Combination of bifunctional aldehydes and poly(vinyl alcohol) as the crosslinking systems to improve paper wet strength

Two bifunctional aldehydes (i.e., glyoxal and glutaraldehyde) are used as the crosslinking agents to improve paper wet strength in the presence of fully hydrolyzed poly(vinyl alcohol) (PVA) as a co‐reactant. These bifunctional aldehydes alone improve paper wet strength but diminish its folding endurance. The use of PVA as a co‐reactant not only improves paper wet strength but also increases its dry strength and folding endurance. Glutaraldehyde is able to impart much higher levels of wet strength to the treated paper than glyoxal when a catalyst is present. The wet strength of the treated paper increases as the amount of PVA added is increased, and it also increases as the molecular weight (M_w) of the PVA increases. The data suggest that the reaction between glutaraldehyde and PVA promotes the formation of interfiber crosslinking, thus improving the wet strength without diminishing the flexibility of the treated paper. The use of a catalyst is critical to achieve high levels of durable wet strength of the treated paper. We studied the effects of different Lewis acids as the catalysts for crosslinking of pulp cellulose by glutaraldehyde and found that Zn(NO₃)₂ is the most effective one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1673–1680, 2004     

含DMAA热膨胀性微球的制备与性能

通过悬浮聚合法制备了高温发泡热膨胀性核壳结构微球,重点考察了单体N,N-二甲基丙烯酰胺用量、反应温度、发泡剂用量、交联剂种类和用量对热膨胀性微球合成和发泡性能的影响。利用粒度分析仪、光学显微镜、精密恒温控制热台发泡技术和金相分析软件等对产物进行了表征。结果表明:在N,N-二甲基丙烯酰胺用量(质量分数,下同)11.1%,交联剂三羟甲基丙烷三甲基丙烯酸酯用量0.22%,异辛烷用量27.8%,可制备出集中发泡温度高达195℃,微球发泡前后的平均直径之比可达5.2,稳泡温程宽达34℃的微球;所得到的微球粒径分布范围较窄,球形圆整;热膨胀性微球具有较好的耐溶剂性能和密封性能。     

Catalytic Hydroprocessing of p-Cresol: Metal, Solvent and Mass-Transfer Effects

A systematic study of the comparative performances of supported Pt, Pd, Ru and conventional CoMo/Al₂O₃, NiMo/Al₂O₃, NiW/Al₂O₃ catalysts as well as the effects of solvent, H₂ pressure and temperature on the hydroprocessing activity of a representative model bio-oil compound (e.g., p-cresol) is presented. With water as solvent, Pt/C catalyst shows the highest activity and selectivity towards hydrocarbons (toluene and methylcyclohexane), followed by Pt/Al₂O₃, Pd and Ru catalysts. Calculations indicate that the reactions in aqueous phase are hindered by mass-transfer limitations at the investigated conditions. In contrast, with supercritical n-heptane as solvent at identical pressure and temperature, the reactant and H₂ are completely miscible and calculations indicate that mass-transfer limitations are eliminated. All the noble metal catalysts (Pt, Pd and Ru) show nearly total conversion but low selectivity to toluene in supercritical n-heptane. Further, conventional CoMo/Al₂O₃, NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts do not show any hydrodeoxygenation activity in water, but in supercritical n-heptane, CoMo/Al₂O₃ shows the highest activity among the tested conventional catalysts with 97?% selectivity to toluene. Systematic parametric investigations with Pt/C and Pt/Al₂O₃ catalysts indicate that with water as the solvent, the reaction occurs in a liquid phase with low H₂ availability (i.e., low H₂ surface coverage) and toluene formation is favored. In supercritical n-heptane with high H₂ availability (i.e., high H₂ surface coverage), the ring hydrogenation pathway is favored leading to the high selectivity to 4-methylcyclohexanol. In addition to differences in H₂ surface coverage, the starkly different selectivities between the two solvents may also be due to the influence of solvent polarity on p-cresol adsorption characteristics.     

改善焦炭热性能的探讨

取国内具有代表性的生产入炉煤,进行常规炼焦、捣固炼焦、配型煤炼焦、配黏结剂炼焦实验,并对常规焦炭进行钝化,以探讨改善焦炭热性能的可能性。结果表明,与常规焦炭相比,捣固炼焦、配型煤炼焦、配黏结剂炼焦反应后强度平均分别提高8.39%、8.20%、5.13%;采用质量分数1.0%的硼酸、硼砂、硼酸-硼砂-二氧化硅复合钝化剂处理焦炭,可使反应后强度分别提高6.59%、8.63%、6.10%。     

海水淡化水与地表水联合供水地区市政管网水质变化研究

研究了我国某海岛地区以淡化水与地表水联合供水时,城市管网的水质变化情况,对比分析了淡化水与地表水的化学稳定性情况,考察了浊度、Cl-和总铁含量等主要参数在管网内的变化规律。结果表明,虽然淡化水其化学稳定性较差,但在优质管网中完全能够满足城市供水水质要求;联合供水地区城市管网水质与管道属性和停留时间存在较大关系,这与普通供水地区城市管网情况基本类似。     

黔中地区电、铝、磷联合开发的经济分析

电、铝、磷联合开发是一个战略性的经济研究新课题。本文论述了电、铝、磷联合开发的可能性、必要性与经济合理性;总结了电、铝、磷开发的三种模式;提出了联营体内各联营项目开发规模优化选择的数学模型。继而以黔中地区电、铝、磷为研究对象,选定了各联营项目的最优开发规模,并对各项目联合开发与单独开发进行财务评价和国民经济评价。通过分析对比,论证了电、铝、磷联营的巨大经济效益及其来源,探讨了联营体内各联营项目之间联营效益的分配原则,为今后的电、铝、磷联营提供理论依据。     

园林与文化环境

本文讨论了中西园林的基本差异,指出了这种差异源于各自所属的文化系统。并从中西文化系统植根的“土壤”的分析比较着手,进一步探索了文化类型与特质是园林风格形成的决定性因素。最后提出随着中国现代文化的创立,必然产生新的园林文化意蕴与形态。     

Effects of the Change in Average Permittivity and Conductivity of Grating on Diffraction Efficiency

A model describing the propagation of optical waves in a hologram volume grating is studied. Then the effects of the change in the average permittivity and conductivity of a grating on diffraction efficiency are discussed. Finally a comparision of the results of this model with those by Solymar is made. The authors come to a conclusion that the effects of the change can be compensated.     

Zn-Mg复合氧化物催化大豆油甘油解合成单甘酯

采用共沉淀法制备了一系列不同Zn、Mg物质的量比的Zn-Mg复合氧化物,将其用于催化大豆油甘油解合成单甘酯(MG),采用XRD、氮气吸附-脱附仪、SEM、TEM对Zn-Mg复合氧化物结构与性能进行了表征,并测定了催化剂的表面碱强和碱量。优化了合成单甘酯的工艺条件,并考察了Zn-Mg复合氧化物的重复使用性能。结果表明,改变Zn、Mg物质的量比不仅可以调控Zn-Mg复合氧化物的碱强与碱量,还可以调控其比表面积、孔容等结构参数;不同Zn、Mg物质的量比复合氧化物的催化活性变化趋势与其碱强度(H)在15.0H17.2间碱量变化趋势相一致;n(Zn)/n(Mg)=0.1时,复合氧化物(ZM0.1)具有最好的催化甘油解反应活性;使用该催化剂合成单甘酯的适宜条件为:n(甘油)∶n(大豆油)=3∶1,反应温度210℃,反应时间2 h,催化剂用量为大豆油质量的0.6%,该条件下大豆油转化率达95.6%,单甘酯收率为58.5%。ZM0.1催化剂重复使用4次时大豆油转化率仍达80.9%。