Surface-modified Calcium Carbonate Research Articles

Spatiotemporal based response for methylene blue removal using surface modified calcium carbonate microspheres coated with Bacillus sp.

Calcium carbonate microspheres are attractive for their biocompatibility, high loading capacity and easy preparation. They can be used in biomedicine and catalytic applications. In the present work, calcium carbonate microspheres were surface modified with polyvinylpyrrolidone (PVP) followed by irradiation at 5 kGy prior to coating with Bacillus sp. cells. To provide cell protection and internal energy storage, polyhydroxybutyrate (PHB) was induced using 3 factors 2 levels factorial design where the order of effect on PHB% was pH > incubation time > glucose concentration. The highest production was 81.68 PHB% at pH 9, 20 g L-1 glucose and 4 days incubation time. Bacillus sp. cells grown under PHB optimal conditions were used to coat the surface modified calcium carbonate microspheres. Characterization was performed using X-ray diffraction, Fourier Transform Infrared Spectroscopy, Dynamic light Scattering, Zeta potential and Scanning Electron Microscopy. The results obtained confirm the formation and coating of microspheres of 2.34 μm and -16 mV. The prepared microspheres were used in bioremoval of methylene blue dye, the results showed spatiotemporal response for MB-microsphere interaction, where PHB induced Bacillus sp. coated microspheres initially adsorb MB to its outer surface within 1 h but decolorization takes place when the incubation time extends to 18 h. The microspheres can be reused up to 3 times with the same efficiency and with no desorption. These results suggest that the surface modified calcium carbonate can be tailored according to the requirement which can be delivery of biomaterial, bioadsorption or bioremediation.

Structure-Dielectric Property Relationship in Polypropylene/Multi-Element Oxide Nanocomposites

This paper reports on an investigation into the effects of different multi-element oxide nanofillers on the structure and dielectric properties of polypropylene (PP)-based nanocomposites. Magnesium aluminate (MgAl2O4), calcium carbonate (CaCO3) and surface-modified calcium carbonate (CaCO3T) have been added to the PP to determine their effects on thermal properties, structural changes, dielectric response and breakdown strength. The results show that PP nanocomposites containing MgAl2O4 possess lowered breakdown strength compared to unfilled PP. In contrast, adding CaCO3 to PP results in a higher breakdown strength of the nanocomposites compared to nanocomposites containing MgAl2O4. Meanwhile, nanocomposites containing CaCO3T possess the highest breakdown strength among the systems considered. Possible mechanisms governing these dielectric property changes under alternating current and direct current electric fields are discussed.

Influence of the Surface Modification of Calcium Carbonate on Polyamide 12 Composites.

In previous investigations, it was found that the thermal properties of a polyamide 12 compound can be manipulated, using a designed filler, to improve the melting as well as crystallization behavior, determined for selective laser sintering. A common downside of the introduction of a non-flexing mineral filler is the reduction of the mechanical properties, such as ductility. This paper investigates the influence of content and surface modification of limestone on the mechanical properties. The aim is to understand the effect of an optimized coupling agent on the properties of a compound, containing polyamide 12 filled with 10 wt % of surface modified calcium carbonate. A range of four mineral filler modifications was chosen to investigate their coupling effect, namely 6-amino hexanoic acid, ε-caprolactam, l-arginine or glutamic acid. The in advance surface modified fillers were then each used in combination with the polyamide 12 in a twin-screw extrusion process. With an optimized surface modifying agent, the tensile strength as well as elongation at break can be improved in comparison with uncoated filler implementation, such that up to 60% of the loss of ductility and toughness of a final part when using an untreated filler could be regained using an optimized surface modifier at a correct amount. With the tested filler grade and the specific tested filler amount, the optimized amount of 6-amino hexanoic acid was approx. 2.5 mmol of treatment agent per 100 m2 of CaCO3. These found improvements in a twin-screw extruded polyamide 12 compound show the possible usage of modified calcium carbonate as a functional filler in additive manufacturing and can potentially be transferred in a subsequent investigation in the selective laser sintering process.

Fabrication and characterization of composites composed of a bioresorbable polyester matrix and surface modified calcium carbonate whisker for bone regeneration

This work aims to evaluate the potential of a bioresorbable composite as material for bone regeneration. Surface‐modified calcium carbonate whiskers (CCWs) were prepared by grafting of ethylene glycol (EG) using 1,6‐hexamethylene diisocyanate as coupling agent, followed by ring‐opening polymerization of l‐lactide initiated by the hydroxyl group of EG. The resulting PLLA‐EG‐g‐CCW was used as filler to reinforce a bioresorbable terpolymer, poly(l‐lactide‐co‐trimethylene carbonate‐co‐glycolide) (PLTG). The mechanical properties and thermal stability of the PLTG/PLLA‐EG‐g‐CCW composites were greatly improved. Compared with neat PLTG, a 39.3% increase in tensile strength and 26.7% increase in elongation at break were obtained for the composite with 2 wt% PLLA‐EG‐g‐CCW filler. This was assigned to the reinforcement effect of evenly dispersed PLLA‐EG‐g‐CCW in the polymeric matrix. In fact, entanglement of PLLA grafts at the surface of PLLA‐EG‐g‐CCW with PLTG chains results in a homogeneous distribution of the filler in the matrix. Thus, the composites are simultaneously strengthened and toughened. The cytocompatibility of the materials was evaluated from cell morphology and 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay using L929 mouse fibroblast cell line. The results indicate that the composite presents very low cytotoxicity. Copyright © 2017 John Wiley & Sons, Ltd.

Rheological investigation of complex micro and nanofibrillated cellulose (MNFC) suspensions: Discussion of flow curves and gel stability

Micro and nanofibrillated cellulose in aqueous suspension presents many challenges when considering its use, for example, in forming nanocomposites. The inclusion of filler particles either as extender or as functional additive allows the range of strength and deformation properties to be extended. These properties, however, are linked in many cases to the rheological properties of the raw material mix. Interactions under dynamic shear or under controlled stress at low amplitude reveal the potential to generate functional interactions, not only between the cellulose components themselves but also between the cellulose and polymer additives, as well as surface modified pigment fillers. Examples are given demonstrating the action of adding cellulosic polymer in the form of carboxymethyl cellulose (CMC) to micro and nanofibrillated cellulose (MNFC). Rheological studies show how these combinations with CMC, added either in free form or preadsorbed onto calcium carbonate filler particles, lead to a variety of responses. Dispersability of the MNFC is increased by the use of free CMC polymer addition, and the usually expected flocculating action on added filler is seen not to occur. Alternatively, the preadsorbed CMC on the calcium carbonate pigment filler leads to an interaction between the fibrillar cellulose and the surface modified calcium carbonate pigment filler, to which incorporation of cationic polymer leads to a reduction of interaction, provided theaddition level does not exceed the isoelectric point of the mix. The observations are viewed in the context of a combination of proposed physical contact dynamics in the form of disordered and ordered alignment.

Composites of poly(l-lactide-trimethylene carbonate-glycolide) and surface modified calcium carbonate whiskers as a potential bone substitute material

Calcium carbonate whiskers are surface modified by grafting of poly(l-lactide) chains, and used to reinforce a biodegradable terpolymer matrix. Optimal properties are obtained for composites with a PLLA-g-CCW content of 2 wt%.

Ultraviolet-curable polyurethane acrylate nanocomposite coatings based on surface-modified calcium carbonate

Abstract Polyurethane acrylate/surface-modified colloidal calcium carbonate (PUA/SCaCO3) nanocomposite coatings were successfully prepared via a UV-curing technology. The structural and morphological features of the PUA/SCaCO3 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), and wide angle X-ray diffraction (XRD). The physical properties were strongly dependent upon chemical and morphological structures that originated from differences in SCaCO3 loading. A critical SCaCO3 concentration was observed for the evolution of both the structure and physical properties of the PUA/SCaCO3 nanocomposites as a function of SCaCO3 content. The thermal stability was measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively, and displayed some enhancement with the incorporation of SCaCO3 into PUA. Although the nanomechanical properties increased up to 3 wt% SCaCO3 content, they decreased due to lack of interfacial interaction with high SCaCO3 loading. Most importantly, the water uptake and water vapor transmission rate (WVTR) varied from 5.51 to 1.78 wt% and 28.9 to 19.9 g/m2 day, respectively, exhibiting significant enhancement in water resistance. The results clearly reveal that the performance of UV-curable PUA/SCaCO3 nanocomposites is strongly dependent on organically-modified colloidal SCaCO3 nanoparticles.

Preparation of Polypropylene Composites Filled with Surface-modified Calcium Carbonate by in-situ Solid Phase Grafting

The surface of calcium carbonate( CaCO3) was firstly pretreated with maleic anhydride( MAH) to introduce active double bond groups,then grafted chemically by polypropylene wax( PPW) via in-situ solid phase grafting to increase its compatibility with polypropylene. Three kinds of modified CaCO3 with different chemical grafting ratio of PPW were prepared by changing experimental conditions,and their PP-based composites were produced. The effects of interfacial interaction between CaCO3-MAH-PPW and PP matrix on the strength of PP-based composite filled with modified CaCO3 were studied. The results show that the dispersibility of CaCO3-MAH-PPW in PP is improved,suggesting an improved compatibility between them.With the improvement of grafting ratio of PPW on the surface of CaCO3,the interfacial interaction between CaCO3 and PP increases gradually. When the grafting ratio of PPW is 4. 48 mg PPW / g CaCO3,the interfacial interaction between CaCO3 and PP is strongest and the decrease of tensile strength of composites is the least,the young' s modulus increases most at the same time. When m( PP) ∶ m( CaCO3) = 100∶50,the young's modulus reaches 0. 86 GPa,which is the 1. 63 times of PP' s. When the grafting ratio of PPW is 2. 49 mg PPW / g CaCO3,the interfacial interaction between CaCO3 and PP is suitable and the notch impact strength of composites improves the most. And when m( PP) ∶ m( CaCO3) = 100 ∶ 10,its notch impact strength is3. 91 kJ / m2,which is the 1. 35 times of PP's.

Tensile Properties of Natural Rubber Nanocomposites Affected by Crosslink Density

The aim of this study was to investigate the tensile properties of the natural rubber nanocomposites containing surface modified calcium carbonate nanofiller. All nanocomposites were prepared at various nanofiller contents, using a laboratory scale two-roll mill. The results revealed that the ultimate tensile properties altered by changing nanofiller content throughout the elastomeric matrix, which could be ascribed to the particular interactions at the filler/matrix interface. At 10 parts by weight of nanofiller, based on 100 parts by weight of natural rubber, the highest value of tensile properties was achieved as a result of crosslink density being at its highest level, as measured by swelling method.

Ink jet paper prepared by using surface-modified calcium carbonate

Varied reaction condition parameters of the carbonation process provide various particle diameters and shapes of the calcium carbonate products. Those calcium carbonates are potential to replace silica and alumina used for commercial ink-jet paper. Ultra-fine particles of calcium carbonate were so synthesized in the aim of improved print quality that could not be attained by conventional types of calcium carbonate. Nevertheless, the ultra-fine particles tended to provide smaller pore size and thus low rate of liquid absorption to the coat layer of paper. Therefore, the surface properties were altered for enhancing ink absorption rate and improved printability. Trial ink-jet paper prepared from the novel calcium carbonate with modified surfaces was evaluated in terms of print quality and microscopic ink dot shape using confocal laser scanning microscope.

Determination of the surface energetics of surface modified calcium carbonate using inverse gas chromatography

AbstractStearic acid and several silane surface coating agents, including propyltriethoxysilane, aminopropyltriethoxysilane, and diphenyldimethoxysilane, were applied to uncoated calcium carbonate samples at coating levels ranging from 0 to 2.0% by weight. The surface energy of these coated calcium carbonate samples, as determined by inverse gas chromatography, decreased relative to that of the native mineral with increasing coating level for both the stearic acid and the diphenyldimethoxysilane. This decrease in energy arises from the nonpolar functionality of the coating masking the high energy surface of the mineral. The propyltriethoxysilane generated a decreasing surface energy with increase in coating level up to a theoretical monolayer coating. Above this coating level, an inverted bilayer formed that increased the surface energy of the mineral. Aminopropyltriethoxysilane caused an initial decrease in surface energy relative to that of the native mineral but then retained an approximately constant surface energy at all coating levels. This observation arises from the energetic groups presented at the surface of the mineral regardless of the orientation of the silane. J. VINYL ADDIT. TECHNOL., 12:174–182, 2006. © 2006 Society of Plastics Engineers

Mechanical Properties of Plasma Surface-Modified Calcium Carbonate-Polypropylene Composites

Calcium carbonate was surface-modified by plasma-polymerized acetylene and the effect of surface modification on the mechanical properties of calcium carbonate–polypropylene composites was investigated. Two different plasma polymerization conditions were selected and applied. Chemical structures of plasma-polymerized acetylene products were identified. Mechanical and thermal properties of the composites prepared were evaluated and the effects of surface modification on the extent of adhesion of filler to the matrix, as well as on polymer phase, were investigated with the help of scanning electron microscopy. Some of the composite samples prepared with surface-modified calcium carbonate are found to yield higher percentage elongations and are mechanically superior compared to those prepared with unmodified filler. © 1997 SCI.

Acoustic Microscopy Evaluation of Polypropylene Filled with Surface Modified Calcium Carbonate

The Dispersion behavior of a heterogeneous structure, which consists of an aggregate or agglomerate of particles and voids at the polymer-particle interface, has been studied by acoustic microscopy for polypropylene (PP) filled with surface modified calcium carbonate (CaCO3). In order to improve the affinity at the interface between PP and CaCO3, mono alkyl dihydrogen phosphate of different carbon number (MAPn) were tested as modiflers for CaCO3, PP and CaCO3 were mixed on a two-roll mill and the films were prepared by compressing the mixed compound.Using ultrasonic images, a binarization method was carried out to obtain the area fraction of the heterogeneous tructure in PP/CaCO3 composites. Next, the relationships between the area fraction of the heterogeneous structure and carbon number of MAPn density, void at polymer-particle interface accompanying the elongation, mechanical propreties (tensile elongation at break, modulus, yield stress) of PP/CaCO3 composites have been investigated. The area fraction of heterogeneous structure largely decreased with the modification of CaCO3 surface. The dependence of heterogeneous structure on the value of MAPn was determined in this work. Although the tensile elongation at break and void at polymer-particle interface depended on the heterogeneous structure, the density, yield stress and the modulus of PP/CaCO3 composites were nearly constant, irrespective of the area fraction of heterogeneous structure.

Crystallization behavior of polypropylene filled with surface‐modified calcium carbonate

AbstractPolypropylene (PP) and calcium carbonate (CaCO3) were mixed in a two‐roll mill. The mixed compounds were molded on the plate by using a compression press heater. To improve the affinity of the relation between CaCO3 and the PP matrix, we modified the CaCO3 surface through chemical reaction with alkyl dihydrogen phosphates. The CaCO3 content and size modification affected the crystallization behavior of the filled PP composites. The crystallization temperature in the nonisothermal crystallization process increased with the increase of CaCO3 content and the decrease of CaCO3 size. The crystallization temperature revealed the function of log (1 + Ts) (Ts, total surface area of CaCO3) irrespective of CaCO3 content and size for modified and unmodified systems, respectively. The shoulder or double crystallization peak of PP composites is recognized for the unmodified system (particle sizes: 1.0 and 4.5 μm).