Nanosized Calcium Carbonate Research Articles

Nanocomposites Prepared by Solution Blending: Microstructure and Mechanical Properties

Composites of poly(vinyl chloride) (PVC) filled with micron‐ and nanosized calcium carbonate (CaCO3) particles were prepared by solution blending. The influences of particle size and CaCO3 content on the microstructure and mechanical properties of the PVC composites were investigated by means of polarized optical microscopy and mechanical testing. The polarized optical microscope images revealed that nanosized CaCO3 particles were more agglomerated than micron‐sized CaCO3 particles and the amount of agglomerates increased with increasing particle content. PVC/CaCO3‐0.22 composites (PVC nanocomposite filled with 220‐nm‐particle‐sized CaCO3) 5 phr CaCO3 content had the maximum tensile strength. The Young's modulus of all composites increased with increasing particle content. The energy at break of all composites showed a decreasing trend as a function of CaCO3 content and varied with particle size.

Properties of recycled material containing poly(vinyl chloride), polypropylene, and calcium carbonate nanofiller

AbstractEven at low content, polypropylene significantly worsens mechanical properties of the recycled PVC composite, i.e. tensile strength at break and elongation at break. But, if small quantities of surface modified nanofiller calcium carbonate is added, an applicable composite that contains 10–30% of waste material can be made. It was determined that nanosized calcium carbonate lowers melting point of polypropylene, perhaps by changing its crystalline form and has no influence on thermooxidative degradation of poly(vinyl chloride). Addition of nanofiller slightly lowers the surface free energy of the composites what is more prone when the low content of polypropylene is present. The recovery of tensile strength and elongation at break occurs and those properties reach the highest value at about 6% of CaCO3. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

The chemical characterization of tribofilms using XANES — Interaction of nanosize calcium-containing detergents with zinc dialkyldithiophosphate

A Plint friction and wear tester was used to investigate the effect of several calcium-containing detergents on the tribological and tribochemical performance of a zinc dialkyldithiophosphate (ZDDP) lubricating oil additive in a low-sulfur base stock, 100N. Thus, the friction and wear behavior of a steel-on-steel contact lubricated by 100N oil containing ZDDP alone and ZDDP–detergent mixtures at 100 °C was evaluated in a pin-on-disc configuration. The wear scar width of the upper steel pins was determined using an optical microscope, while the tribofilms formed on the lower steel discs were analyzed using X-ray absorption near edge structure (XANES) spectroscopy and X-ray photoelectron spectroscopy (XPS). At the same time, the thermal-oxidation films of the oil blends containing different additives were also prepared on the same steel discs and analyzed using XANES spectroscopy for comparative studies. It was found that in simple formulations the three kinds of calcium-containing detergents improved the friction-reducing and antiwear abilities of the 100N base stock. This was related to the individual tribochemical reactions and the deposition (in one case) of nanosized CaCO3 on the rubbing steel surface, indicating that the calcium-containing detergent had a synergistic antiwear performance with the ZDDP tested in the present work. Moreover, the calcium-containing detergents contributed to retarding the thermo-oxidation and friction-induced decomposition of ZDDP in 100N oil and influenced the composition and thickness of the tribofilms, which could be dependent on the molecular structures of the detergents and directly related to the tribochemistry of ZDDPs in mineral oil. The rubbing of the steel–steel pair at 100 °C was more beneficial for the deposition of nanosized calcium carbonate on the steel surface than heating at 150 °C. The calcium-containing detergents alone in the base stock also experienced tribochemical reactions, leading to obvious changes in the oxidation state of S in the corresponding tribofilms. Therefore, it was supposed that the tribochemical reactions of the ZDDP and detergents together with the deposition of nanosized CaCO3 on the rubbing steel surfaces accounted for the good antiwear performance of the blended oils.Key words: ZDDP, detergent, thermal film, tribofilm, tribochemistry, XANES, XPS.

On the strain rate sensitivity of HDPE/CaCO 3 nanocomposites

In the current study the role of both nano-sized calcium carbonate and strain rate on the tensile properties of HDPE was studied. For this purpose standard tensile samples of HDPE and HDPE/10 vol.% CaCO 3 were performed using extrusion and injection molding methods. Tensile test was done at different strain rates. The results of tests showed that addition of 10 vol.% of nano-sized calcium carbonate made an increase in both yield stress and Young's modulus of HDPE unlike its elongation. Also it was concluded that strain-rate sensitivity of HDPE decreased as nano-sized calcium carbonate was added to it. The data obtained from the tests indicated that the variation of Young's modulus of HDPE nanocomposite could be obtained from the following equation, i.e. E / E 1 = [ 1.0 + 5 φ 2 + 15.5 φ 2 2 ] .

Fabrication and anti-frosting performance of super hydrophobic coating based on modified nano-sized calcium carbonate and ordinary polyacrylate

Nano-sized calcium carbonate (CaCO 3) particles were modified by heptadecafluorodecyl trimethoxysilane under acidic water condition. An ordinary polyacrylate prepared via radical copolymerization of methyl methacrylate, butyl acrylate, acrylic acid and β-hydroxyethyl methacrylate was used as the binder to form hydrophobic coatings with the modified CaCO 3. Super hydrophobic coating with water contact angle of 155° was obtained from modified CaCO 3 and the polyacrylate at their weight ratio of 8/2 by a simple procedure. Based on surface analysis by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), the super hydrophobicity can be attributed to both the surface microstructure and surface enrichment of fluoroalkyl chains. Due to a low water sliding angle, carbon black powder on super hydrophobic surface was easily removed by rolling water droplet. Furthermore, the anti-frosting performance of different surfaces was investigated, which indicated that the frost formed on superhydrophobic surface was greatly retarded compared with that on bare copper surface. The surface kept super hydrophobicity even after freezing–thawing treatment for 10 times.

Micro- and Nano-Sized Calcium Carbonate Toughened Polystyrene

Polystyrene (PS)/CaCO3 micro- and nanocomposites were prepared by melt mixing in a twin screw extruder using four particles with average diameters of 55 nm, 70 nm, 240 nm, and 10 /microm in various loadings. It was found that PS can be effectively toughened with 1 wt% cubic shaped CaCO3 particles (55 nm, 70 nm, 10 microm) achieving significant increases of impact strength by 52%, 95%, and 190% respectively relative to neat PS. However, the needle shaped nanoparticles (240 nm) were not effective for improving the toughness of the matrix. SEM analysis of the fractured surfaces indicated good fillers dispersion at the optimum filler loading of 1 wt%, and the cavitations-induced shear yielding in the polymer matrix are shown to be the main toughening mechanism.

Morphology prediction of ternary polypropylene composites containing elastomer and calcium carbonate nanoparticles filler

AbstractIn this work, the morphology was studied in ternary composites of polypropylene (PP) with nanosized calcium carbonate (nano‐CaCO3) fillers and elastomer inclusions and the thermodynamic consideration was used to analyze the formation of phase structure of the composites. The wetting coefficient (ωa), interfacial tension (γAB), and work of adhesion (WAB) were calculated to predict dispersion state of nano‐CaCO3 fillers. A comparison of the prediction and SEM analysis was given. The results show that three types of phase structures were formed: an encapsulation of the filler by elastomer, a separate dispersion of the filler and elastomer, and a particular structure of the filler at the PP/elastomer interface. The predictions by ωa were all successfully supported‐up by SEM analysis and the predictions by WAB were however trustless. Both γAB and WAB can predict a separate dispersion or an encapsulation phase structure, but they were not available for the particular structure of the filler at the PP/elastomer interface. ωa was competent and favored for the prediction of all three types of morphology among the three parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1578–1584, 2007

Novel rigid poly(vinyl chloride) ternary nanocomposites containing ultrafine full-vulcanized powdered rubber and untreated nano-sized calcium carbonate

Novel rigid poly(vinyl chloride)/ultrafine full-vulcanized powdered rubber (UFPR)/untreated nano-sized calcium carbonate (UNCC) ternary nanocomposites were fabricated. TEM observation revealed that good dispersion of UNCC particles (about 40 nm) in the PVC matrix was achieved with the help of UFPR (about 150 nm). Interestingly, the PVC ternary nanocomposites excel corresponding PVC binary ones, as well as neat rigid PVC, in both heat resistance and toughness due to the synergistic effect of UNCC and NBR-UFPR.

Coated Nano-Sized CaCO3 Reinforced Semi-Crystalline EPDM

Nano-sized calcium carbonate (CaCO3) was used to reinforce a semi-crystalline ethylene-propylene-diene monomer rubber (EPDM). For comparison, micron-sized CaCO3 was also studied. It was found that both nano-sized CaCO3 and micron-sized CaCO3 improved the mechanical properties of the EPDM vulcanizates, and nano-sized CaCO3 exhibited better reinforcement effect than micron-sized CaCO3. The difference in reinforcement effects of nano-sized CaCO3 and micron-sized CaCO3 was explained in terms of the filler particle size and the crosslink density of the vulcanizates. The nano-sized CaCO3 was also modified by titanate, borate, and aluminate-titanate complex coupling agents and used to reinforce EPDM vulcanizates. The results showed that titanate coupling agent coated nano-sized CaCO3 exhibited the best reinforcement ability. FE-SEM micrographs showed that stearic acid, titanate, and aluminate-titanate complex coupling agents could improve the dispersion of the CaCO3 in the rubber matrix remarkably, whereas borate coupling agent could not. The effect of modified nano-sized CaCO3 on the dynamical mechanical properties was also studied. Incorporation of CaCO3 reduced the glass transition temperature (Tg) of the vulcanizates. In comparison with nano-sized CaCO3, micron-sized CaCO3 depressed the Tg more remarkably.

One-step synthesis of magnetic hollow silica and their application for nanomedicine

Magnetic nanoparticles are usually present in the form of magnetic carriers and used in nanomedicine and biosystem. In this paper, magnetic hollow silica (MHS) nanoparticles were fabricated by a one-step synthesis of Fe3O4 nanoparticles and then coating of silica on nanosized spherical calcium carbonate under alkaline conditions, in which nanosized calcium carbonate (CaCO3, 25–60nm) was used as a scarified template, tetraethoxysilane as a precursor, and Fe3O4 nanoparticles (∼5nm), formed in the initial reaction stage, as magnetic agents. The as-synthesized nanoparticles were immersed in a weak acetic acidic solution to remove CaCO3, forming MHS carriers. The nanostructures of the MHS carriers were characterized by scanning electron microscope, transmission electron microscope, and x-ray diffraction. Superconducting quantum interference device measurement exhibited that the MHS nanoparticles were superparamagnetic. Toxicity was tested for MHS carriers using rat brain microvascular endothelial cells. The cells treated with concentration lower than 50μg∕ml of the MHS nanoparticles showed no significant toxicity. After modification by silane coupling agent, the MHS carriers have strong absorption for ibuprofen in nanomedicine field.

Nucleation activity of nanosized CaCO 3 on crystallization of isotactic polypropylene, in dependence on crystal modification, particle shape, and coating

A detailed analysis of the effect of calcium carbonate nanoparticles on crystallization of isotactic polypropylene (iPP) is reported in this contribution. CaCO 3 nanoparticles with different crystal modifications (calcite and aragonite) and particle shape were added in small percentages to iPP. The nanoparticles were coated with two types of compatibilizer (either polypropylene- g-maleic anhydride copolymer, or fatty acids) to improve dispersion and adhesion with the polymer matrix. It was found that the type of coating agent used largely affects the nucleating ability of calcium carbonate towards formation of polypropylene crystals. CaCO 3 nanoparticles coated with maleated polypropylene can successfully promote nucleation of iPP crystals, whereas the addition of nanosized calcium carbonate coated with fatty acids delays crystallization of iPP, the effect being mainly ascribed to the physical state of the coating in the investigated temperature range for crystallization of iPP, as well as to possible dissolution by fatty acids of heterogeneities originally present in the polypropylene matrix.

Synthesis of nanosized calcium carbonate (aragonite) via a polyacrylamide inducing process

A carbonation route for the synthesis of nanosized calcium carbonate (aragonite) was studied. In the process, polyacrylamide was used as an organic substrate to induce the nucleation and growth of calcium carbonate. The calcium carbonate particles were produced by means of carbonation of the mixture of calcium hydroxide and polyacrylamide by bubbling CO 2/N 2 gas mixture . The operating parameters such as the concentration of organic substrate and temperature were varied to study their influences on the polymorph and crystal sizes of calcium carbonate particles. The morphology of the calcium carbonate particles was characterized with transmission electron micrograph (TEM). The synthesized calcium carbonate particles in the presence of organic substrate are the mixture of aragonite with needle shape and calcite with cubic shape. Fourier transform infrared spectroscopy (FTIR) analysis reveals the presence of aragonite and calcite. The polymorphs and their crystal sizes were characterized with X-ray diffraction (XRD). The calcium carbonate nucleated in the organic substrate exhibited different endothermic peak in differential thermal gravity (DTG) results compared to one coexisting with the organic substrate.

Morphology and mechanical properties of polypropylene/calcium carbonate nanocomposites

Three polypropylene (PP) matrices with different intrinsic toughness were used to study the morphology and mechanical properties of polypropylene filled with nano-sized calcium carbonate particles. PP1 was a homopolymer, PP2 was a propylene-ethylene copolymer, and PP3 was a mixture of PP1 and PP2 (PP1:PP2 = 1:1, weight ratio). The precipitated calcium carbonate (CC0.07) with an average particle size of 0.07 μm was used. Only the yield strength of PP1 nanocomposites filled with low CC0.07 contents (from 2 to 10 wt.%) could increase. When the CC0.07 content was appropriate, the impact strength of all three PP nanocomposites could improve. It was interesting that the intrinsic toughness of PP matrix would influence the toughening effect of the nanoparticles. Only in the case of the moderate matrix toughness (PP3 matrix), the nanocomposites could receive the highest extent of toughness increase (4.3 times that of matrix).

Nanostructured modification of mineral particle surfaces in Ca(OH) 2–H 2O–CO 2 system

Traditionally pulverized particulates of raw minerals, such as ground calcium carbonate (GCC), wollastonite and dolomite, are usually of smooth/flat surface and pointed edges angles which have disadvantageous effects on the mechanical properties of composite polymer materials filled with the powders. On the other hand, dispersion of nanoscaled calcuim carbonate powders can not be easily achieved when filled in organic polymer, because of their huge specific surface energy and intense/strong conglomeration. Aiming at utilizing the advantages of both traditionally pulverized particles and nanosized ones and overcoming their disadvantages, a wet-coating method is developed and three kinds of raw-mineral-based composite powders have been successfully prepared by chemical precipitation in Ca(OH) 2–H 2O–CO 2 system on the pulverized particles in our group. It is shown that the composite powders of traditionally pulverized particles coated by nanosized calcium carbonate particles of 20–100 nm are of rough surface, blunt edges, larger specific surface area, compared with the uncoated powders. Some technological parameters are mainly analyzed for the coating process in the paper. Blending the coated powders to polypropylene demonstrates significant improvement in filling properties to the uncoated ones.

Cure Characteristics and Mechanical Properties of NR/ SBR Blends Filled with Nano-sized CaCO3

Four kinds of nano-sized calcium carbonate (CaCO3) surface-modified with stearic acid, aluminate, titanate and aluminate-titanate complex coupling agents, were used to reinforce natural rubber (NR)/styrene-butadiene rubber (SBR) blends. The effects of surface modification and CaCO3 content on the cure characteristics, swelling behaviour, and mechanical properties of NR/SBR blends were studied. The surface modification of CaCO3 improved the processing and mechanical properties, and the stearic acid coated CaCO3 (SA-CaCO3) had finer dispersion and produced a better reinforcement effect than the other modified CaCO3. Furthermore, a commercial high abrasion furnace carbon black (HAF) was used for comparison. The results showed that both CaCO3 and HAF increased the cure rate, reduced the optimum cure time and improved the mechanical properties of NR/SBR blends at appropriate filler contents. The tensile strength of filled NR/SBR composites reached its maximum value when the SA-CaCO3 content was 50 phr or the HAF content was 30 phr. The modulus at 200%, tear strength, and Shore A hardness of filled NR/SBR composites all increased with increasing filler content. The CaCO3 reinforced the NR/SBR blends to some extent, though it was still not as effective as HAF.

Effect of nanosized calcium carbonate on the mechanical properties of latex films

AbstractAn acrylic dispersed nanosized calcium carbonate filler was added to a prevulcanized latex compound in different amounts. The effect of filler content on the curing time, modulus, tensile strength, elongation at break (Eb) before and after ageing, and the morphology of the films was investigated. Results showed that the curing time decreased with filler loading because of the increased interaction between the filler and rubber matrix, as reflected by the decrease in the apparent swelling index. Modulus at 100% elongation and modulus at 300% elongation increased with filler loading. Tensile strength and Eb increased up to 10 phr of filler loading and then decreased again. Aged films showed improved mechanical properties compared to those of unaged films. Micrographs showed that agglomeration occurred as the filler content was increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1550–1556, 2005

Study on mechanical property of epoxy composite filled with nano-sized calcium carbonate particles

Epoxy resin (EP) is used widely nowadays as a structural, adhesive and electronic material due to exhibiting high strength, high elastic modulus, high insulation etc. [1]. However, EP may show limitations, especially over-fragility in application, so other constituents have to be added to improve its performance. Methods of toughening EP has long been sought, and one of the most common methods is the incorporation into EP of a dispersed rubbery elastomer, which can enhance impact strenght of EP at the expense of weakening rigidity and heat-resistance of the matrix as well as raising cost [2]. Calcium carbonate is considered as a suitable substitute for rubbery elastomer in EP matrix because it demonstrates high rigidity and may overcome the shortcomings of rubbery elastomer if incorporated well into the EP matrix. Traditionally, micron-sized calcium carbonate is added into polymers for the purpose of reducing formulation cost of the polymer-based composites. Nevertheless, micron-sized calcium carbonate may have negative impact on the mechnical performance of polymers. It was reported that mechanical properties of polymers could be otherwise improved by adding nano-sized fillers. Generally, mechanical behaviors of particulate-filled polymers, which have a very complex dependence on the interfacial bonding between the filler and the matrix, are influenced strongly by factors such as size, content and shape of the filler. Of these fillers, nano-sized calcium carbonate (nano-CaCO3) particles have attracted considerable attention and play effective role in many composite systems [3]. This work reports an investigation of the influence of nano-CaCO3 on the mechanical properties fo EP composite. Nano-CaCO3 employed in this experiment, with a cubic shape and an average diameter of 40 nm (Fig. 1), was synthesized by the reactive precipitation reaction method under high gravity environment. Detailed methodology and basic theory about the preparation of nano-CaCO3 by this method can be found in the reference [4]. The dispersion degree of the filler in the matrix will significantly influence the properties of composite. However, it is very difficult to disperse nano-sized particles in a high viscous polymer matrix. Generl method is to introduce a high shearing force to the mixture in order to intermix the fillers with the matrix [5].

Synthesis of Hollow Titania Using Nanosized Calcium Carbonate as a Template

Abstract Spherical hollow titania materials with a diameter of 60–100 nm and wall thickness of approximately 10 nm were synthesized using nanosized CaCO3 particles as inorganic templates. BET surface area of as-synthesized titania was 381.15 m2/g, and decreased to 124.36 m2/g after calcination at 500 °C for 2 h.

Irradiation-induced surface graft polymerization onto calcium carbonate nanoparticles and its toughening effects on polypropylene composites

Nano-sized calcium carbonate was pretreated with silane coupling agent and then mixed with butyl acrylate that is of larger amount than the nanoparticles. Under γ-irradiation, graft polymerization occurred on the nanoparticle surface, forming a nanocomposite structure consisting of grafted poly(butyl acrylate) (PBA), homopolymerized PBA, and the segregated nanoparticles. It was found that the silane pretreatment significantly promoted the graft reaction. When the grafted nano-CaCO3 particles were melt compounded with polypropylene (PP), an obvious synergistic effect, offered by (i) the chemical bonding between the elastomer type grafted PBA and nano-CaCO3 and (ii) the deliberately introduced thick interlayer mainly constructed by the homopolymerized PBA, led to a significant increase in notch impact strengths and elongation to break of PP at a rather low content of nano-CaCO3. Meanwhile, the tensile stiffness of the composites was also slightly increased and the yielding strength of the composites was almost unchanged. The results are different from those with conventional rubber-toughened plastics, in which the improvement of ductility is acquired at high additive fraction and a great expense of strength performance. POLYM. ENG. SCI., 45:529–538, 2005. © 2005 Society of Plastics Engineers

Synthesis of CaCO 3 Nanoparticles by Carbonation of Lime Solutions in Reverse Micellar Systems

Application of reverse micelles for the synthesis of nano-sized calcium carbonate particles in different solvents (cyclohexane, decane and heptane) has been investigated. The effect of the mole ratio of water-to-surfactant (R) and type of solvent has been studied on the size and nature of the carbonate particles. The results indicate that an increase in water-to-surfactant ratio results in a larger particle size.