Calcium Carbonate Composites Research Articles

Different β nucleants and the resultant microstructural, fracture, and tensile properties for filled and unfilled ISO polypropylene

AbstractThis article explores the use of two β nucleants to improve the fracture behavior of filled and unfilled homo‐polypropylene (PP). The first was based upon an organic quinacridone, whereas the second was based upon the inorganic calcium pimelate. Formulations containing various concentrations of nucleant were prepared using single screw extrusion and then characterized by X‐ray diffraction, differential scanning calorimetry (DSC), Izod impact strength, and tensile testing. The quinacridone nucleating agent produced higher levels of β crystallinity and better improvement in strain to failure, whereas the calcium pimelate imparted greater improvement in impact strength regardless of whether the PP was filled or unfilled. No direct relationship between β crystallinity and fracture properties was observed though synergistic enhancement in impact strength was evident. By varying the concentration of calcium carbonate in the calcium pimelate from 10 : 1, 5 : 1, 2 : 1, and 1 : 1 weight composition of calcium carbonate to pimelic acid, similar property enhancements were achieved regardless of composition although the 10 : 1 sample did produce superior elongation to break. The importance of cooling rate on microstructure within each sample was explored via a through the thickness study using DSC and nano‐indenting methods. Variations in the β content through the thickness were related to cooling and found to be independent of sample composition and processing. Elastic properties varied inversely with β content. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Crystallization of CaCO3 in the presence of sulfate and additives: Experimental and molecular dynamics simulation studies

The effects of sulfate and BHTPMP (Bis (hexamethylene) triaminepentakis (methylene phosphonic acid)) on the crystallization rate, phase composition and morphology of calcium carbonate have been studied. It was observed that sulfate reduces the nucleation rate and favors the formation of aragonite form in the calcium carbonate precipitate. Moreover, in the presence of sulfate the rhombohedral morphology of the calcite crystals is modified, and during the formation of calcite, the development of {104} faces are more significantly prohibited than {110} faces. In the presence of sulfate together with BHTPMP, the crystallization process is inhibited and the modified morphology and the dominant calcite form are observed in the solid. The results from molecular dynamics simulations show the more strong combination of sulfate with calcite surface, in particular the {104} face, in comparison with the aragonite surface. The strong interaction of BHTPMP with sulfate and the aragonite surface favors the formation of the dominant calcite phase in the precipitate.

A universal carbonate ion effect on stable oxygen isotope ratios in unicellular planktonic calcifying organisms

Abstract. The oxygen isotopic composition (δ18O) of calcium carbonate of planktonic calcifying organisms is a key tool for reconstructing both past seawater temperature and salinity. The calibration of paloeceanographic proxies relies in general on empirical relationships derived from field experiments on extant species. Laboratory experiments have more often than not revealed that variables other than the target parameter influence the proxy signal, which makes proxy calibration a challenging task. Understanding these secondary or "vital" effects is crucial for increasing proxy accuracy. We present data from laboratory experiments showing that oxygen isotope fractionation during calcification in the coccolithophore Calcidiscus leptoporus and the calcareous dinoflagellate Thoracosphaera heimii is dependent on carbonate chemistry of seawater in addition to its dependence on temperature. A similar result has previously been reported for planktonic foraminifera, supporting the idea that the [CO32−] effect on δ18O is universal for unicellular calcifying planktonic organisms. The slopes of the δ18O/[CO32−] relationships range between –0.0243‰ (μmol kg−1)−1 (calcareous dinoflagellate T. heimii) and the previously published –0.0022‰ (μmol kg−1)−1 (non-symbiotic planktonic foramifera Orbulina universa), while C. leptoporus has a slope of –0.0048 ‰ (μmol kg−1)−1. We present a simple conceptual model, based on the contribution of δ18O-enriched HCO3− to the CO32− pool in the calcifying vesicle, which can explain the [CO32−] effect on δ18O for the different unicellular calcifiers. This approach provides a new insight into biological fractionation in calcifying organisms. The large range in δ18O/[CO32−] slopes should possibly be explored as a means for paleoreconstruction of surface [CO32−], particularly through comparison of the response in ecologically similar planktonic organisms.

Soundproofing effect of polypropylene/inorganic particle composites

Two inorganic particle-filled polypropylene (PP) composites including PP/hollow glass bead (HGB) composite and PP/nanometer calcium carbonate (nano-CaCO3) composite were prepared by means of a twin-screw extruder in the present paper. The transmission loss was measured, to identify the effects of sound frequency and the filler content on the sound insulation properties of these filled systems. The results showed that the sound insulation effect of the PP/nano-CaCO3 obeyed roughly the law of mass, the transmission loss of the two composites increased nonlinearly with an increase of the filler volume fraction, and the value of the transmission loss for the PP/HGB system was higher than that of the PP/nano-CaCO3 system under the same level of sound frequency. The transmission loss increased roughly with an increase of sound frequency for the two composites except to individual sound frequency. The mechanisms of the sound insulation of these composites were discussed.

Characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene

There is a high content of calcium carbonate in mussel and oyster shells, which can be used in the formulation of medicine, in construction or as filler in polymer materials. This work has as its main objective to obtain calcium carbonate from mussel and oyster shells and used as filler in polypropylene compared their properties with polypropylene and commercial calcium carbonate composites. The shellfish was milling and heated at 500 ºC for 2 hours. The powder obtained from shellfish were characterized by scanning electron microscopy (SEM), X-ray fluorescence, particle size distribution and abrasiveness and compared with commercial CaCO3 and mixed with polypropylene. The thermal and mechanical properties of polypropylene with CaCO3 obtained from oyster and mussel shells and with commercial CaCO3 were analysed. The results showed that CaCO3 can be obtained from oyster and mussel shell and is technically possible to replace the commercial CaCO3 for that obtained from the shells of shellfish in polypropylene composites.

Effects of SEBS-g-MAH on the properties of injection moulded poly(lactic acid)/nano-calcium carbonate composites

Poly(lactic acid)/nano-precipitated calcium carbonate (PLA/NPCC) composites toughened with maleated styrene-ethylene/butylene-styrene (SEBS-g-MAH) were prepared by melt-compounding on a co-rotating twin-screw extruder followed by injection moulding. The mechanical properties of the PLA nanocomposites were characterized by ten- sile, flexural and impact tests, while their morphology were investigated using transmission electron microscopy (TEM). The thermal properties of the composites were examined with differential scanning calorimeter (DSC) and thermogravi- metric analyzer (TGA). The elongation at break and impact strength of the PLA/NPCC nanocomposites increased signifi- cantly after addition of SEBS-g-MAH. Both nano-dispersed NPCC and small NPCC clusters were found in PLA matrix. Also, some SEBS-g-MAH encapsulated NPCC can be observed. Thermal stability of PLA/NPCC was enhanced promi- nently by the addition of SEBS-g-MAH.

Analysis on interfacial stress in impact of polyphenylene sulfide/CaCO3 composites

The interfacial stress and its distribution during impact of inorganic particulate‐filled polymer composites were analyzed in the present paper by means of a three‐dimensional (3D) finite element method, and the software used was the ANSYS/LS‐DYNA (ANSYS Inc., Canonsburg, PA, USA). The simulation results showed that the normal stress, the shear stress, and the equivalent stress reached the maximum at the particle equator, and then they reduced quickly toward the direction of the particle pole along the interface between the particle and the matrix and achieved the minimum from about 0.5 to 2.0 µm from the equator. Finally, they tended to gently or somewhat increase. Furthermore, the ways and mechanisms of the major fail or fracture of the polyphenylene sulfide (PPS)/calcium carbonate (CaCO3) composites under impact load were discussed. The mechanism of impact fracture or failure of inorganic particle‐filled PPS composites might be that the matrix around the neighboring inclusions will first yield owing to the stress concentration in the interface between the inclusion and the matrix to induce crazes and extend quickly. Copyright © 2011 John Wiley & Sons, Ltd.

Population dynamics and biogeochemical significance of Limacina helicina antarctica in the Scotia Sea (Southern Ocean)

Limacina helicina antarctica is a common part of the Southern Ocean zooplankton community but little is known about its life cycle. Here we determine the population structure and standing stock biomass of this species in the Scotia Sea region and use this information to derive estimates for rates of growth, mortality and secondary productivity. Three non-overlapping cohorts were present in the size–frequency distribution, a G2 generation (0-year) with a modal peak at 0.3 mm shell diameter, a G1 generation (1-year) with a modal peak at 2.7 mm and a G generation (2-year) cohort with sizes between 4 and 10 mm. We surmise that at least some L. helicina ant. are capable of living 3 years or more, growing at an average rate of 0.01 mm d −1. Mortality rates were 0.01 d −1 or 3.83 year −1, with 2% of individuals surviving beyond 1 year of age and 0.05% beyond 2 years of age. Standing stock biomass was 178 mg DW m −2 or 32 mg C m −2, divided between 23 mg C org m −2 and 9 mg C inorg m −2. The inorganic fraction had a calcium carbonate composition equivalent to 72 mg CaCO 3 m −2. Maximum daily productivity during the summer was 1.8 mg C m −2 d −1, made up of 1.3 C org mg m −2 d −1 and 0.5 mg C inorg m −2 d −1, and equivalent to 4.2 mg CaCO 3 m −2 d −1. The mass specific growth rate (P:B d −1) was 0.06 within the summer period. Growth and production appeared to continue over the autumn and winter months at rates almost equivalent to those in summer. We propose that autumn peaks in sedimenting L. helicina ant., reported by other studies, do not appear to be the consequence of the termination of the life-cycle but are more likely to result from a combination of environmental and behavioural factors.

Mechanical properties, thermal stability, and crystallization kinetics of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)/calcium carbonate composites

AbstractBacterial polyester poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3/4HB) containing 5 mol% 4HB was composited with different calcium carbonate (CaCO3) fillers. The effect of CaCO3 contents on thermal properties, mechanical property, and crystallization kinetics was evaluated. The thermal stability of P3/4HB was reduced by mixing with CaCO3 particles. With increasing CaCO3 content, the elongation at break, tensile strength, and impact strength decrease; however, elastic modulus increases. When P3/4HB with 20 mol% 4HB was added into the P3/4HB/CaCO3 composite, the impact strength were enhanced significantly; however, the elongation at break and tensile strength were only slight to moderate improvements. However, when compared with nano‐ and light‐CaCO3, heavy CaCO3 had the best mechanical properties. The nonisothermal and isothermal crystallization results demonstrated that the crystallization rate of P3/4HB was reduced and the highest crystallinity was obtained for all kinds of CaCO3 fillers at 40 phr content. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Influence of Dicumyl Peroxide and Maleic Anhydride on the Tensile Properties of HDPE–Calcium Carbonate Composites

PE is modified basically with inorganic matter (generally CaCO3) and some auxiliaries, but because of the interattraction of the particles, CaCO3 is easy to agglomerate, so we must add some dispersants(generally stearic acid ) ,but some study suggested that, with stearic acid , tensile strength, yield strain and ultimate elongation reduced. But we find that adding dicumyl peroxide and Maleic Anhydride can make up for the defects even increase these properties. As initiator and crosslinker ,dicumyl peroxide is usually used in synthesis of polymers. And is also Maleic Anhydride. However,in this experiment, we add a certain amount of them, dicumyl peroxide initiated Maleic Anhydride to ingraft, also,it initiated the molecular chains of PE to be cross-linked. So, the tensile properties of HDPE–calcium carbonate composites increased obviously, nevertheless ,we must add appropriate amount, if exceeded ,the mechanical properties would reduce.

Probing into double crystallisation behaviour of polypropylene/CaCO3 composites

A series of isotactic polypropylene (iPP)/calcium carbonate (CaCO3) composites are prepared by melt blending, and the crystallisation behaviours of these composites are investigated by differential scanning calorimetry (DSC). The results show that the crystallisation exotherms displayed double peaks as the concentration of CaCO3 reaches a critical value of typically ∼8 wt-% for nano-CaCO3 and ∼20 wt-% for micron-CaCO3. With increasing content of CaCO3, the intensity of the higher temperature crystallisation peak increases, while that of the lower one decreases. Modifying the surface of CaCO3 with stearic acid leads to the increase in the critical concentration to trigger double crystallisation peaks, which is 50 wt-% for nano-CaCO3 filled iPP. The results of isothermal crystallisation, transmission electron microscopy (TEM) and polarised light optical microscope (POM) experiments indicate that the different nucleating abilities of CaCO3 composites are mainly responsible for the occurrence of the double crystallisation peaks in the composites.

The Research of Biology Coupling Characteristics on the Shells of Haliotis discus hannai Ino

The surface morphologies, structures and materials of Haliotis discus hannai Ino shells were qualitatively studied by means of a stereoscopic microscope，a field emission scanning electronic microscopy, energy dispersive spectrometer and X-ray diffractometer, and abrasive particle wear was qualitatively and quantitatively studied by means of a pin-on-disc apparatus. The results showed that the outer layer surface of Haliotis discus hannai Ino shells was non-smooth and had some strumae or similar parallel convex wave. The shells of Haliotis discus hannai Ino are polycrystalline composites of calcium carbonate and proteins and glycoproteins and consist of the periostracum, prismatic and nacreous layers with calcite in the outer prismatic layer and aragonite in the inner nacreous layer. Nacreous layer is a natural composite comprised of calcium carbonate in the aragonite polymorph with organic macromolecules sandwiched in between, and the coupling of platelet interlocks and organic materials makes nacreous layer to be strong and tough.The abrasive particle wear tests showed that the abrasion resistance was different on the different parts of the shells, and the left of the shells possessed the highest abrasion resistance and the abrasion resistance of the shells was the lowest on the edge of the right. The nacreous layer possessed higher abrasion resistance than prismatic layer because of the coupling of structure and materials of nacreous layer. Key words: Haliotis discus hannai Ino shells; morphology; structure; materials; anti-wear; biological character; coupling

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

Modification of nanometre calcium carbonate and its application on PVC composites in situ suspension polymerisation

With the aim to synthesise well proportioned disperse poly(vinyl chloride) (PVC)/nanometre calcium carbonate (nano-CaCO3) composites, the authors used emulsifier tx10 polyoxyethylene octylphenol ether to prepare emulsion liquid for modifying nano-CaCO3. Let nano-CaCO3 well proportionedly disperse into the water, the authors created a new method for the characterisation of emulsion liquid and use the emulsion to synthesise PVC/nano-CaCO3 composite. The microstructure, particle size distribution and thermal properties of composite were respectively evaluated by TEM, laser particle size analyser and thermogravimetry analysis tests. The results showed that nano-CaCO3 were uniformly distributed in the PVC with 5·2 wt-%. Compared with the pristine PVC, the particle size distribution of the composite is more uniform and the thermal stability increases.

Effect of uncoated calcium carbonate and stearic acid coated calcium carbonate on mechanical, thermal and structural properties of poly(butylene terephthalate) (PBT)/calcium carbonate composites

PBT/CaCO3 composites were prepared in a single screw extruder with particle content varying from 0–30% by weight. The influence of surface treatment of the particles, with and without stearic acid (SA), on the mechanical, thermal and structural properties was studied. The experiments included tensile tests, impact tests, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The composite systems containing SA coated CaCO3 were found to exhibit better mechanical properties as compared to composite systems containing uncoated CaCO3, with the S3 system (20% of SA coated CaCO3) exhibiting best combination of mechanical properties. Thermal study revealed that particle type and content had no influence on the melting temperature but the crystallization temperature, % crystallinity and thermal stability increased on increasing the CaCO3 content in PBT matrix. Morphological observation indicated that in PBT composites containing SA coated CaCO3, the coupling agent favours a better polymer filler interaction rendering inorganic polymer interface compatible, which is also evident from better mechanical and thermal properties.

Litiasis prostática: cálculos silentes

Introduction Introduction and Objectives Prostate stones are frequently encountered during transurethral resection of the prostate in urology practice. We aimed to demonstrate the physical and chemical properties of prostate stones. We also aimed to determine possible relationship between inflammation of prostate gland and prostate stones. Methods The consecutive patients (excluding subjects with PSA≥4 ng/ml and urolithiasis), who underwent TURP operation and who were observed to have prostatic calculi during TURP, were included in the study. The prostatic stones obtained from each patient during TURP were analysed for chemical composition and observed under electron microscopy (SEM) for structure and surface morphology. The pathological specimens were assessed by the uropathologist for the final diagnosis and existence and degree of inflammation. Results Five patients were included in the study. From each patient at least three (range 3–8) samples of stones (diameter varying from 1 mm up to 5 mm) were obtained. The stones were made of mixed composition of calcium phosphate and calcium carbonate. The stones were found to have lobular surface made up of small spheres under SEM. Histopathological examination of the TURP specimens revealed being prostatic hyperplasia accompanied with inflammation of mild to severe degree. Conclusions Prostatic stones are concentrically precipitated calcium stones within the prostatic ductuli with granular grape like morphology. Histopathological inflammation seems to be associated with these prostatic calculi.

TRADITIONAL AND EMERGING GEOCHEMICAL PROXIES IN FORAMINIFERA

Geochemical analyses of the carbonate tests calcified by foraminifera have provided much of the foundation for reconstructions of past ocean and climate conditions, and for chemostratigraphy. In particular, reconstructions of climate history (including temperature, salinity, and ice volume), ocean paleocirculation patterns, the carbon cycle, paleoproductivity, marine carbonate chemistry, and chemostratigraphy have relied on measurements of isotopic and trace element composition of foraminiferal calcium carbonate, and variations in these geochemical records through time and space. Substantial work has been done on details of traditional proxies (e.g., d 18 O, d 13 C) and on emerging proxies (e.g., d 11 B, eNd) in recent years; hence, a new overview of these proxies provides a timely reference and educational tool. We review the geochemical proxies that utilize foraminiferal carbonate tests, including potential uses of the proxies for reconstructions through time: d 18 O, d 13 C, trace elements (Mg, Cd, Ba, Zn, B, U), 87 Sr/ 86 Sr, d 26 Mg, d 11 B, and eNd. Both planktic and benthic foraminifera are included; planktic foraminifera provide information on the upper few hundred meters of the surface ocean, whereas benthic foraminifera provide information on conditions at the seafloor and in shallow porewaters, from shallow seas to deep ocean basins.

Prostatic calculi: Silent stones

Introduction and objectivesProstate stones are frequently encountered during transurethral resection of the prostate in urology practice. We aimed to demonstrate the physical and chemical properties of prostate stones. We also aimed to determine possible relationship between inflammation of prostate gland and prostate stones. MethodsThe consecutive patients (excluding subjects with PSA≥4ng/ml and urolithiasis), who underwent TURP operation and who were observed to have prostatic calculi during TURP, were included in the study. The prostatic stones obtained from each patient during TURP were analysed for chemical composition and observed under electron microscopy (SEM) for structure and surface morphology. The pathological specimens were assessed by the uropathologist for the final diagnosis and existence and degree of inflammation. ResultsFive patients were included in the study. From each patient at least three (range 3–8) samples of stones (diameter varying from 1mm up to 5mm) were obtained. The stones were made of mixed composition of calcium phosphate and calcium carbonate. The stones were found to have lobular surface made up of small spheres under SEM. Histopathological examination of the TURP specimens revealed benign prostatic hyperplasia accompanied with inflammation of mild to severe degree. ConclusionsProstatic stones are concentrically precipitated calcium stones within the prostatic ductuli with granular grape-like morphology. Histopathological inflammation seems to be associated with these prostatic calculi.

Atmospheric CO2concentrations during ancient greenhouse climates were similar to those predicted for A.D. 2100

Quantifying atmospheric CO(2) concentrations ([CO(2)](atm)) during Earth's ancient greenhouse episodes is essential for accurately predicting the response of future climate to elevated CO(2) levels. Empirical estimates of [CO(2)](atm) during Paleozoic and Mesozoic greenhouse climates are based primarily on the carbon isotope composition of calcium carbonate in fossil soils. We report that greenhouse [CO(2)](atm) have been significantly overestimated because previously assumed soil CO(2) concentrations during carbonate formation are too high. More accurate [CO(2)](atm), resulting from better constraints on soil CO(2), indicate that large (1,000s of ppmV) fluctuations in [CO(2)](atm) did not characterize ancient climates and that past greenhouse climates were accompanied by concentrations similar to those projected for A.D. 2100.

An investigation on the mechanical and dynamic rheological properties of single and hybrid filler/polypropylene composites based on talc and calcium carbonate

AbstractSome results of experiments on the mechanical and rheological properties of mineral filled polypropylene were presented. Single filler and hybrid filler composites of talc and calcium carbonate (CaCO3) were prepared in a co‐rotating twin‐screw extruder. The effect of filler type, filler content, and coupling agent on the mechanical and rheological properties of the polypropylene were studied. The coupling agent was maleic anhydride‐grafted polypropylene (PP‐g‐MA). It was found that the mechanical properties are affected by filler type, filler concentration, and the interaction between filler and matrix. The tensile strength of the composite is more affected by the talc while the impact strength is influenced mostly by CaCO3 content. The elongation at break of PP/CaCO3 composites was higher than that of PP/talc composites. The incorporation of coupling agent into PP/mineral filler composites increased the mechanical properties. Rheological properties indicated that the complex viscosity and storage modulus of talc filled samples were higher than those of calcium carbonate filled samples while the tan δ was lower. The rheological properties of hybrid‐filler filled sample were more affected by the talc than calcium carbonate. The PP‐g‐MA increased the complex viscosity and storage modulus of both single and hybrid composites. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers