Ecofriendly latex films from cassava starch-filled radiation pre-vulcanized natural rubber latex

ABSTRACT

The demands of the usage of hazardous ingredients for sulfur curing system in latex industries decrease with an increase in health-conscious and environmental awareness. This work demonstrates the incorporation of cassava starch (CS) as biodegradable fillers with natural rubber latex (NRL) through a sulfur-free crosslinking technique using radiation pre-vulcanization natural rubber latex (RVNRL) in comparison to sulfur pre-vulcanized natural rubber latex (PvNRL). The 20% CS dispersion was prepared, and 5–25?phr of dispersed CS content were compounded with NRL and formed into films by the coagulant dipping method. Microstructures and crystallinity of the films were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, and their mechanical properties of NRL/CS films were characterized by tensile and tear tests. The result revealed that the crystallinity of RVNRL films was lower than PvNRL films. The total bond of S?C from PvNRL contributes to high tensile strength compared to C?C intermolecular rubber bond from radiation vulcanization system. The trend of decrement of tensile properties from sulfur crosslinking was larger than radiation crosslinking, and both systems gave similar tensile behavior at 25?phr of CS content. This attributed to the better dispersion of CS in RVNRL as confirmed by SEM micrographs. It was found that the optimum tear strength of RVNRL/CS and PvNRL/CS films was obtained at 10 and 5?phr of filler content, respectively. The result presented in this study may facilitate a contribution to the current literature on the development of latex film by radiation pre-vulcanization for rubber industry in the future.     

Effect of curing temperature,fibre loading and bonding agent on the equilibrium swelling of isora-natural rubber composites

Isora fibre-reinforced natural rubber (NR) composites were cured at 80, 100, 120 and 150°C using a low temperature curing accelerator system. Composites were also prepared using a conventional accelerator system and cured at 150°C. The swelling behavior of these composites at varying fibre loadings was studied in toluene and hexane. Results show that the uptake of solvent and volume fraction of rubber due to swelling was lower for the low temperature cured vulcanizates which is an indication of the better fibre/rubber adhesion. The uptake of aromatic solvent was higher than that of aliphatic solvent, for all the composites. As the fibre content increased, the solvent uptake decreased, due to the superior solvent resistance of the fibre and good fibre–rubber interactions. The bonding agent improved the swelling resistance of the composites due to the strong interfacial adhesion. Due to the improved adhesion between the fibre and rubber, the ratio of the change in volume fraction of rubber due to swelling to the volume fraction of rubber in the dry sample (V_τ ) was found to decrease in the presence of bonding agent. At a fixed fibre loading, the alkali treated fibre composite showed a lower percentage swelling than untreated one for both systems showing superior rubber–fibre interactions.     

Synthesis and characterization of ZnO nanoparticles using polyethylene glycol (PEG)

ZnO nanoparticles and ZnO encapsulated with polyethylene glycol (PEG) was synthesized using zinc acetate as a precursor at low temperature and characterized by different techniques. The influence of the types of solvent, synthesis parameters, and PEG encapsulation on the crystallization, the surface morphology, and the luminescent properties of ZnO nanoparticles prepared by the sol–gel process were investigated. The influence of different addition molar masses of the PEG during the synthesis on the ZnO emission peaks was systematically monitored. The crystallinity, the surface morphology, and the photoluminescence (PL) properties of ZnO depended highly on the synthesis process and PEG encapsulation. X-ray diffraction (XRD) spectra of ZnO nanoparticles show that all the peaks corresponding to the various planes of wurtzite ZnO indicate the formation of a single phase. The absorption edges of these ZnO nanoparticles are shifted by additions of the PEG polymer. The photoluminescence (PL) characterization of the ZnO nanostructures exhibited a broad emission in the visible range with maximum peak at 450 and/or 560 nm.     

The crystallization and physical properties of Al-doped ZnO nanoparticles

Un-doped Al (0-9 at.%) nanoparticles and doped ZnO powders were prepared by the sol-gel method. The nanoparticles were heated at 700-800 °C for 1 h in air and then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectra and photoluminescence (PL). The results of un-doped (ZnO) and Al-doped ZnO (AZO) nanoparticles were also compared to investigate the structural characteristics and physical properties. XRD patterns of AZO powders were similar to those of ZnO powders, indicating that micro-Al ions were substituted for Zn atoms and there were no variations in the structure of the ZnO nanoparticles. From the XRD and SEM data, the grain size of the AZO nanoparticles increased from 34.41 to 40.14 nm when the annealing temperature was increased. The Raman intensity of the AZO nanoparticles (Al = 5 at.%) increased when the annealing temperature was increased. Increasing the degree of crystalline not only reduced the residual stress, but also improved the physical properties of the nanoparticles.     

Preparation, characterization and surface morphology of novel optically active poly(ester-amide)/functionalized ZnO bionanocomposites via ultrasonication assisted process

Novel bionanocompoites (BNCs) were prepared using zinc oxide (ZnO) nanoparticles which functionalized by γ-methacryloxypropyltrimethoxysilane (KH570) as a coupling agent. Poly(ester-amide) (PEA) based on tyrosine natural amino acid was synthesized and used as a polymer matrix. PEA/ZnO BNCs were characterized by fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). All the results confirmed that the surface of ZnO particle has sufficient compatibility with PEA through the link of the coupling agent between ZnO and polymer and also proved that the presence of ZnO nanoparticles appeared to be dispersed in nanosize in polymer composite matrix. In addition, thermogravimetric analysis (TGA) data indicated an enhancement of thermal stability of new BNC materials compared with the pure polymer.     

凹凸棒石/硅橡胶复合材料的热氧化降解和老化性能研究

本文采用高压均质结合对辊挤压工艺对天然凹凸棒石进行棒晶解离得到了纯度较高和比表面积较大(133.7 m²/g)的纳米解离凹凸棒石. 进一步通过机械共混法分别将天然凹凸棒石和纳米解离凹凸棒石与硅橡胶生胶复合制备了天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶材料,研究了天然凹凸棒石和纳米解离凹凸棒石对凹凸棒石/硅橡胶复合材料热氧化降解和老化性能的影响. 结果表明,天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶在300 oC热氧老化处理0.5 h后,相比于纯硅橡胶,初始5%失重温度从385 oC提高至396∽399 oC. 系列表征结果表明,天然凹凸棒石和纳米解离凹凸棒石增强了纳米粒子与硅橡胶之间的相互作用从而抑制了纳米颗粒聚集,并且可显著提高硅橡胶侧链Si-CH₃的保存率,从而提高了该复合材料的热氧化降解和老化性能. 此外,纳米解离凹凸棒石可大大抑制纳米粒子的长大;因此老化后,纳米解离凹凸棒石-硅橡胶表现出了比硅橡胶(10.6%、7.4%和5.0%)更高的拉伸强度、断裂伸长率和撕裂强度保留率(40.6%、34.9% 和30.1%).     

Fe2O3 nanoparticles dispersed unsaturated polyester resin based nanocomposites: effect of gamma radiation on mechanical properties

ABSTRACT

In this work, unsaturated polyester resin (UPR) matrix based nanocomposite was fabricated using synthesized Fe₂O₃ nanoparticle as reinforcement and methyl ethyl ketone peroxide as curing agent by solution casting method. The Fe₂O₃ nanoparticles were synthesized using the sol–gel method and the formation of nanoparticle was confirmed by X-ray diffraction, Scanning electron microscope, Energy dispersive spectrometry analysis. Interactions between metal oxide nanoparticles and polymer molecules in fabricated nanocomposite were investigated by Fourier transform infrared spectrometer analysis. Pure UPR and Fe₂O₃/UPR composite were irradiated with various gamma radiation doses (0–15?kGy). At the 0?kGy (without radiation), the nanoparticles loaded composite showed better mechanical properties (increased in tensile strength and Young’s modulus and decreased in elongation) compared to that of pure UPR sheet. At the 5?kGy radiation dose, the tensile strength and Young’s modulus were further increased; whereas, the elongation was decreased in both samples.     

Characterization of undoped and Co doped ZnO nanoparticles synthesized by DC thermal plasma method

ZnO nanopowders doped with 5 and 10 at% cobalt were synthesized and their antibacterial activity was studied. Cobalt doped ZnO powders were prepared using dc thermal plasma method. Crystal structure and grain size of the particles were characterized by X-ray diffractometry and optical properties were studied using UV-vis spectroscopy. The particle size and morphology was observed by SEM and HRTEM, revealing rod like morphology. The antibacterial activity of undoped ZnO and cobalt doped ZnO nanoparticles against a Gram-negative bacterium Escherichia coli and a Gram-positive bacterium Bacillus atrophaeus was investigated. Undoped ZnO and cobalt doped ZnO exhibited antibacterial activity against both E. coli and Staphylococcus aureus but it was considerably more effective in the cobalt doped ZnO.     

The Effect of Epoxidized Natural Rubber and Two Kinds of Organoclay upon Molecular Interaction,Structure and Mechanical Properties of (Styrene-Butadiene Rubber/Acrylonitrile-Butadiene Rubber/Organoclay) Nanocomposites

Epoxidized natural rubber (ENR50) and two different kinds of organoclay (C30B and C15A) were used in blends of styrene-butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR) and their effects upon interaction between phases, morphology, and mechanical properties of the blends were investigated. The compounds were characterized by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and differential scanning calorimetry (DSC). The obtained results showed formation of hydrogen bonding between the compounds ingredients due to incorporation of C30B, especially in presence of ENR. AFM and FE-SEM analysis revealed good dispersion of the nanoparticles in the polymer matrix upon addition of ENR as well as better dispersion of C30B than C15A in the NBR phase. XRD results showed a greater expansion of the silicate layers by simultaneous use of organoclay and ENR Incorporation of organoclay alone or in combination with ENR in the blends caused shifting of the SBR T_g toward the NBR T_g. The tensile properties of the blends showed improvement by using nanoparticles in the presence of ENR.     

Natural rubber nanocomposites using polystyrene-encapsulated nanosilica prepared by differential microemulsion polymerization

In this study, nanocomposites of natural rubber (NR) and polystyrene (PS)-encapsulated nanosilica were prepared by latex compounding method. The nanolatex of PS-encapsulated silica was synthesized via in situ differential microemulsion polymerization. The resulted hybrid nanoparticles showed core-shell morphology with an average diameter of 40 nm. The silica hybrid nanoparticles were subsequently used as filler for the NR nanocomposite. The properties of NR were found to be improved as a result of the incorporation of PS-encapsulated nanosilica at 3 and 3-9 parts per hundred rubber (phr) for tensile strength and modulus at 300% strain, respectively, except the elongation at break, and up to 9 phr for flammability. The results from dynamic mechanical analyzer showed that the elastic properties of NR near the glass transition temperature increased with the inclusion of increasing concentration of the PS-encapsulated nanosilica, causing by the semi-interpenetrating nanostructure in the NR nanocomposites.     

ZnO nanoparticles favours heterogeneous nucleation in PET–ZnO nanocomposites

The structural and chemical properties with non-isothermal crystallization kinetics of PET–ZnO nanocomposites have been reported in this article. ZnO nanoparticles have been synthesized via chemical route with average diameter 19 nm which made confirm by transmission electron microscopy and X-ray diffractometer (XRD) techniques. PET–ZnO nanocomposites have been prepared by solution casting method. The structural and chemical changes occurred in poly (ethylene terephthalate) after inclusion of ZnO nanoparticles have been studied with the help of XRD and Fourier transform infrared spectroscopy, respectively. It was observed from differential scanning calorimeter that ZnO nanoparticles work as nucleating agent for heterogeneous nucleation in PET matrix under non-isothermal crystallization process. The combined Avrami and Ozawa models have been proved adequate to explain non-isothermal crystallization kinetics of PET–ZnO nanocomposites, and also, ZnO nanoparticles have been caused to reduce crystallization activation energy in pristine PET as per the applied Kissinger model.     

The structure and magnetic properties of Cu-doped ZnO prepared by sol-gel method

The Cu-doped ZnO and pure ZnO powders were synthesized by sol-gel method. The structural properties of the samples were investigated by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. All the results confirmed that copper ions were well incorporated into the ZnO lattices by substituting Zn sites without changing the wurtzite structure and no secondary phase existed in Cu-doped ZnO nanoparticles. The Zn_0.97Cu_0.03O nanoparticles exhibited ferromagnetism at room temperature, as established by the vibrating sample magnetometer analysis.     

Visible-light photocatalytic degradation of methylene blue with laser-induced Ag/ZnO nanoparticles

The preparation of Ag doped ZnO nanoparticles conducted through the method of laser-induction is presented in this work. The Ag/ZnO nanoparticles attained from various weight percentages of added AgNO₃ relative to ZnO were applied under visible-light irradiation for evaluating the heterogeneous photocatalytic degradations of methylene blue (MB) solutions. It was shown that the catalytic behavior of Ag/ZnO nanoparticles in the visible-light range is notably improved through the Ag deposition onto ZnO nanoparticles by the method of laser-induction with a maximum effectiveness of 92% degradation. The properties of the nanoparticles were characterized by the employments of UV-vis spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED).     

Influence of Curing Pressure on the Structure and Properties of Epoxy Adhesive Films

The effects of different curing pressures on the structure and properties of bisphenol A type epoxy adhesive film (METLBOND 1515-4, Cytec Industries Inc. Germany) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), nano-indentation analysis, and tensile testing. When the curing pressure was increased from 0?MPa to 0.5?MPa FTIR showed that more rigid carbonyl groups were found in the polymers. In addition, the microscopic and macroscopic mechanical properties of the cured adhesive films were improved. Nano-indentation analysis showed that the elastic modulus of the cured product increased significantly, from 2.92?GPa to 3.49?GPa. However, the tensile tests showed that the breaking-elongation increased only slightly, from 3.10% to 3.73%, when the curing pressure was increased from 0?MPa to 0.5?MPa. DMA results showed that the crosslinking densities of the cured epoxy films were improved by the increased curing pressure. These results indicated that a higher modulus of the cured product could be gained by increasing the curing pressure appropriately.     

Influence of stabilizing agents on structural and optical properties of cobalt oxide nanoparticles synthesized by an ultrasound-assisted method

Abstract

Cobalt oxide nanoparticles were synthesized using a facile and convenient sonochemical method, followed by a calcination process. For the synthesis, cobalt nitrate, and sodium borohydride were used as precursors. Polyvinyl alcohol, 3-mercaptopropionic acid, and styrene were used as a stabilizing agent. To identify the structure, optical properties and morphology, the synthesized nanoparticles were characterized using X-ray diffraction, Ultraviolet-Visible Spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy. To explain the formation mechanism of cobalt oxide nanoparticles, some investigations were carried out before thermal annealing. In addition, the particle size was tuned by variation of the concentration of 3-mercaptopropionic acid.     

Fabrication and Characterization of Polyethylene Nanocomposite Films Containing Zinc Oxide (ZnO) Nanoparticles Synthesized by a Cost-Effective and Safe Method

ZnO nanoparticles were synthesized through a cost-effective and safe method followed by fabrication and characterization of polyethylene/ZnO nanocomposite films and investigation of their properties. The morphology and size of the synthesized nanoparticles were evaluated by field emission scanning electron microscopy (FE-SEM). It was found that nanoparticles with a plate-like morphology with an average thickness of 50-70?nm were synthesized. The nanocomposites were characterized by using Fourier transform infrared analysis (FTIR) and ultraviolet–visible spectroscopy (UV-VIS). In addition, the effects of the amount of zinc oxide nanoparticles (ZnO-NPs) on the mechanical properties of the films and particles and their antibacterial properties against a gram-negative bacterium (Escherichia coli) and gram-positive bacteria (Staphylococcus aureus) were investigated. In the case of nanoparticles, one more gram-positive bacterium (Staphylococcus aureus) was studied. The results demonstrated an inhibition of growth of all bacteria in a broth medium for both the nanoparticles and nanocomposites. The FE-SEM micrographs revealed that by increasing the nanofiller content an inferior quality of dispersion was obtained which was reflected in the lower tensile strength of the nanocomposites compared to the pure PE. It was demonstrated that the addition of poly ethylene graft maleic anhydride (PE-g-MA), as compatibiliser, improved the dispersion state of the nanoparticles and, consequently, the ultimate mechanical properties. In addition, it was shown that the fabricated nanocomposites exhibited considerable UV-shielding properties.     

ZnO nanoparticles obtained by mechanochemical technique and the optical properties

Crystalline ZnO nanoparticles were synthesized by mechanochemical method. Mechanochemical processing involves the mechanical activation of solid-state displacement reactions at low temperatures in a ball mill. Statistical design was used to investigate the effect of main parameters (i.e. time, milling rate and calcination temperature) on ZnO crystallite size and morphology. After annealing at 400 °C in air, zinc oxide (ZnO) nanoparticles were obtained. The milled powders are analyzed by X-ray diffraction (XRD), TG/DTA and transmission electron microscope (TEM).The crystallite size of ZnO samples calculated from XRD is consistent with the TEM images and estimated to be less than 20 nm. The optical properties of the samples were studied by UV-vis spectrophotometer.     

Light-induced antifungal activity of TiO2 nanoparticles/ZnO nanowires

Antifungal activity of TiO₂/ZnO nanostructures under visible light irradiation was investigated. A simple chemical method was used to synthesize ZnO nanowires. Zinc acetate dihydrate, Polyvinyl Pyrrolidone and deionized water were used as precursor, capping and solvent, respectively. TiO₂ nanoparticles were deposited on ZnO nanowires using an atmospheric pressure chemical vapor deposition system. X-ray diffraction pattern of TiO₂/ZnO nano-composite has represented the diffraction peaks relating to the crystal planes of the TiO₂ (anatase and rutile) and ZnO. TiO₂/ZnO nanostructure antifungal effect on Candida albicans biofilms was studied and compared with the activity of TiO₂ nanoparticles and ZnO nanowires. The high efficiency photocatalytic activity of TiO₂ nanoparticles leads to increased antifungal activity of ZnO nanowires. Scanning electron microscope was utilized to study the morphology of the as prepared nanostructures and the degradation of the yeast.     

Melt flow and mechanical properties of sulfonated sbr ionomers and their polymer blends

Highly unsaturated rubber, styrene-butadiene rubber (SBR), was sulfonated successfully by sulfuric acid and acetic anhydride as sulfonating agent in a mixed solvent of petroleum ether and methyl ethyl ketone at high concentration, and neutralized with metallic acetate to form ionomer. Melt flow and mechanical properties of the ionomers and their blends with other polymers were studied. The results showed that the SBR ionomers can be melt processed easily in the presence of zinc stearate and that they behave like thermoplastic elastomers. Zinc stearate lowered the melt viscosity represented by the torque value of a Brabender mixer, and increased both the flow activation energy and the tensile strength of the ionomer. Sulfonate content of the ionomer enhanced both the melt viscosity and tensile strength. Type of cations used in neutralization significantly affected the properties of the ionomers. Blends of the ionomer with polypropylene or SBS showed synergistic behavior with respect to tensile strength, whereas those with polystyrene or cis-1,4-polybutadiene exhibited antagonistic behavior.     

Microstress,strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young’s modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson–Hall (W–H) method and the size–strain plot (SSP) method. Stress and the energy density were calculated using the W–H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV–visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.