Effect of calcium carbonate nanoparticles on barrier properties and biodegradability of polylactic acid

In this study, the effect of calcium carbonate (CaCO₃) nanoparticles on the barrier properties and biodegradability of polylactic acid (PLA) was investigated. For this purpose, nanocomposite films with various CaCO₃ nanoparticle contents (0, 3, 5, 10, and 15 wt%) were prepared by solution casting method. The gas permeability of nitrogen (N₂), oxygen (O₂), and carbon dioxide (CO₂) was evaluated through a constant volume and variable pressure apparatus at different pressures and temperatures. According to results, barrier properties were improved by loading CaCO₃ nanoparticles up to 5 wt%, and the gas permeability of CO₂, O₂, and N₂ was decreased from 1.4, 0.31, and 0.07 Barrer to 0.48, 0.095, and 0.019 Barrer, respectively. In addition, it was also observed that the gas permeability of samples was decreased by increasing feeding pressure and increased by enhancing temperature. Furthermore, morphological results confirmed the formation of agglomerations and large clusters over 5 wt% CaCO₃ nanoparticles. Finally, the thermal properties and biodegradability of PLA were increased by employing CaCO₃ nanoparticles. These results suggested PLA nanocomposites as favorable candidates for food packaging applications.     

In-situ preparation of multi-walled carbon nanotube (MWNT)/cellulose nanocomposites and their physical properties

The multi-walled carbon nanotube (MWNT)/cellulose nanocomposites were prepared by using monohydrated Nmethylmorpholine-N-oxide (NMMO) as a solvent for dispersing the acid-treated MWNTs (A-MWNTs) as well as for dissolving the cellulose. The A-MWNTs were well dispersed in both monohydrated NMMO and the nanocomposite films. The nanocomposite films were prepared by a film-casting method onto a glass plate. The tensile strain at break, Young’s modulus, and toughness of nanocomposite films increased by ～5, ～2 and ～12 times, respectively at ? (A-MWNT content in the nanocomposite)=0.8 wt%, as compared to those of the pure cellulose film. The thermal degradation temperature of the nanocomposite films also increased from 329 to 339 oC by incorporation of 1 wt% A-MENTs. The electric conductivities of the A-MWNT/cellulose nanocomposites at ? =1 and 10 wt% were 2.09×10^?5 and 3.68×10^?3 S/cm, respectively. The transmittances were 86, 69 and 55 % at 550 nm for 0.4, 0.8 and 1 wt% nanocomposite films, respectively. Thus, these nanocomposites are promising materials in terms of all the properties studied in this paper and can be used for many applications, such as toughened cellulose fibers, transparent electrodes, etc.     

Preparation and properties of polypropylene nanocomposites reinforced with exfoliated graphene

We have prepared a series of polypropylene/exfoliated graphene (PP/EG) nanocomposite films via efficient meltcompounding and compression, and investigated their morphology, structures, thermal transition behavior, thermal stability, electrical and mechanical properties as a function of EG content. For the purpose, EG, which is composed of disordered graphene platelets as reinforcing nanoscale fillers, is prepared by the oxidation/exfoliation process of natural graphite flakes. SEM images and X-ray diffraction data confirm that the graphene platelets of EG are well dispersed in PP matrix for the nanocomposites with EG contents less than 1.0 wt%. It is found that thermo-oxidative degradation of PP/EG nanocomposites is noticeably retarded with the increasing of EG content. Electrical resistivity of the nanocomposite films was dramatically changed from ∼10¹⁶ to ∼10⁶ Ω·cm by forming electrical percolation threshold at an certain EG content between 1 and 3 wt%. Tensile drawing experiments demonstrate that yielding strength and initial modulus of PP/EG nanocomposite films are highly improved with the increment of EG content.     

Preparation of collagen fiber/CaCO3 hybrid materials and their applications in synthetic paper

The collagen fiber/CaCO₃ hybrid materials were successfully prepared via in situ organic-inorganic hybrid technique. The surface morphology, hybrid mechanism, thermal and hydrothermal stability of these materials were investigated, respectively. Scanning electron microscopy (SEM) analysis showed that the size scale and distribution of CaCO₃ particles in collagen fiber relied on the concentration of CaCl₂. When the CaCl₂ was at low concentration, for example 6 wt%, the in-situ produced CaCO₃ particles were distributed evenly around the collagen fiber, the particle size could be controlled in the range of 2–4 µm and no apparent coagulation of CaCO₃ particles was found. Fourier transform infrared spectroscopy (FTIR) study revealed the interactions between the collagen fiber and CaCO₃ particles. The water solubility test and TGA analysis indicated that the solubility of collagen fiber in hot water decreased significantly after hybridization with CaCO₃ particles, whereas, the decomposition temperature was improved with increasing of the production of CaCO₃ particles. Moreover, the hybrid materials were used in conjunction with polyurethane and CaCO₃ powder to fabricate a novel synthetic paper. The result showed that the synthetic paper had good writing and printing.     

Hybrid organic-inorganic POSS (polyhedral oligomeric silsesquioxane)/polypropylene nanocomposite filaments

Octamethyl-POSS and Octaphenyl-POSS reinforced polypropylene nanocomposite monofilaments were prepared by melt blending route. It was observed that incorporation of Octamethyl-POSS and Octaphenyl-POSS in polypropylene show improvement in mechanical as well as thermal properties. Octaphenyl POSS/PP nanocomposites show significant increase in thermal stability even at very low concentration as compared to neat polymer matrix. An increase of 100 and 140 °C was observed in thermal degradation temperature at 5 wt% loss and maximum degradation over neat PP filaments respectively at low OP-POSS loadings (<5 wt%). Both Octamethyl-POSS and Octaphenyl-POSS act as lubricating agents facilitating drawing which results in improvement in orientation as well as mechanical properties.     

Enhanced physico-mechanical properties of polyester resin film using CaCO<Subscript>3</Subscript> filler

Bio-based CaCO₃ powder was synthesized via size reduction method from waste eggshells. The XRD analysis revealed that eggshell powder consists of CaCO₃ in calcite form. The inclusion level of CaCO₃ contents were varied of 5, 10, 15, 20 and 25 wt.% of prepared CaCO₃-polyester film. Effects of different proportions of prepared chicken eggshell and commercial CaCO₃ filler on the polyester resin composites films were compared by means of mechanical and physical test. It was found that the addition of CaCO₃ filler to the polyester films leads to improve the mechanical properties. The findings revealed that the best and optimum CaCO₃ filler content was 10 wt.% and among the prepared polyester films, eggshell CaCO₃-polyester films showed the best performance. The mechanical properties of CaCO₃-polyester films were measured in terms of tensile strength, elongation-at-break, tensile modulus, flexural strength and impact strength. For eggshell CaCO₃- polyester films, the maximum values of the aforementioned mechanical properties were 52.70 MPa, 4.63 %, 1868.70 MPa, 101.20 MPa and 8.40 kJ/m², respectively, whereas for commercial CaCO₃-polyester films those values were 48.12 MPa, 4.50 %, 1790.30 MPa, 97.50 MPa and 8.21 kJ/m², respectively. Further, water absorption of the composite films as a function of time had also been investigated at 10 wt.% filler content.     

Chitosan boehmite-alumina nanocomposite films and thyme oil vapour control brown rot in peaches (Prunus persica L.) during postharvest storage

Brown rot (Monilinia spp.) affects the shelf life, fruit quality and marketability of peaches (Prunus persica L.). Increasing consumer concern regarding food safety makes it necessary to search for natural environmentally friendly alternative products for postharvest disease control. In this investigation, polyethylene terephthalate (PET) punnets containing thyme oil (TO sachets) and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the incidence and severity of brown rot caused by Monilinia laxa in artificially inoculated peach fruits (cv. Kakawa) held at 25 °C for 5 days. Furthermore, PET punnets containing TO sachets and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the brown rot incidence to 10% in naturally infected fruits stored at 0.5 °C, 90% RH for 7 days and at the simulated market shelf conditions for 3 days at 15 °C, 75% RH. The chitosan/boehmite nanocomposite lidding films maintained the active components of thyme oil, thymol (56.43% RA), caryophyllen (9.47% RA) and β-linalool (37.6% RA) within the (head space volatiles) punnet. Panellists preferred fruits packed from commercial punnet containing thyme oil (sachets) and sealed with chitosan/boehmite nanocomposite lidding films due to overall appearance, taste, and natural peach flavour.     

Digestibility and Structural Properties of Thermal and High Hydrostatic Pressure Treated Sweet Potato (Ipomoea batatas L.) Protein

This study assessed the effects of thermal (40, 60, 80, 100 and 127 °C) and high hydrostatic pressure (HHP, 200, 400 and 600 MPa) treatments on the in vitro digestibility and structural properties of sweet potato protein (SPP). The results showed that the in vitro digestibility of SPP increased significantly with increasing heating temperature and heating time (0–60 min), while HHP treatment had little or no effect. Native SPP denaturation temperature (T _d ) and enthalpy change (ΔH) were 89.0 °C and 9.6 J/g, respectively. Thermal and HHP treated SPP had T _d of 84.6–88.9 °C and 86.4–87.6 °C, respectively. ΔH of thermal treated SPP was 3.6–6.4 J/g, while that of HHP treated SPP was 5.9–7.8 J/g. The differential scanning calorimetry (DSC) results demonstrated that HHP and thermal treatments both significantly reduced SPP thermodynamic stability. Circular dichroism analyses revealed that native SPP contains α-helixes, β-sheets and random coils (4.3, 48.0 and 47.7 %, respectively). After thermal treatment at 127 °C for 20 min, the content of α-helixes and turns increased significantly (13.2 and 27.6 %, respectively), whereas the content of β-sheets decreased significantly (12.3 %). In contrast, HHP treatment increased the content of β-sheets, but decreased the content of random coils. This study suggested that the SPP structure changes might be the main reason affecting the in vitro digestibility of SPP, and thermal treatment was more effective at changing SPP secondary structures and improving in vitro SPP digestibility than HHP treatment.     

Synthesis,analysis and simulation of carbonized electrospun nanofibers infused carbon prepreg composites for improved mechanical and thermal properties

This paper reports the fabrication, characterization and simulation of electrospun polyacrylonitrile (PAN) nanofibers into pre-impregnated (prepreg) carbon fiber composites for different industrial applications. The electrospun PAN nanofibers were stabilized in air at 270 °C for one hour and then carbonized at 950 °C in an inert atmosphere (argon) for another hour before placing on the prepreg composites as top layers. The prepreg carbon fibers and carbonized PAN nanofibers were cured together following the prepreg composite curing cycles. Energy dispersive X-ray spectroscopy (EDX) was carried out to investigate the chemical compositions and elemental distribution of the carbonized PAN nanofibers. The EDX results revealed that the carbon weight % of approximately 66 (atomic % 72) was achieved in the PAN-derived carbon nanofibers along with nitrogen and lower amounts of nickel, oxygen and other impurities. Thermomechanical analysis (TMA) exhibited the glass transition regions in the prepreg nanocomposites and the significant dependence of coefficient of thermal expansion on the fiber directions. The highest value of coefficient of thermal expansion was observed in the temperature range of 118-139 °C (7.5×10^-8 1/°C) for 0 degree nanocomposite scheme. The highest value of coefficient of thermal expansion was observed in the temperature range of 50-80 °C (37.5×10^-6 1/°C) for 90 degree nanocomposite scheme. The test results were simulated using ANSYS software. The test results may be useful for the development of structural health monitoring of various composite materials for aircraft and wind turbine applications.     

Preparation and crystallization behavior of polylactide nanocomposites reinforced with POSS-modified montmorillonite

We herein report the preparation and crystallization behavior of polylactide (PLA) nanocomposites reinforced with polyhedral oligomeric silsesquioxane-modified montmorillonite (POSS-MMT), which is prepared by exchanging sodium cations of pristine sodium montmorillonite (Na-MMT) with protonated aminopropylisobutyl polyhedral oligomeric silsesquioxane (POSS-NH₃ ⁺). PLA nanocomposites with 1–10 wt% POSS-MMT contents are manufactured via melt-compounding, and their structures and melt-crystallization behavior are investigated. It is characterized that POSS-MMT nanoparticles in the nanocomposites have an exfoliated structure of MMT silicates with POSS-NH₃ ⁺ and partial POSS-NH₂ crystals. DSC cooling thermograms suggest that the overall melt-crystallization rates of the nanocomposite with only 3 wt% POSS-MMT are remarkably enhanced in comparison with the neat PLA. From the isothermal crystallization analysis based on the Avrami model, the overall melt-crystallization of PLA/POSS-MMT nanocomposites is found to be dominated by the heterogeneous nucleation and three-dimensional spherulite growth. Isothermal melt-crystallization experiments using a polarized optical microscope show that the spherulite nucleation density of PLA/POSS-MMT nanocomposites is much higher than that of the neat PLA, whereas the spherulite growth rates of all the nanocomposites are almost identical with the rate of the neat PLA. It is concluded that the highly enhanced melt-crystallization rates of PLA/POSS-MMT nanocomposites stem from the dominant nucleation effect of POSS-MMT nanoparticles for PLA crystals.     

Multifunctional melt-mixed Ag/TiO2 nanocomposite PP fabrics: Water vapour permeability, UV resistance, UV protection and wear properties

This research deals with the investigating the effect of nanoparticles on the various properties of nanocomposite fabrics produced from melt spinning of various blend ratios of prepared masterbatch containing Ag/TiO₂ nanoparticles. The results revealed that the wear properties of modified fabrics improved as compared to pure fabrics with a trend justified considering modulus or crystallinity of fabrics with opposite effects. About 40 % UV protection enhancement has been obtained applying this kind of nanoparticles in the close relationship with the crimp contraction of textured yarns. A considerable improvement in the garment comfort has been recorded for nanocomposite sample containing 1 wt% nanoparticles. The lower permeability at low environment temperature and a higher at higher one, as compared to the pure sample, were obtained using this sample. It is highly interesting that these desirable changes in permeability can be achieved in the range of common environment temperatures (15–35 °C) being adapted to the human body requirements. The changing point is about 25 °C exactly meeting the body requirements by changing environment temperatures. A UV-induced solid state nanocomposite interaction increasing wear properties of UV-irradiated nanocomposite fabrics has been discovered.     

Electrospinning and microwave absorption of polyaniline/polyacrylonitrile/multiwalled carbon nanotubes nanocomposite fibers

Electrical conductive nanocomposite fibers were prepared with polyaniline (PANI), polyacrylonitrile (PAN) and multi-walled carbon nanotubes (MWCNTs) via electrospinning. The morphology and electrical conductivity of the PANI/PAN/MWCNTs nanocomposite fibers were characterized by scanning electron microscope (SEM) and Van De Pauw method. Electrical conductivity of nanocomposite fibers increased from 1.79 S·m^?1 to 7.97 S·m^?1 with increasing the MWCNTs content from 3.0 wt% to 7.0 wt%. Compared with PANI/PAN membranes, the mechanical property of PANI/PAN/MWCNTs nanocomposites fiber membranes decreased. The microwave absorption performance of composite films was analyzed using waveguide tube, which indicated that with the thickness increasing the value of R_L reduced from ?4.6 to ?5.9 dB.     

Development of nanofibrous membranes with far-infrared radiation and their antimicrobial properties

This study investigated the incorporation of nanoscale germanium (Ge) and silicon dioxide (SiO₂) particles into poly(vinyl alcohol) (PVA) nanofibers with the aim of developing nanostructures with far-infrared radiation effects and antimicrobial properties for biomedical applications. Composite fibers containing Ge and SiO₂ were fabricated at various concentrations of Ge and/or SiO₂ using electrospinning and layered on polypropylene nonwoven. The morphological properties of the nanocomposite fibers were characterized using a field-emission scanning electron microscope and a transmission electron microscope. The far-infrared emissivity and emissive power of the nanocomposite fibers were examined in the wavelength range of 5-20 μm at 37 °C. The antibacterial properties were quantitatively assessed by measuring the bacterial reductions of Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. Multi-component composite fibers electrospun from 11 wt% PVA solutions containing 0.5 wt% Ge and 1 wt% SiO₂ nanoparticles exhibited a far-infrared emissivity of 0.891 and an emissive power of 3.44·102 W m^?2 with a web area density of 5.55 g m^?2. The same system exhibited a 99.9 % bacterial reduction against both Staphylococcus aureus and Escherichia coli, and showed a 34.8 % reduction of Klebsiella pneumoniae. These results demonstrate that PVA nanofibrous membranes containing Ge and SiO₂ have potential in medical and healthcare applications such as wound healing dressings, skin care masks, and medical textile products.     

Preparation of magnetic and conductive graphite nanoflakes/SrFe<Subscript>12</Subscript>O<Subscript>19</Subscript>/polythiophene nanofiber-nanocomposites and its radar absorbing application

This study, we synthesized graphite-nanoflakes (GNFs) by acid treatment and thermal shock and then using the ultrasonic irradiation technique to exfoliate flake-carbon. The SrFe₁₂O₁₉ nanoparticles (NPs) were coated by co-precipitate method on GNFs after by alkaline treatment. Finally nanocomposite (GNF/SrFe₁₂O₁₉/PTh) was prepared by in-situ oxidative polymerization method in presence of thiophene (Th) as monomer. The magnetic and electrical conducting properties of the resulting nanocomposites were measured by using vibrating sample magnetometer and standard four-point-probe method, respectively. The synthesized nanocomposites were characterized by X-ray diffraction (XRD) and fourier transform infrared spectra (FTIR). In addition, morphological analyses were investigated by scanning electron microscopy (SEM). A minimum reflection loss (RL) of GNFs/SrFe₁₂O₁₉/PTh with 50 % wt GNFs/SrFe₁₂O₁₉ as core were observed ?28 and ?39 dB at 9.7 and 12 GHz for a 1.5 mm thickness. The results indicated that we can perform good microwave shielding in X-band (8–12 GHz) by these nanocomposites.     

Structures and physical properties of graphene/PVDF nanocomposite films prepared by solution-mixing and melt-compression

We have manufactured poly(vinylidene fluoride) (PVDF)-based nanocomposite films with different graphene contents of 0.1～10.0 wt% by ultrasonicated solution-mixing and melt-compression. As a reinforcing nanofiller, graphene sheets are prepared by rapid thermal expansion of graphite oxide, which are from the oxidation of natural graphite flakes. Graphene sheets are characterized to be well exfoliated and dispersed in the nanocomposite films. X-ray diffraction data confirm that the α-phase crystals of PVDF are dominantly developed in the nanocomposite films during the meltcrystallization. DSC cooling thermograms show that the graphene sheets serve as nucleating agents for the PVDF α-form crystals. Thermal stability of the nanocomposite films under oxygen gas atmosphere is noticeably improved, specifically for the nanocomposite with 1.0 wt% graphene. Electrical volume resistivity of the nanocomposite films is substantially decreased from ～10¹⁴ to ～10⁶ W cm, especially at a critical graphene content between 1.0 and 3.0 wt%. In addition, mechanical storage modulus is highly improved with increasing the graphene content in the nanocomposite films. The increment of the storage modulus for the nanocomposite film at 30 °C with increasing the graphene content is analyzed by adopting the theoretical model proposed by Halpin and Tsai.     

Evaluating the Mechanical Behavior of Basalt Fibers/Epoxy Composites Containing Surface-modified CaCO<Subscript>3</Subscript> Nanoparticles

Polymer matrix composites (PMCs) owing to their outstanding properties such as high strength, low weight, high thermal stability and chemical resistance are broadly utilized in various industries. In the present work, the influence of silanized CaCO₃ (S-CaCO₃) with 3-aminopropyltrimethoxysilane (3-APTMS) coupling agent at different values (0, 1, 3 and 5 wt.% with respect to the matrix) on the mechanical behavior of basalt fibers (BF)/epoxy composites was examined. BF-reinforced composites were fabricated via hand lay-up technique. Experimental results from three-point bending and tensile tests showed that with the dispersion of 3 wt.% S-CaCO₃, flexural strength, flexural modulus, tensile strength and tensile modulus enhanced by 28 %, 35 %, 20 % and 30 %, respectively. Microscopic examinations revealed that the development of the mechanical properties of fibrous composites with the incorporation of modified CaCO₃ was related to enhancement in the load transfer between the nanocomposite matrix and BF as well as enhanced mechanical properties of the matrix part.     

Thermal stability and pyrolysis kinetics of organosolv lignins obtained from Eucalyptus globulus

In the present work, thermogravimetric analysis of 17 organosolv lignin samples was carried out to determine their thermal stability and calculate the kinetic parameters of their pyrolysis. The thermal stability has been estimated by the measurement of the degradation temperature (T_d), calculated according to the maximum reaction rate. In addition, degradation temperature at 10% of conversion (T_10%) has been obtained in order to compare the initial stability of the samples with T_d for all samples. The values of T_d are comprised between 262 and 389 °C and the average value is 340 °C. The range for T_10% is 251–320 °C and the average value is 270 °C. The ashes content of the samples has been analyzed and all the residues presented values lower than 4 wt%. Kinetic parameters of lignin pyrolysis were calculated by Borchardt–Daniels’ method assuming nth order reaction. The activation energy values obtained are comprised between 17.9 and 42.5 kJ/mol and the average value is 28.1 kJ/mol. These results are in agreement with the bibliography.     

Heat resistance,impact strength,and transparency of PET copolymer containing fluorenylidene bis(2-phenoxyethanol)

Poly(ethylene terephthalate) (PET) copolymers containing fluorenylidene bis(2-phenoxyethanol) (FBPE) were prepared. The glass transition temperature of copolymers increased continuously with the composition of FBPE. The glass transition temperature of PET/FBPE copolymer at loading of 15 mol% FBPE was 107 °C, which was 35 °C higher than that of PET. The melting temperature of PET/FBPE copolymers was decreased with the composition of FBPE, and it disappeared above 6 mol% of FBPE. The heat deflection temperature of copolymers increased from 60.7 °C for PET to 89.9 °C for the copolymer containing 15 mol% of FBPE. The values of optical transmittance of copolymers were 89-90 % at 550 nm, and no significant change was observed with the FBPE composition. The impact strength value of copolymer at loading of 10 mol% FBPE was 26 J/m, which was 20 J/m higher than that of PET.     

Novel nanocomposites based on hydroxyethyl cellulose and graphene oxide

In the present study, nanocomposites films formed by hydroxyethyl cellulose (HEC) and graphene oxide (GO) were synthesized and characterized. Compared with pure hydroxyethyl cellulose film, the thermal stability and mechanical properties of the composite materials were significantly improved. When the graphene loading was only 1.0 wt%, the maximum weight loss temperature increased 11.14 °C. The tensile strength and Young’s modulus of HEC/GO nanocomposites films were increased by 30.28 and 75.63 % compared to the pure HEC films, with only 1.0 wt% GO. The X-ray diffraction and Fouriertransform infrared spectroscop showed that GO sheets were completely exfoliated in the HEC matrix and suggested the presence of the weak interaction between HEC and GO sheets because of large number of oxygen-containing hydrophilic functional groups on the surface and edge of GO sheets. Furthermore, the well-dispersed GO nanosheets in the films can be inferred from the SEM and Halpin-Tsai model analysis. On the other hand, the composite films showed improved barrier properties against oxygen. This simple process for preparation of HEC/GO films is attractive for potential development of high-performance films for packing applications.     

Effect of phase transformation on physical and biological properties of PVA/CaFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocomposite

The thermal treatment method was employed to achieve higher homogeneity of calcium ferrite (CaFe2O4) and Poly (vinyl alcohol) (PVA) nanocomposites. The influences of phase transformation on physical and biological properties of calcined specimens were investigated by various experimental techniques including X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), high resolution Field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FT-IR). Heat treatment was conducted at temperatures between 723 and 923 K, so that a phase transformation occurred from cubic to orthorhombic spinel structure at 923 K. The chemical analysis of the PVA/CaFe₂O₄ nanocomposite was performed by energy dispersion X-ray analysis (EDXA), demonstrated the PVA/CaFe₂O₄ nanocomposites contained the elements of C, Ca, Fe, and O. The formed nanocomposites exhibited ferromagnetic behaviors which were confirmed by using a vibrating sample magnetometer (VSM). The calcined specimens were carried out to an antimicrobial or antifungal test.