Cellulose-precipitated calcium carbonate composites and their effect on paper properties

A cellulose-PCC composite was synthesised using the CaCl₂ reaction with dimethyl carbonate (DMC) under alkaline conditions and in the presence of cellulose fibrils made from highly refined bleached softwood kraft pulp. The results showed that the ash content in the synthesised cellulose-PCC composite increased by increasing the reaction temperature from 25°C to 70°C, the reaction time from 3.5 min to 7.5 min and the cellulose consistency from 0.05 % to 0.1 %. The ratio of calcium carbonate generated to the calcium chloride used initially was increased by increasing the reaction temperature and time. The XRD pattern of the cellulose-PCC composite indicated no modification micro-crystal habit of the deposited CaCO₃. The SEM images showed that the cellulose-PCC composite filler had a rhombohedral shape as opposed to the scalenohedral shape of common PCC. The paper filled with the cellulose-PCC composite had much higher bursting and tensile strengths, at a tearing strength similar to common PCC.     

Anchoring calcium carbonate on graphene oxide reinforced with anticorrosive properties of composite epoxy coatings

Calcium carbonate nanoparticles (nano‐CaCO₃) anchored graphene oxide (GO) sheet nanohybrids (GO‐CaCO₃) are fabricated, and their structure can be measured by scanning electron microscope, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction and Fourier‐transform infrared spectroscopy analysis. Afterwards, composite epoxy coatings, filled with GO and GO‐CaCO₃ nanohybrids, are prepared via a curing process. The dispersion and anticorrosive properties of composite epoxy coatings are investigated. The results reveal that GO‐CaCO₃ nanohybrids achieve a homogeneous dispersion as well as reinforce corrosion resistance of epoxy coatings. Furthermore, the anticorrosive mechanisms are tentatively proposed for the GO‐CaCO₃/epoxy coatings. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of organic pigment on the grinding of calcium carbonate

Summary Mixtures of-copper phthalocyanine-calcium carbonate, and-quinacridone-calcium carbonate were ground together in various proportions, and the surface properties of the ground specimens were investigated at various grinding times by means of X-ray diffraction analysis, electron micrography, and specific surface area measurement. The addition of sufficient amounts of organic pigment to calcium carbonate retarded the calcite-aragonite transition of calcium carbonate. This was explained by the assumption that the surface of calcium carbonate was covered with organic pigment and its lubricating action interfered with that transformation. The strength of the lubricating action of organic pigment depends on the amount of its addition. Furthermore, the lubricating action of-quinacridone was stronger than that of-copper phthalocyanine.

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Zusammenfassung Mischungen von Calciumcarbonat- und -Kupfer-phthalocyanin-Pigment bzw. Calciumcarbonat- und-Chinacridon-Pigment wurden in verschiedenen Gewichtsverhältnissen gemahlen. Die Änderungen der Oberflächeneigenschaften während der Mahldauer wurden durch Röntgenbeugung, Elektronenmikroskopie und die Messung der spezifischen Oberfläche untersucht. Ein Zusatz von organischem Pigment zum Calciumcarbonat verzögert die Calzit-Aragonit Umwandlung von Calciumcarbonat. Dies könnte mit der Annahme erklärt werden, daß die Oberfläche des Calciumcarbonats von dem organischen Pigment bedeckt wird und die Umwandlung durch die Schmierwirkung behindert wird. Die Stärke der Schmierung hängt von der zugesetzten Menge ab. Ferner war die Schmierwirkung von-Chinacridon stärker als die von-Kupferphthalocyanin.

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The kinetic compensation effect in the decomposition of calcium carbonate

Some specific factors which may cause the kinetic compensation effect (k.c.e.) during the decomposition of CaCO₃ are identified. The role of the CO₂ equilibrium pressure is examined in relation to the k.c.e. The article also shows why non-isothermal experiments must sometimes necessarily yield a value of activation energy different from the value obtained from isothermal experiments.

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Zusammenfassung Einige spezifische Faktoren, welche den sogenannten kinetischen Kompensationseffekt (k. c. e.) während der Zersetzung von CaCO₃ herbeiführen können, werden identifiziert. Die Rolle des Gleichgewichtsdruckes des CO₂ wird im Zusammenhang mit dem k. c. e. geprüft. Der Beitrag zeigt, warum die nicht-isothermen Versuche manchmal zwangläufig zu einem von den isothermen Versuchen abweichenden Wert der Aktivierungsenergie führen.

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Fabrication and properties of poly(propylene carbonate)/calcium carbonate composites

Composites of poly(propylene carbonate) (PPC) reinforced with micrometric and nanometric calcium carbonate particles were prepared via melt mixing followed by compression molding. The morphology and mechanical and thermal behaviors of the composites were investigated. Static tensile tests showed that the tensile strength, stiffness, and ductility of the composites tended to increase with increasing contents of micrometric calcium carbonate particles. This improvement in the tensile properties was attributed to good interfacial adhesion between the fillers and matrix, as evidenced by scanning electron microscopy examination. However, because of the agglomeration of calcium carbonate nanoparticles during blending, those composites with nanoparticles exhibited the lowest tensile strength. Thermogravimetric measurements revealed that the incorporation of calcium carbonate into PPC resulted in a slight improvement in its thermooxidative stability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1806–1813, 2003     

Impact of coated calcium carbonate nanofillers and annealing treatments on the microstructure and gas barrier properties of poly(lactide) based nanocomposite films

Amorphous poly(lactide) (PLA) and nanocomposite films were prepared from melt‐blending with precipitated calcium carbonate nanofillers (PCC). Nanocomposites based on uncoated PCC (PCC‐UT), stearic acid coated PCC (PCC‐S), and poly(ε‐caprolactone) coated PCC (PCC‐P) were investigated for an inorganic content fixed to 8 wt %. Using coated nanofillers allowed preserving both PLA average molar mass and thermal stability while enhancing the nanofiller dispersion state. Poly(ε‐caprolactone) was identified as the best coating for optimized morphology and thermal properties. Maxwell law accurately described the increase in oxygen barrier properties observed for the nanocomposites based on PCC‐S. A modified Maxwell law was proposed to take account of the additional increase in barrier properties evidenced for the PLA/PCC‐P nanocomposites and assigned to the particularly strong compatibility between PCL and PLA. Different annealing conditions were investigated to respectively study the impact of physical ageing and PLA crystallization on gas permeability. Different extents of physical ageing did not significantly modify the oxygen transport properties. However, a high permeability decrease was observed for the semicrystalline nanocomposites with respect to the amorphous reference PLA film. Finally, the gain in barrier properties was shown to result from both contribution of the nanofillers and the crystalline phase. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 649–658     

The compensation effect in the kinetics of the thermal decomposition of calcium carbonate

The kinetic parameters of the Arrhenius equation for the thermal decomposition of CaCO₃ depending on the values of the sample weight and of the linear heating rate are interrelated by the compensation relationship lgA=a+bH*.     

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.     

一种杂化型分散剂对纳米碳酸钙分散作用的研究

本文制备了一种有机无机杂化型分散剂,该分散剂由聚(丙烯酰氧乙基三甲基氯化铵-丙烯酸钠)(P(DAC-AAS))与多金属簇硅钨酸H4O40Si W12·x H2O(Si W12)通过静电相互作用复合得到。研究了该类分散剂应用于纳米碳酸钙水溶液的分散过程,并使用动态光散射法进行监测。与此同时运用红外光谱及热重分析对包覆改性前后的纳米碳酸钙进行了表征,结果显示分散剂通过吸附和化学键合来包覆改性纳米碳酸钙。     

The effect of procedural variables on TG,DTG and DTA curves of calcium carbonate

The effect of procedural variables, including sample mass, heating rate, particle size and partial pressure of carbon dioxide, on TG, DTG and DTA curves for the decomposition of A. R. calcium carbonate and limestone has been studied. Such variables have a marked effect, similar in magnitude for both DTG and DTA. The effect of sample mass, or depth of undiluted sample, is shown to be due to an increase in the partial pressure of carbon dioxide within the reacting powder and has been called the bed-depth effect. This effect is most pronounced in nitrogen but is much reduced in carbon dioxide. Inert diluents have little effect on the TG curves but changing the composition of the inert carrier gas causes variations which are correlated with the thermal conductivity of the gas. Water vapour causes a lowering of the DTG and DTA peak temperatures.

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Zusammenfassung Bei der Zersetzung von A.R. Calciumcarbonat bzw. Kalkstein wurde der Einflu\ der Versuchsparameter, einschlie\lich Probenmasse, Aufheizgeschwindigkeit, Partikelgrö\e und Partialdruck von CO₂ auf den Verlauf der TG-, DTG- und DTA-Kurven untersucht. Diese Parameter haben einen deutlichen Einflu\ auf DTG und DTA, der sich in beiden FÄllen im gleichen Ausma\ bemerkbar macht. Der Einflu\ der Masse bzw. Tiefe einer unverdünnten Probe Äu\ert sich in einem Ansteigen des Partialdruckes von Kohlendioxid innerhalb des reagierenden Pulvers und wird als Bett-Tiefen-Effekt bezeichnet. Dieser Effekt kommt in Stickstoff besonders zur Geltung und tritt in Kohlendioxid in den Hintergrund. Inerte Verdünnungsmittel haben einen nur geringen Effekt auf die TG-Kurve aber eine Änderung der Zusammensetzung des inerten TrÄgergases verursacht VerÄnderungen, die auf der WÄrmeleitfÄhigkeit des Gases begründet sind. Wasserdampf verursacht, da\ DTG- und DTA-Signale bei niedrigeren Temperaturen auftreten.

     

Effects of calcium carbonate polymorph on the structure and properties of soy protein-based nanocomposites

Novel protein-based nanocomposites were well prepared by in vivo synthesis and co-precipitation of soy protein isolate (SPI) with calcium carbonate (CaCO3) in an aqueous solution. The resultant CaCO3 in the nanocomposites was identified as calcite- and aragonite-type, respectively. The morphology and structure of the CaCO3/SPI composites were investigated by means of wide-angle X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, and high-resolution transmission electron microscopy. The results revealed that the polymorph and the size of CaCO3 in the nanocomposites were dependent on its content, pH, and the conformation of soy protein. At the content of more than 5%, CaCO3 was changed into calcite crystal with the preference of growing along (104) plane. However, at lower content of less than 5%, CaCO3 preferred to form aragonite in the composite as a result of the modulation by soy protein. The aragonite nanocrystals were arrayed in the direction of (111) plane and self-assembled along beta-sheet planes of soy protein polypeptides. The mechanical properties, thermal stability, and water resistance of the CaCO3/SPI nanocomposites were significantly improved as a result of the nanosized effects. Interestingly, the aragonite/SPI nanocomposite exhibited higher tensile strength (about 50 MPa) than that of calcite/SPI, owing to a good compatibility and strong interaction between aragonite and soy protein polypeptides. This work provided a simple pathway to develop the soy protein-based bio-hybrid materials with high mechanical strength and valuable information on their structure-properties relationship.     

Comparative study on the effect of partial replacement of silica or calcium carbonate by bentonite on the properties of EPDM composites

The effects of the partial replacement of silica or calcium carbonate (CaCO₃) by bentonite (Bt) on the curing behaviour, tensile and dynamic mechanical properties and morphological characteristics of ethylene propylene diene monomer (EPDM) composites were studied. EPDM/silica/Bt and EPDM/CaCO₃/Bt composites containing five different EPDM/filler/Bt loadings (i.e., 100/30/0, 100/25/5, 100/15/15, 100/5/25 and 100/0/30 parts per hundred rubber (phr)) were prepared using a laboratory scale two-roll mill. Results show that the optimum cure (t₉₀) and scorch (t_S2) time decreased, while the cure rate index (CRI) increased for both composites with increasing Bt loading. The tensile properties of EPDM/CaCO₃/Bt composites increased with the replacement of CaCO₃ by Bt from 0 to 30 phr of Bt. For EPDM/silica/Bt composites, the maximum tensile strength and E_b were obtained at a Bt loading of 15 phr, with enhanced tensile modulus on further increase of Bt loading. The dynamic mechanical studies revealed a strong rubber-filler interaction with increasing Bt loading in both composites, which is manifested by the lowering of tan δ at the glass transition temperature (Tg) for EPDM/CaCO₃/Bt composites and tan δ at 40 °C for EPDM/silica/Bt composites. Scanning electron microscopy (SEM) micrographs proved that incorporation of 15 phr Bt improves the dispersion of silica and enhances the interaction between silica and the EPDM matrix.     

The effect of substitution on the properties of a chemical group

The effect of the substituent R(R = F, OH, NH₂, CH₃) on the electron distribution of the C=C group of ethylene and acrylonitrile may be fairly well represented in terms of classical interactions between the and components of this group and the molecular remainder. A distinction between direct and indirect effects is made, and an estimate of the relative importance of conjugative versus inductive effects is done.This analysis has been performed on a set of 22 SCF wavefunctions calculated with the 4-31G basis set.     

Technology for production of calcium carbonate with prescribed properties

Physicochemical conditions for production of calcium carbonate with prescribed size and shape of particles and crystal structure by reaction of CaCl₂ and Na₂CO₃ solutions were studied. A technology for manufacture of calcium carbonate with prescribed properties was developed.     

The effect of polyacrylic acid and reaction conditions on nanocluster formation of precipitated calcium carbonate on microcellulose

The precipitation of micro- and nanoparticles of calcium carbonate onto lignocellulosic microfibers was investigated at different microfiber concentrations with and without polyacrylic acid (PAA), i.e. a polymer commonly used to form polymer-induced liquid precursors of CaCO₃. Concentrations of PAA, Ca(OH)₂, CO₂ and microfiber were varied in order to study the impact of reaction conditions on PCC formation in a batch reactor operated at ambient temperature. High resolution scanning electron micrographs of the samples show that both microfiber concentration and PAA dosage affected the nucleation and crystal growth of PCC filler on cellulosic fiber. Interestingly, at higher microfiber concentrations, larger amount of nano-sized spherical crystals were formed on the microfibers. A higher dosage of PAA, on the other hand, resulted in less nucleation on the microfiber, suggesting a preferential bulk nucleation mechanism. A higher concentration of PAA during the precipitation also led to the formation and stabilization of amorphous CaCO₃, which was supported by SEM images and XRD analysis (lack of characteristic crystal structure).     

Effect of calcium carbonate on the properties of noncuring sealants based on butyl rubber and thermoplastics

The effect of the content, dispersity, and surface polarity of calcium carbonate on the physicomechanical and rheological properties of filled noncuring hot melt sealant formulations based on butyl rubber and various thermoplastics was examined. In the formulations based on nonpolar polymers, the cohesion strength and viscosity increase with an increase in the content and dispersity of calcium carbonate, with the strongest reinforcing effect observed with hydrophobized grades of calcium carbonate. With an increase in the polarity of the polymer base, untreated natural carbonate (chalk) becomes more efficient.