯乙烯-马来酸酐共聚物(SMA)共混物,利用差示扫描量热法、热重分析、热变形温度测试及力学测试等手段研究了SMA含量对PA6/SMA共混物熔融结晶行为、热性能及力学性能的影响。结果表明,SMA的加入使共混物的熔融温度、结晶温度及结晶度降低;当SMA用量为5份时,共混物最大分解温度较纯PA6提高了33.5℃;共混物的弯曲强度和弯曲模量在SMA用量为2.5份时达到最大,分别为115.0、3 227 MPa,比纯PA6提高了26.4%、37.0%,拉伸强度在SMA用量为5份时达到最大87.5 MPa,比纯PA6提高了25.9%。     

PA6含量对PVC/PA6共混物形态结构与力学性能的影响

以EVA-g-MAH为相容剂,将PVC与自制的低熔点PA6共混制备了PVC/PA6共混物。通过扫描电子显微镜(SEM)和力学性能测试研究了PA6含量对PVC/PA6共混物形态结构及力学性能的影响。SEM分析结果显示:随着PA6含量的增加,PVC/PA6共混物的分散相尺寸逐渐增大,当PA6含量为10%时,共混物中分散相的分散尺寸最小为1μm;当PA6含量为50%时,共混物为两相共连续结构;当PA6含量为60%时,共混物中PA6为连续相,PVC为分散相。力学性能测试结果表明:当PA6含量为10%时,共混物的缺口冲击强度和拉伸强度都较PVC有明显提高,分别提高了约50%与30%,达到了6.29kJ/m2和60MPa。采用差示扫描量热仪(DSC)研究了PVC/PA6共混物的结晶温度,检测结果显示:PVC/PA6共混物呈现非晶结构。     

PA6/PA102共混物性能研究

本文通过混合注塑制备了不同含量PA102的PA6/PA102共混物,并对共混物的性能进行了研究。结果表明共混物两相呈相分离,熔融与结晶温度有所偏移,热分解性能与纯PA相当,热变形温度随PA102含量增加而增加。共混物干态下均呈脆性断裂,拉伸、冲击强度在两相比例接近时最低。平衡吸水后,共混物韧性增加;拉伸和弯曲强度降低,降低程度随着PA102添加量的增加而变小。因此PA102加入改善了PA6的吸水性和吸水后的稳定性。     

接枝聚丙烯增容改性PP/PA合金性能的研究

用PP接枝物增容PP/PA6共混体系,观察分析了共混合金的形态结构特点,测试了共混物的力学性能.结果表明：单独加入PP-g-MAH,力学性能均呈现先升后降的趋势,峰值时拉伸强度比未加接枝物时可提高20%,弯曲强度比未加接枝物时提高了54%,冲击强度比不添加接枝物时提高了3.6%.添加PP-g-MAH对不同比例PP/PA6共混物力学性能的影响不同,固定PP-g-MAH用量为4%,PA6质量分数为30%时共混物的综合力学性能达到最好.用PP-g-MAH和PP-g-GMA两种接枝物共同作为相容剂加入到PP/PA6共混物中比单独使用一种的效果要好,拉伸、弯曲和冲击强度都得到显著的提高.由共混物的SEM照片可以看到,PP-g-MAH使分散相的粒径变小,分布均匀,界面相互作用加强,所以是PP/PA6共混物的有效增容剂.     

芳纶纤维增强聚苯醚/尼龙6合金的性能研究

通过马来酸酐接枝苯乙烯-丁二烯嵌段共聚物(SEBS-MAH)对聚苯醚/尼龙6(PPO/PA6)合金进行增容增韧改性,制备芳纶纤维(AF)增强PPO/PA6/SEBS-MAH复合材料。实验结果表明:SEBS-MAH能够提高PPO/PA6共混体系的相容性,并且能够提高其力学性能,添加10份SEBS-MAH比不添加SEBS-MAH共混体系的拉伸、弯曲和冲击强度各增加了19.1%、49.3%和46.8%,共混物的玻璃化转变温度得到提高;AF能够提高PPO/PA6/SEBS-MAH共混体系的力学性能以及摩擦性能,并使共混体系的刚性得到提高,添加7.5份AF的复合材料的拉伸、弯曲和冲击强度分别比未添加AF时提高了22.1%、13.1%和12.9%,摩擦系数降低了0.18。     

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.