Nuchnapa Tangboriboon

Preparation and properties of calcium oxide from eggshells via calcination

Duck eggs are one of the most versatile cooking ingredients in which residue eggshells are discarded. Raw duck eggshells were calcined at temperatures between 300 to 900 °C, for 1, 3, and 5 h. Both the raw and calcined duck eggshells were characterized by FTIR, STA, XRD, XRF, TEM, BET, a particle size analyzer, and an impedance analyzer. The proper calcination conditions are: 900 °C and 1 h, yielding calcium oxide with a purity of 99.06 % w/w. The calcium carbonate of the rhombohedral form (CaCO3) transforms completely into the calcium oxide or lime of the face centered cubic form (CaO) at 900 °C, as shown by XRD diffraction patterns. The transmission electron microscopy (TEM) images of the calcium oxide reveal a moderately good dispersion of nearly uniform particles. The calcium oxide has a white color, a spherical shape, high porosity, and narrow particles size distribution. The percentage of ceramic yield of the calcium oxide is 53.53, as measured by STA (TG-DTA-DTG). The calcium oxide has a N2 adsorption-desorption isotherm indicating the meso-porosity range. The dielectric constant and the electrical conductivity of the calcined calcium oxide are 35 and 1:0×10−6(Ω·m)−1, respectively, at the frequency of 500 Hz.

Processing of Kaolinite and Alumina Loaded in Natural Rubber Composite Foams

Composite natural rubber foams were successfully prepared from the vulcanization of natural rubber in a sulfur curing system. The natural rubber matrix phase was added with chlorinated polyethylene, kaolinite, and alumina. The morphology of natural rubber composite foams was altered when a gas was generated at the vulcanization temperature of 150°C to obtain open and closed cell structures. Furthermore, the kaolinite and alumina reinforced the mechanical properties and increased the thermal resistance of the composite foams. The composite foams were light in weight and had good thermal, mechanical, and electrical properties, suitable for energy absorption, thermal insulation, and structural uses.

Electromechanical responses of dielectric elastomer composite actuators based on natural rubber and alumina

The deflection responses of the dielectric elastomer actuators are investigated under the electrical field strengths between 0 and 650 V/mm at room temperature (27°C). The Standard Thai Rubber 5L (STR 5L)/aluminum oxide (Al2O3) composite (60 wt% Al2O3) cross-linked with 1 wt% dicumyl peroxide (DCP)/Irganox 1076 and cured at 170°C starts to deflect toward the anode side at the yield electrical field strength of 200 V/mm; the degree of bending increases monotonically with increasing electrical field strength of up to 650 V/mm. As the applied electric field is released, the elastomer composite recovers its original position and shape. The X-ray diffraction pattern of the STR 5L/Al2O3 composite (60 wt% Al2O3) cross-linked with 1 wt% DCP/I 1076 and cured at 170°C suggests that the highly ionic conductive Al2O3 generates the dipole moments in addition to that of the elatomer matrix. Scanning electron microscope micrograph of the composite shows a fairly uniform distribution of alumina particles in the natural rubber (STR 5L) matrix.

Mechanical and Electrical Properties of Alumina/Natural Rubber Composites

The mechanical and electrical properties of natural rubber (STR 5L)/alumina (Al2O3) composites with dicumyl peroxide (DCP) functioning as the crosslinking agent and as the filler in the composites were investigated. SEM micrographs indicate that the alumina particles are moderately dispersed in the matrix and some thread-like structures form. Both dicumyl peroxide and the alumina particles act the bi-dispersed particles in the composites. The XRD patterns indicate that Al2O3 is of the β-phase polytype that possesses high ionic conductivity. The electrical conductivity of the composites with DCP loading increases by nearly two and three orders of magnitude, compared to those of the STR 5L/Al2O3 composite without DCP and the pristine natural rubber (STR 5L), respectively. The increase in the electrical conductivity originates from the strong C–C and the Al–O–C bonds, the ionic polarization of the alumina particles, and the induced dipole moments set up in the natural rubber matrix.

Removal of water extractable proteins from concentrated natural rubber latex by eggshells

The protein allergy caused by latex products has become an acute problem to human and animals; sweat removes proteins, which then comes in contact with the skin causing the sensitization or allergic reactions. Eggshells from chickens, ducks, and birds are potential starting materials to be used in reducing the water extractable proteins in concentrated natural rubber latex (NRL). The pyrolysis of eggshells at 900°C for 2 h transforms the crystal structure of calcium carbonate into calcium oxide with a high purity, creates a small and uniform particle size, a suitable specific surface area, and an average pore diameter that is suitable for reacting with hydrochloric acid to obtain calcium chloride (CaCl2). The additions of CaCl2 solution and sodium dodecyl sulphate into concentrated NRL are shown and reported here to extract effectively the proteins from the NRL film.

Electrical and electromechanical properties of alumina/natural rubber STR 5L composites

Abstract The influence of micrometre-sized inorganic alumina particles embedded in a natural rubber (NR) on its electrical and electromechanical properties was investigated. Scanning electron micrographs and X-ray diffraction patterns show that the alumina (Al2O3) particles are moderately dispersed within the NR matrix. Without an electric field, the Al2O3 particles merely act as a filler to absorb or store an additional stress. The storage modulus increases by nearly a factor of 4 as the alumina volume fraction is varied from 0 to 0·009. With an electric field on, the ionic and the orientation polarisations and induced dipole moments were generated, leading to interparticle interactions, and an additional increase in the storage modulus; the storage modulus sensitivity at the electric field strength of 2 kV mm−1 varied from 0·10 to 0·20 within the same volume fraction range.

Electrical and Electrorheological Properties of Alumina/Natural Rubber (STR XL) Composites

The electrorheological properties (ER) of natural rubber (XL)/alumina (Al2O3) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and particles that are moderately dispersed in the matrix. The XRD patterns indicate Al2O3 is of the β-phase polytype which possesses high ionic conductivity. The storage modulus (G′) of the composites, or the rigidity, increases by nearly two orders of magnitude, with variations in particle volume fraction and electrical field strength. The increase in the storage modulus is caused the ionic polarization of the alumina particles and the induced dipole moments set up in the natural rubber matrix.

Lead zirconate (PbZrO3) embedded in natural rubber as electroactive elastomer composites

Perovskite lead zirconate (PbZrO3) was synthesized in an orthorhombic form at a temperature below the Curie temperature, TC. The orthorhombic form is a noncentrosymmetric structure which is capable of spontaneous polarization. Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns confirm the successful synthesis of the lead zirconate; and scanning electron microscopy (SEM) micrographs indicate that PbZrO3 particles are moderately dispersed in the natural rubber (NR) matrix. Without an electrical field, the particles merely act as a ferroelectric filler, which can absorb and store additional stress. Under an electrical field, particle-induced dipole moments are generated, leading to interparticle interaction and a substantial increase in the storage modulus. At a small amount of lead zirconate particulates present in the natural rubber matrix, at a volume fraction of 0.007306, the electrical conductivity increases dramatically by nearly two orders of magnitude at the electrical frequency of 500 kHz.

Embedded Eggshells as a Bio-Filler in Natural Rubber for Thermal Insulation Composite Foams

Thermal insulation composite foams were prepared from the natural rubber as a matrix phase and an eggshell powder as a calcium carbonate dispersed phase, using chlorinated polyethylene acting as a flame retardant and curing agent at the vulcanization temperature 150°C in a two-roll mill. The main composition of eggshell is calcium carbonate which is more than 96.35 wt%. The obtained composite rubber foams with 50 phr eggshell added possessed the thermal conductivity, compression set, crosslink density, bulk density, and relative foam density values equal to 0.070 W/m.K, 45.0%, 6.95 × 10−5mol/cm3, 0.58, and 0.63, respectively. The obtained composite rubber foams were of good thermal resistance, good compression set, short curing time, good crosslink density, and light weight, suitable for various applications such as automobiles, storage tank, and transport packaging. Furthermore, the scanning electron micrographs, X-ray diffraction patterns, specific heat, and physical properties (bulk density, crosslink density, and relative foam density) were taken or measured to investigate the microstructures, phase compositions, thermal properties, and characteristics of the insulating composite foams and were reported here.

REMOVING EXTRACTABLE PROTEINS IN NATURAL RUBBER LATEX BY CALCIUM CHLORIDE FROM CHICKEN EGGSHELLS

Abstract Controlling the level of the extractable protein contents in a natural rubber latex is important to the sensitization of natural rubber latex products users. Allergies caused by latex products cause a serious problem in which the sweat removes proteins and allowing a skin contact causing allergic reactions. Calcium oxide from calcined chicken eggshells at 900 °C for 1 h was dissolved in 2M HCl (CaCl2) and used as the thickening agent in which it can modify the protein structure. The eggshells were characterized by the particle size analysis, the impedance analysis, simultaneous thermal analysis (STA), x-ray diffraction (XRD), and Fourier transform infrared spectra (FTIR). Calcium chloride (CaCl2) interacts with the protein molecules and the solvent ions through the hydrogen bonding and the electrostatic interactions driving the extractable protein toward the film surface. Sodium dodecyl sulphate was used as the stabilizer in the natural rubber latex film formation. The extractable protein content...