Surface modification of CaCO3 filler and its characterization using inverse gas chromatography (IGC)

A CaCO₃ filler was treated by generally used coupling agents and a special one — ethylene-octene copolymer (POE)-g-maleic anhydride (MAH). Fourier transform infrared spectroscopy (FTIR) results show that the special coupling agent POE-g-MAH, in a chemical reaction with CaCO₃, can produce an interfacial layer stronger than simple physical adhesion attained with usual coupling agents. Inverse gas chromatography (IGC) was used to investigate the surface free energy of CaCO₃ after surface modification and to optimize the monolayer content of coupling agents. Based on the IGC results, it can be deduced that the monolayer cover is around 1.9% for CaCO₃ treated with a titanate coupling agent. Scanning electron microscope (SEM) observation results show that the separated morphology existed in the ternary composites containing CaCO₃ after surface treatment with coupling agents, whereas the core-shell morphology was obtained in the ternary composites with POE-g-MAH. The encapsulation of the CaCO₃ filler treated with POE-g-MAH was caused by the strong chemical reaction between the elastomer and CaCO₃ particles. __________ Translated from Journal of Northwestern Polytechnical University, 2007, 25(2): 274–278 [译自: 西北工业大学学报]     

Thermal stability and UV-shielding properties of polymethyl methacrylate and polystyrene modified with calcium carbonate nanoparticles

The influences of nanosized CaCO₃ on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated. Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO₃ and PS/CaCO₃ were prepared with different filler loading (0–4 wt%) of CaCO₃ nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO₃ nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation of CaCO₃ nanoparticles could significantly improve the thermal properties of PMMA/CaCO₃ and PS/CaCO₃ nanocomposites. The glass transition temperature (T _g ) and decomposition temperature (T _d ) of nanocomposites with 4 wt% of CaCO₃ nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO₃ and 32  and 15 K in the case of PS/CaCO₃ nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption band in ultraviolet (UV) region is increased with CaCO₃ nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers.     

The influence of CaCO3 filler component on thermal decomposition process of PP/LDPE/DAP ternary blend

Polypropylene‐low density polyethylene (PP‐LDPE) blends involving PP‐LDPE (90/10 wt%.) with (0.06 wt%) dialkyl peroxide (DAP) and different amounts (5, 10, 20 wt%) of calcium carbonate (CaCO₃) were prepared by melt‐blending with a single‐screw extruder. The effect of addition of CaCO₃ on thermal decomposition process and kinetic parameters, such as activation energy and pre‐exponential factor of PP‐LDPE blend with DAP matrix, was studied. The kinetics of the thermal degradation of composites was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at different heating rates. TG curves showed that the thermal decomposition of composites occurred in one weight‐loss stage. The apparent activation energies of thermal decomposition for composites, as determined by the Tang method (TM), the Kissinger–Akahira–Sunose method (KAS), the Flynn–Wall–Ozawa method (FWO), and the Coats–Redfern (CR) method were 156.6, 156.0, 159.8, and 167.7 kJ.mol^?1 for the thermal decomposition of composite with 5 wt% CaCO₃, 191.5, 190.8, 193.1, and 196.8 kJ.mol^?1 for the thermal decomposition of composite with 10 wt% CaCO₃, and 206.3, 206.1, 207.5, and 203.8 kJ mol^?1 for the thermal decomposition of composite with 20 wt% CaCO₃, respectively. The most likely decomposition process for weight‐loss stages of composites with CaCO₃ content 5 and 10 wt% was an A_n sigmoidal type. However, the most likely decomposition process for composite with CaCO₃ content 20 wt% was an R_n contracted geometry shape type in terms of the CR and master plots results. It was also found that the thermal stability, activation energy, and thermal decomposition process were changed with the increase in the CaCO₃ filler weight in composite structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of CaCO3 Filler Component on Solid State Decomposition Kinetic of PP/LDPE/CaCO3 Composites

In this study, the effect of addition Calcium carbonate (CaCO₃) filler component on solid state thermal decomposition procedures of Polypropylene-Low Density Polyethylene (PP-LDPE; 90/10 wt%) blends involving different amounts (5, 10, 20 wt%) Calcium carbonate (CaCO₃) was investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. An integral composite procedure involving the integral iso-conversional methods such as the Tang (TM), the Kissinger-Akahira-Sunose method (KAS), the Flynn-Wall-Ozawa (FWO), an integral method such as Coats-Redfern (CR) and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. The Iso-conversional methods indicated that the thermal decomposition reaction should conform to single reaction model. The results of the integral composite procedures of TG data at various heating rates suggested that thermal processes of PP-LDPE-CaCO₃ composites involving different amounts of CaCO₃ filler component (5, 10, 20 wt%) followed a single step with approximate activation energies of 226.7, 248.9, and 252.0 kJ.mol^{? 1} according to the FWO method, respectively and those of 231.3, 240.1 and 243.0 kJ mol^{? 1} at 5°C min^{? 1} according to the Coats-Redfern method, the reaction mechanisms of all the composites was described from the master plots methods and are P_n model for composite C-1, R_n model for composites C-2 and C-3, respectively. It was found that the thermal stability, activation energy and thermal decomposition process changed by the increasing CaCO₃ filler weight in composite structure.     

Non-isothermal crystallization kinetics of UHMWPE composites filled by oligomer-modified CaCO3

The processability of ultrahigh molecular weight polyethylene (UHMWPE) improved by oligomer-modified calcium carbonate (CaCO₃) was observed in our previous work. In order to understand the effect of oligomer-modified CaCO₃ on the crystallization of UHMWPE, the non-isothermal crystallization behavior and crystallization kinetics of UHMWPE composites filled by oligomer-modified CaCO₃ was studied by differential scanning calorimetry in this work. Jeziorny and Mo methods were used to describe the non-isothermal crystallization kinetics of UHMWPE composites. The effect of modified filler content and cooling rate on the crystallization temperature and crystallization rate was discussed. The heterogeneous nucleation of modified CaCO₃ slightly increases the crystallization temperature of UHMWPE. The crystallization enthalpy of UHMWPE composites is significantly higher than that of UHMWPE. The crystallization rate of UHMWPE composites depends on the filler contents and cooling rate.

     

Reinforcement effect of MAA on nano‐CaCo3‐filled EPDM vulcanizates and possible mechanism

Methacrylic acid (MAA) was used as in situ surface modifier to improve the interface interaction between nano‐CaCO₃ particle and ethylene–propylene–diene monomer (EPDM) matrix, and hence the mechanical properties of nano‐CaCO₃‐filled EPDM vulcanizates. The results showed that the incorporation of MAA improved the filler–matrix interaction, which was proved by Fourier transformation infrared spectrometer (FTIR), Kraus equation, crosslink density determination, and scanning electron microscope (SEM). The formation of carboxylate and the participation of MAA in the crosslinking of EPDM indicated the strong filler–matrix interaction from the aspect of chemical reaction. The results of Kraus equation showed that the presence of MAA enhanced the reinforcement extent of nano‐CaCO₃ on EPDM vulcanizates. Crosslink density determination proved the formation of the ionic crosslinks in EPDM vulcanizates with the existence of MAA. The filler particles on tensile fracture were embedded in the matrix and could not be observed obviously, indicating that a strong interfacial interaction between the filler and the matrix had been achieved with the incorporation of MAA. Meanwhile, the presence of MAA remarkably increased the modulus and tensile strength of the vulcanizates, without negative effect on the high elongation at break. Furthermore, the ionic bond was thought to be formed only on filler surface because of the absolute deficiency of MAA, which resulted in the possible structure where filler particles were considered as crosslink points. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1226–1236, 2006     

Effect of the Amount of Calcium Carbonate as Filler on the Rheological and Adhesion Properties of a Water-Based Polyurethane Dispersion

In this study, the properties of water-based adhesives based on a polyurethane ionomer (PUD) and a micronised CaCO₃ as filler was analysed. Different amounts of a micronised CaCO₃ (5-25 wt%) were added to water-based polyurethane (PUD) adhesive formulations in order to reduce its relatively high cost. The addition of a micronised calcium carbonate filler increased the viscosity, the storage and loss moduli of the PUD adhesives, and imparted pseudoplasticity and thixotropy, more noticeably for the adhesive with the highest calcium carbonate content. The creation of acid-base interactions seemed to be responsible for the improvement in the rheological properties of the PUD adhesives containing CaCO₃ as filler. On the other hand, the addition of CaCO₃ filler might deteriorate the adhesion properties to PUD adhesives.     

Chiral Biomineralization: Mirror‐Imaged Helical Growth of Calcite with Chiral Phosphoserine Copolypeptides

The O‐phospho‐L ‐serine [Ser(P)] containing peptides and proteins play an important role in controlling the morphology of biominerals. The poly[Ser(P)] and copoly[Ser(P)^xAsp^y] affect the calcium carbonate (CaCO₃) morphology and polymorph. The CaCO₃ helical structures were obtained in the presence of copoly[Ser(P)⁷⁵Asp²⁵]. When the L ‐copolymer was used as an additive, a clockwise P twisted spiral morphology was formed. On the other hand, when using D ‐copolymer, a counterclockwise M twisted spiral morphology was obtained.

Optical micrographs of chiral morphologies of CaCO₃ in the presence of a) L ‐copolymer and b) D ‐copolymer.     

Cuttlebone as reinforcing filler for natural rubber

Cuttlebone was proved to be a biomass for new reinforcing filler for natural rubber (NR). The cuttlebone particles were obtained by crushing cuttlebone and followed by sieving. Density and crystal structure of the cuttlebone were 2.70 g/cm³ and an aragonite form of CaCO₃, respectively. The surface area and average diameter of the cuttlebone particles were measured and the reinforcement effect as filler for NR was investigated. The cuttlebone particles did not prevent a peroxide cross-linking reaction of NR, and mechanical properties of peroxide cross-linked NR filled with cuttlebone particles were found to be comparable with those of peroxide cross-linked NR filled with commercial CaCO₃ filler. Presence of chitin on the surface of the cuttlebone particles was speculated to result in a good interaction between cuttlebone particles and NR, which may be ascribed to the mechanical properties of cuttlebone filled NR samples.     

Peanut-shaped aggregation of CaCO<Subscript>3</Subscript> crystallites in the presence of an amphiphilic derivative of carboxymethylchitosan

An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic additive in the precipitation process of calcium carbonate (CaCO₃). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation and crystallization of CaCO₃. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown CaCO₃ crystals, depending upon the molar ratio of the initial Ca²⁺ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy on the precipitated CaCO₃ crystals proved that concentrations of HBP-CMCS and Ca²⁺ exert great influence on the crystallization habit of CaCO₃, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO₃ particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO₃ nanocrystals.     

Tuning the Stability of CaCO3 Crystals with Magnesium Ions for the Formation of Aragonite Thin Films on Organic Polymer Templates

Thin‐film growth of aragonite CaCO₃ on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg²⁺ into a supersaturated solution of CaCO₃. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg²⁺ in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg²⁺. Molecular dynamics simulation of the CaCO₃ precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg²⁺. The role for ionic additives in the crystallization of CaCO₃ on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.     

Assembled structures of nanocrystals in polymer/calcium carbonate thin-film composites formed by the cooperation of chitosan and poly(aspartate)

Assembled structures of calcium carbonate (CaCO₃) nanocrystals have been examined for polymer/CaCO₃ thin-film composites synthesized through a self-organization process inspired by biomineralization. For the crystallization of CaCO₃, a thin-film matrix of chitosan has been used as a polymeric substrate. When the matrix is immersed into a supersaturated aqueous solution of CaCO₃ containing 1.4 × 10⁻³ wt % poly(aspartate) (PAsp), thin-film crystals of CaCO₃ are formed spontaneously. Three kinds of disklike films have been observed under a polarizing optical microscope. Electron diffraction analyses of each film have revealed that one is aragonite, displaying radial orientation of the c axes, and the others are vaterite, exhibiting different orientations. Detailed observation by scanning electron microscopy has clarified that these films are assemblies of crystalline particles 10–20 nm in size. The thin-film composites have been obtained over a PAsp concentration range of 4.4 × 10⁻⁴ to 1.0 × 10⁻² wt %. Vaterite formation becomes dominant when the concentration of PAsp is increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5153–5160, 2006     

Influence of CaCO<Subscript>3</Subscript> nanoparticles shape on thermal and crystallization behavior of isotactic polypropylene based nanocomposites

Summary The influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated. CaCO₃ nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix. The nanocomposites were prepared by melt mixing and subsequent compression molding. A remarkable effect of CaCO₃ on the thermal properties of iPP was observed. Moreover, the analysis of crystallization kinetics showed that CaCO₃ nanopowder coated with PP-MA are efficient nucleating agents for iPP, and the overall crystallization rate results higher than plain iPP.     

Synthesis of branched polyethylenes by the tandem catalysis of silica‐supported linked cyclopentadienyl‐amido titanium catalysts and a homogeneous dibromo nickel catalyst having a pyridylimine ligand

The synthesis of branched polyethylenes by ethylene polymerization with new tandem catalyst systems consisting of methylaluminoxane‐preactivated linked cyclopentadienyl‐amido titanium catalysts [Ti(η⁵:η¹‐C₅Me₄SiMe₂NR)Cl₂ (R = Me or ^tBu)] supported on pyridylethylsilane‐modified silica (PySTiNMe and PySTiN^tBu) and homogeneous dibromo nickel catalyst having a pyridyl‐2,6‐diisopropylphenylimine ligand (PyminNiBr₂) in the presence of modified methylaluminoxane was investigated. Ethylene polymerization with only PyminNiBr₂ yielded a mixture of 1‐ and 2‐olefin oligomers with methyl branches [weight‐average molecular weight (M_w) ～ 460)] with a ratio of about 1:7. By the combination of this nickel catalyst with PySTiN^tBu, polyethylenes with long‐chain branches (M_w = 15,000–50,000) were produced. No incorporation of 2‐olefin oligomers was observed in the ¹³C NMR spectra. Unexpectedly, the combination of the nickel catalyst with PySTiNMe produced lower molecular weight polyethylenes with only methyl branches. The molecular weight distributions of branched polyethylenes obtained with both PySTiNMe and PySTiN^tBu combined with the nickel catalyst were broad (weight‐average molecular weight/number‐average molecular weight < 9). Bimodal gel permeation chromatography (GPC) curves were clearly observed in the PySTiNMe system, whereas GPC curves with small shoulders in low molecular weight areas were observed for PySTiN^tBu. The synthesis of branched polyethylenes with tandem catalyst systems of corresponding homogeneous titanium catalysts and the nickel catalyst was also investigated for comparison. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 528–544, 2003     

Investigation of photo‐oxidative effect on morphology and degradation of mechanical and physical properties of nano CaCO3 silicone rubber composites

Photo‐oxidative degradation of treated and untreated nano CaCO₃: silicone rubber composite was studied under accelerated UV irradiation (≥290 nm) at different time intervals. Prolonged exposure to UV leads to a progressive decrease in mechanical and physical properties along with the change in behavior of filler‐matrix interaction. This was due to decrease in cross‐linking density with increase in mobility of rubber chains. Meanwhile, synthesized nano CaCO₃ was modified with stearic acid for uniform dispersion in rubber matrix. The increase in carbonyl (>CO), hydroxyl (? OH), CO₂, and alkene functional groups on the UV exposed surface of treated and untreated nano CaCO₃: silicone rubber composites at different time intervals was studied using Fourier transform infrared (FTIR) spectroscopy. The change in morphological behavior of filler‐matrix interaction after UV exposure was studied using SEM. Overall, the study showed that the treated nano CaCO₃: silicone composites were affected more by UV exposure than untreated nano CaCO₃: silicone composites and pristine composite after UV exposure. This effect was due to peeling of stearic acid from the surface of CaCO₃, which makes the rubber chains slippery and thus separation of filler and rubber chains takes place with initiation of fast‐degradation. Copyright © 2011 John Wiley & Sons, Ltd.     

聚电解质膜PDAC/PSS诱导CaCO3结晶的研究

以模拟软体动物珍珠层的周期性基质控制形成过程制备仿生层状复合材料. 将聚苯乙烯磺酸钠(PSS)与聚二烯二甲基氯化铵(PDAC)用逐层浸渍的方法使其组装成多层膜, 用于诱导过饱和溶液中CaCO₃的结晶, 详细研究了膜紫外吸收随组装层数增加的线性变化. 扫描电镜和X射线衍射表征了晶体的形貌和结构. (PDAC/PSS)₁₅PDAC膜诱导获得的CaCO₃晶体为六面体结构, 晶体尺寸为30～40 μm; (PDAC/PSS)₁₅膜诱导CaCO₃结晶, 可以在膜表面获得形貌与珍珠层非常相似的CaCO₃晶体, 结晶10 h获得的晶片结构呈规则的六边形, 片尺寸约为10～20 μm. X射线衍射结果表明两种晶体的晶格结构与天然珍珠层差异明显, 说明静电作用为晶体形貌的主控因素之一, 但不是晶格结构的决定因素. 复合材料断面电镜照片表明其为层状结构.     

Toughness mechanism of polypropylene/elastomer/filler composites

The toughening mechanisms of polypropylene filled with elastomer and calcium carbonate (CaCO₃) particles were studied. Polypropylene/elastomer/CaCO₃ composites were prepared on a twin‐screw extruder with a particle concentration of 0–32 vol %. The experiments included tensile tests, notched Izod impact tests, scanning electron microscopy, and dynamic mechanical analysis. Scanning electron microscopy showed that the elastomer and CaCO₃ particles dispersed separately in the matrix. The modulus of the composites increased, whereas the yield stress decreased with the filler concentration. The impact resistance showed a large improvement with the CaCO₃ concentration. At the same composition (80/10/10 w/w/w), three types of CaCO₃ particles with average diameters of 0.05, 0.6, and 1.0 μm improved the impact fracture energies comparatively. The encapsulation structure of the filler by the grafting elastomer had a detrimental effect on the impact properties because of the strong adhesion between the elastomer and filler and the increasing ligament thickness. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1113–1123, 2005     

Highly Efficient Copper(II) Ion Sorbents Obtained by Calcium Carbonate Mineralization on Functionalized Cross‐Linked Copolymers

A new type of Cu^II ion sorbents is presented. These are obtained by CaCO₃ mineralization from supersaturated solutions on gel‐like cross‐linked polymeric beads as insoluble templates. A divinylbenzene–ethylacrylate–acrylonitrile cross‐linked copolymer functionalized with weakly acidic, basic, or amphoteric functional groups has been used, as well as different initial inorganic concentrations and addition procedures for CaCO₃ crystal growth. The morphology of the new composites was investigated by SEM and compared to that of the unmodified beads, and the polymorph content was established by X‐ray diffraction. The beads, before and after CaCO₃ mineralization, were tested as sorbents for Cu^II ions. The newly formed patterns on the bead surface after Cu^II sorption were observed by SEM, and the elemental distribution on the composites and the chemical structure of crystals after interaction with Cu^II were investigated by EDAX elemental mapping and by FTIR‐ATR spectroscopy, respectively. The sorption capacity increased significantly after CaCO₃ crystals growth on the weak anionic bead surface (up to 1041.5 mg Cu^II/g sample) compared to that of unmodified beads (491.5 mg Cu^II/g sample).     

Synthesis and characterization of well-defined poly(methyl methacrylate)/CaCO3/SiO2 three-component composite particles via reverse atom transfer radical polymerization

The attempt to prepare structurally well-defined polymer/inorganic composite particles, i.e., poly(methyl methacrylate) (PMMA)/CaCO₃/SiO₂ three-component composite particles, via reverse atom transfer radical polymerization (ATRP), using 2-2′-azo-bis-isobutyronitrile as initiator and Cu(II) bromide as catalyst was reported. CaCO₃/SiO₂ two-component composite particles were first obtained through sol–gel method, and their morphology and surface element information were determined by transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The results indicate that the CaCO₃ was encapsulated by the obtained SiO₂. After being modified by silane coupling agent, the CaCO₃/SiO₂ composite particles copolymerized with methyl methacrylate (MMA) under standard reverse ATRP conditions to produce PMMA/CaCO₃/SiO₂ three-component composite particles. In the case concerned, first-order kinetic plots and linear increase of molecular weight (Mn) vs conversion and narrow molecular weight distribution for the graft polymer samples were observed. Furthermore, the gel permeation chromatography results illustrated that both the free PMMA chains from the solvent and the graft PMMA chains from the surface of CaCO₃/SiO₂ two-component composite particles were growing at the same rate. Characterizations of the PMMA-grafted CaCO₃/SiO₂ composite particles were done by Fourier transform infrared and thermogravimetric analysis. The results showed that the surface of the modified inorganic particles was grafted by the MMA and that the grafting percentage was about 8.7%.     

CO2鼓泡法可控制备单层中空CaCO3微球:染料负载及细胞生物成像

在L-蛋氨酸（L-Met）的导向下,可控制备了一种单层中空CaCO₃微球。考察了L-Met的加入量、CO₂流速和反应温度等重要参数对CaCO₃形貌、尺度和晶相的影响。作为一种客体分子载体,该单层中空CaCO₃微球可负载罗丹明B（RhB）,得到一种发光复合材料（RhB@hollow-CaCO₃）。RhB@hollow-CaCO₃）对A-549肺癌细胞（A549 LCCs）和HO8910人卵巢癌细胞（HO8910 OCCs）表现出良好的生物相容性。