POE-g-MAH改性PA6/BF复合材料的力学和摩擦磨损性能研究

采用马来酸酐接枝聚烯烃弹性体(POE-g-MAH)为增韧剂,通过熔融挤出制备马来酸酐接枝聚烯烃弹性体(POE-g-MAH)/尼龙(PA6)/玄武岩纤维(BF)复合材料,研究了POE-g-MAH含量对PA6/BF复合材料力学性能和摩擦磨损性能的影响。结果表明,POE-g-MAH粒子的加入显著提高了复合材料的冲击强度,当POE-g-MAH质量分数为20%时,POE-g-MAH/PA6/BF复合材料的冲击强度达到13.6 k J/m~2,比PA6/BF(4.7 k J/m~2)提高了190%,拉伸强度与弯曲强度分别下降40%和41%。随着POE-g-MAH含量的增加,摩擦因数随着POE-g-MAH含量增加呈现先减小后增大趋势,磨损逐渐增大。     

相容剂对HDPE/PA6共混体系性能的影响

采用双螺杆挤出机,制备了乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)以及高密度聚乙烯接枝马来酸酐(HDPE-g-MAH)2种增容剂改性的高密度聚乙烯(HDPE)/尼龙(PA6)共混物,研究了不同增容剂对共混物力学性能、耐温性能的影响。采用扫描电镜对共混物的冲击断面进行观察分析。结果表明:相容剂POE-g-MAH的增容效果优于HDPE-g-MAH。PA6添加量为15%时,相容剂HDPE-g-MAH的耐热改性效果优于POE-g-MAH,比纯HDPE的维卡软化点提高了5.8℃,共混物的断裂伸长率为35.0%,降低了1%,拉伸强度为22 MPa,提高了1 MPa,冲击强度为70.6 k J/m2;相容剂为POE-g-MAH时,共混物的断裂伸长率为60.2%,降低了8.4%,共混物的拉伸强度为18.9 MPa,提高了0.4 Mpa,冲击强度为86.7 k J/m2。     

增容剂对PP/PA66共混物力学性能和结晶行为的影响

采用熔融共混法制备了聚丙烯(PP)/聚酰胺66(PA66)共混物,研究了聚丙烯接枝马来酸酐(PP-g-MAH)和乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)作为增容剂对PP/PA66共混物力学性能和非等温结晶行为的影响。结果表明:PP-g-MAH提高了共混体系的拉伸强度,加入5份POE-g-MAH能显著提高共混物的断裂伸长率;PA66可起到异相成核作用,使PP的结晶峰温度升高;加入PP-g-MAH进一步提高了PP的结晶峰温度;PA66使PP的结晶活化能增大,增容剂的加入则使共混体系中PP的结晶活化能降低。     

芳纶浆粕增强聚丙烯复合材料的结构与性能

利用双螺杆挤出机制备了聚丙烯(PP) /芳纶浆粕(PPTA-pulp)以及聚丙烯(PP)/芳纶浆粕(PPTA-pulp)/马来酸酐接枝聚丙烯(MAH-g-PP)复合材料。采用力学性能测试、差示扫描量热仪（DSC）、扫描电子显微镜(SEM)、平板流变仪,研究了PP/ PPTA-pulp复合材料的力学性能、结晶行为、断面形态结构及流变行为。结果表明：随着PPTA-pulp含量的增加,复合材料的拉伸强度和弯曲模量增加,缺口冲击强度和断裂伸长率下降,芳纶浆粕对聚丙烯结晶起了成核剂的作用。马来酸酐接枝聚丙烯(MAH-g-PP)作为相容剂,改善了PPTA-pulp与基体PP分子之间的亲和性,提高了界面作用力,并使复合材料的储存模量、损耗模量和力学性能进一步改善。     

POE-g-MAH对PP/PA6共混体系形态结构与力学性能的影响

研究了乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)作为相容剂对PP/PA6共混体系相容性、形态结构和宏观力学性能的影响.研究结果表明在PP/PA6共混体系中加入相容剂POE-g-MAH,不仅能够显著改善PP/PA6共混物的相容性,明显降低分散相的粒径,而且能够使PP/PA6共混物在保持较高的拉伸强度和弹性模量的同时,大幅度地提高共混物的缺口冲击强度和断裂伸长率,与纯PP相比提高幅度分别达到198.3%和778.8%.POE-g-MAH增容PP/PA6共混体系的非等温结晶行为的研究表明,PA6作为成核剂使PP的结晶温度提高,POE-g-MAH的加入能进一步促进PA6对PP基体的异相成核作用.     

马来酸酐含量及制备工艺对PA6/POE/POE-g-MAH/Nano-CaCO_3复合材料形态及力学性能的影响

通过改变共混物中乙烯-辛烯共聚物(POE)与马来酸酐接枝POE(POE-g-MAH)的比例,研究了MAH含量对聚酰胺6(PA6)/POE/POE-g-MAH/纳米碳酸钙(nano-CaCO3)复合材料的微观结构和力学性能的影响。结果表明,MAH含量较高时,POE-g-MAH与PA6基体的相容性好,复合材料的冲击强度最高;制备工艺对复合材料的形态及力学性能有很大影响,采用两步法制备的复合材料中nano-CaCO3分散效果更好,其增容作用使弹性体分散相直径增大约100 nm,冲击强度较一步法提高21%。     

尼龙-6/蒙脱土纳米复合材料用POE-g-MAH改性及性能研究

制备了尼龙-6(PA6)/马来酸酐接枝乙烯-1-辛烯共聚物(POE-g-MAH)和PA6-蒙脱土纳米复合物(NCH)/POE-g-MAH两种复合材料,其脆韧转变点都是在POE-g-MAH质量分数为8%～10%。在脆韧转变点前,PA6/POE-g-MAH和NCH/POE-g-MAH的缺口冲击强度几乎相同;在脆韧转变点后,NCH/POE-g-MAH的冲击强度远高于PA6/POE-g-MAH。复合材料的拉伸强度都随POE-g-MAH的增加而线性下降,在相同POE-g-MAH含量时,NCH/POE-g-MAH的拉伸强度比PA6/POE-g-MAH的低4MPa左右。     

PA6/POE-g-MAH/PE–UHMW材料的制备及性能

以耐热改性组分尼龙6(PA6)为基体材料,超高分子量聚乙烯(PE-UHMW)为综合性能平衡组分,增韧剂马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)为相容剂,制得PA6/PE-UHMW/POE-g-MAH三元复合材料。研究结果表明,POE-g-MAH的加入可改善PA6的韧性,但降低了PA6的拉伸强度,随着POE-g-MAH加入量增加,PA6断裂伸长率逐渐增加,当添加量为30%时,断裂伸长率达到最大值397%,拉伸强度为39 MPa。PE-UHMW组分不仅提高了复合材料的拉伸强度和韧性,同时改善了其耐水解性能。当PA6∶POE-g-MAH∶PE-UHMW=70∶30∶10时,断裂伸长率提高至477%,拉伸强度为42 MPa。通过扫描电子显微镜分析观察复合材料的微观形态,发现在PA6基体中POE-g-MAH和PE-UHMW形成"核–壳"结构,对PA6韧性的提高起到了协同作用。     

BP神经网络在POE-g-MAH/HDPE增韧PA6研究中的应用

运用BP神经网络研究了马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)/高密度聚乙烯(HDPE)对尼龙6(PA6)的增韧作用,并在此基础上建立了PA6/POE-g-MAH/HDPE复合材料各组分用量与复合材料冲击强度的关系模型。结果表明:该模型和实验结果基本吻合,可信度较高;当POE-g-MAH质量分数为12%,HDPE质量分数为16%时,PA6的缺口冲击强度达到95.02 kJ/m2。     

POE-g-MAH对PP/PA6/纳米TiO2复合材料力学性能的影响

通过力学性能测试、SEM和DSC分析,研究了马来酸酐接枝乙烯-1-辛烯共聚物（POE-g-MAH）对聚丙烯（PP）/聚酰胺6（PA6）/纳米TiO2复合材料的相容性和力学性能的影响。结果表明：POE-g-MAH显著改善了PP/PA6/纳米TiO2复合材料的相容性,使复合材料在保持与纯PP相当的拉伸强度和弯曲强度的同时,大幅度地提高了其缺口冲击强度和断裂伸长率;PA6对PP基体有异相成核作用,POE-g-MAH的加入进一步促进了这种异相成核作用。     

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.     

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.     

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.     

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.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

The System Si3N4-SiO2-Y2O3

Subsolidus phase relations were established in the system Si₃N₄-SiO₂-Y₂O₃. Four ternary compounds were confirmed, with compositions of Y₄Si₂O₇N₂, Y₂Si₃O₃N₄, YSiO₂N, and Y₁₀(SiO₄)₆N₂. The eutectic in the triangle Si₃N₄-Y₂Si₂O₇-Y₁₀(SiO₄)₆N₂ melts at 1500°C and that in the triangle Si₂N₂O-SiO₂-Y₂Si₂O₇ at 1550°C. The eutectic temperature of the Si₃N₄-Y₂Si₂O₇ join was ∼ 1520°C.