Carbonate Nanocomposites Research Articles

Effects of nanoparticle treatment on the crystallization behavior and mechanical properties of polypropylene/calcium carbonate nanocomposites

AbstractEffects of nanoparticle surface treatment on the crystallization behavior and mechanical properties of polypropylene (PP)/CaCO3 nanocomposites were investigated by using differential scanning calorimetry (DSC), polarized optical microscope (POM), X‐ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results demonstrated that the interfacial interaction formed between PP and nanoparticles significantly influenced the thermal and mechanical properties of nanocomposites. It was found that CaCO3 nanoparticles modified by a single aluminate coupling agent (CA‐1) could improve the onset crystallization temperature more effectively than that modified by a compound surface‐treating agent (CA‐2) could. However, there is no significant difference in total rate of crystallization for the two PP/CaCO3 nanocomposites (PPC‐1 and PPC‐2), which contained CA‐1 and CA‐2, respectively. In contrast, CA‐2 modified nanoparticles could cause smaller spherulites and induce much more β‐phase crystal in nanocomposites than that of CA‐1 modified nanoparticles. This may be explained by a synergistic effect of aluminate coupling agent and stearic acid in CA‐2, which also resulted in an improved toughness for PPC‐2. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 3480–3488, 2006

Rheology enhancement of polycarbonate/calcium carbonate nanocomposites prepared by melt-compounding

The focus of the letter is to investigate the influence of calcium carbonate (CaCO 3) nanoparticles on the rheology enhancement of polycarbonate (PC) melt. The PC/CaCO 3 nanocomposites with different compositions of CaCO 3 were prepared by melt-compounding. Characterizations via energy-dispersive X-ray spectrometer (EDS) and field-emission scanning electron microscopy (FE-SEM) confirm the random dispersion of CaCO 3 in the PC/CaCO 3 masterbatch. The rheological experiments investigated with Rosand Presicion Rheometer show the remarkable rheology enhancement of PC melt due to the addition of CaCO 3 nanoparticles. Mechanical tests show that, upon incorporation of only 1 wt.% CaCO 3, the tensile modulus, the bending modulus, and the bending strength of PC are improved; however, the tensile strength and elongation at break are depressed.

Vanadium oxide–propylene carbonate composite as a host for the intercalation of polyvalent cations

A vanadium oxide/propylene carbonate nanocomposite has been synthesized by the sol–gel method using vanadium alkoxide as a precursor. The resulting bicontinuous structure consisted of mesopores filled with PC molecules and a network of hydrated vanadium oxide. The structure, engineered for the insertion of polyvalent cations, resulted in a specific capacity as high as 465 mAh per gram of vanadium oxide when Ca 2+ was the guest cation. This is close to 80% of the theoretical capacity for 2 e − per V. The critical role of the PC has been clearly demonstrated. The specific capacity of the nanocomposite when Ca 2+ was used as the guest cation was two to ten times better when the propylene carbonate or its decomposition products was present in the structure as opposed to when it was either not added or extracted. It has also been shown that the nanocomposite exhibited better electrochemical performances with Ca 2+ as the guest cation than with Li +.

Rheological and mechanical properties of PVC/CaCO 3 nanocomposites prepared by in situ polymerization

Poly(vinyl chloride) (PVC)/calcium carbonate (CaCO 3) nanocomposites were synthesized by in situ polymerization of vinyl chloride (VC) in the presence of CaCO 3 nanoparticles. Their thermal, rheological and mechanical properties were evaluated by dynamic mechanical analysis (DMA), thermogravimetry analysis (TGA), capillary rheometry, tensile and impact fracture tests. The results showed that CaCO 3 nanoparticles were uniformly distributed in the PVC matrix during in situ polymerization of VC with 5.0 wt% or less nanoparticles. The glass transition and thermal decomposition temperatures of PVC phase in PVC/CaCO 3 nanocomposites are shifted toward higher temperatures by the restriction of CaCO 3 nanoparticles on the segmental and long-range chain mobility of the PVC phase. The nanocomposites showed shear thinning and power law behaviors. The ‘ball bearing’ effect of the spherical nanoparticles decreased the apparent viscosity of the PVC/CaCO 3 nanocomposite melts, and the viscosity sensitivity on shear rate of the PVC/CaCO 3 nanocomposite is higher than that of pristine PVC. Moreover, CaCO 3 nanoparticles stiffen and toughen PVC simultaneously, and optimal properties were achieved at 5 wt% of CaCO 3 nanoparticles in Young's modulus, tensile yield strength, elongation at break and Charpy notched impact energy. Detailed examinations of micro-failure micromechanisms of impact and tensile specimens showed that the CaCO 3 nanoparticles acted as stress raisers leading to debonding/voiding and deformation of the matrix material around the nanoparticles. These mechanisms also lead to impact toughening of the nanocomposites.

Crystallization and impact energy of polypropylene/CaCO 3 nanocomposites with nonionic modifier

Isotactic polypropylene (PP) and calcium carbonate (CaCO 3) nanocomposites were prepared by melt extrusion in a twin screw extruder. The commercial CaCO 3 nanoparticles had a poor dispersion in PP matrix. The addition of a small amount of a nonionic modifier during melt extrusion greatly improved the dispersion of CaCO 3 nanoparticles. The influence of CaCO 3 nanoparticles on the crystallization of PP was studied by wide angle X-ray diffraction and polarized optical microscopy. The introduction of CaCO 3 particles resulted in small and imperfect PP spherulites, decreased spherulite growth rate and induced formation of β-form PP. The yield strength of PP decreased gradually while its Young's modulus increased slightly with increasing CaCO 3 loading. By adding 1.5 wt% of nonionic modifier to PP/CaCO 3 (85/15) nanocomposite these tensile properties were not changed much but the notched Izod impact energy of the composites was significantly increased.

Investigation Into Poly(propylene)/Montmorillonite/Calcium Carbonate Nanocomposites

AbstractSummary: A novel method was used to prepare poly(propylene)/montmorillonite/calcium carbonate nanocomposites by melt‐mixing, using pristine montmorillonite (MMT), hexadecyltrimethylammonium bromide (C16), calcium carbonate (CaCO3) and a matrix in a twin‐screw extruder. Two different sizes of calcium carbonate were used (nanosized CaCO3 and micron‐sized CaCO3, the average sizes being 60 nm and 12 μm respectively). The nanocomposite structure was evidenced using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution electronic microscopy (HREM). Tensile tests and Izod notch impact tests suggested that the incorporation of nanosized CaCO3 into PP/montmorillonite nanocomposites increased the mechanical properties of the composites, but the improvement in the micro‐sized CaCO3‐filled PP/montmorillonite nanocomposites was found to be minimal. The thermal stability and flammability properties were characterized by thermogravimetric analysis (TGA) and a cone calorimeter respectively. magnified image

Polypropylene/calcium carbonate nanocomposites

Polypropylene (PP) and calcium carbonate nanocomposites were prepared by melt mixing in a Haake mixer. The average primary particle size of the CaCO 3 nanoparticles was measured to be about 44 nm. The dispersion of the CaCO 3 nanoparticles in PP was good for filler content below 9.2 vol%. Differential scanning calorimetry (DSC) results indicated that the CaCO 3 nanoparticles are a very effective nucleating agent for PP. Tensile tests showed that the modulus of the nanocomposites increased by approximately 85%, while the ultimate stress and strain, as well as yield stress and strain were not much affected by the presence of CaCO 3 nanoparticles. The results of the tensile test can be explained by the presence of the two-counter balancing forces—the reinforcing effect of the CaCO 3 nanoparticles and the decrease in spherulite size of the PP. Izod impact tests suggested that the incorporation of CaCO 3 nanoparticles in PP has significantly increased its impact strength by approximately 300%. J-integral tests showed a dramatic 500% increase in the notched fracture toughness. Micrographs of scanning electron microscopy revealed the absence of spherulitic structure for the PP matrix. In addition, DSC results indicated the presence of a small amount of β phase PP after the addition of the calcium carbonate nanoparticles. We believe that the large number of CaCO 3 nanoparticles can act as stress concentration sites, which can promote cavitation at the particle–polymer boundaries during loading. The cavitation can release the plastic constraints and trigger mass plastic deformation of the matrix, leading to much improved fracture toughness.