可得然胶凝胶性能影响因素的研究

研究了3种物质PS、DS、WG对可得然胶凝胶强度和高温状态脱水率的影响。结果表明。PS对可得然胶凝胶强度具有显著提高作用,PS、DS、WG均对可得然胶高温状态脱水率有一定的降低作用,PS-DS-WG复配体在显著提高可得然胶凝胶强度的同时,还能降低其高温状态脱水率。     

可得然胶凝胶高温稳定性的改进

为了扩展可得然胶在三次采油等领域的应用,通过单因素实验与正交实验研究了提高可得然胶凝胶高温稳定性的方法。结果表明:添加适量的韦兰胶(0.15%)、小核菌多糖(0.15%)、四硼酸钠(2.00%)及Na_2SO_3(0.3%)能够显著提高可得然胶凝胶(2%含量)在高温(100℃)条件下的稳定性,保温60 d,凝胶强度保留率达到75%以上,凝胶脱水率低于15%,提高稳定性效果理想,为可得然胶后续深入拓展开发提供了实验数据。     

甘蔗渣微晶纤维素特性及其对可得然胶溶液流变特性的影响

为丰富甘蔗渣的综合利用,提高综合产业价值,采用酸解法制备甘蔗渣微晶纤维素,分析甘蔗渣微晶纤维素理化性质及结构,构建甘蔗渣微晶纤维素/可得然胶混合液体系,研究甘蔗渣微晶纤维素对可得然胶溶液流变特性的影响。结果表明,甘蔗渣微晶纤维素聚合度为143,持水力7.55,直径约为10μm,熔融温度为169.5℃,FTIR、XRD分析表明其保留了纤维素基本化学结构。甘蔗渣微晶纤维素能增强可得然胶溶液,在扫描范围内,G′>G″,其流变表现为典型的弱凝胶特性,表明甘蔗渣微晶纤维素在可得然胶溶液中分散性良好,有助于增强溶液体系网络结构,溶液稳定性良好。     

纳米二氧化硅改性SA P内养护水泥基材料的力学性能研究

为了研究纳米二氧化硅(NS)改性高吸水性树脂(SAP)内养护水泥基材料的力学性能,在水泥和混凝土中掺入不同掺量的SAP和NS,从宏观和微观的角度对单掺SAP、单掺NS以及复掺下的水泥胶砂强度和混凝土力学性能进行分析,结果表明:在掺量范围内,SAP对水泥胶砂抗折强度提高不大,却会降低水泥胶砂的抗压强度;NS对水泥胶砂的抗折强度和抗压强度仅略有提高;SAP会降低混凝土的抗压强度和劈裂抗拉强度,其强度随着SAP掺量的增加而降低;NS对混凝土抗压强度和劈裂抗拉强度略有提高,且都随着NS掺量的增加而提高.基于NS本身固有的特性能够较好弥补SAP所带来的负面影响,混凝土抗压强度的最佳掺量为0.16％SAP和1.5％NS,而水泥的胶砂强度和混凝土的劈裂抗拉强度的最佳掺量为0.08％SAP和1.5％NS.SAP的掺入使内部结构生成大量的钙矾石穿插于水化硅酸钙凝胶之中,且NS的掺入使内部结构更加密实.     

可得然胶功能特性及在肉及肉制品中的应用进展

可得然胶是一种微生物胞外多糖,因其良好的增稠、持水、凝胶以及成膜等性能,近些年在肉类加工及保鲜领域得到了广泛的应用。该文综述了可得然胶的功能特性,重点阐述了可得然胶对肉及肉制品品质特性的影响及其对肉品的品质提升机制,最后总结了由可得然胶制备的不同类型可食性复合膜在肉类保鲜中的应用效果,以期为可得然胶在肉类加工和保鲜领域的广泛应用提供理论参考。     

油藏环境对高温交联聚合物凝胶成胶性能的影响

采用高温高压稠化法在稳态剪切条件下模拟凝胶溶液自井口注入地层时的升温加压过程,研究高温高压下成胶环境即溶液初始p H值、温度、金属盐离子对PAM/PEI体系的凝胶化过程和成胶强度的影响。通过高温高压稠化曲线,可将高温高压下PAM/PEI体系的凝胶化过程分为诱导期、加速反应期、平衡期3个阶段。结果表明：引入H+改变凝胶溶液初始p H值,发现凝胶溶液初始黏度先增加后降低,体系可在碱性和中性条件下稳定成胶,而在酸性条件下,体系无法凝胶化。凝胶体系中引入Na⁺、Ca²⁺后,成胶时间被不同程度的延长,且Ca²⁺对凝胶体系的影响远大于Na⁺。体系中Na⁺质量浓度增加,其缓交联作用有限,且不会大幅度降低凝胶成胶强度;Ca²⁺质量浓度增加,凝胶成胶时间明显延长,但其对凝胶成胶强度影响较大,Ca²⁺质量浓度过高,会导致凝胶脱水。     

γ-聚谷氨酸/可得然胶共混膜的制备研究

本研究的目的是制备一种可以生物医用的新型材料。以可得然胶和γ-聚谷氨酸为原料,通过溶液共混法制备可得然胶/γ-聚谷氨酸共混吸水膜材料。产物用吸水率测试和力学性能测试等方法对共混膜进行了表征。结果显示,当可得然胶与γ-PGA质量比为2∶1,反应温度为50℃,交联剂为季戊四醇时,共混膜的各项性能达到最佳,其吸水率为1200,透气性为152.625 g/（h.m2）,力学强度为10.6 MPa。     

甲基丙烯酸β-羟乙酯共聚水凝胶的合成及性能研究

以HEMA、AAM为共聚单体,采用溶液聚合法合成了HEMA/AAM共聚水凝胶,并对其溶胀动力学、离子强度、温度、pH值等性能进行了测定。实验表明:合成的水凝胶初始溶胀迅速,达到平衡溶胀比平衡约6h;在不同离子强度的水溶液中,随着离子强度I的增大,凝胶的ESR不断降低;在pH<7时,其EKR随pH值的增加而减少,在pH>7时,其ESR随pH值的增加而猛增,因为发生了水解反应;凝胶的ESR随温度的升高而降低。     

纳米SiO2对超硫酸盐水泥性能影响研究

为了克服超硫酸盐水泥(SSC)早期强度低的难题,探究了纳米SiO₂(NS)对SSC水化硬化性能的调控效果与机理。研究了NS对SSC力学性能、产物组成、微观结构和形貌,以及孔隙结构的影响规律。结果表明:掺入NS可显著提升SCC力学性能,其中3 d抗压强度提升了32%,3 d抗折强度提升了28%,90 d抗压强度提升了近一倍;同时,NS能够显著密实SSC孔隙结构,使其临界孔径从72.8 nm降低至6.5 nm。NS的增强机理主要为促进矿粉水化,增加产物中C-(A)-S-H凝胶的生成量和聚合度。本文证明了NS提升SSC水化硬化性能的可行性,为低碳SSC的性能提升提供了新思路。     

点胶式导热凝胶的制备与老化性能研究

以双组分硅凝胶为基料,氧化铝和氧化锌为导热填料,通过气相法白炭黑调整触变性,制得点胶式导热凝胶,并对其硫化后的老化性能进行了探讨。结果表明,老化后导热凝胶的热导率都有所增加,其中高温老化热导率升高最为显著,表明老化后导热凝胶的导热能力没有损失;老化后导热凝胶的电气强度有所降低,但仍然能够保持60%以上;老化后导热凝胶的硬度显著升高了50%以上;老化后导热凝胶0.34 MPa下的压缩形变降低,压缩形变量可保持原来的40%以上。     

Microstructure and properties of aluminum nitride ceramics prepared by aqueous gelcasting method with nontoxic curdlan as gelling agent

Aluminum nitride ceramics were prepared by aqueous gelcasting method and pressureless sintering technique in N₂ atmosphere using Y₂O₃ as sintering additives with nontoxic curdlan as gel system. The solidification mechanism of curdlan was studied. The effects of curdlan content and solid content on the microstructure, relative density and flexural strength of green bodies were investigated. The influences of Y₂O₃ content and sintering soaking time on the microstructure and properties of sintered bodies were also studied. The results show that, as the temperature increases to 80 °C, the ceramic powders solidify through three-dimensional gel networks of curdlan during gelling process. The green bodies can be successfully fabricated through aqueous gelcasting method with modified powder as original materials. Suitable curdlan content and solid content contribute to fabricating green body with uniform microstructures and high flexural strength. The relative density and flexural strength of sintered bodies enhance as the Y₂O₃ content and soaking time increase. The flexural strength and thermal conductivity are about 107.5∼172.3 MPa and 75.2∼112.5 W/(m·K), respectively. The sintered body with 4 wt% Y₂O₃ soaking for 3 h exhibits the highest thermal conductivity because of appropriate relative density, uniform microstructure and reasonable intergranular phase distribution. The mechanical property and thermal conductivity of sintered bodies can be improved by optimizing the gelcasting process parameter, Y₂O₃ content, and soaking time. The nontoxic gelling system will have wide application for aqueous gelcasting ceramic with complex shape.     

可德胶膜的制备及其性能分析

可德胶是一种新型的微生物多糖。由于可德胶独特的凝胶特性和生理功能,使其有较好的应用前景。本文主要研究不同温度和增塑剂对可德胶膜强度和韧性的影响。改变温度和增塑剂种类及用量制备一系列可德胶膜。对可德胶膜进行差示扫描量热分析（DSC）,研究DSC升温速率对可德胶膜热转变的影响。     

Liquid chromatography of polymer mixtures applying combination of exclusion and full adsorption mechanisms. I. Analysis of polystyrene in its mixture with polymethylmethacrylate single column/single eluent approach

Components of polymer mixtures with different chemical composition can be separated by liquid chromatography by applying appropriate conditions (column packing, eluent, temperature, and pressure) in which just one type of macromolecule is eluted in the size exclusion mode while the other component is fully retained within on column packing. The feasibility of this idea has been demonstrated using the mixtures of polystyrene (PS) plus polymethylmethacrylate (PMMA) with silica gel as the column packing and toluene as an eluent. The PMMA was retained by the silica get at ambient temperature and moderate pressures of several MPa while the PS was eluted by a typical SEC mecahanism. Furthermore, the molar mass distribution of the PS could be determined in one step with the same precision as if injected alone. Surprisingly large amounts of PMMA were trapped within the column prior to its SEc characteristics being influenced. After a series of analyses the column has to be regenerated with a brief flushing with a desorbing liquid, tetrahydrofuran in the system studied. The re-equilibrization of the column with the initial eluent, toluene, was fast and a new series of analyses could be started soon after the characterization step had seen finished. © 1995 John Wiley & Sons, Inc.     

Ultrasonic improvement of weld line strength of injection‐molded polystyrene and polystyrene/polyethylene blend parts

The effect of melt temperature, ultrasonic oscillations, and induced ultrasonic oscillations modes on weld line strength of polystyrene (PS) and polystyrene/polyethylene (PS/HDPE) (90/10) blend was investigated. The results show that the increase of melt temperature is beneficial to the increase of weld line strength of PS and PS/HDPE blend. Compared with PS, the increase of melt temperature can greatly enhance the strength of PS/HDPE blends. For PS, the presence of ultrasonic oscillations can enhance the weld line strength of PS at different melt temperatures. But for PS/HDPE blends, the presence of ultrasonic oscillations can improve the weld line strength when the melt temperature is 230°C, but when the melt temperature is 195°C, the induced ultrasonic oscillations hardly enhance the weld line strength. Compared with Mode I (ultrasonic oscillations were induced into the mold at the whole process of injection molding), the induced ultrasonic oscillations as Mode II (ultrasonic oscillations were induced into the mold after injection mold filling) is more effective at increasing the weld line strength of PS and PS/HDPE blends. The mechanism for ultrasonic improvement of weld line strength was also studied. POLYM. ENG. SCI., 45:1666–1672, 2005. © 2005 Society of Plastics Engineers     

非共价改性法制备聚苯乙烯/高分散石墨烯复合材料

以工业化石墨烯粉体(IGN)与苯乙烯为原料,聚乙烯醇、磷酸三钙为分散剂,过氧化苯甲酰为引发剂,聚苯乙烯(PS)树脂作为非共价改性组分,通过超声分散、悬浮聚合法制备了聚苯乙烯/高分散石墨烯复合材料,探究了超声分散时间与PS含量对IGN在复合材料中的分散性影响机理。结果表明,PS可提高IGN在苯乙烯(St)单体中的相容性;超声时间30 min,PS添加量为St单体质量的3 %时,复合材料微观形貌较好,IGN分散性较佳;随着PS/IGN中IGN含量的增加,复合材料的外延起始降解温度逐渐提高40 ℃,玻璃化转变温度最大提升7.3 ℃,拉伸强度由43.5 MPa增强至68.3 MPa,提升近65 %。     

A granular adsorbent-supported Fe/Ni nanoparticles activating persulfate system for simultaneous adsorption and degradation of ciprofloxacin

In this work, Fe/Ni nanoparticles were produced through Fe(II) and Ni(II) reduction by NaBH_4 and they were stabilized by a kind of prepared granular adsorbent(Fe/Ni@PGA). Fe/Ni@PGA as an environment-friendly activator was used to activate persulfate(PS) for the removal of ciprofloxacin from aqueous solution. Fe/Ni@PGA was systematically characterized via Brunauer–Emmett–Teller(BET) method, X-ray diffraction(XRD), scanning electron microscopy(SEM), and Fourier transform infrared spectroscopy(FTIR). The effects of PS concentration, initial solution pH, Fe/Ni@PGA dosage, initial ciprofloxacin concentration, reaction temperature, anions, and natural organic matters on the removal of ciprofloxacin by Fe/Ni@PGA/PS were analyzed. The removal efficiency of ciprofloxacin by Fe/Ni@PGA/PS was 93.24% under an initial pH of 3.0, PS concentration of 10 mM, Fe/Ni@PGA dosage of 0.1 g, and reaction temperature of 30℃. Fe/Ni@PGA could still exhibit high catalytic activity after nine cycles of regeneration. The removal mechanisms for ciprofloxacin by the Fe/Ni@PGA/PS system were proposed. In summary, the Fe/Ni@PGA/PS system could be applied as a promising technology for ciprofloxacin removal.     

Ultrahigh compressive strength and heat resistance of polystyrene/polyphenylene oxide foams of supercritical carbon dioxide foaming

Polystyrene (PS) foam materials are lightweight, but suffer from poor compressive strength and heat resistance, among other problems, which limit their application. Herein, a method for preparing PS foam with high compressive strength and high heat resistance using supercritical CO₂ is proposed. PS/polyphenylene oxide (PPO) blends were prepared using a corotating intermeshing twin-screw extruder. The results showed that PPO exhibited excellent molecular-level compatibility with PS, which substantially improved mechanical properties and heat resistance of PS. Foam samples of PS/PPO blends with the same expansion ratio were prepared via batch foaming experiments, and the compressive strength of different foams was determined at different temperatures. At room temperature, the compressive strength of the PS/PPO-30% foam increased by 173% compared with pure PS foam. As the testing temperature increased from 30 to 120°C, the compressive strength of pure PS foams decreased rapidly. Nevertheless, PS/PPO foams maintained high compressive strength at high temperatures.     

Synthesis and physical properties of Curdlan branched Ester derivatives

Curdlan is a high-molecular-weight linear β-1,3-glucan synthesized by microorganisms. A series of curdlan branched esters with a degree of substitution of three were synthesized and their physical properties and structures were compared with those of curdlan linear esters. Thermal degradation temperatures of all the curdlan branched esters were ca. 360 °C; almost the same as those of curdlan linear esters. The curdlan branched esters had melting temperatures (T _m ) higher than those of the corresponding curdlan linear ester with the same side-chain carbon number. In particular, comparing T _m of curdlan propionate, curdlan isobutyrate, and curdlan pivalate, the latter two had high T _m of over 335 °C, suggesting that the degree of branching of the side chain affects the stability of molecular chains with helix structure in their crystals. Highly transparent films were prepared from the curdlan branched esters. These films exhibited higher Young’s modulus and tensile strength compared with those of films composed of the linear equivalents with the same side-chain carbon numbers. These results indicate that curdlan branched esters are promising thermoplastics with favorable thermal and mechanical properties because of the closer packing structure of their molecular chains than that of the corresponding curdlan linear esters.