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.     

Effect of Surface Structure of Nano-CaCO3 Particles on Mechanical and Rheological Properties of PVC Composites

To study the effect of different surface structures on resultant mechanical and rheological properties, nano-CaCO₃ particles were treated with isopropyl tri-stearyl titanate (H928), isopropyl tri-(dodecylbenz-enesulfonyl) titanate (JN198), and isopropyl tri-(dioctylpyrophosphato) titanate (JN114). Scanning electron microscopy (SEM) and dynamic mechanic analysis (DMA), carried out to characterize the effective interfacial interaction between the nano-CaCO₃ particles and a poly(vinyl chloride) (PVC) matrix, indicated that JN114 treated nano-CaCO₃ particles had the strongest interfacial interaction with a PVC matrix, while H928 treated nano-CaCO₃ had the weakest. The rheological and mechanical properties of PVC/nano-CaCO₃ composites were investigated as a function of surface structure and filler volume fraction. The tensile yield stress and elongation at break decreased with the increasing of calcium carbonate content while tensile modulus increased. PVC filled with JN114 treated nano-CaCO₃ had the highest tensile modulus and tensile yield stress, while those filled with H928 treated nano-CaCO₃ had the highest elongation at break at the same filler content. The impact strength of PVC/nano-CaCO₃ composites increased with the increasing of CaCO₃ content, and PVC composites filled with JN198 treated nano-CaCO₃ particle had a higher impact strength than those with JN114 or H928 treated, with the value reaching 23.9 ± 0.7 kJ/m² at 11 vol% CaCO₃, four times as high as that of pure PVC. Rheological properties indicated that a suitable interfacial interaction and a good dispersion of inorganic filler in a PVC matrix could reduce the viscosity of PVC/nano-CaCO₃ composites. The interfacial interaction was quantitatively characterized by semiempirical parameters calculated from the tensile strength of PVC/nano-CaCO₃ composites to confirm the results from the SEM and DMA experiments.     

Filler treatment effects on the weathering of talc-, CaCO3- and kaolin-filled polypropylene hybrid composites

Talc, calcium carbonate (CaCO₃), and kaolin hold considerable promise in the development of polymer composites for good mechanical properties and stability. Comparative studies on the usage of these minerals as single fillers in polypropylene (PP) have shown varying degrees of reinforcement due to their differences in terms of particle geometry, surface energy and affinity towards the matrix polymer. In this study, comparisons were made in terms of mechanical, thermal and weatherability properties between hybrid-filler PP composites (i.e. PP filled with either talc–CaCO₃ or talc–kaolin hybrid filler combinations), with particular attention directed towards the effect of surface modification of the fillers. The talc/CaCO₃ hybrid composites have shown exceptional performance in terms of flexural and impact properties. The contribution of talc in the talc–kaolin hybrid composite system has been significant in terms of enhancing the overall tensile and flexural properties. The ability of silane and titanate coupling agents in boosting the resistance of the composites to severe damage and degradation due to natural weathering has been shown.     

Crystallization and Thermal Conductivity of CaCO3 Nanoparticle Filled Polypropylene

Isotactic polypropylene (IPP) and calcium carbonate (CaCO₃) nanocomposites were prepared by melt extrusion in a twinscrew extruder. The effect of CaCO₃ nanoparticles on the crystallization and thermal conductivity (TC) of PP was studied by thermal analysis (DSC) and thermal conductivity analysis (TCA). The introduction of CaCO₃ nanoparticles resulted in an increase in crystallinity. The incorporation of this nanoparticle (up to 15 phr) caused a significant increase of TC of PP, especially for larger filler content. Several models were used for prediction of TC of the nanocomposites. The experimental results had a good correlation with the Ce Wen Nan Model.     

Flexural Properties of Poly-L-Lactide and Polycaprolactone Shape Memory Composites Filled with Nanometer Calcium Carbonate

The flexural properties of poly-L-lactide (PLLA) and polycaprolactone (PCL) shape memory composites filled with nanometer calcium carbonate (nano-CaCO₃) were determined at room temperature. The results showed that with the increase of the nano-CaCO₃ weight fraction the flexural moduli and strength of PCL/nano-CaCO₃ composites increased roughly linearly and reached a maximum at the filler content of 2%, while the flexural strength of the composites decreased. The flexural moduli and strength of the composites decreased roughly linearly with increasing PLLA/PCL ratio for the PLLA/PCL/nano-CaCO₃ composites.     

Size-Dependent HCl Generation of PVC/SiO2 Micro- and Nanocomposites

In this study HCl generation of polyvinyl (chloride) (PVC)/SiO₂ composites during its combustion was investigated. SiO₂ with different particle sizes were used as HCl absorbers and their HCl uptake ability results were compared to that of CaCO₃. It was found that the amount of released HCl gas during PVC combustion decreased in the presence of SiO₂. The HCl uptake ability of SiO₂ improved with decreasing of its particle size. Although thermogravimetric analysis (TGA) results showed that SiO₂ particles decreased the first thermal degradation temperature (T _onset) of PVC by initiating dehydrochlorination of PVC at lower temperatures, SiO₂ particles had more effective HCl uptaking ability than that of CaCO₃. Scanning electron microscopy (SEM) micrographs showed that some aggregates whose size was less than 100 nm were formed when Si-25 nm was used as filler. When SiO₂ with micron size was added to PVC as filler, more uniform and better distribution of the SiO₂ on the surface was observed.     

In situ preparation of hydrophobic CaCO3 in the presence of sodium oleate

Hydrophobic CaCO₃ particles were directly prepared via carbonation of Ca(OH)₂ slurry in the presence of sodium oleate at room temperature. Sodium oleate was used to modify the surface property of CaCO₃ particles. The measurement of relative contact angle and active ratio indicated that CaCO₃ samples were hydrophobic. DTG, FT-IR and TEM analysis of the obtained product indicated that the hydrophobic property was attributed to the deposition of calcium oleate, produced in the reaction mixture, onto the surface of calcium carbonate particles. They were covered on the CaCO₃ crystals surface and modified their surface property; at the same time they own CC bonds and could be polymerized or copolymerized later to give a polymeric monolayer.     

Toughening of Propylene‐ethylene Copolymer/Calcium Carbonate Composites with High‐Density Polyethylene

Propylene‐ethylene copolymer/calcium carbonate (CaCO₃) composites (weight ratio=50/50) toughened with high density polyethylene (HDPE) were prepared using a twin‐screw extruder; the HDPE content in composites was in the range of 0–4 wt.%. The notched impact strength of propylene‐ethylene copolymer/CaCO₃ composites with 1.5 wt.% HDPE was 46% higher than that of propylene‐ethylene copolymer/CaCO₃ composites. Differential scanning calorimetry (DSC) experiments showed that good miscibility between propylene‐ethylene copolymer and HDPE enhanced the interpenetration of the macromolecules located in the interface. It was shown that debonding of the small HDPE particles within the propylene‐ethylene copolymer matrix resulted in the formation of small voids; the subsequent plastic deformation of the propylene‐ethylene copolymer matrix next to the voids thinned the ligaments and led to large energy consumption.     

Effect of Inorganic Fillers on Morphology and Mechanical Properties of PA66/POE-g-MAH/Filler Composites

Composites of polyamide 66 (PA66)/maleic anhydride grafted poly(ethylene-co-octene) (POE-g-MAH)/nano-calcium carbonate (nano-CaCO₃) and PA66/POE-g-MAH/talc were prepared by a one-step blending method. Morphology, crystallization, and mechanical properties of the composite materials were characterized with respect to different amounts of both inorganic fillers, nano-CaCO₃ and talc. Results showed that the tensile yield strength and tensile modulus of the composites were increased remarkably with introduction of nano-CaCO₃ or talc, but the notched impact strength was significantly lowered for both kinds of composites. Mechanical properties exhibited little difference between the PA66/POE-g-MAH/nano-CaCO₃ and PA66/POE-g-MAH/talc composites both for the different shapes and sizes of nano-CaCO₃ and the flake-like talc. Results of scanning electron microscopy exhibited agglomeration of the fillers. Differential scanning colorimetry analysis suggested that introduction of the inorganic fillers cause the crystallinity of PA66 to decrease by heterogeneous nucleation. The study provides a basic investigation on polymer/elastomer/rigid filler composites.     

Kinetic analysis of thermal and thermo-oxidative degradation of polyethylene (nano)composites

Thermal properties and degradation of polyethylene LDPE (nano)composites were investigated by isoconversional thermogravimetric analysis in air and nitrogen atmosphere by applying the Kissinger–Akahira–Sunose method. Low-density polyethylene (LDPE) composites containing 3 wt.% nanofiller Cloisite 20A and 4, 6, and 8 wt.% of natural zeolite were prepared using extrusion/injection moulding. The parameters of thermal stability of the samples were determined i.e. onset temperature of the degradation (T₉₀), which exhibit initial mass loss (10 mass %) and maximum loss rate temperature (T_max). Also, activation energy (E_a) of samples was calculated and interpreted in terms of thermal degradation mechanisms. Under nitrogen, the thermal degradation of LDPE (nano)composites follows a random scission pathway but it was retarded and slowed by the presence of the fillers. The results show that thermo-oxidative degradation of studied (nano)composites is induced at lower temperatures and appears as much more complex and multi-stage process.     

Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing

Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm³, had a specific surface area of 65 m²/g and a composition of CaCO₃•0.5H₂O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature.     

The Construction of Sandbag Microstructure in Polyamide 6/Ethylene-Propylene-Diene Terpolymer/Nanometer Calcium Carbonate Ternary Composite

A sandbag microstructure was constructed in Polyamide 6(PA6)/ethylene-propylene-diene terpolymer (EPDM)/nanometer calcium carbonate (nano-CaCO₃) ternary composites by the addition of maleinated EPDM (EPDM-g-MA) to reduce the interfacial tension between EPDM and PA6 and EPDM and nano-CaCO₃. Scanning electron microscopy (SEM) observation and differential scanning calorimetry (DSC) analysis revealed that the microstructure of the ternary composites evolved from the initial separated EPDM and nano-CaCO₃ dispersion structure to the sandbag structure and finally to the separated dispersion structure again with the increase of EPDM-g-MA content in the elastomer phase. The mechanical results showed the composites with the sandbag microstructure exhibited excellent toughness and stiffness.     

The Construction of Sandbag Microstructure in Polyamide 6/Ethylene–Propylene–Diene Terpolymer/Nanometer Calcium Carbonate Ternary Composite

A sandbag microstructure was constructed in polyamide 6 (PA6)/ethylene– propylene–diene terpolymer (EPDM)/nanometer calcium carbonate (nano-CaCO₃) ternary composites by the addition of maleinated EPDM (EPDM-g-MA) to reduce the interfacial tension between EPDM and PA6 and EPDM and nano-CaCO₃. Scanning electron microscopy observation and differential scanning calorimetry analysis revealed that the microstructure of the ternary composites evolved from the initially separated EPDM and nano-CaCO₃ dispersion structure to the sandbag structure and finally to the separated dispersion structure again with the increase of EPDM-g-MA content in the elastomer phase. The mechanical results showed the composites with the sandbag microstructure exhibited excellent toughness and stiffness.     

Effect of Filler Treatment on Crystallization,Morphology and Mechanical Properties of Polypropylene/Calcium Carbonate Composites

Pimelic acid (PA) was used as a new surface modifier for CaCO₃. The effects of PA treatment on the crystallization, morphology, and mechanical properties of PP/CaCO₃ composites were investigated. Fourier transform infrared (FTIR) spectroscopy analysis revealed that PA bonded to CaCO₃ and formed a calcium pimelate surface layer after reacting with CaCO₃. The results of wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and polarized light microscopy (PLM) proved that the PA treated CaCO₃ induced a large amount of β -iPP and decreased the spherulitic size of PP. The results of scanning electron microscopy (SEM) showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between PP and CaCO₃. The toughness of the composites was improved by the more ductile β -form spherulites. When 1% of PA treated CaCO₃ was added, the notched impact strength reached its maximum, a value of 19.79 kJ/m², which was 3.64 times greater than that of the pure PP.     

Phase transformations in CaCO3/iron oxide composite induced by thermal treatment and laser irradiation

Calcium carbonate (CaCO₃)/iron oxide composites were synthesized through a simple one‐step impregnation procedure by mixing iron oxide nanoparticles (γ‐Fe₂O₃ and Fe₃O₄) of about 6 nm in size and CaCO₃ microparticles (Φ = 2 µm–8 µm, vaterite phase). The morphology and structural properties of CaCO₃, iron oxide nanoparticles and CaCO₃/iron oxide composites were characterized as a function of low iron content (0 %w to 3.2 %w) by scanning electron microscopy and transmission electron microscopy, X‐ray diffraction and ⁵⁷Fe Mössbauer spectrometry. The phase transformations induced by thermal treatment and laser irradiation were investigated in situ by X‐ray thermodiffraction (XRTD) and Raman spectroscopy. We have shown that the phase transformations observed by XRTD are also observed under laser irradiation as a consequence of the absorption of the laser irradiation by iron oxide nanoparticles. Copyright © 2012 John Wiley & Sons, Ltd.     

Electromagnetic and mechanical properties of Fe3O4-coated amorphous carbon nanotube/polyvinyl chloride composites

Electromagnetic wave absorbing properties of absorbing composites depend on the dielectric and magnetic loss generally. In this paper, using Fe₃O₄-coated amorphous carbon nanotubes (ACNTs-Fe₃O₄) fabricated using a chemical synthesis–hydrothermal treatment method as an absorber and polyvinyl chloride (PVC) as a matrix, electromagnetic and mechanical properties of ACNT-Fe₃O₄/PVC composite were investigated. The results showed that the dielectric and magnetic losses of ACNT-Fe₃O₄/PVC composite were significantly enhanced in 8.2–12.4 GHz compared to ACNT/PVC composite, which improved absorbing properties, while slightly changing the mechanical properties.     

Composites of polyester + glass fiber residues vs. composites with mineral fillers

Polymer composites, such as those composed of a polyester, glass fibers (GFs), and mineral fillers (e.g. CaCO₃), pose a threat to the environment because of the growing amount of residues and due to difficulties in their recycling. Therefore, we have studied effects of incorporation of (polyester?+?GFs) waste material as a filler into virgin composites. Two types of polyester?+?glass fiber composites were developed using hot compression molding, one of them with recycled (polyester?+?glass fiber) material obtained via knife or ball milling; the other, a control group, contained CaCO₃, a traditional filler in this field. Dynamic friction and wear rate were determined using a pin-on-disk tribometer and a stylus profilometer, respectively. As expected, the presence of the residues significantly decreases dynamic friction and wear rate when compared to CaCO₃, since the main constituent of the residues is a polymeric material. Thus, polyester?+?glass fiber composite residues are a candidate for a partial substitution of CaCO₃. This should lower the environmental contamination caused by discarding the residues as well as provide composites with lower wear rates.     

A Study on the Morphology and Mechanical Properties of PVC/nano‐SiO2 Composites

Three methods were used to modify nano‐SiO₂ particles with various interfaces and interfacial interactions between the particles and Poly(vinyl chloride) (PVC) matrix. The experimental results show that direct surface treatment of nano‐SiO₂ particles with a silane coupling agent (KH‐550) is not effective for improving the mechanical properties of PVC/SiO₂ composites. Both ultrasonic oscillations and high energy vibromilling improve the interfacial interactions between SiO₂ particles and PVC matrix. With these methods, the aggregation of SiO₂ particles was inhibited and a good dispersion of SiO₂ particles in PVC matrix was obtained, which improved the mechanical properties of the PVC/SiO₂ composite. The mechanical properties of the PVC/SiO₂ composite with high energy vibromilling modified SiO₂ particles were remarkably improved. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic mechanical analysis (DMA), and theoretical calculations demonstrate these improvements.     

Thermal Degradation Kinetics of Plasticized Poly (Vinyl Chloride) with Six Different Plasticizers

Plasticized PVC formulated with different kinds of normally used plasticizers, including bis(2-ethylhexyl) phthalate (DOP), dioctyl terephthalate (DOTP), acetyl tri-n-butyl citrate (ATBC), acetyl trioctyl citrate (ATOC), trioctyl trimellitate (TOTM), and a new vegetable devived plasticizer, isosorbide ester (ID-37), were prepared by a melt blending method. The effect of plasticizer on the thermal degradation behavior of plasticized PVC was investigated by thermal gravimetric analysis (TGA). The activation energies were calculated by three well known methods, developed by Flynn-Wall-Ozawa (FWO), Friedman and Kissinger, respectively. The TGA conducted in N₂ atmosphere showed that the type of plasticizer had an obvious influence on the thermal stability of plasticized PVC. It was found that the peak temperatures (T_P) of the thermal degradation processes shifted to higher temperature with the increase of the heating rate, with two processes being shown. The activation energy of the first thermal decomposition process (E₁), calculated by the Kissinger method, was between 118 and 130 kJ/mol, while the activation energy of the second thermal decomposition process (E₂) was between 261 and 305 kJ/mol, except 499 kJ/mol for the PVC/TOTM formulation. The corresponding values of E₁ and E₂ obtained by the Flynn-Wall-Ozawa method were similar to the above data. E of the sample with TOTM also showed a higher value than the others; the results demonstrated that the PVC plasticized with TOTM was more thermally stable than with the others. The activation energies for certain conversion degrees were calculated by the Friedman method and the FWO method. The value of activation energy for 20%, 50%, and 80% conversion calculated by the Friedman method, exhibited an apparent difference from that calculated by the Flynn-Wall-Ozawa method; the results showed that the value of E obtained by the Friedman method was much more reasonable than that obtained by the Flynn-Wall-Ozawa method.     

Mechanical and electrical properties of radiation-vulcanized natural rubber latex with waste eggshell powder as bio-fillers

ABSTRACT

This work investigated the mechanical, physical, morphological, and electrical (volume) resistivity properties of radiation-vulcanized natural rubber latex (RVNRL) with additions of waste eggshell (WES) powder, which contained primarily CaCO₃ (calcite). The results showed that increasing gamma irradiation doses from 0 to 30?kGy in 10-kGy increments led to decreases in the swelling ratio and elongation at break but increases in the crosslink density, tensile modulus at 500% elongation, and tensile strength of the composites. The results also suggested that increasing the WES contents from 0 to 2, 4, or 6 parts per hundred parts of rubber by weight (phr) in the composites improved the tensile modulus at 500% elongation, tensile strength, hardness (Shore A), and electrical (volume) resistivity. In addition, after undergoing thermal aging at 70°C for 96?h, the tensile modulus and hardness (Shore A) increased, while the tensile strength and elongation at break decreased. This work also compared the properties of WES/RVNRL with commercial CaCO₃/RVNRL samples at the same 4-phr content. The results indicated that both composites had similar tensile properties, implying possible replacement of commercial CaCO₃ with WES powder as an effective reinforcing filler in RVNRL.