PP/HDPE/滑石粉复合材料微孔发泡实验研究

为了改善聚丙烯(PP)的微孔发泡性能,将PP与高密度聚乙烯(HDPE)共混,提高其熔体强度;然后在PP/HDPE共混体系中加入少量滑石粉,研究滑石粉的用量对共混体系熔体强度及微孔发泡过程的影响。研究结果表明,滑石粉的加入使体系的熔体强度提高,发泡样品的泡孔结构变得更均匀。而且,随着滑石粉用量的增加,泡孔尺寸减小,泡孔密度增加。     

马来酸酐接枝物对PE/PA6共混物相容性的影响

采用熔融共混法制备了PP/PA6/POE-g-MAH和PP/PA6/PP-g-MAH共混物。通过扫描电子显微镜(SEM)、差示扫描量热(DSC)仪分析和力学性能测试研究了增容剂POE-g-MAH和PP-g-MAH对PP/PA6共混物相容性、形态结构和宏观力学性能的影响。结果表明,在PP/PA6共混体系中分别加入POE-g-MAH和PP-g-MAH不仅能显著改善两相界面的相容性,减小分散相的粒径,而且能使共混物的力学性能显著提高。当增容剂的用量为5份时,PP/PA6共混物有较好的综合力学性能。POE-g-MAH和PP-g-MAH增容PP/PA6共混体系非等温结晶行为的研究表明,POE-g-MAH和PP-g-MAH均能促进PA6对PP基体的异相成核作用。     

弹性体接枝马来酸酐对PP/PA6 的增容作用

以4种弹性体接枝马来酸酐(MAH)共聚物作为聚丙烯/聚酰胺6(PP/PA6)共混体系的增容剂,从界面相互作用、形态结构和力学性能等方面比较了它们的增容作用。乙烯-辛烯共聚物接枝马来酸酐(POE-g-MAH)和乙丙三元共聚物接枝MAH(EPDM-g-MAH)使PP与PA6两相间的界面相互作用增强,增容效果较好;POE-g-MAH为增容剂时,PA6粒子分布较均匀,粒径约为1μm。POE-g-MAH能明显改善PP/PA6共混体系的韧性和强度,具有良好的增容作用。当w(POE-g-MAH)为10%时,w(PA6)为60%的共混体系拉伸强度最高,达到53.4MPa;适当增加PA6用量,可明显改善共混体系的流动性。     

HDPE/PA 6/有机蒙脱土复合体系的结构及性能

采用熔融共混法制备高密度聚乙烯(HDPE)/聚酰胺(PA)6/有机蒙脱土(OMMT)多元复合材料,借助X射线衍射仪、扫描电子显微镜、透射电子显微镜等分析了OMMT对HDPE/PA 6体系结构、性能的影响及作用机理。加入的少量OMMT以剥离形态分散在基体中,能起到较好的增容作用,并且改善了材料的冲击性能。但OMMT的加入使材料的熔体流动速率降低,剪切黏度增大。     

尼龙6/聚烯烃弹性体合金的形态与性能

采用双螺杆挤出机,通过熔融共混法分别制备了PA6/EVA-g-MAH、PA6/POE-g-MAH和PA6/EPDM-g-MAH 共混合金,研究了各种接枝弹性体用量对合金形态结构及性能的影响.结果表明:合金的拉伸强度和熔体指数均随弹性体用量的增加而减小.3种接枝弹性体的加入对PA6的冲击韧性都有一定的改善,POE-g-MAH和EPDM-g-MAH的增韧效果尤为明显.     

HDPE/PP/EPDM共混物的性能研究

研究了PP对HDPE性能的影响,随着PP用量增加,HDPE的熔体流动速率提高,冲击强度下降,PP含量为25%时,拉伸强度提高10%.三元乙丙共聚物可作为相容荆,改善HDPE/PP间的相容性,EPDM含量为8份时,能同时提高共混物的拉伸强度和冲击强度,当HDPE/PP/EPDM的质量比为77/23/8时,HDPE/PP/EPDM共混体系的综合性能较好.     

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.     

PP/PA66/POE-g-MAH共混体系的熔体强度

将尼龙66( PA66)、普通聚丙烯(PP)、POE-g-MAH共混,改善聚丙烯的熔体强度,应用熔体强度测试仪直接测量了改性PP的熔体强度,并对改性PP的红外光谱及微观形态进行了研究分析.研究结果表明:该方法可以提高聚丙烯的熔体强度,其改性效果与PA66和POE-g-MAH的用量及配比有关.     

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。     

共混方式对尼龙6/EVA/纳米蒙脱土复合材料性能影响的研究

通过改变共混加料顺序,并使用极性有机化蒙脱土,制备了尼龙/EVA-g-MAH/蒙脱土共混材料。研究了蒙脱土种类、乙烯-醋酸乙烯共聚物(EVA)接枝状况以及共混加料顺序对尼龙6/EVA/蒙脱土共混材料力学性能和热学性能的影响。结果表明,尼龙6中加入极性较强的有机化蒙脱土,并使用EVA接枝马来酸酐(MAH),对尼龙6冲击韧性的改性效果明显。采用母料法制备PA6/EVA-g-MAH/有机化蒙脱土材料,可使蒙脱土有效分散到尼龙6相或EVA相中时,增韧效果最好,拉伸和弯曲强度的损失最小。     

Polymorphism of LiGa5O8 and of LiGa5O8-MgGa2O4Solid Solutions

High-temperature X-ray diffraction and differential thermal analyses showed that LiGa₅O₈ exists in two polymorphs related by the first-order transition at 1138°±3°C of the low-temperature simple-cubic form, space group (probably) O⁷, to the high-temperature spinel (fcc) form, space group O _h ⁷. The transition is rapid, and the high-temperature form in pure LiGa₅O₈ could not be quenched to room temperature under the conditions used. However, the high-temperature polymorph can be quenched under equilibrium conditions when 40 mol% or more MgGa₂O₄ is present. The subsolidus equilibrium relations in the system MgGa₂O₄-LiGa₅O₈ are discussed.     

Magnetoresistance of CuxCo1-xFe2O4 Ferrites

Magnetoresistance measurements (Δ/R) were carried out on Cu _x Co_{1- x} Fe₂O₄ samples with x =1, 0.75, 0.50, 0.25 and cobalt ferrite in the range of magnetic intensity (H) from 1.0 to 4.5 kG. Linear plots were obtained between log (Δ/R) and log H for all compositions except that of cobalt ferrite. The values of n at x =0.5 do not agree with the results of some authors. The discrepancy may be attributed to the value of magnetic field intensity at which such measurements were carried out. The similarity of features of n and μ_D with composition leads us to believe that the magnetoresistance may arise from the scattering of conduction electrons by localized electrons involving the s-d exchange interaction.     

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.     

Expansive properties of the mixture C4ASH12 − 2CS III. Effects of temperature and restraint

The effects of temperature and restraint upon the hydration and the expansion of $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}\text{? 2}\text{C}\text{S}$ mixture compacts in different contact solutions have been investigated. Temperatures above 20°C do apparently hinder the formation of an impervious felt-like layer of ettringite around the $\text{C}{}_4\text{A}\text{S}\text{H}{}_{12}$ particles, thus greatly reducing the retarding effect of the lime. An uniaxial restraint of 1 Kg/cm² is enough to reduce sensibly the expansions which remain however high (about 100%). The results can be satisfactorily interpreted by the reaction and expansion mechanism hypothesized in our previous papers.     

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.     

Raman Study of Glasses of Ba2TiSi2O8 and Ba2TiGe2O8

Raman spectra are reported for fresnoite (Ba₂Ti(Si,Ge)₂O₈ glasses, and comparison is made between the Raman spectra of the corresponding crystalline powders and glasses of Ba₂TiSi₂O₈ and Ba₂TiGe₂O₈. The Ba₂TiGe₂O₈ glass spectra show correspondence with the Ba₂TiGe₂O₈ crystalline Raman spectra; the v _s(Ge–O–Ge) mode occurs at 518 cm⁻¹ in the glass and at 521 cm⁻¹ in the crystalline material. Five-fold coordinated titanium is the majority species present in the Ba₂TiGe₂O₈ glass as revealed by a strong band at 824 cm⁻¹ in the I glass spectrum. The Ba₂TiSi₂O₈ glass spectra are similar to the Ba₂TiSi₂O₈ crystalline spectrum; the strongest band is found at 836 cm⁻¹ in the I glass spectrum. Through comparison with the previous Raman data of other titania silicate glasses, we conclude that the Ba₂TiSi₂O₈ glass has a structure similar to the crystalline phase.     

Effects of metal-support interactions on the hydrogenation of CO over PdSiO2 and PdLa2O3

A study of CO hydrogenation over $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$ has been carried out for the purpose of identifying the effects of Pd dispersion, Pd morphology, and support composition on the catalytic activity of supported Pd. The specific activity of each catalyst for methanol and methane synthesis was determined from microreactor studies carried out at a fixed set of reaction conditions. Palladium dispersion was measured by H₂O₂ titration, and the morphology of the Pd crystallites, as expressed by the distribution of Pd(100) and Pd(111) planes, was determined from in situ infrared spectra of adsorbed CO. The crystallite morphology of the $\text{Pd}\text{SiO}{}_2$ catalysts is the same, independent of Pd weight loading: 90% of the surface is comprised of Pd(100) planes and 10% of the surface is comprised of Pd(111) planes. By contrast, the crystallite morphology of the $\text{Pd}\text{La}{}_2\text{O}{}_3$ catalysts changes with Pd loading. Primarily Pd(100) planes are exposed at low-weight loadings while Pd(111) planes are exposed at high-weight loadings. The Pd dispersion has little effect on the methanol turnover frequency over both $\text{Pd}\text{SiO}{}_2$ and $\text{Pd}\text{La}{}_2\text{O}{}_3$, for dispersions between 10 and 20%. On the other hand, the methane turnover frequency is independent of Pd dispersion over $\text{Pd}\text{SiO}{}_2$, but increases with decreasing dispersion over $\text{Pd}\text{La}{}_2\text{O}{}_3$. It is further observed that the Pd morphology influences the specific activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ for methanol synthesis: Pd(100) is nearly threefold more active than Pd(111). For a fixed morphology, the specific methanol synthesis activity of $\text{Pd}\text{La}{}_2\text{O}{}_3$ is a factor of 7.5 greater than that of $\text{Pd}\text{SiO}{}_2$.     

In situ laser raman spectroscopy of the sulfiding of Moγ-Al2O3 catalysts

Raman spectra of sulfided $\text{Mo}\text{γ-}\text{Al}{}_2\text{O}{}_3$ catalysts were obtained using in situ techniques for two sulfiding methods. For samples sulfided by 10% $\text{H}{}_2\text{S}\text{H}{}_2$ at 400 °C, MoS₂ structures were observed. A stepwise sulfiding using 10% $\text{H}{}_2\text{S}\text{H}{}_2$, with spectra recorded at 150, 250, and 350 °C, resulted in observation of molybdenum oxysulfide, reduced molybdate, and surface “MoS₂” phases. Reexposure of these samples to air led to radical modification of the oxysulfide structures as well as transformation of some sulfide phases. A model incorporating terminal and bridging MoS bonding and anion vacancies is proposed. This model is based on the conversion of isolated and aggregated molybdate and MoO₃ species to oxysulfide and reduced molybdenum phases. Conversion of reduced molybdenum phases to sulfides is observed to be slow.     

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.