PE-LLD/玻璃微珠复合材料的熔融与非等温结晶行为研究

采用X射线衍射法、偏光显微镜和差示扫描量热法考察了玻璃微珠(GB)对线形低密度聚乙烯(PE-LLD)的结晶形态以及非等温结晶与熔融行为的影响。通过Jeziorny法和莫志深法研究了复合材料的非等温结晶动力学,并利用Kissinger方程计算了PE-LLD/GB复合材料的非等温结晶活化能。结果表明,GB的加入细化了PE-LLD的晶粒,降低了晶粒尺寸和晶体完善程度;当GB含量为5 %（质量分数,下同）时,复合材料的结晶结构完善程度的分散性最大;GB起到了异相成核作用,提高了PE-LLD的结晶起始温度,当GB含量为8 %时,复合材料的结晶速率达到最大值;当GB含量低于5 %时,复合材料结晶活化能高于纯PE-LLD。     

La_2O_3/LDPE复合材料非等温结晶性能研究

利用差示扫描量热仪(DSC)考察了氧化镧(La2O3)/低密度聚乙烯(LDPE)复合材料的非等温结晶行为。通过Jeziorny法、Ozawa法及莫志深法研究了复合材料的非等温结晶动力学。结果表明:在添加La2O3后,LDPE成核速率降低,结晶度下降,晶体粒径分布变宽。在非等温结晶动力学分析中,Jeziorny法lg[-ln(1-Xt)]～lgt关系曲线在结晶前期和中期具有较好的线性关系,结晶后期产生较大偏离;Ozawa法并不适用;而莫志深法适用于该体系的研究,表明La2O3的加入使LDPE结晶速率增大。     

PP/空心玻璃微珠复合材料非等温结晶研究

采用熔融共混挤出的方法,制备了聚丙烯(PP)/空心玻璃微珠(HGB)复合材料,用差示扫描量热法研究了PP和PP/HGB复合材料的非等温结晶过程,并通过Jeziorny和莫志深方程研究了非等温结晶动力学。结果表明,随降温速率的增大,PP和PP/HGB复合材料的结晶峰温和结晶度降低,结晶速率增大;HGB的加入降低了PP的结晶速率。     

LLDPE/粉煤灰复合材料非等温结晶动力学研究

利用差示扫描量热法(DSC)结合Avrami方程研究了线性低密度聚乙烯(LLDPE)、LLDPE/Fly Ash(粉煤灰)的非等温结晶动力学。通过Jeziorny法、Ozawa法和莫志深法分别对非等温结晶过程进行处理,采用Kissinger法和Takhor法得到迁移活化能。结果显示,粉煤灰粉体的加入阻碍了LLDPE分子链的规则排列,影响了链段的结晶扩散迁移规整排列,使LLDPE的结晶速率变慢,对LLDPE晶体生长起了抑制作用。由Ozawa法分析实验数据,得到的线性关系很差,因此也很难得到可靠的动力学参数。在所有结晶速率下,样品的Avrami指数n值在1.42～2.09之间变化,说明粉煤灰的加入对LLDPE的成核与生长方式的影响有限。用莫志深法得出的结论与Jeziorny法一致,b值在0.76～1.13之间变化。     

PE-LLD/纳米Al2O3复合材料非等温结晶动力学研究

采用差示扫描量热法研究了线形低密度聚乙烯（PE-LLD）/纳米氧化铝（Al2O3）复合材料的非等温结晶行为,分别利用Avrami方程和莫志深方程对结晶动力学进行了分析,运用Kissinger方程计算了结晶过程中的活化能。结果表明,添加5 %（质量分数,下同）和10 %的纳米Al2O3,在PE-LLD的非等温结晶过程中起到的异相成核作用较为微弱,PE-LLD/纳米Al2O3复合材料的结晶起始温度、峰值温度和结晶速率均较PE-LLD略有提高,但结晶活化能有所降低。     

尼龙6/高岭土复合材料的非等温结晶行为研究

用差示扫描量热法研究了尼龙6/高岭土复合材料的熔融结晶行为,并用Jeziorny法、Ozawa法、Mo法对复合材料的非等温结晶动力学进行研究。结果表明,3种高岭土的加入均使复合体系的熔融峰变窄,熔点增加;结晶峰温和结晶起始温度提高,结晶速率增大;高岭土填料起到异相成核作用;Jeziorny法、Mo法均适合分析尼龙6及复合体系的非等温结晶动力学过程,而Ozawa法不适合。     

T-ZnOw和POE改性聚丙烯的非等温结晶动力学

用 DSC 考察了 PP、PP/POE 和 PP/POE/T-ZnOw 复合材料的非等温结晶行为,并用 Jeziorny 法、Ozawa 法和莫志深法计算了复合材料的非等温结晶动力学参数,发现 Jeziorny 法和莫志深法能很好地分析 PP 及其复合材料的非等温结晶行为,而 Ozawa 方程则不适用。分析结果表明:POE 和 T-ZnOw 的加入起到了异相成核的作用,提高了PP 基体的结晶速率,其中 T-ZnOw 的作用更为明显。Kissinger 公式的分析结果显示 PP 的结晶活化能（339.94 kJ/mol）大于 PP/POE（262.03 kJ/mol）和 PP/POE/T-ZnOw（259.79 kJ/mol）复合材料的结晶活化能。     

TPU和纳米SiO2改性聚丙烯的非等温结晶动力学

采用示差扫描量热法研究PP、PP/TPU、PP/TPU/纳米SiO2复合材料的非等温结晶动力学.采用 Jeziorny法、Ozawa法和莫志深法研究结晶动力学参数.研究发现Ozawa法不适合处理PP及其复合材料的非等温结晶行为,而Jeziorny法和莫志深法则能很好处理.结果表明:TPU和纳米SiO2起到异相成核的作用,使PP的结晶峰温升高,结晶速率加快.TPU和纳米粒子的填充使PP的结晶活化能增大.     

乙烯-丙烯酸甲酯共聚物/丁腈橡胶热塑性硫化胶的非等温结晶动力学

采用动态硫化法制备了乙烯-丙烯酸甲酯共聚物(EMA)/丁腈橡胶(NBR)热塑性硫化胶(TPV),利用差示扫描量热法研究了EMA/NBR TPV及纯EMA的非等温结晶动力学,并采用Jeziorny法和莫志深法对TPV及EMA的非等温结晶机理进行了探讨。结果表明,TPV、EMA的非等温结晶行为均可用Jeziorny和莫志深法的动力学方程进行描述;与EMA相比,TPV具有较高的结晶起始温度、较慢的结晶速率及稳定的结晶度。     

聚苯硫醚/多壁碳纳米管复合材料非等温结晶研究

采用DSC法研究了聚苯硫醚(PPS)及多壁碳纳米管(MWCNT)复合材料的非等温结晶过程,采用莫志深方程分析了复合材料的非等温结晶动力学特性。结果表明,莫志深方程能够较好地描述PPS/MWCNT复合材料的非等温结晶动力学,MWCNT的加入促进了PPS结晶,材料的结晶温度、结晶速率都明显上升。复合材料的结晶温度和结晶速率随MWCNT用量的增加呈先上升后下降的变化趋势,当MWCNT质量分数为3%时两者都达到最大。     

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.