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Effect of Curing Regime on Degree of Al^(3+) Substituting for Si^(4+) in C-S-H Gels of Hardened Portland Cement Pastes 被引量:5
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作者 胡晨光 胡曙光 +2 位作者 DING Qingjun FENG Xiaoxin HUANG Xiulin 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2014年第3期546-552,共7页
The effect of curing regime on degree ofAl3+ substituting for Si^4+ (Al/Si ratio) in C-S-H gels of hardened Portland cement pastes was investigated by 29Si magic angel spinning (MAS) nuclear magnetic resonance ... The effect of curing regime on degree ofAl3+ substituting for Si^4+ (Al/Si ratio) in C-S-H gels of hardened Portland cement pastes was investigated by 29Si magic angel spinning (MAS) nuclear magnetic resonance (NMR) with deconvolution technique. The curing regimes included the constant temperature (20, 40, 60 and 80 ℃) and variable temperature (simulated internal temperature of mass concrete with 60 ℃ peak). The results indicate that constant temperature of 20 ℃ is beneficial to substitution ofAl3+ for Si4+, and AI/Si ratio changes to be steady after 180 d. The increase of Al/Si ratio at 40 ℃is less than that at 20℃ for 28 d. The other three regimes of high temperature increase Al/Si ratio only before 3 d, on the contrary to that from 3 to 28 d. However, the 20 ℃ curing stage from 28 to 180 d at variable temperature regime, is beneficial to the increase of AI/Si ratio which is still lower than that at constant temperature regime of 20 ℃ for the same age. A nonlinear relation exists between the Al/Si ratio and temperature variation or mean chain length (MCL) of C-S-H gels, furthermore, the amount ofAl3+ which can occupy the bridging tetrahedra sites in C-S-H structure is insufficient in hardened Portland cement pastes. 展开更多
关键词 constant temperature variable temperature degree of Al3+ substituting for Si4+ C-S-H hardened cement pastes
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Optical and Mechanical Properties of CMCNF-dispersed MMT/CMC-Na Nanocomposite Films: Influence of the Degree of Substitution of CMCNFs 被引量:1
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作者 Guanhui Li Gaoyuan Hou +3 位作者 Hong Xie Dejian Zhang Jinyi Cui Zhiqiang Fang 《Paper And Biomaterials》 2020年第4期18-26,共9页
Carboxymethylated cellulose nanofibril(CMCNF)is an effective green dispersant to prepare well-dispersed monolayer montmorillonites(MMTs)in water,thereby facilitating the preparation of a high-performance MMT/polymer n... Carboxymethylated cellulose nanofibril(CMCNF)is an effective green dispersant to prepare well-dispersed monolayer montmorillonites(MMTs)in water,thereby facilitating the preparation of a high-performance MMT/polymer nanocomposite film.However,not enough attention has been paid to correlating the degree of substitution(DS)of CMCNFs with the mechanical and optical properties of the final nanocomposite films.In this study,a series of homogeneous monolayer MMT nanoplatelet dispersions was prepared initially using CMCNFs with different DS as a dispersant,and the as-prepared CMCNF-dispersed MMT dispersions were then mixed with sodium carboxymethyl cellulose(CMC-Na)to fabricate nacre-like nanocomposite films with different contents of MMTs through self-assembly.The layered nanostructure and optical and mechanical properties of the asprepared CMCNF-dispersed MMT/CMC-Na nanocomposite films were investigated,which demonstrated that CMCNFs with lower DS have a positive effect on their optical and mechanical properties.This study sheds light on the preparation of MMT-based nanocomposite films with superior optical and mechanical properties. 展开更多
关键词 carboxymethylated cellulose nanofibril degree of substitution green dispersant MONTMORILLONITE nanocomposite film
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Study of Structural Characteristics of Cellulose Esters with Different Degrees of Substitution
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作者 Michael Ioelovich 《Organic Polymer Material Research》 2022年第1期38-43,共6页
In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphat... In this article,structural characteristics of amorphous mono-,di-,and tri-substituted esters of cellulose have been studied.These esters were synthesized under homogenous conditions using anhydrides of various aliphatic acids.The specific gravity of the highly substituted samples was measured by a pycnometric method in the aqueous medium.To calculate the molar,Van der Waals,and free volumes,as well as the packing coefficient of amorphous esters the method of additive contributions of partial volumes of atoms and atom groups in the volumes of polymers was used.Based on the molar volume,also specific gravity of cellulose esters was calculated.The coincidence of calculated and experimental characteristics was shown.In addition,the relationship between glass transition temperature and free volume was found for the esters.The theoretical equations were derived,which provide predicting the structural characteristics of cellulose esters with different degrees of substitution. 展开更多
关键词 Esters of cellulose Substitution degree Structural characteristics STUDY CALCULATIONS
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Preparation and Characterization of Acylated Chitosan 被引量:2
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作者 LIMing-ehun LIUChao XINMei-hua ZHAOHuang WANGMin FENGZhen SUNXiao-li 《Chemical Research in Chinese Universities》 SCIE CAS CSCD 2005年第1期114-116,共3页
Fully acylated chitosan and N, N-diacyl chitosan were prepared. The products were characterized by elemental analysis, FTIR and 1H NMR. The experimental results indicate that the average degree of acylation depends ... Fully acylated chitosan and N, N-diacyl chitosan were prepared. The products were characterized by elemental analysis, FTIR and 1H NMR. The experimental results indicate that the average degree of acylation depends on the volume ratio of pyridine to chloroform in the reaction medium, the chain length of the acylation agent used, and the molecular weight of chitosan raw materials. The XRD measurements were carried out for pure chitosan, fully acylated chitosan and N, N-diacyl chitosan to verify the crystallinity change caused by the acylation. 展开更多
关键词 CHITOSAN ACYLATION degree of substitution XRD
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STUDY ON THE CHARACTERIZATION OF DISTRIBUTION OF SUBSTITUENTS ALONG THE CHAINOF CARBOXYMETHYL CELLULOSE
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作者 马志艺 张维邦 李卓美 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 1989年第1期45-53,共9页
Four new paranmeters, and , and have been proposed to describe the average length of the sequence of substituted anhydroglucose units and that of unsubstituted ones respectively along the CMC chain. The methods for de... Four new paranmeters, and , and have been proposed to describe the average length of the sequence of substituted anhydroglucose units and that of unsubstituted ones respectively along the CMC chain. The methods for determining those parameters have also been presented . Six CMC samples have been characterized in terms of intrinsic viscosity, degree of substitution (DS), index of substitution(SI);and . It has been proved experimentally that, not only can describe the sequence distribution along the CMC chain, but also can be used for calculating SI and estimating the average degree of substitution in the substituted glucose rings. 展开更多
关键词 CARBOXYMETHYLCELLULOSE degree of substitution Sequence distribution
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Chiral Separation Abilities of Homogeneously Synthesized Cellulose 3,5-Dimethylphenylcarbamates: Influences of Degree of Substitution and Molecular Weight 被引量:1
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作者 Wei-wei Chen Mei-chun Ding +4 位作者 Mei Zhang 张金明 Xia Gao Jia-song He 张军 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2015年第12期1633-1633,1634-1639,共7页
A series of cellulose 3,5-dimethylphenylcarbamates (CDMPCs) with different degrees of substitution (DS) and degrees of polymerization (DP) were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride ... A series of cellulose 3,5-dimethylphenylcarbamates (CDMPCs) with different degrees of substitution (DS) and degrees of polymerization (DP) were homogeneously synthesized in 1-allyl-3-methylimidazolium chloride (AmimC1). Then, the CDMPCs were coated on silica gel and used as chiral stationary phases (CSPs), and their chiral recognition abilities for seven racemates were evaluated by high performance liquid chromatography. The results showed that DS and DP of CDMPCs had a great influence on chiral recognition abilities of the CSPs. The CSPs with the DS ~ 1 gives a low chiral recognition to most racemates. On the contrast, the CSPs with the DS _〉 2 exhibited high chiral separation abilities. For example, six racemates could be separated on the CSP with CDMPC of DS ~ 2 (CSP-2). Especially, for the enantioseparation of 1-(2-naphthyl) ethanol and Tr6ger's base, CSP-2 gave the highest separation ability in all of CSPs. On the other hand, when the DP of cellulose was in a range from 39 to 220, the chiral separation abilities of CDMPCs increased as the DP increased. This work demonstrates that the structure of cellulose esters such as DS and DP has important effect on their chiral separation ability, and therefore provides a practical method to design and prepare desirable CSPs for different racemates. 展开更多
关键词 Cellulose phenylcarbamate Ionic liquid degree of substitution degree of polymerization Chiral separation.
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Effects of degree of substitution on stearic acid-modified Bletilla striata polysaccharides nanoparticles and interactions between nanoparticles and bovine serum albumin 被引量:1
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作者 Guangyuan Zhang Ji Wu +5 位作者 Yuran Liu Long Huang Jin Qiao Xin Liu Jingyan Wei Qingxiang Guan 《Chinese Chemical Letters》 SCIE CAS CSCD 2018年第12期1861-1864,共4页
Three kinds of stearic acid(SA)-modified Bletilla striata polysaccharides(BSPs-SA) conjugates with different degrees of substitution(DS) values of SA moiety were synthesized. The impacts of the DS values on the ... Three kinds of stearic acid(SA)-modified Bletilla striata polysaccharides(BSPs-SA) conjugates with different degrees of substitution(DS) values of SA moiety were synthesized. The impacts of the DS values on the properties of BSPs-SA self-aggregated nanoparticles were determined. The interactions between bovine serum albumin(BSA) and the BSPs-SA nanoparticles were characterized using spectroscopic observations. The cytotoxicity was measured through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) method. The critical aggregation concentration and the average particle sizes reduced from 16.81 μg/mL to 3,09 μg/mL and 192.70 nm to 125.29 nm when the DS values of SA segment increased from 4.98% to 12.94%, respectively. The cumulative release percentage of docetaxel in BSPs-SA nanoparticles decreased whereas encapsulation efficiency and loading capacity increased along with the DS increase of SA moiety. The fluorescence and ultraviolet results demonstrated that the conformation of BSA did not show significant change after incubating with BSPs-SA nanoparticles.Besides, the mass ratio of BSA/BSPs-SA affected their affinity intensity. The inhibition capability of cell proliferation of docetaxel-loaded BSPs-SA nanoparticles against 4 T1 was superior to that of Duopafei;.BSPs-SA nanoparticles may become a promising nanocarrier for anticancer drugs by adjusting the DS values of the hydrophobic SA groups. 展开更多
关键词 Bletilla striata NANOPARTICLES Bovine serum albumin INTERACTION degree of substitution
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Sustainable conversion regenerated cellulose into cellulose oleate by sonochemistry
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作者 De-Fa Hou Pan-Pan Yuan +4 位作者 Zi-Wei Feng Meng An Pei-Yao Li Can Liu Ming-Bo Yang 《Frontiers of Chemical Science and Engineering》 SCIE EI CSCD 2023年第8期1096-1108,共13页
Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly... Derivatization has great potential for the high-value utilization of cellulose by enhancing its processability and functionality.However,due to the low reactivity of natural cellulose,it remains challenging to rapidly prepare cellulose derivatives with high degrees of substitution.The“cavitation effect”of ultrasound can reduce the particle size and crystalline index of cellulose,which provides a possible method for preparing cellulose derivatives.Herein,a feasible method was proposed for efficiently converting regenerated cellulose to cellulose oleate with the assistance of ultrasonic treatment.By adjusting the reaction conditions including ultrasonic intensity,feeding ratios of oleic acid,reaction time,and reaction solvent,a series of cellulose oleates with degrees of substitution ranging from 0.37 to 1.71 were synthesized.Additionally,the effects of different reaction conditions on the chemical structures,crystalline structures,and thermal behaviors were investigated thoroughly.Cellulose oleates with degrees of substitution exceeding 1.23 exhibited amorphous structures and thermoplasticity with glass transition temperatures at 159.8 to 172.6℃.This study presented a sustainable and practicable method for effectively derivatizing cellulose. 展开更多
关键词 regenerated cellulose cellulose oleate SONOCHEMISTRY degree of substitution THERMOPLASTICITY
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Cationic content effects of biodegradable amphoteric chitosan-based flocculants on the flocculation properties 被引量:8
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作者 Zhen Yang Yabo Shang +8 位作者 Xin Huang Yichun Chen Yaobo Lu Aimin Chen Yuxiang Jiang Wei Gu Xiaozhi Qian Hu Yang Rongshi Cheng 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2012年第8期1378-1385,共8页
A series of biodegradable amphoteric chitosan-based flocculants (3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) modified carboxymethyl chitosan, denoted as CMC-CTA) with different substitution degrees ... A series of biodegradable amphoteric chitosan-based flocculants (3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) modified carboxymethyl chitosan, denoted as CMC-CTA) with different substitution degrees of CTA were prepared successfully. The content of carboxymethyl groups in each CMC-CTA sample was kept almost constant. The solubility of the various flocculants showed that, higher cationic content of flocculants caused a better solubility. The flocculation experiments using kaolin suspension as synthetic water at the laboratory scale indicated that the substitution degree of CTA was one of the key factors for the flocculation properties. With the increase of cationic content, the flocculants were demonstrated better flocculation performance and lower dosage requirement. Flocculation kinetics model of particles collisions combining zeta potential and turbidity measurements was employed to investigate the effects of the cationic content of the flocculants on the flocculation properties from the viewpoint of flocculation mechanism in detail. Furthermore, flocculation performance using raw water from Zhenjiang part of Yangtze River at the pilot scale showed the similar effects to those at the laboratory scale. 展开更多
关键词 amphoteric chitosan-based flocculants substitution degree of CTA flocculation kinetics and mechanism
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