Thermal stability and UV-shielding properties of polymethyl methacrylate and polystyrene modified with calcium carbonate nanoparticles

The influences of nanosized CaCO₃ on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated. Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA/CaCO₃ and PS/CaCO₃ were prepared with different filler loading (0–4 wt%) of CaCO₃ nanoparticles by solution mixing technique. The Fourier transform infrared analysis confirmed that CaCO₃ nanoparticles were present in the polymers matrices. The morphology and elemental composition of nanocomposites were evaluated by SEM and energy dispersive X-ray spectroscopy. The thermal properties of nanocomposites were characterized by differential scanning calorimetric, thermogravimetric, and differential thermogravimetry analysis, and the results indicate that the incorporation of CaCO₃ nanoparticles could significantly improve the thermal properties of PMMA/CaCO₃ and PS/CaCO₃ nanocomposites. The glass transition temperature (T _g ) and decomposition temperature (T _d ) of nanocomposites with 4 wt% of CaCO₃ nanoparticles were increased by 30 and 24 K in case of PMMA/CaCO₃ and 32  and 15 K in the case of PS/CaCO₃ nanocomposites, respectively. The obtained transparent nanocomposites films were characterized using UV–Vis spectrophotometer which shows the transparencies of nanocomposites are almost maintained in visible region while the intensity of absorption band in ultraviolet (UV) region is increased with CaCO₃ nanoparticles contents and these composites particles could enhance the UV-shielding properties of polymers.     

Nano-silica and SiO2/CaCO3 nanocomposite prepared from semi-burned rice straw ash as modified papermaking fillers

Silica (SiO₂) nanoparticles and silica/calcium carbonate (SiO₂/CaCO₃) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites was carried out using Na₂SiO₃ solution that was prepared from SBRSA and CaCO₃ nanoparticles of 30–70 nm. The targeted SiO₂/CaCO₃ nanocomposites were prepared with different molar ratio of SiO₂:CaCO₃ 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800 °C for 2 h. The prepared SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO₂ nanoparticle and semi-crystalline shell of SiO₂ coated CaCO₃ core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper.Application of the prepared SiO₂ nanoparticles and SiO₂/CaCO₃ nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO₃ (PCC) filler.The results showed that the retention of SiO₂ nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO₂:CaCO₃ molar ratio.     

Nylon Based Nanocomposites: Influence of Calcium Carbonate Nanoparticles on the Thermal Stability

In this paper thermal and thermo-oxidative stability of nylon 6 based nanocomposites containing up to 5% by weight of fatty acid coated calcium carbonate (CaCO₃) nanoparticles is studied. Thermal stability of compression-moulded samples was evaluated by thermogravimetric analysis (TG) under air and nitrogen atmosphere. Kinetic analysis of TG data was performed by using the Flynn-Wall-Ozawa method. Results show that the presence of coated nanoparticles adversely affects the thermal and thermo-oxidative stability of nylon 6. Kinetic analysis shows that a complex, multi-step decomposition process occurs. Moreover, the presence of nanoparticles do not affect the rate limiting step of nylon 6 decomposition in air, while under nitrogen atmosphere the decomposition process occurs through a diffusion-driven regime in presence of high amounts of CaCO₃.     

Effect of industrial water components on thermal stability of nitrocellulose

In order to prevent the spontaneous ignition of nitrocellulose (NC), NC is stabilized by washing with industrial water in its synthesis process. However, there is a possibility that the components in industrial water contribute to the thermal stability of NC. In this way, the purpose of this study is to clarify the effect of industrial water components on the thermal stability of NC. In experiments, a heat flux calorimeter was used to observe the thermal behavior of NC with the residue of vaporized industrial water. The induction period of heat release of NC with 2-mass% residues was approximately 2–5 h shorter than that of NC alone whose induction period was observed at 7 h. Those results indicate that the residue destabilized NC. On the other hand, when the additive amount of the residue was increased, the induction period gradually increased as well. Based upon these results, we assume that inorganic salts contributing to stabilization and destabilization competitively coexist in the industrial water components. The same thermal analysis was performed on NC with CaCO₃, CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl. Those salts are predicted to exist in the industrial water. In the results, the induction period of NC with 2-mass% CaCO₃ was approximately 15-h longer than that of NC alone, while the induction period with the inorganic salts CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl was 4–5-h shorter. Therefore, when the industrial water components accumulate in NC, the destabilization by inorganic salts such as CaSO₄, CaCl, ZnSO₄, NaCl, and CuCl and the stabilization by compounds such as CaCO₃ are thought to countervail against each other.     

Liquid crystalline polymers XVI*. Thermotropic liquid crystalline copoly(arylidene-ether)/TiO2 Nanocomposites: synthesis,characterisation and applications

ABSTRACT

Polymer nanocomposites are already a part of many important worldwide businesses. Among many nanocomposite precursors, titanium dioxide (TiO₂) nanopowder is increasingly being investigated due to its special properties. In this work, the feasibility of synthesising a new series of materials, copoly(arylidene-ether)/titanium dioxide nanocomposites, using in-situ copolymerisation technique has been investigated. This can be performed by the interaction of both cyclohexanone and 4-tert-butylcyclohexanone monomers with 4,4′-diformyl-2,2′-dimethoxy-α,ω-diphenoxyalkanes Ia–e, respectively, using different additions of titanium dioxide-P25. The structure of the prepared nanocomposites IIa–e/TiO₂ (0.2–3.0%) was confirmed by elemental analysis (energy dispersive X-ray spectroscopy) and spectral data (Fourier transform-infrared [FT-IR]). FT-IR verified the dispersion of nanofillers in the copolymer. Then, the characterisation and applications of these nanocomposites are extensively discussed depending on the investigation of how the addition of titanium dioxide nanoparticles affected on their properties using various techniques, such as X-ray diffraction, SEM, transmission electron microscopy, Water Contact Angle (WCA), thermogravimetric analysis, differential thermogravimetric, differential thermal analysis (DTA), polarising optical microscope and UV–vis absorption spectroscopy. The nanoparticles affected on the copolymer thermal behaviour in different ways (discrepancy results) depending on how these nanoparticles are dispersed in the copolymer matrix. UV–vis absorption spectra displayed a decrease in the optical band gap of some nanocomposites, which resulted from the addition of titanium dioxide to these copolymers, and this can improve the efficiency of them as organic emitting materials.     

Preparation of Polyvinyl Acetate (PVAc) and PVAc–Ag–Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Composite Nanofibers by Electro-spinning Method

Magnetite (Fe₃O₄) and silver nanoparticles were synthesized via simple chemical reactions at room temperature. Poly vinyl acetate (PVAc) nano-fibers and their nanocomposites with Ag and Fe₃O₄ were prepared by electro-spinning method. Effect of various electric potentials and distance on the morphology and diameter of fibers were investigated. Photocatalytic properties of silver in degradation five different dyes as organic pollutants in water were investigated. Fe₃O₄ nanoparticles exhibit a super-paramagnetic behavior at room temperature. Nontoxic nanoparticles appropriately enhanced both thermal stability and flame retardant property of the PVAc matrix. In the presence of flame, Fe₃O₄ nanoparticles remain together (show resistance to drip falling because of magnetic interaction) and build a barrier against flame.     

Thermal and morphological investigation of the effect of POSS-(PEG2000)8 addition to UV curable PEGMEA/PEGDA formulation and simultaneously in situ formed silver nanoparticles

In this study, hybrid nanocomposites were synthesized by photo-crosslinking of poly (ethylene glycol) methyl ether acrylate/poly (ethylene glycol) diacrylate monomer system using 2- (carboxymethoxy) thioxanthone and POSS-(PEG₂₀₀₀)₈. Additionally, AgNO₃ was added to this formulation and in situ formation of silver nanoparticles onto hybrid nanocomposites were achieved in one-step. UV–Vis spectroscopy technique was used as a very useful tool for surface plasmon resonance band detection of silver nanoparticles. In addition to thermogravimetric analyses which were performed in nitrogen atmosphere to determine the thermal stability of the nanocomposites, dynamic light scattering, and scanning electron microscopy techniques were also used for size and morphology of silver nanoparticles in a hybrid network. TGA analyses proved that even the addition of a very low amount of POSS-(PEG₂₀₀₀)₈ made noteworthy contribution to thermal stability especially in the presence of silver nanoparticles in the hybrid network. The swelling capacities of the prepared films were examined at 1, 3 and 24 h in phosphate buffer solution (pH = 7.4). It was found that film containing only POSS-(PEG₂₀₀₀)₈ had the highest swelling ratio in the shortest time.     

PMMA Based Nanocomposites Filled with Modified CaCO3 Nanoparticles

PMMA based nanocomposites filled with calcium carbonate nanoparticles (CaCO₃) have been prepared by in situ polymerization approach. In order to improve inorganic nanofillers/polymer compatibility, PBA chains have been grafted onto CaCO₃ nanoparticle surface. Morphological analysis performed on nanocomposite fractured surfaces has revealed that the CaCO₃ modification induces homogeneous and fine dispersion of nanoparticles into PMMA as well as strong interfacial adhesion between the two phases. Mechanical tests have shown that both unmodified and modified CaCO₃ are responsible for an increase of the Young's Modulus, whereas only PBA-grafted nanoparticles allow to keep unchanged impact strength, strongly deteriorated by adding unmodified CaCO₃. Finally, the presence of CaCO₃ nanoparticles significantly improves the abrasion resistance of PMMA also modifying its wear mechanism.     

Effect of nanoclay and barium sulfate nanoparticles on the thermal and morphological properties of polyvinylidene fluoride nanocomposites

The thermal, morphological and optical studies of BaSO₄ and MMT (nanoclay) embedded in PVDF were investigated. Nanocomposites samples of PVDF–BaSO₄–MMT were prepared by varying the loadings (1–4 mass%) in case of BaSO₄ and MMT nanomaterials, respectively. Polyvinylidene fluoride–barium sulfate-montmorillonite (PVDF–BaSO₄–MMT) nanocomposites were prepared by solvent-mixing technique. Nanoparticles were synthesized by in situ deposition technique with the help of nonionic polymeric surfactant, and the particle size of nanoparticles was recognized by scanning electron microscopy (SEM) analysis which confirms that the particle has diameter of 80–90 nm. As prepared, nanocomposites films (thickness, 25 μm) were characterized by Fourier transform infrared microscopy (FTIR), SEM and electron diffraction spectroscopy (EDS). FTIR shows that all the chemical constituents were present in the nanocomposites, whereas SEM analysis suggested that the nanofillers dispersed well in polymer matrix and EDS showed the elemental composition of nanocomposite samples. Thermal properties of nanocomposites were studied by using TG/DTA/DTG. TG/DTA studies showed decomposition temperature of pure PVDF is 473.5 °C. The decomposition temperature (T _d) of nanocomposites was increased by 93 °C in case of nanocomposites with addition of both BaSO₄ and MMT nanomaterials. The difference in the thermal degradation temperature was found to be 1.2% higher in case of addition of BaSO₄ nanoparticle as compared to nanoclay. The obtained transparent nanocomposite films were characterized by using UV–Vis spectrophotometer which shows that transparencies of nanocomposites are maintained in visible region, the intensity of absorption band in UV region is increased with the addition of BaSO₄ nanoparticles, while in case of addition of nanoclay the UV region does not show drastic changes. Addition of both nanoparticle and nanoclay shows higher absorption in comparison with the individual samples. But further, doubling the amount of nanoparticle and nanoclay shows decrease in UV absorption. Overall, the results of thermal studies show that the incorporation of BaSO₄ and MMT could significantly improve the thermal properties of nanocomposites.     

The influence of the nanofiller on thermal properties of thermoplastic polyurethane elastomers

Pure Fe₃O₄ and Mn-doped Fe₃O₄ nanoparticles were synthesized by simple wet chemical reduction technique using nontoxic precursors. Manganese doping of two concentrations, 10 and 15%, were employed. All the three synthesized nanoparticles were characterized by stoichiometry, crystal structure, and surface morphology. Thermal studies on as-synthesized nanoparticles of pure ferrite (Fe₃O₄) and manganese (Mn) doped ferrites were carried out. The thermal analysis of the three as-synthesized nanoparticles was done by thermogravimetric (TG), differential thermogravimetric, and differential thermal analysis techniques. All the thermal analyses were done in nitrogen atmosphere in the temperature range of 308–1233 K. All the thermocurves were recorded for three heating rates of 10, 15, and 20 K min^?1. The TG curves showed three steps thermal decomposition for Fe₃O₄ and two steps thermal decompositions for Mn-doped Fe₃O₄ nanoparticles. The kinetic parameters of the three as-synthesized nanoparticles were evaluated from the thermocurves employing Kissinger–Akahira–Sunose (KAS) method. The thermocurves and evaluated kinetic parameters are discussed in this paper.     

Synthesis and properties of Fe0.83V1.17O4

Thermal properties of the organic–inorganic bicontinuous nanocomposites prepared via in situ two-stage polymerization of various silanes, epoxy, and amine monomers are investigated, and the impact of filler content and its organic compatibility on thermal stability of these nanocomposites is studied. Two series of epoxy–silica nanocomposites, namely, EpSi-A and EpSi-B containing 0–20 wt% silica, are synthesized. An epoxy–silane coupling agent is employed to improve the organic compatibility of silica in EpSi–B nanocomposites. The composites synthesized via two-stage polymerization are characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric (TG) analysis. DSC and TG/differential thermogravimetric results reveal substantially high glass transition (T _g) and excellent thermal stability of the bicontinuous nanocomposites as compared with pristine epoxy polymer. Both T _g and thermal properties, however, considerably vary depending on the organic compatibility of the nanocomposites. Significantly higher decomposition temperatures are recorded in case of EpSi-B nanocomposites owing to the chemical links between the epoxy and silica phases. Kinetic studies also show relatively higher activation energies of pyrolysis for EpSi-B nanocomposites.     

Preparation of CaCO3/Polystyrene Inorganic/Organic Composite Nanoparticles

CaCO₃/polystyrene inorganic/organic composite nanoparticles (50 nm) with a core/shell structure were synthesized in 80% yield by emulsion polymerization. Nanometer CaCO₃ was pretreated with γ‐methacryloxypropyltrimethoxysilane in order to introduce polymerizable groups onto its surface. Soxhlet extraction experiments have shown that only 4% of total encapsulating polystyrene (PS) was removable when the ratio of CaCO₃ to styrene was relatively low (14.8–29.6%), indicating strong adhesion between CaCO₃ and PS.     

Influence of CaCO<Subscript>3</Subscript> nanoparticles shape on thermal and crystallization behavior of isotactic polypropylene based nanocomposites

Summary The influence of calcium carbonate nanoparticles with different shapes (spherical and elongated) on the thermal properties and crystallization behavior of isotactic polypropylene was investigated. CaCO₃ nanoparticles were covered by an appropriate coating agent to improve the interfacial adhesion between the filler and the polyolefin matrix. The nanocomposites were prepared by melt mixing and subsequent compression molding. A remarkable effect of CaCO₃ on the thermal properties of iPP was observed. Moreover, the analysis of crystallization kinetics showed that CaCO₃ nanopowder coated with PP-MA are efficient nucleating agents for iPP, and the overall crystallization rate results higher than plain iPP.     

Effect of different nanoparticles on thermal decomposition of poly(propylene sebacate)/nanocomposites: Evaluation of mechanisms using TGA and TG–FTIR–GC/MS

In the present study poly(propylene sebacate) (PPSeb) nanocomposites containing 2 wt% of fumed silica nanoparticles (SiO₂) or multiwalled carbon nanotubes (MWCNTs), or montmorillonite (MMT) were prepared by in situ polymerization. The thermal degradation of nanocomposites was studied using thermogravimetric analysis (TGA). It was found that the addition of MWCNTs and MMT enhances the thermal stability of the polymer, while SiO₂ nanoparticles do not affect it. From the variation of the activation energy (E) with increasing degree of conversion it was found that the decomposition of nanocomposites proceeded with a complex reaction mechanism with the participation of at least two different steps. To evaluate the thermal decomposition mechanisms and mainly the effect of nanoparticles on the thermal decomposition of PPSeb, TGA/FTIR and a combination of TG-gas chromatography–mass spectrometry (TG/GC–MS) were used. From mass ions detection of the formed decomposition compounds it was found that the decomposition of PPSeb and its nanocomposites, takes place mainly through β-hydrogen bond scission and, secondarily, through α-hydrogen bond scission. The main decomposition products were aldehydes, alcohols, allyl, diallyl, and carboxylic acids.     

Synthesis and characterization of poly(ɛ-caprolactone)/Fe3o4 nanocomposites by in situ polymerization

A series of magnetic nanocomposites based on poly(?-caprolactone) (PCL) and Fe₃O₄ nanoparticles were prepared using a facile in situ polymerization method. The chemical structures of the PCL/Fe₃O₄ nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Results of wide-angle X-ray diffraction (WAXD) showed that the incorporation of the Fe₃O₄ nanoparticles did not affect the crystallization structure of the PCL. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the morphology and dispersion of the Fe₃O₄ nanoparticles within the as-synthesized nanocomposites. Results of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) showed that the crystallization temperature was raised and the spherulites size decreased by the presence of Fe₃O₄ nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. The thermal stability of the PCL was depressed by incorporation of Fe₃O₄ nanoparticles from thermogravimetric analysis (TGA). The superparamagnetic behavior of the PCL/Fe₃O₄ nanocomposites was testified by the superconducting quantum interference device (SQUID) magnetometer analysis. The obtained biodegradable nanocomposites will have a great potential in magnetic resonance imaging contrast and targeted drug delivery.     

Preparation and characterization of flexible polyurethane foam nanocomposites reinforced by magnetic core-shell Fe3O4@APTS nanoparticles

Novel magnetic polyurethane flexible foam nanocomposites were synthesized by incorporation of aminopropyltriethoxysilane (APTS) functionalized magnetite nanoparticles (MNPs) via one-shot method. The functionalized MNPs (Fe₃O₄@APTS) were synthesized by co-precipitation of the Fe²⁺ and Fe³⁺ with NH₄OH and further functionalization with APTS onto the surface of MNPs by sol–gel method. The magnetic core-shell NPs were used up to 3.0 % in the foam formulation and the magnetic nanocomposites prepared successfully. The results of thermogravimetric analysis (TGA) showed an increasing in thermal stability of polyurethane nanocomposite foam at initial, 5 and 10 %, and maximum thermal decomposition temperatures by incorporation of Fe₃O₄@APTS. In addition SEM images revealed the uniformity of the foam structures and decreasing in pore sizes. Furthermore, VSM result showed super paramagnetic behavior for Fe₃O₄@APTS-PU nanocomposites.     

Mineralization of simulated flue gas to prepare CaCO3 whisker using suspended CaSO4

CaCO₃ whiskers were synthesized controllably by introducing simulated flue gas containing CO₂ and N₂ into a CaSO₄ suspension. The effects of solution pH, reaction temperature, and simulated flue gas on the formation of CaCO₃ whiskers were studied. The growth mechanism and growth model of CaCO₃ whiskers had also been provisionally recommended. The reaction product was characterized by scanning electron microscopy analysis, thermogravimetric analysis, and X-ray diffraction analysis. CaCO₃ whiskers with 97% purity were synthesized at pH 7.5, 80°C, 0.1 L/min CO₂ flow rate, and 16.7% CO₂ purity, with a length between 15 and 20 μm and an aspect ratio of about 12.     

Effect of manganese nanoparticles on the mechanical, thermal and fire properties of polypropylene multifilament yarn

Polypropylene filled with 10 wt% of inorganic nanoparticles has been prepared by melt blending. The fillers investigated were manganese oxides (MnO and Mn₂O₃) and manganese oxalate (MnC₂O₄). The morphology and thermal stability of these nanocomposites have been studied by transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The experimental results reveal that the addition of 10 wt% manganese oxides improves the thermal stability in air of polypropylene by about 70-80 °C. In a second step, these nanocomposites have been processed by melt spinning in order to produce multifilament yarn. The mechanical properties of these filaments have then been characterized. It is shown that just the addition of Mn₂O₃ improves the mechanical properties of polypropylene filaments. The flammability of these nanocomposites used as knitted fabrics has finally been evaluated with a mass loss calorimeter at 35 kW/m². This kind of experiment has not revealed a real improvement of fire properties.     

Sinterization and hydration of synthesized cement clinker doped with sulfates

This paper aims to evaluate the influence of three kinds of sulfates from the green production of cement on its sintering and hydration. The properties of clinker and hydration were monitored by thermogravimetric and differential thermal analysis (TG–DTA), X-ray diffraction, X-ray fluorescence and isothermal conduction calorimeter. Results indicate that gypsum lowers the decomposition temperature of CaCO₃ and all these Sulfates will enhance the solid-phase reaction but increase melting temperature. Sulfates reduce the content of C₃S, but K₂SO₄ and 2CaSO₄·K₂SO₄ is conducive to the formation of β-C₂S. The hydration induction period is shortened by the sulfates. K₂SO₄ and 2CaSO₄·K₂SO₄ improve the early hydration of clinker, but gypsum may lightly reduce the hydration reactivity of clinker in acceleration period. 2CaSO₄·K₂SO and K₂SO can significantly accelerate the compressive strength development of cement clinker before 3 d; by contrast, gypsum is detrimental for that. The precipitation of hydration products (CH and C–S–H) in clinker with sulfates is more than that of clinker without sulfates at 9 h. K₂SO₄ can accelerate the hydration of clinker without forming ettringite.

     

A novel method for preparing poly(ethylene terephthalate)/BaSO4 nanocomposites

We developed a novel method for preparing poly(ethylene terephthalate)/BaSO₄ nanocomposites, which were synthesized by in situ polymerization of terephthalic acid (TPA), ethylene glycol (EG) and BaSO₄ nanoparticles prepared by reacting H₂SO₄ with Ba(OH)₂ in ethylene glycol (EG). It was shown that the addition of BaSO₄ would not influence the synthesis of PET. The structure of the nanocomposites was characterized by transmission electron microscopy (TEM), and the nanoscale dispersion of BaSO₄ particles in the PET matrix was observed when the BaSO₄ content is below 4 wt%. Moreover, the thermal properties of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results suggest that the degree of dispersion of BaSO₄ particles in the PET matrix has important effect on the thermal properties of the nanocomposites. The existence of BaSO₄ nanoparticles enhances the crystallization rate of PET. Besides, it was found that the thermal stability of PET was improved by the addition of the BaSO₄ nanoparticles.