Effect of pulverization on hydration kinetic behaviors of creatine anhydrate powders

The crystal orientation of creatine monohydrate varies significantly with tableting performance and pulverizing mechanism. Furthermore, the X-ray diffraction patterns of anhydrous forms of untreated creatine monohydrate and of pulverized creatine monohydrate exhibit different crystal orientations. However, hygroscopic forms of unpulverized creatine anhydrate and pulverized creatine anhydrate was exhibit the same diffraction peak pattern. The hygroscopicity of unpulverized and pulverized creatine anhydrate has been investigated by hydration kinetic methods using isothermal differential scanning calorimetry data. Testing of the hygroscopicity of unpulverized and pulverized creatine anhydrate at various levels of relative humidity (RH) at 25 °C revealed that the anhydrate was stable at less than 33% RH, but was transformed into the monohydrate at more than 52% RH. Hydration data of unpulverized and pulverized creatine anhydrate at 60% and 75% RH were calculated to determine hydration kinetics using various solid-state kinetic models. The hydration type of unpulverized and pulverized creatine anhydrate powder follows the zero-order mechanism (Polany–Winger equation) R1. The transition rate constant of pulverized creatine anhydrate, calculated from the slope of the straight line, was about 1.34–1.36 times higher than that of unpulverized creatine anhydrate.     

Characterization of dehydration and hydration behavior of calcium lactate pentahydrate and its anhydrate

The use of calcium lactate pentahydrate (CLP) as an additional filler-binder for direct compaction of tablets has been reported to result in a short disintegration time and rapid drug release. The aim of this study was to understand the dehydration and hydration behavior of CLP and calcium lactate anhydrate (CLA) under various conditions of storage temperature and relative humidity. The removal and acquisition of crystal water were investigated by using differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA), powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). The PXRD results indicated that CLP exists as a crystalline solid and CLA as an amorphous solid. Dehydration of CLP resulted in aggregated particles of CLA with an increase in average particle size. The dehydration and hydration kinetics of CLP were analyzed with the Hancock-Sharp equation on the basis of the isothermal DSC data. The dehydration of CLP followed a zero-order mechanism (Polany-Winger equation). In contrast, the surface roughness of CLA was significantly decreased by hydration. The hydration of CLA followed a three-dimensional diffusion model (Ginstling-Brounshtein equation).     

Effect of pulverization of the bulk powder on the hydration of creatine anhydrate tablets and their pharmaceutical properties

The hydration behavior and expansion properties of untreated and pulverized creatine anhydrate (CRA) tablets were studied under 60 and 75%RH at 25 degrees C by using differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD). The tablet hardness of untreated and pulverized CRA tablets was significantly decreased after hydration. There was a linear relationship between the degree of hydration and the tablet hardness of untreated CRA tablets compressed at 1000 kg/cm2. In contrast, the relationship between the degree of hydration and the tablet hardness of pulverized CRA tablets was nonlinear. These results suggest that the reduction in hardness of pulverized CRA tablets does not depend solely on the hydration level of crystal water. PXRD analysis indicated that the diffraction pattern of the pulverized CRA powder was similar to that of the untreated CRA powder. However, the diffraction intensity of the pulverized CRA powder was slightly lower than that of the untreated CRA powder at high angle. The micropore radius of both untreated and pulverized CRA tablets was significantly increased after hydration, but analysis of the relationship between micropore radius and fractional hydration of crystal water showed that untreated CRA tablets were more affected than pulverized CRA tablets. Therefore, the reduction in tablet hardness depends not only on the hydration behavior but also on the crystal orientation of the CRA powder.     

Influence of calcium lactate and pH on emulsification of low-methoxylated citrus pectin in a Pickering emulsion

An emulsion was prepared by homogenizing 30% rapeseed oil with 70% (w/w) aqueous solution. The emulsion viscosity increased when the concentrations of calcium lactate and low-methoxylated citrus pectin (LMP) in the emulsion were increased. A stable emulsion was obtained when the concentrations of LMP and calcium lactate were 1% and 9?mM at pH 3, respectively. Optical microscopy and laser scanning confocal microscopy revealed that the stable emulsion was a Pickering emulsion. In the Pickering emulsion, LMP with calcium formed micro gels that can be absorbed on the oil surface. The emulsifying property of LMP could widen the applications of pectin.     

Effect of methyltin trichloride on the activity of lactate dehydrogenase

The effect of MeSnCl₃, which is a highly toxic compound, on the activity of L-lactate:NAD oxidoreductase (lactate dehydrogenase) in the extract from the liver of Russian sturgeon (Asipenser gueldenstaedtiB.). Noncompetitive inhibition of the enzymatic reaction was discovered. This can be due to a change in the enzyme conformation caused by the action on the thiol groups, important for enzyme activity.     

Effects of composition and sequential structure on thermal properties for copolymer of 3-hydroxybutyrate and lactate units

Copolymers of (R)-3-hydroxybutyrate (3HB) and (R)-lactate ((R)-2-hydroxypropionate: 2HP) units were synthesized by polycondensation reaction from methyl esters of 3HB and 2HP in the presence of titanium-based catalyst. Mixing of two monomers from the beginning of polymerization yielded random copolymers of 3HB and 2HP units. On the other hand, by controlling the time of mixing of two monomers, copolymers with blocking tendency were obtained. The structure and thermal properties of the obtained copolymers were characterized by ¹H and ¹³C NMR, X-ray diffraction, differential scanning calorimetry, and optical microscopy. Glass-transition temperature of the copolymers was mainly governed by the copolymer composition, and the values varied linearly with the composition. In contrast, the melting temperature was strongly depending on the sequential length of crystallizable monomeric unit, and the values were in inverse proportion to the number-averaged sequential length of crystallizable monomeric unit. The crystallinity of the copolymer samples was affected by both the composition and sequential length of crystallizable monomeric unit. The finding is valuable for design of copolymer molecules with desirable thermal properties by controlling both the copolymer composition and sequential structure.     

Preparation and properties of gluten/calcium carbonate composites

Environment friendly thermosetting composites were prepared by blending wheat gluten （WG） as matrix, calcium carbonate （CaCO3） as filler and glycerol as plasticizer followed by compression molding the mixture at 120 ℃ to crosslink the WG matrix. Morphology observation showed that the CaCO3 particles were finely dispersed in matrix. Incorporation of CaCO3 up to 10 wt% into the composites caused Young＇s modulus and tensile strength to increase markedly. On the other hand, the moisture absorption and elongation at break decreased slightly.     

Structure and properties of chitosan derivatives modified calcium polyphosphate scaffolds

Organic and inorganic composite material is becoming a solution on making the mechanical and degradation properties of biomaterial more suited. Porous calcium polyphosphate was immersed into different concentrations of carboxymethyl chitosan before immersing 10% alginate dialdegyde. After freeze-drying, the scaffolds were performed in physiologic saline. At stated day, the weightloss, Ca²⁺ concentration, pH value and morphology were measured. The biocompatibility of the composite was demonstrated by extract and direct contact tests. As the results showed, the degradation rates of composites were faster, and the compressive strength became bigger because of the cross-linked network formed by Carboxymethyl chitosan (CMC) and alginate dialdehyde (ADA). The pH value of composite was higher than that of calcium polyphosphate (CPP) due to the organic part of composite’s pH was in slight alkaline. From the SEM, the cross-linked network structure could be observed clearly. Because the glycosaminoglycans-like chains in CMC molecules, which are typically presented in extracellular matrix (ECM), extractions of composite material gave the cells good adhesion and growth condition. All the results testified the composite scaffold was a good candidate for bone repair.     

Effect of agar hydrogel and magnesium ions on the biomimetic mineralization of calcium carbonate

Here, agar hydrogel was selected as diffusion medium and template to control the biomimetic mineralization of calcium carbonate (CaCO₃). Due to three dimensional network structures and abundant functional groups (such as, hydroxyl groups), Ca²⁺ ions were uniformly distributed in the network and electrostatically attracted. The diffusion speed and range of CO₃^2? ions were mediated by the concentration of hydrogel medium. Under the synergistic effect of Mg²⁺ ions, the crystal CaCO₃ was induced by gas phase diffusion method in the hydrogel system. The results showed that the concentrations of Mg²⁺ ions and agar hydrogel had no obvious effect on the calcite phase of CaCO₃, but the morphologies and sizes changed with concentrations of medium and Mg²⁺ ions. Attribute to template effect, the crystallization behavior and growth rate of CaCO₃ crystals were regulated. Since Mg²⁺ ions were easily adsorbed on the surfaces of unit cell, the unique structure of CaCO₃ was precisely controlled. This study provides a useful reference and inspiration for the understandings of the contributions of ion supply rate in bio-mineralization and hydrogel medium in biomimetic mineralization.     

乳酸类合成子构建的四连接螺旋手性配位聚合物的合成、结构和光催化性质

通过乳酸衍生物和3-溴-4-羟基苯甲酸的组合得到对映体3-溴-4-(((1R)-1-羧基乙基)氧基)苯甲酸(R-H₂bba)和3-溴-4-(((1S)-1-羧基乙基)氧基)苯甲酸(S-H₂bba)。以其为手性合成子在水热条件下分别与1,3-二(吡啶-4-基)丙烷(1,3-dpp)和Ni²⁺反应,构建了对映手性配位聚合物{[Ni(R-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n(HU12-R)和{[Ni(S-bba)(1,3-dpp)(H₂O)_0.5]·1.5H₂O}_n(HU12-S)。结构分析揭示HU12-R和HU12-S是具有dia网络特征的三维螺旋骨架。在骨架中,阴离子配体R-bba^2-和S-bba^2-分别与Ni²⁺中心连接在一起围绕2,螺旋轴得到一对小的对映螺...     

Effect of butyl lactate methacrylate content on the properties of acrylic acid copolymers

In the present work, the effect of butyl lactate methacrylate (BLM) content on the properties of acrylic acid (AA) copolymers was investigated. The BLM monomer was synthesized by reacting butyl lactate with methacrylic acid through azeotropic distillation method, which was confirmed by Mass spectrometric technique. Copolymers were synthesized by free-radical solution polymerization technique to obtain poly(BLM-co-AA). BLM monomer and copolymers were characterized by Fourier transform infrared (FTIR), ¹H-nuclear magnetic resonance (¹H-NMR) and proton decoupled ¹³C-NMR spectroscopic techniques. The Finemann-Ross method was used to determine the reactivity ratio of AA and BLM and the values were found to be 0.79 and 0.39, respectively. The wide angle X-ray scattering (WAXS) studies exhibited that the increase in BLM content in copolymers, shifted the amorphous halo from 21.34° to 15.39° and also increased the average molecular interchain spacing (〈R〉) from 5.20 to 7.18 Å, which was calculated from 2θ values of amorphous halo of copolymers. Moisture absorption of polymers followed Fickian absorption. Depending upon the copolymer composition, relative humidity and time, the moisture absorption of copolymers can be tuned to a wide range from 11 to 35% (wt/wt). Glass transition temperature of copolymers decreased from 106 to 72.1°C with increase in BLM content. Copolymers were thermally stable up to 150°C and thereafter exhibited three-step thermal degradation in nitrogen atmosphere. Thermal stability of copolymers can be explained on the basis of 〈R〉 value.     

Studies on the dehydration and decomposition of calcium and dicalcium magnesium aconttate hydrates

The thermal decomposition of calcium and dicalcium magnesium aconitate hydrates were studied by TG/DTG, DTA, EGA, SEM and other physico-chemical techniques. The decomposition proceeds in four stages: dehydration; oxidation of the carboxylic acid portion of the salt; complete fragmentation of the hydrocarbon portion; and finally, decarboxylation of the metal carbonate to the oxide. The crystal morphologies of the hydrate and anhydrous salts of each compound are very similar. Tricalcium aconitate consists of well-developed twinned crystals and stellate clusters intergrown with flat platy crystals. On the other hand, dicalcium magnesium aconitate crystals are monoclinic with well-developed pinacoidal faces. The activation energy,E _d (43±2 kJ mol^?1 water), calculated from Borchardt and Daniels' method, for the dehydration process of calcium aconitate trihydrate is of the same order of magnitude as some simple metal salt hydrates. The rate constant, k_d increased from 0.04/min at 238°C to greater than 0.86/min at 295°C. It is concluded that the dehydration process is due to cation bound water.     

Effect of ternesite on the hydration and properties of calcium sulfoaluminate cement

Journal of Thermal Analysis and Calorimetry - Ternesite is an intermediate phase formed during clinkering of calcium sulfoaluminate (CSA) cement. This paper presents an experimental study on the...     

Influence of melt behaviour on the flame retardant properties of ethylene copolymers modified with calcium carbonate and silicone elastomer

This work describes a halogen-free flame retardant material consisting of a polar ethylene copolymer, calcium carbonate and silicone elastomer. The flame retardant properties when using poly(ethylene-co-methacrylic acid) (EMAA) and poly(ethylene-co-butyl acrylate) (EBA) as the copolymer have been compared. Rheological measurements showed an increase in complex viscosity above 250 °C due to ionomer formation between acidic groups in the polymer and calcium ions. The increase in viscosity occurs at lower temperatures with the EMAA material and the increase is stronger. This has great impact on the fire performance, as shown with cone calorimetry and dripping test. In order to further elucidate the flame retardant mechanism in detail, thermogravimetric analysis and infrared spectroscopy have been used. The influence of the amount of comonomer and melt flow ratio of the polymer is also commented.     

Polylactide compositions. The influence of ageing on the structure, thermal and viscoelastic properties of PLA/calcium sulfate composites

High-performance composites prepared by melt-blending polylactide (PLA, l/d isomer ratio of 96/4) with various amounts of β-anhydrite II (AII), the dehydrated form of calcium sulfate hemihydrate obtained by a specific thermal treatment at 500 °C, have been aged to study the evolution of their physical and mechanical properties with time. The effect of 1-year ageing under ambient conditions (below T_g of PLA) for selected composites, i.e., filled with 20 and 40 wt% AII, was determined and compared to unfilled PLA with the same processing and ageing history. Samples with an initial amorphous PLA matrix, obtained by fast quenching from the melt, were characterized before and during ageing. The changes in physical parameters have been studied using dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and density measurements. Surprisingly, for all the samples, an increase of the storage modulus (E′) was recorded, as a result of ageing. This improvement was ascribed to the reorganization of the PLA structure induced by ageing. The structural reorganization was also reflected by a slight increase of PLA density and changes in thermal behaviour. The X-ray investigations showed unchanged crystallographic structure of AII both during blending with molten PLA and in the composite systems after ageing. The surprising stability of the thermo-mechanical properties of PLA and PLA/AII composites is in agreement with the results of size exclusion chromatography analysis (SEC) which did not show significant changes of PLA molecular weights brought out by ageing.     

残留钠离子对Co/SiO2材料结构及乳酸酯

通过控制制备过程中的洗涤次数,采用沉淀凝胶法制备了一系列不同钠离子含量的Co/SiO2催化材料,并采用X射线衍射、N2吸脱附、X射线能谱衍射、H2-程序升温还原、透射电镜和原子吸收光谱等多种表征手段系统研究了材料中残留钠离子对Co/SiO2材料的结构、分散性、氧化还原性和形貌的影响.结果表明,残留的钠离子使得样品比表面积下降,平均孔径增大,导致Co3O4的颗粒尺寸迅速增大.同时钠离子对Co3O4的还原具有抑制作用,使得样品的还原难度增大.结果导致Co/SiO2催化材料在乳酸酯加氢反应中的活性大大降低,同时造成丙酸乙酯副产物增加,对1,2-丙二醇(1,2-PDO)选择不利.     

The influence of matrix crystallinity,filler grain size and modification on properties of PLA/calcium carbonate composites

Thermal and mechanical properties of polylactide (PLA) composites with different grades of calcium carbonate, 40 nm and 90 nm nanoparticles, and also with submicron particles, unmodified and modified with calcium stearate or stearic acid, obtained by melt mixing, were compared. Films with amorphous and crystalline matrices were prepared and examined.T_g of PLA in the composites remained unaffected whereas its cold crystallization was enhanced by the fillers and predominantly depended on filler content. Filling decreased thermal stability of the materials but their 5% weight loss temperatures well exceeded 250 °C, evidencing stability in the temperature range of PLA processing. The amorphous nanocomposites with modified nanoparticles exhibited improved drawability and toughness without a significant decrease of tensile strength; nearly two-fold increase of the elongation at break and tensile toughness was achieved at 5 wt% content of the modified nanofiller. Lack of surface modification of the filler, larger grain size with an average of 0.9 μm, and matrix crystallinity had a detrimental effect on the drawability. However, the presence of nanofillers and crystallinity improved tensile modulus of the materials by up to 15% compared to neat amorphous PLA.     

Computational study on the properties and structure of methyl lactate

A theoretical study on the properties and molecular level structure of the very important green solvent methyl lactate is carried out in the gas phase and methanol and water solutions, with the solvent treated both explicitly and as a continuum. Torsional barriers giving rise to different conformers by rotation of the hydroxyl and methyl groups were analyzed using density functional theory (DFT) to establish the most stable conformer both in gas phase and solution. DFT computations on lactate dimers were also done to study short-range features, and the effect of the surrounding solvent on intra- and intermolecular hydrogen bonding was analyzed according to the polarizable continuum model approach. We have also studied lactate/water and lactate/methanol small clusters together with the corresponding binding energies. Moreover, classical molecular dynamics simulations (MD) were carried out to study medium- and large-range effects at lower computational cost. MD simulations at different pressure and temperature conditions on pure lactate were carried out, and mixtures with water and methanol of different compositions were also studied. Structural information, analyzed through the radial distribution functions, together with dynamic aspects of pure and mixed fluids were considered. The intramolecular hydrogen bonding ability of methyl lactate together with the possibility of homo- and hetero-intermolecular association determines the behavior of this molecule in pure fluids or in mixed.     

薄层树脂相分光光度法测定痕量钙的研究

利用Na 型732#阳离子交换树脂优先与Ca(Ⅱ)交换缔合,形成二元缔合体系(R- Ca(Ⅱ)),在酸性介质中离子交换树脂负载的Ca(Ⅱ)与乙酰基偶氮羧在树脂上配位显色,形成离子交换树脂 Ca(Ⅱ) 乙酰基偶氮羧三元缔合配位显色体系,该三元体系在720nm波长处有最大吸收,建立了薄层树脂相测定钙的新方法。由于离子交换树脂与Ca(Ⅱ)二元交换缔合和树脂负载Ca(Ⅱ)与乙酰基偶氮羧配位的选择性,使本法选择性极高(EDTA存在下大多数共存离子不影响测定)。由于三元缔合配位体系的形成增大了吸光截面积,扩大了π电子离域空间,加之树脂颗粒变小(孔径为0 074mm以下),晾干浓缩提高了方法灵敏度,表观摩尔吸光系数ε720=9 1×105L·mol-1·cm-1,比水相光度法灵敏度提高15 4倍,测定5 0μgCa(Ⅱ)6次,RSD=2.9%,实测了二次精制盐水中Ca(Ⅱ),线性范围为0～9 0μg/mL,检出限为1 4μg/L。