Analysis of Air Voids Evolution in Cement Pastes Admixed with Non-ionic Cellulose Ethers

Four cellulose ethers（CEs） were compared for their effects on the pore structure of cement paste using mercury intrusion porosimetry. The experimental results show that the total pore volume and porosity of cement pastes containing the four cellulose ethers are significantly higher than that of the pure cement pastes and the total pore volume and porosity of cement pastes containing HEC（hydroxyethyl cellulose ether） or low viscosity cellulose ethers are low in four CEs. By changing the surface tension and viscosity of liquid phase and the strengthening of liquid film between air voids in cement pastes, CEs affect the formation, diameter evolution and upward movement of air voids and the pore structure of hardening cement paste. For the four CEs, the pore volume of cement pastes containing HEC or low viscosity cellulose ethers is higher with the diameter of 30-70 nm while lower with the diameter larger than 70 nm. CEs affect the pore structure of cement paste mainly through their effects on the evolvement of the small air voids into bigger ones when the pore diameter is below 70 nm and their effects on the entrainment and stabilization of air voids when the pore diameter is above 70 nm.

Early Stage Hydration Mechanism of Cellulose Ether Modified Thin Layer Cement Pastes

The early stage hydration mechanism of cellulose ether modified thin layer cement pastes was studied, using brick as the matrix. Samples of 6 h, 24 h, and 3 d and 7 d hydration time were analyzed to study the hydration law on the surface of high water-absorbing matrix. Hydration products were qualitatively and semi-quantitatively analyzed using XRD, TG-DSC-DTG, FTIR and SEM. The experimental results show that there is no enough water for 2 mm thick cement pastes to hydrate, because of rapid water absorption of matrix. Trace amounts of Ca （OH）2 was detected after three days hydration. With the prolongation of hydration time, the category and concentration of hydration products do not change. Compared with 2 mm thick cement pastes, 6 mm thick cement pastes and 10 mm thick cement pastes have lower dehydration rate and water loss. The humidity field of the cement paste show different changes within the same time. 6 mm thick cement paste and 10 mm thick cement pastes have longer time and more water to hydrate. Ca（OH）2 and ettringite were detected after 6 hours hydration and the concentrations of hydration products increased from 24 hours to 7 days.

Hydration Heat Effect of Cement Pastes Modified with Hydroxypropyl Methyl Cellulose Ether and Expanded Perlite

Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca （OH）2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.

Thermal Behavior and Thermal Safety of Nitrate Glycerol Ether Cellulose

The thermal behavior, nonisothermal decomposition reaction kinetics and specific heat capacity of nitrate glycerol ether cellulose（NGEC） were determined by thermogravimetric analysis（TGA）, differential scanning calori- metry（DSC） and microcalorimetry. The apparent activity energy（Ea）, reaction mechanism function, quadratic equa- tion of specific heat capacity（Cp） with temperature were obtained. The kinetic parameters of the decomposition reac- tion are Ea=170.2 kJ/mol and lg（A/s^-l）=16.3. The kinetic equation isf（α）=（4/3）（1-α）[-ln（1-α）]^1/4. The specific heat capacity equation is Cp=1.285-6.276×10^-3T＋1.581×10^-5T^2（283 K〈T〈353 K）. With these parameters, the thermal safety properties of NGEC were studied, such as the self-accelerating decomposition temperature（TSADT）, critical temperature of thermal explosion（Tb） and adiabatic time-to-explosion（tTlad）. The results of the thermal safety evalua- tion of NGEC are： TSADV=459.6 K, Tb=492.8 K, tTlad=0.8 S.

Influence of Cellulose Ethers on Hydration Products of Portland Cement

Cellulose ethers are widely used to mortar formulations,and it is significant to understand the interaction between cellulose ethers and cement pastes.FT-IR spectra,thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article.The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste,but the major hydration products,such as CH（calcium hydroxide）,ettringite and C-S-H,appeared later in the modified cement pastes than in the unmodified cement paste.The cellulose ethers decrease the outer products and increase inner products of C-S-H gels.Compared to unmodified cement pastes,no new products are found in the modified cement pastes in the present experiment.The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

A Review on the Structure and Biodegradation of Cellulose-Lignin Complexes

Cellulose is the most abundant organic macromolecule in nature and is renewable,degradable,and biocompatible.The structure of native cellulose has not yet been completely elucidated.Part of cellulose is tightly combined with lignin macromolecules through chemical bonds to form cellulose-lignin complexes(CLC).The existence of the CLC structure inhibits the complete separation of cellulose from lignocellulosic material,which not only increases the consumption of chemicals in the cooking process and causes environmental pollution,but also makes the cellulose subject to certain degradation during the deep delignification process.Therefore,elucidation of the relationship between the cellulose-lignin connection structure and performance is of great significance for efficient separation of cellulose.This article reviews the current research status of CLC and discusses the research progress regarding its biodegradation characteristics.

Preparation of Carboxymethylcellulose from Waste Paper

We aimed at producing sodium carboxymethylcellulose (CMC) from waste paper cellulose.For this etherification,the raw material was waste paper,the cellulose was initially alkalized with NaOH,the etherifying agent was sodium chloroacetate,and the reaction medium was water or ethanol.The method provided by us,i e,a method for preparing CMC from waste paper,was environment-friendly,could be easily implemented,and could be conveniently applied to make waste paper efficiently used with high profit,and to expand the range of usable raw materials for CMC production.We successfully synthesized CMC and prepared CMC plastic membrane.This practice changes waste into valuables,which is beneficial to our living environment.For preparation of CMC,one of the crucial factors is appropriate pretreatment of the cellulose from waste paper.The pretreatment was done with a self-built hydrolysis method.We experimentally examined the effects of the mass ratios of reactants,reaction temperature,time,and reaction environment of homogeneous or heterogeneous on CMC yield.The innovative points of this research could be stated as follows:the reaction activity of cellulose was improved by pre-hydrolysis;synthesizing CMC with cellulose from waste paper changes waste into valuables is beneficial to our living environment;and a freezing treatment for the cellulose-alkali mixture was innovatively added.The effects were exhibited by a desired final conversion efficiency.

蒸压轻质混凝土板专用粘结砂浆的制备与性能研究

采用P·O42.5水泥、粉煤灰、石灰石超细粉、矿粉以及外加剂为原料制备水泥基粘结砂浆。采用正交试验确定水泥基胶凝材料的最优配合比,研究淀粉醚对纤维素醚取代率和膨胀剂对水泥基粘结砂浆的性能影响,并利用XRD和SEM分析水化产物和微观形貌,研究外加剂的作用机理。结果表明,m(水泥)∶m(粉煤灰)∶m(矿粉)∶m(石灰石超细粉)=22∶4∶4∶5时,水泥基胶凝材料的性能最优;淀粉醚适量取代纤维素醚可以增强砂浆保水性,提高砂浆强度,减少收缩;少量膨胀剂可以提高砂浆的早期强度,增加掺量则降低早期强度,提高砂浆后期强度。制备的水泥基粘结砂浆符合JC/T 890—2017《蒸压加气混凝土墙体专用砂浆》的要求。

纤维素醚结构对CSA水泥砂浆拉伸黏结强度的影响

研究了固定水灰比条件下具有不同取代度和取代基团的5种纤维素醚在0.3%和0.6%掺量时对硫铝酸盐(CSA)水泥砂浆拉伸黏结强度的影响,并结合保水率测试及压汞法对砂浆孔结构进行分析,探讨了纤维素醚结构对其拉伸黏结强度的影响机制.结果表明:对于同类纤维素醚,高取代度的引气多,改性砂浆孔隙率大、拉伸黏结强度低;对于不同类纤维素醚,羟乙基甲基纤维素醚改性砂浆的孔隙率较羟丙基甲基纤维素醚改性砂浆的要小,拉伸黏结强度更高.基于测试结果提出了CSA水泥砂浆拉伸黏结强度影响因子模型.

纤维素醚基传感器的研究进展

随着柔性可穿戴设备的快速发展,传统的半导体、陶瓷等材料难以广泛地单独应用于柔性传感器领域。天然纤维素来源广泛,是一种良好的柔性材料,但存在不能熔融、难溶于常规溶剂、理化性能差等问题,而纤维素醚能有效改善天然纤维素的上述问题,因此在传感、储能、产能和柔性器件等领域作为绿色基材得到了初步开发。基于纤维素醚基材料在便携化、多功能化、生物相容性等方面的良好性能,及其应用于柔性传感领域的巨大潜力,本文综述了纤维素醚的制备及纤维素醚基材料在应力应变传感、温/湿度检测、气体传感、离子检测等领域的最新研究进展,分析了纤维素醚基传感器应用前景和未来发展面临的挑战。

纤维素醚在聚合物水泥防水浆料中的应用研究

研究了纤维素醚MFS6003对聚合物水泥防水浆料性能的影响。结果表明,随着MFS6003用量的增加,聚合物水泥防水浆料的施工性能、抗流挂性和憎水能力显著提高,对聚合物水泥防水浆料的抗压、抗折强度,横向变形能力及抗渗性能几乎没有影响。当MFS6003用量为0.07%时,制得的防水浆料抗渗压力大于0.5 MPa,横向变形能力为2.5 mm,28 d收缩率为0.28%,符合JC/T2090—2011《聚合物水泥防水浆料》中I型产品的要求。

刨花板纹清水混凝土研究与应用

为制备优质刨花板纹清水混凝土,研究了纤维素醚、水胶比、粉煤灰微珠以及引气剂+消泡剂对刨花板纹清水混凝土的影响。发现纤维素醚能提高保水性和工作性能,但若过量会使和易性变差;降低水胶比可提高保水性,但减少用水量会使流动性变差;粉煤灰微珠能更有效地减水润滑、提高抗氯离子渗透性,但降低保水性;引气剂+消泡剂可改善混凝土外观质量。

预分散高活性硅灰浆体的试验研究

本文通过配合使用几种无机、有机悬浮剂,探究不同悬浮剂对硅灰浆体的性能影响,并尝试制备悬浮稳定性、粘度、活性各项性能良好的预分散高活性硅灰浆体。实验结果表明:有机悬浮剂提供良好的悬浮性能并在一定程度上提高浆体的粘度和活性,无机悬浮剂A及膨润土具有提高浆体触变性,静置时稳定浆体的作用;纤维素醚则会极大地的增加浆体的粘度,不利于浆体的使用。

石膏基自流平砂浆流动性研究与应用

研究了石膏浆液pH值、纤维素醚类型、胶凝材料体系、石膏缓凝剂对石膏基自流平砂浆流动性的影响。结果表明:与以上其他影响因素相比,浆液pH值对石膏基自流平砂浆流动性的影响最大;提高石膏缓凝剂用量,在增加流动度的同时也增加了砂浆泌水、沉降程度;以石膏为主要胶凝材料的自流平砂浆中,掺入粉煤灰、矿粉及普通硅酸盐水泥均能提高流动性;缓溶型纤维素醚更适用于石膏基自流平砂浆。配合比优化后的石膏基自流平砂浆流动度高、稳定性好,满足相关标准要求,有效改善了石膏基自流平砂浆目前存在的流动性缺陷问题。

低水敏性套筒灌浆料试验研究

制备了用水量11.5%~13.0%时均满足使用要求的套筒灌浆料。通过正交试验研究了粉煤灰、硅灰、沉珠对套筒灌浆料流动度及早期强度的影响,并确定各材料最佳用量;通过单因素及复掺试验研究了木质纤维和低黏度纤维素醚对套筒灌浆料流动度、强度及水敏性的影响,并确定二者最佳掺量。结果表明,低水敏性套筒灌浆料配比为:P·Ⅰ52.5水泥410 g、粉煤灰10 g、硅灰30 g、沉珠30 g、石膏20 g、40~80目石英砂200 g、80~120目石英砂300 g、消泡剂0.3 g、塑性膨胀剂0.15 g、PC-G2 g、木质纤维0.1 g、MHPC0.005 g,在用水量较低(11.5%)时略低于JG/T 408—2019《钢筋连接用套筒灌浆料》要求,但满足施工要求,用水量较高(13.0%)时流动度及强度均符合JG/T 408—2019要求。工程应用表明,该套筒灌浆料流动性好,不同用水量均满足施工所需,强度符合JG/T408—2019要求。

纤维素醚调整剂对MIBC泡沫性能的影响研究

浮选泡沫的性能对矿物的浮选效果具有重要影响。以甲基异丁基甲醇(MIBC)为起泡剂,研究羟丙甲基纤维素(HPMC)、羧甲基纤维素(CMC)和3-氯-2-羟丙基三甲基氯化铵纤维素醚三种泡沫调整剂对起泡剂MIBC泡沫的稳定性、表面张力、气泡尺寸和数量等特性的影响。结果表明,随着泡沫调整剂浓度的增加,表面张力降低,泡沫稳定性增强,HPMC对泡沫稳定性的增强效果最好。通过自建图像法测量系统、采用Image-Pro-Plus软件测定、分析气泡数量和尺寸,试验结果显示,泡沫调整剂的加入减少了气泡的数量、减小了泡沫尺寸、增大颗粒与气泡的碰撞概率。透射电镜表明,在纤维状纤维素醚分子链上吸附了MIBC颗粒。黄铁矿纯矿物的浮选试验结果表明,泡沫调整剂的加入提高了黄铁矿纯矿物的回收率。

Cellulose Nanofibrous Membranes Modified with Phenyl Glycidyl Ether for Efficient Adsorption of Bovine Serum Albumin

Hydrophobic interaction chromatography(HIC)as an indispensable method for protein purification has attracted considerable attentions of researchers as well as biopharmaceutical industries.However,the low binding capacity and slow adsorption rate of the currently available HIC media lead to a little supply and high price of the highly purified proteins.Herein,nanofibrous membranes with hydrophobic binding sites were developed for HIC by directly coupling phenyl glycidyl ether on the hydrolyzed cellulose acetate nanofiber membrane(cellulose-phenyl NFM).Scanning electron microscope(SEM),water contact angle(WCA),Fourier transform infrared(FTIR),thermogravimetric analysis(TGA),Brunauer-Emmett-Teller(BET)surface area analysis and capillary flow porometer(CFP)were applied to evaluate the physically and chemically structural transformation.The obtained cellulose-phenyl NFMs showed a proper hydrophilcity(WCA=37°),a relatively high BET surface area(3.6 times the surface area of commercial fibrous membranes),and tortuous-channel structure with through-hole size in the range of 0.25-1.2μm,which led to a little non-specificity adsorption,high bovine serum albumin adsorption capacity of 118 mg g^(−1),fast adsorption process within 12 h,good long-term stability and reusability.Moreover,compared with traditional modification methods which always include activation and graft two steps,direct coupling method is more efficient for HIC media fabrication.Therefore,cellulose-phenyl NFMs with outstanding protein adsorption performance could be a kind of promising candidate for HIC.

固废基聚苯颗粒轻质保温墙体的制备及性能研究

以水泥20%、脱硫石膏40%、粉煤灰24%、矿渣6%、铁尾矿10%为胶凝体系,掺加聚苯颗粒及纤维素醚、乳胶粉、聚乙烯醇溶液等外加剂制备聚苯颗粒轻质保温墙体材料,研究了聚苯颗粒及外加剂对其抗压强度、体积密度、吸水率、软化系数和导热系数的影响,确定了制备工艺参数。试验确定的外加剂最佳配比为:聚苯颗粒体积掺量94%、纤维素醚0.4%、乳胶粉0.4%、聚乙烯醇溶液1%,原材料中固废掺量达80%,制备的聚苯颗粒轻质保温墙体抗压强度1.46 MPa、干密度560 kg/m^(3)、导热系数0.132 W/(m·K)、吸水率17%,符合JG/T 266—2011《泡沫混凝土》中A06级的要求。

高涂布率轻质抹灰石膏的研制

通过研究建筑石膏种类、轻骨料种类、纤维素醚种类的选择,纤维素醚的黏度和用量,普硅水泥用量及缓凝剂用量等对轻质抹灰石膏的涂布率、抗压强度、拉伸粘结强度等性能的影响,确定了高涂布率轻质高强抹灰石膏的配比组成为:石膏粉88%~90%,普硅水泥2.0%~4.0%,轻骨料8.0%,掺黏度为50 000 m Pa·s的EH纤维素醚0.25%~0.35%,蛋白质类缓凝剂用量为0.015%~0.020%。制备的高涂布率轻质抹灰石膏施工顺滑,物理性能符合GB/T 28627—2023的技术要求。

羟丙基甲基纤维素醚对干混砂浆性能的影响

研究了不同掺量及不同粘度的羟丙基甲基纤维素(HPMC)对干混砂浆工作性能和力学性能的影响规律,并研究了HPMC对水泥水化进程和水化产物的影响,最终分析了HPMC对水泥浆体的作用机理。结果表明:HPMC具有保水增稠能力,当掺量高于0.6%时,砂浆流动度降低;当掺量为0.4%时,砂浆保水率可达100%;HPMC大幅降低强度,降幅高达75%;HPMC掺量越大、粘度越低对水泥水化的延迟效果越明显;HPMC不改变水泥水化生成物种类,主要晶体产物依然为Ca(OH)_(2)。