Modified Nano-calcium Carbonate Research Articles

Fluor-silane modified nano-calcium carbonate (CaCO3) as a hydrophobic coating for the conservation of sandstone via bio-inspired design

Ancient cultural relics built of red sandstone have high historical value. However, due to the acceleration of the industrialization process of human civilization, increasingly frequent acid rain has caused irreversible damage to the surface of red sandstone artifacts. In this research, a fluor-silane modified nano-calcium carbonate (CaCO3) was prepared as a biomimetic hydrophobic coating for the conservation of red sandstone inspired by the lotus leaf effect. Characterizations and immersion tests were carried out to assess the protective properties of the coating. XRD, FT-IR, TEM and SEM were combined to characterize the morphology of the coating. In addition, the water contact angle was measured before and after immersion in the simulated acid rain. The results indicate that this kind of hydrophobic nano-CaCO3 coating effectively protected the sandstone from the deleterious effects of acid rain.

Effect of Anionic Surfactant on Adsorption Properties of Nano Calcium Carbonate

Because of its superior surface properties, nanocalcium carbonate can be applied to the adsorption of heavy metals in wastewater. However, because of the easy aggregation of nanocalcium carbonate, high surface energy and poor dispersibility in water, it is not conducive to the process of adsorption. Therefore, surface modification of nanocalcium carbonate is needed. In this paper, nanocalcium carbonate was prepared by liquid phase method. And the nanocalcium carbonate was surface modified by sodium dodecyl sulfate. The effects of modifier amount, modification temperature, and modification time on the activation and absorbance of nanocalcium carbonate were investigated. And the morphology and particle size of modified nanocalcium carbonate were tested by SEM and XRD patterns.The results show that the dispersion and surface activity of the modified nanocalcium carbonate have been improved remarkably. Moreover, the Cu2+ was adsorbed by sodium dodecyl sulfate modified nanocalcium carbonate and unmodified nanocalcium carbonate under the optimum modification conditions. And the effects of nanocalcium carbonate initial concentration on the adsorption performance were studied. The results show that the adsorption performance of modified calcium carbonate is better than that of the unmodified. Moreover, the adsorption process is studied by adsorption isotherm. By drawing the adsorption isotherms lines and by comparing the fitting result of the experimental data based on the Langmuir model and that of Freundlich model, it is found that the adsorption of Cu2+ by modified nanocalcium carbonate meets the Langmuir model.

Modification of Syndiotactic Polypropylene with Nano-Calcium Carbonate and Halloysite

Abstract Composites of syndiotactic polypropylene (sPP) with 5 to 17 vol.° of halloysite and 2.5 to 7.5 vol.° of stearic acid modified nano-calcium carbonate, having an average grain size of 80 nm, were prepared and examined. The effect of fillers on thermal properties of sPP was different; halloysite increased markedly peak crystallization temperature. The composites with the highest filler contents, 7.5 vol.° of calcium carbonate and 17 vol.° of halloysite, exhibited a solid-like behavior at 170 °C, with the storage modulus exceeding the loss modulus in the entire frequency range, that is 512 to 0.1 rad s−1. The composites with halloysite exhibited decreased Izod impact strength compared to neat sPP. On the contrary, 2.7 fold improvement of the impact strength was found for the composites with nano-calcium carbonate. Moreover, nano-calcium carbonate did not worsen the drawability of the materials during uniaxial drawing. It was found that debonding at calcium carbonate/sPP interface occurred both during the impact test and tensile drawing facilitating the plastic deformation of the polymer.

Synthesis, mechanical properties and iron surface conservation behavior of UV-curable waterborne polyurethane-acrylate coating modified with inorganic carbonate

The performances of UV-curable waterborne polyurethane-acrylate (WPUA) composite modified with nano calcium carbonate (NCA) were highlighted in this work. The γ-methacryloxy propyl trimethoxyl silane (KH-570) and polysorbate 80 (Tween-80) were used to enhance interfacial interaction between NCA and WPUA matrix. Transmission electron microscopy (TEM), particle size analysis and Fourier transfer infrared (FT-IR) spectrometry were employed to examine the micromorphology and the variation of function group of modified nano calcium carbonate (MNCA). Three different WPUA oligomers were investigated to obtain the optimized R value (the molar ratio of –NCO:–OH) via in situ polymerization and anion self-emulsification process. Results showed that WPUA displayed excellent film-forming ability and mechanical properties when R value was 2.2:1.0. These UV-curable WPUA films modified with MNCA (UV-MNCA/WPUA) were prepared through environmentally friendly UV-curable technology and investigated by thermogravimetric (TG) analysis, scanning electron microscope (SEM), X-ray diffractometer (XRD) and FT-IR. UV-MNCA/WPUA-3-3 film had the best overall performances with MNCA-2 and UV-WPUA at the mass ratio of 3.6%. Finally, the experimental results demonstrated that the as-obtained UV-curable coating had outstanding conservation effect to iron surface, providing a promising way for protection of iron cultural relics.

有机改性纳米碳酸钙的制备与性能研究

本文研究了以碳化法结合有机包覆制备纳米碳酸钙的工艺与性能。以氧化钙和二氧化碳为原料，柠檬酸为表面控制剂，并添加适量的分散剂对其进行表面改性，制备出有机改性的纳米碳酸钙。通过多种仪器手段对所制备的样品进行了形貌、粒径、元素、化学成分等定量与定性分析。结果表明，所制备的球形碳酸钙颗粒的粒径从十几纳米到几十纳米不等，存在软团聚现象，粒径分布窄，表面存在有离子键合的有机物。 This research studied the preparation technology and properties of nanometer calcium carbonate by carbonization and organic coated method. Calcium oxide and carbon dioxide were used as raw materials, citric acid was used as the surface control agent, and appropriate amount of dispersing agent was used as surface modification to prepare organically modified nano-calcium carbonate. The product was quantitatively and qualitatively analyzed by a variety of instruments, such as the morphology of the sample, size, elements and chemical composition. The results showed that the prepared calcium carbonate’s average particle size was 60 nm; there was a slight soft reunion phenomenon; particle size distribution was narrow; surface has ionic bonded organic matter.

Effects of cationic surfactant during the precipitation of calcium carbonate nano-particles on their size, morphology, and other characteristics

Microsized calcium carbonates, including precipitated and ground calcium carbonates have been widely used in paper industry. One of the most interesting perspectives to filler technology is the development of nano-sized, high performance, and low cost fillers. However, due to the high cost of nano-sized filler, it is critically important to develop a technique that achieve this perspective. The main goals of this study were to prepare unmodified and CTAB modified nano-calcium carbonate fillers. The effect of CaO concentration, CO2 flow rate and CTAB surfactant on size and morphology of the prepared CaCO3 particles were investigated. X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), zeta potential and Fourier transformer infra-red (FT-IR) were used for the characterization of the prepared nano-sized calcium carbonate particles. The results showed that the obtained calcium carbonate was calcite phase. The particle sizes and morphologies of CaCO3 varied from rhombohedral (15–35nm) to scalenohedral (400nm in diameter and 2μm length) with changing the operating variables, CaO concentration, CO2 flow rate and surfactants concentration. CTAB neutralized the negative surface charge developed at the CaCO3 surface and the zeta potential approached to zero. On the other hand, the suggested mechanism of CTAB for synthesis of nano-calcium carbonate was also studied.

α‐Amylase immobilization on functionalized nano CaCO3 by covalent attachment

AbstractIn this study, α‐amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO3) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (50–90°C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. Vmax values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.

Crystallization kinetics of polypropylene composites filled with nano calcium carbonate modified with maleic anhydride

AbstractThe subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano‐CaCO3) composites. In this study, 5 wt % nano‐CaCO3 modified with different contents of MAH was filled into a PP matrix. X‐ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nano‐CaCO3 modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano‐CaCO3 filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano‐CaCO3. We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the β‐form crystal into the α‐form crystal took place in the composite system and the β‐form crystal had a higher nucleation rate and growth process than the α‐form crystal in the PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Preparation of new Environmental Materials from Poplar Wood as Raw Material

The objective of this paper is to use the modified nano-calcium carbonate compositing directly or sol-gel compositing with poplar wood by the vacuum infusion methods to prepare new environmental materials. This paper introduces promotion effects of nano-technology on the development of fast-growing poplar wood, the problems and research of fast-growing poplar wood compositing with nano-materials. By preparing the new environmental materials, we implement the use of plantation timber to produce high value-added products, and the use of a variety of nano-technology to improve the performances of wood, and improve timber utilization.

Effect of unsaturated hydroxyl-fatty acid modified nano-CaCO3 on the morphological and rheological behavior of PP

A modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of unsaturated hydroxylfatty acid on the surface of CCR powders using a solid state method; the latter were commercial nano-CaCO3 modified with stearic acid. FTIR studies indicate that the modifier is combined on the surface of CaCO3. PP/EPDM/nano-CaCO3 ternary composites were prepared by a melt-mixing method. SEM and TEM were utilized to examine the morphology of the composites. The tensile fractured surface of PP/EPDM/R-CCR showed a fibroid morphology and large-scale yield deformation. The impact fractured surface showed that the amount of cavities in the PP/EPDM/R-CCR system was increased, however their size diminished obviously. R-CCR particles were dispersed uniformly in the PP matrix, and their compatibility was distinctly improved as compared to CCR when the amount of R-CCR was 15 h−1. The tensile strength remained nearly constant (reduced from 27.6 MPa to 27.5 MPa), while the impact strength increased from 9.6 kJ/m2 to 15.4 kJ/m2 as CCR was replaced by R-CCR. Meanwhile, the bending strength and bending modulus also increased correspondingly. Furthermore, the impact strength of PP/EPDM/R-CCR was maintained at a high level (15.4 kJ/m2), which was more than the sum of that of PP/EPDM and PP/R-CCR (6.6 kJ/m2 and 6.1 kJ/m2 respectively). This indicates that the R-CCR and EPDM have a significant synergistic toughening effect on PP while maintaining the strength and modulus of virgin PP. Both the storage modulus G′ and loss modulus G″ of PP/EPDM and PP/EPDM/R-CCR composites increase with increasing frequency, but the values of G′ and G″ of the tertiary composite are relatively higher than those of the binary system. The loss factor and viscosity decrease with increasing frequency, but there is little difference between tertiary and binary composites. The apparent viscosity η of the tertiary system containing R-CCR is lower than that of the tertiary system containing CCR and virgin PP. The viscosity of the composites sig-nificantly decreases with increasing shear rate. The mea-sured mechanical properties of the composites indicate that replacing CCR with R-CCR for binary composites could simultaneously enhance the toughness and strength of PP.

Nonisothermal crystallization behavior and crystals morphology of poly(trimethylene terephthalate)/nano‐calcium carbonate composites

AbstractNonisothermal crystallization behavior and crystal morphology of poly(trimethylene terephthalate) (PTT) composites filled with modified nano‐calcium carbonate (CaCO3) had been investigated by using differential scanning calorimetry and polarized optical microscopy. The modified Avrami equation and Ozawa theory were used to investigate the nonisothermal crystallization, respectively. The particles of nano‐CaCO3, acting as a nucleation agent in composites, accelerated the crystallization rate by decreasing the half‐time of crystallization or increasing the parameters of Zc and K(T). Moreover, the nano‐composite with 2 wt% nano‐CaCO3 exhibited the highest crystallization rate. The Avrami and the Ozawa exponents, n and m of the nano‐composites, were higher than those of neat PTT, suggesting more complicated interaction between molecular chains and the nanoparticles that cause the changes of the nucleation mode and the crystal growth dimension. The effective activation energy calculated from the Friedman formula was reduced as nano‐CaCO3 content increased, suggesting that the nano‐CaCO3 made the molecular chains of PTT easier to crystallize during the nonisothermal crystallization process. The optical micrographs showed that much smaller or less perfect crystals were formed in composites because of the presence of the nano‐CaCO3 particles. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Crystallization Behavior of PP in Composites with EPDM and a Surface Modified Nano-Calcium Carbonate

A modified nano-CaCO3 (RCCR) was prepared by mixing the stearic acid treated nano-CaCO3 (CCR) with organic agent containing —OH, —COOH, and C=C groups and it was then melt compounded with polypropylene PP and Ethylene-propylene-diene mischpolymer (EPDM) to prepare PP/EPDM/nano-CaCO 3 composites. The effects of RCCR on the crystallization behavior of PP in the composites were studied by DSC. The crystal type structure of PP in the composites was studied by X-ray diffraction and polarized optical microscope (POM). It was found that RCCR acts as a nucleating agent. It initiates PP crystallizing at higher temperature, and lowers degree of crystallinity and crystal size, and induces the formation of β crystallite. RCCR in collaboration with EPDM can obviously increase the content of β crystallite. Isothermal crystallization studies reveal that the activation energy of PP in PP/EPDM/RCCR is lower than that of PP/EPDM/CCR.

Polypropylene Composite Toughened by a Novel Modified Nano-CaCO3

A novel modified nano-calcium carbonate (R-CCR) was prepared by coating a layer of organic compound with three functional groups (–OH, –COOH and C=C) on the surface of CCR (a commercial nano-CaCO3 modified with stearic acid) powders in solid state. Fourier transform infrared spectrometer (FTIR) indicated that the modifier is combined on the surface of CaCO3. Transmission electron microscope (TEM) showed the particle sizes of R-CCR and CCR locate in the range of 40 ∼ 90 nm. The mechanical property results show that R-CCR and EPDM have obvious synergistic toughening effects on PP. The determination of density and swelling ratio suggest that the cavitation of PP/EPDM/R-CCR composite is bigger than that of PP/EPDM/CCR. Scanning electronic microscopy (SEM) photographs of the impact-fractured surfaces show that there are many little cavities in the PP/EPDM/R-CCR system, R-CCR particles disperse in the matrix more uniformly and finely, and the agglomeration is weakened. The SEM photographs of the tensile-fractured surface of PP/EPDM/R-CCR show a fibroid morphology and large-scale yield deformation. The addition of R-CCR induces the formation of β–phase PP and the content of β–phase PP increases obviously after addition of EPDM. The synergistic toughening effects of R-CCR and EPDM on PP come from the dual effect of cavitation and β–phase PP. The 5% weight loss temperature of PP/EPDM/R-CCR composite is 70.5°C higher than pure PP. The VICAT of the PP/EPDM/R-CCR composite is 8.4°C higher than the PP/EPDM composite.