THE MODULUS OF ELASTICITY AS AN INDICATION OF THE UNIFORMITY OF ELECTRICAL PORCELAIN1

An electrical porcelain body of the composition 30% H and G A1 china clay, 20% Dorset English ball clay, 20% Ottawa flint, and 30% Buckingham feldspar, fired to cone 11. showed a modulus of elasticity of 9.54 ± 0.02 × 10⁶ 1b. per sq. in. (mean of 164 measurements). A similar body with Kentucky special ball clay substituted for Dorset hall clay gave a value of 10.01 ± 0.02 × 10⁶ 1b. per sq. in. (mean of 69 measurements) The accuracy of the measurements was ± 1.5%. The use of the modulus as a measure on. the uniformity of electrical porcelain gave excellent results The variations were expressed in terms of statistical constants such ac: the standard deviation and the coefficient of variability.     

THE EFFECT OF CALCINED CYANITE IN PORCELAIN BODIES1

A study was made of the physical properties of porcelain bodies containing varying amounts of calcined cyanite (mullite), feldspar, and flint with a constant content of 50% clay. All bodies were made up under uniform conditions and fired to their proper maturing temperatures which varied from cones 8 to 20. Moduli of rupture for correctly fired bars varied from 5100 to 12,100 Ibs. per square inch, those bodies high in mullite being the strongest. The coefficients of linear expansion between 30 and 844° C varied from 4.3 × 10⁻⁶ to 6.6 × 10 ×⁻⁸ 6, those bodies high in mullite having the lower expansion. Thirty per cent or more calcined cyanite (50% or more total mullite as figured from chemical composition) must be present to obtain a marked effect on either of these properties. Triaxial diagrams show the position of various typical porcelain bodies and how they might be affected by additions of this material.     

Preparation of porous spodumene/zircon composite ceramics and its thermal and mechanical properties

Abstract

Porous β-spodumene/zircon (ZrSiO₄) composite ceramics were prepared by addition of zirconia to spodumene mineral using conventional solid reaction methods. The formation of the zircon was investigated by means of the differential scan calorimetry measurements and an X-Ray diffractometer. The microstructure of the composite ceramics was observed through a scanning electron microscope. The results show that the presence of zircon benefited the formation and stability of the porous structure and improved significantly the thermal endurance and mechanical properties of the spodumene matrix. The composites with 10–15% porosity exhibit an excellent thermal shock resistance, a low thermal expansion coefficient of approximately 1·4 × 10^?6 K^?1 in the range of 200–800°C and a high flexural strength about 100 MPa. It is found that the spodumene/zircon composites, widely used as a high temperature structure material, can be synthesised by a cost effective method.     

METHOD FOR DETERMINING TENSILE PROPERTIES OF REFRACTORY MATERIALS AT ELEVATED TEMPERATURES*

Equipment for testing ceramic materials to temperatures of 2000°F. was developed, and a method was devised for evaluating the bending stresses introduced by the test equipment. With this equipment, the tensile strength, stress-to-rupture characteristics, and modulus of elasticity of a sillimanite refractory were investigated at the Cleveland Laboratory of the National Advisory Committee for Aeronautics. The tensile strength varied from a minimum of 8000 lb. per sq. in. at 500°F. to a maximum of 19,000 lb. per sq. in. at 1800°F. Heat-treating the tensile specimens for one half hour at 1800°F. increased the tensile strength 35% at room temperature and 70% at 500°F. No increase in strength was noted at or above 1400°F. The stress-to-rupture in 1000 hours at 1600°F. was 8500 lb. per sq. in. The modulus of elasticity at room temperature was 20.3 × 10⁶.     

Fusion,electrical conductivity,thermal, and mechanical properties of rigid poly(vinyl chloride) (PVC)/carbon black (CB) composites

Rigid and conductive poly(vinyl chloride) (PVC)/carbon black (CB) composites were prepared in a Haake torque rheometer. The results illustrate that the fusion torque of the PVC/CB composite is increased as the amount of CB is increased. Both the fusion percolation threshold and the fusion time of PVC/CB composites are decreased when the amount of CB is increased. Two major weight loss stages are observed in the TGA curve of PVC/CB composite. The first thermal degradation onset temperature (T_onset1) of PVC/CB composite is decreased as the amount of CB is increased. Both the first and second weight loss stages (ΔY₁ and ΔY₂) of PVC/CB composites are decreased as the amount of CB is increased. The surface resistivity of PVC/CB composite remains almost constant up to 6 parts per hundred unit weight of resin (phr) CB. When the amount of CB in PVC/CB composite is increased from 6 to 15 phr, the surface resistivity of PVC/CB composite is dramatically decreased from 10¹⁰ Ω/sq to 10⁴ Ω/sq. Because of the addition of CB, the rigidity of PVC/CB composite is increased and thus the mechanical properties, such as yield strength, tensile strength, and the Young's modulus, are improved. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

CLAY SEWER PIPE MANUFACTURE.—IV. THE INFLUENCE OF DIFFERENT SALT GLAZING TEMPERATURES UPON THE COLOR AND GLOSS OF GLAZES OBTAINED ON CLAYS WITH VARYING SILICA,ALUMINA, AND IRON OXIDE CONTENTS1

Object .—A study was made of the effects of different salt glazing temperatures upon the color and brightness of salt glazes produced upon clays with varying silica, alumina, and iron oxide contents. Results .—In tests conducted in commercial kilns operating under normal conditions, it was found that increasing the salt glazing temperatures has a tendency to produce duller and darker glazes on clays containing iron oxide. The brightness of the glazes produced may be approximately represented by the following formula: -1.00×₁+ 0.376×₂ - (1.885 + 0.385(1.01253)^(T-1110))×₃= 100G ×₁, ×₂ and ×₃ represent the percentages of silica, alumina and iron oxide, respectively. T is the salt glazing temperature in °C. When G was greater than 0, the glazes were bright; when between -0.1337 and 0 they were semi matt; and when less than -0.1337 they were matt. The color obtained may be approximately represented by the following formula: 10.3x₁ - 2.65x₂+ (14.6 + 54.1 (1.0066)^(T-1110))x₃= 100°C When C was between 0 and 2, white to tan glazes were produced; when between 2 and 3.5, light brown glazes were obtained; when between 3.5 and 4.75, brown glazes were produced; when between 4.75 and 8.2, mahogany colors were obtained; and when above 8.2, dark brown to black glazes were produced. Clays containing a high iron oxide content should be salt glazed at low temperatures while clays containing a low iron oxide content should be glazed at high temperatures to produce the best glazes. Decreasing the iron oxide and alumina contents will improve the brightness of the salt glazes. High alumina clays will produce darker colors than high silica clays with the same percentage of iron oxide.     

Development of anorthite based white porcelain stoneware tile compositions

The scope of the present study is to develop alternative white porcelain stoneware tile compositions without using zircon (ZrSiO₄) which have shown better whiteness values than standard white porcelain stoneware tile composition containing zircon. These new compositions are designed to develop anorthite crystals in the microstructure. Technological properties of compositions such as water absorption (%), firing shrinkage (%) and colour (L^⁎, a^⁎, b^⁎) were measured and compared with standard white porcelain stoneware tile. Scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses were also carried out. One of the new anorthite-based compositions was manufactured as white porcelain stoneware tile substitute of standard white porcelain stoneware containing zircon.     

Preparation and characterization of glazes from combinations of different industrial wastes

The work reported here involves the preparation and characterization of ceramic glazes made from combinations of different industrial wastes. The wastes were float glass, granite and lime shale (a raw material waste from the oil shale industry in São Mateus do Sul, state of Paraná, Brazil), which were used to replace natural raw materials in a proportion of up to 50% in weight. The compositions were formulated using the Seger method and prepared by conventional ceramic processing. The stabilized suspensions were applied in commercial wall tile and porcelain stoneware tile, which were sintered at temperatures of 1080 °C and 1150 °C, respectively, using two different heating cycle. Three compositions were developed, two of which yielded opaque glazes and one a transparent glaze. Linear thermal expansion coefficients (α) of 80.10^?7 °C^?1 to 100.10^?7 °C^?1, and glaze softening temperatures of 600–700 °C were characterized by dilatometric analysis. The glaze compositions showed chemical resistance against acid and alkaline attack after 96 h, showing a mass loss of less than 0.1% in weight. The surface hardness of the glazes determined by the Mohs scale, Vickers microhardness and abrasion resistance (PEI indices) were between 6–7, 3–3.7 GPa and 3–4, respectively. These properties are compatible with those of commercial glazes for wall tiles and porcelain stoneware ceramics.     

Synthetic polymeric absorbent for dye based on chemically crosslinked acrylamide/mesaconic acid hydrogels

Adsorption properties of copolymers of acrylamide and mesaconic acid (CAME) in aqueous Basic Blue 12 (Nile blue chloride) solution have been investigated. Chemically crosslinked CAME hydrogels with various compositions were prepared from ternary mixtures of acrylamide (A), mesaconic(ME) acid, and water by free radical polymerization in aqueous solution, using a multifunctional crosslinker such as ethylene glycol dimethacrylate (EGDMA). Dynamic swelling tests in water was applied to the hydrogels. Weight swelling ratio (S) values have been calculated. Sorption of Basic Blue 12 (BB 12) onto CAME hydrogels was studied by batch sorption technique at 25°C. In the experiments of the sorption, L type sorption in the Giles classification system was found. Some binding parameters such as initial binding constant (K_i), equilibrium constant (K), monolayer coverage (n), site‐size (u), and maximum fractional occupancy (Ô) for CAME hydrogels‐BB 12 binding system were calculated by using Klotz, Scatchard, and Langmuir linearization methods. Finally, the amount of sorbed BB 12 per gram of dry hydrogel (q) was calculated to be 2.28 × 10^?6–7.91× 10^?6 mol BB 12 per gram for hydrogels. Sorption % was changed range 16.09–58.86%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 405–413, 2006     

Synthesis and characterization of copolymeric aliphatic–aromatic esters derived from terephthalic acid, 1,4‐butanediol,and ε‐caprolactone by physical,thermal, and mechanical properties and NMR measurements

In this study, a series of aliphatic–aromatic poly(butylene terephthalate‐co‐ε‐caprolactone) (PBTCL) copolyesters were synthesized from various monomeric compositions of terephthalic acid (TPA), 1,4‐butanediol (BDO), and ε‐caprolactone (CL) in the presence of tetrabutyl titanate (Ti(Obu)₄) and stannous octoate (Sn(Oct)₂) as catalysts through a combination of polycondensation and ring opening polymerization. A significant increase in the melting temperature (T_m) of copolyesters was observed by increasing the TPA/(CL+TPA) molar ratio, starting from the low end (T_m 66.2°C) of pure poly‐ε‐caprolactone PCL upward. We found that PBTCL‐50, which has a TPA/(CL+TPA) 50% molar ratio and polycondensation at 260°C for 1.5 h, resulted in a proper T_m of 139.2°C that facilitates thermal extrusion from biomass or other biodegradable polymers of similar T_m. The number–average molecular weight (M_n) of 7.4 × 10⁴ for PBTCL‐50 was determined from the intrinsic viscosity [η] by using the Berkowitz model of M_n = 1.66 × 10⁵[η]^0.9. Good mechanical properties of PBTCL‐50 have been shown by tensile stretching experiment that indicates tensile strength, elongation, and Young's modulus are 11.9 MPa, 132%, and 257 MPa, respectively. Polymers with aforementioned properties are suitable for manufacturing biodegradable plastic films for downstream agricultural applications or merely for trash bag. This article reveals that the PBTCL‐50 contains all five monomers with different molar ratios and characteristical linkages between each other. The novel structure was furthermore analyzed by ¹H‐ and ¹³C‐NMR spectroscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A study of compressive strength between zirconia framework and veneering ceramic as a function of thermal expansion coefficient using Shell–Nielsen test method

This study investigated the adhesion between zirconia framework and four veneering ceramic (VC) materials with varying coefficients of thermal expansions (CTE). Zirconia rods (N?=?40) (ICE Zirkon) (diameter: 4 mm, height: 20 mm) were milled and sintered. After firing, the zirconia rods were air-abraded and cleaned. They were randomly assigned to receive four VCs (n?=?10/group), namely (a) Vita VM9 (VZ; 9–9.2?×?10^?6? K^?1), (b) Cerabien ZR (CZ; 9.1?×?10^?6 K^?1), (c) Matchmaker ZR (MM; 9.4?×?10^?6?K^?1), and (d) Ice Zirconia Ceramic (IZ; 9.6?×?10^?6?K^?1). The VCs were then fired onto zirconia rods (height: 2 mm, thickness: 2 mm) circumferentially and were thermocycled for 6000 times (5/55 °C, dwell time: 30?s). Specimens were loaded from the top of the zirconia rods (0.5 mm/min) in a universal testing machine until debonding. Shell–Nielsen bond strength values were calculated (MPa). Failure types were evaluated under SEM. The data were statistically analyzed (one-way ANOVA, Tukey’s; α?=?0.05). Weibull distribution values including the Weibull modulus (m) (0.05) was calculated. The highest mean bond strength (MPa) was obtained for CZ (42.08?±?4.08), followed by VZ (41.77?±?4.92), MM (40.7?±?3.64), and IZ (40.05?±?5.78). While mean bond strength for VZ, MM, and IZ were not significantly different (p?>?0.05), CZ was significantly higher than that of IZ (p?<?0.05). The lowest shape value was for VZ (m?=?16.94) and the highest for MM (m?=?20.16). Mainly, adhesive failures followed by mixed failures were observed. VCs with a greater mismatch of CTE with the zirconia framework exhibited similar Shell–Nielsen bond strength to those with fewer mismatches. CTE mismatch did not affect the results of CZ (9.1?×?10^?6 K^?1) and IZ (9.6?×?10^?6 K^?1).     

Molecular weights of natural rubbers from selected temperate zone plants

Molecular weights and molecular weight distributions are compared by gel permeation chromatography for rubbers from 33 north temperate zone plants, guayule, and Hevea. Rubbers isolated from all the northern plants had much lower weight-average molecular weight (M _w) values (9.72 × 10⁴–4.95 × 10⁵) than milled Hevea (1.31 × 10⁶) or guayule (1.28 × 10⁶) rubber. Pycnanthemum incanum, Lamiastrum galeobdolon, Monarda fistulosa, and Vernonia fasciculata produced potentially useful natural rubbers having M _w values above 4 × 10⁵ and polydispersity factors of 3.1–4.5.     

Synthesis and characterization of polyaniline/NiO nanocomposite

Spherical nickel oxide (NiO) nanoparticles were prepared by using nickel chloride as precursor in the ethylene glycol as solvent and urea as precipitant. The X‐ray diffraction study showed that NiO has single‐phase cubic structure with average crystallite size of 35 nm. The prepared NiO nanoparticles were incorporated into polyaniline (PANI) matrix during in situ chemical oxidative polymerization of aniline with different molar ratios of aniline: NiO (12 : 1, 6 : 1, and 3 : 1) at 5°C using (NH₄)₂S₂O₈ as oxidant in aqueous solution of sodium dodecylbenzene sulfonic acid, as surfactant and dopant under N₂ atmosphere. The synthesized composites have been characterized by means of X‐ray diffraction (XRD), thermogravimetric analysis, Fourier transform infrared (FTIR), scanning electron microscopy, TEM, and vibrating sample magnetometer for its structural, thermal, morphological, and magnetic investigation. The XRD and FTIR studies show that the NiO particles are in the composite. The room temperature conductivities of the synthesized PANI, PANI/NiO (12 : 1), (6 : 1), and (3 : 1) composites were found to be 3.26 × 10^?4, 1.88 × 10^?4, 1.5 × 10^?4, and 4.61 × 10^?4 S/cm, respectively. The coercivity (H_c) and remnant magnetization (M_r) of NiO, PANI/NiO NCs (12 : 1), (6 : 1), and (3 : 1) at 5 K was found to be 8.22 × 10^?2, 6.31 × 10^?2, 6.42 × 10^?2, 6.27 × 10^?2 T, and 6.64 × 10^?3, 1.83 × 10^?4, 3.07 × 10^?4, and 3.98 × 10^?4 emu/g, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Propylene polymerization with rac‐(EBl)Zr(NC4H8)2 cocatalyzed by MAO or AlR3 and anionic compounds

Propylene polymerization was carried out using an ansa‐zirconocene pyrrolidide based catalytic system of racemic ethylene‐1,2‐bis(1‐indenyl)zirconium dipyrrolidide [rac‐(EBI)Zr(NC₄H₈)₂ or (rac‐1)] and methylaluminoxane (MAO) or a noncoordinating anion. In situ generation of cationic alkylzirconium species was also investigated by NMR‐scale reactions of rac‐1 and MAO, and rac‐1, AlMe₃, and [Ph₃C] [B(C₆F₅)₄]. In the NMR‐scale reaction using CD₂Cl₂ as a solvent, a small amount of MAO ([Al]/[Zr] = 30) was enough to completely activate rac‐1 to give cationic methylzirconium cations that can polymerize propylene. The resulting isotactic polypropylene (iPP) isolated in this reaction showed a meso pentad value of 91.3%. In a similar NMR‐scale reaction rac‐1 was stoichiometrically methylated by AlMe₃ to give rac‐(EBI)ZrMe₂, and the introduction of [Ph₃C] [B(C₆F₅)₄] into the reaction mixture containing rac‐(EBI)ZrMe₂ led to in situ generation of cationic [rac‐(EBI)Zr(μ‐Me)₂AlMe₂]⁺ species that can polymerize propylene to give iPP showing a meso pentad value of 94.7%. The catalyst system rac‐1/MAO exhibited an increase of activity as the [Al]/[Zr] ratio increased within an experimental range ([Al]/[Zr] = 930–6511). The meso pentad values of the resulting iPPs were in the range of 83.2–87.5%. The catalytic activity showed a maximum (R _p = 6.66 × 10⁶ g PP/mol Zr h atm) when [Zr] was 84.9 × 10⁻⁶ mol/L in the propylene polymerization according to the concentration of catalyst. MAO‐free polymerization of propylene was performed by a rac‐1/AlR₃/noncoordinating anion catalytic system. The efficiency of AlR₃ was decreased in the order of AlMe₃ (R _p = 13.0 × 10⁶ g PP/mol Zr h atm) > Al(i‐Bu)₃ (8.9 × 10⁶) > AlPr₃ (8.8 × 10⁶) > Al(i‐Bu)₂H (8.4 × 10⁶) > AlEt₃ (8.4 × 10⁶). The performance of the noncoordinating anion as a cocatalyst was on the order of [HNMePh₂][B(C₆F₅)₄] (R _p = 13.0 × 10⁶ g PP/mol Zr h atm) > [HNMe₂Ph][B(C₆F₅)₄] (10.8 × 10⁶) > [Ph₃C][B(C₆F₅)₄] (8.4 × 10⁶) > [HNEt₂Ph][B(C₆F₅)₄] (7.8 × 10⁶). The properties of iPP were characterized by ¹³C‐NMR, FTIR, DSC, GPC, and viscometry. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 875–885, 1999     

Synthesis,characterization, and thermo‐optical properties of azobenzene polyurethane containing chiral units

An optically active levoazobenzene polyurethane (PU) was synthesized and was based on the chromophore 4‐(4′‐nitrophenylazo) phenylamine, the chiral reagent L (?)‐tartaric acid, and toluene diisocyanate. The chemical structure and thermal properties were characterized by ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and differential scanning calorimetry. The PU had high number‐ and weight‐average molecular weights up to 52 300, a large glass‐transition temperature of 235.7°C, and an optical rotation of ?18.06°, The optical parameters, including the refractive index (n) and thermo‐optic coefficient (dn/dT); the dielectric constant (?) and its variation with temperature; and the thermal volume expansion coefficient and its variation with temperature of PU were obtained. The dn/dT and ? values for the polymer were in the range ?4.1200 to 3.6257 × 10^?4 °C^?1 and 2.00 ± 0.11, respectively. The dn/dT values were one order of magnitude larger than those of inorganic glasses, such as zinc silicate glass (5.5 × 10^?6 °C^?1) and borosilicate glass (4.1 × 10^?6 °C^?1), and were larger than organic materials, such as polystyrene (?1.23 × 10^?4 °C^?1) and poly(methyl methacrylate) (?1.20 × 10^?4 °C^?1). The ? values were lower than that of alicyclic polyimide and semiaromatic polyimide. The obtained PU is expected to be useful for optical switching and optical waveguide areas. The conclusion has a little significance for the development of a new digital optical switch. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Behaviors of polyelectrolyte AAm/AMPS/bentonite composite hydrogels in uptake of uranyl ions from aqueous solutions

Uranyl ion (UO₂²⁺) sorption properties of polyelectrolyte composite hydrogels made by the polymerization of acrylamide (AAm) with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and clay such as bentonite (Bent) were investigated as a function of composition to find materials with swelling and uranyl ion sorption properties. Highly swollen AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels were prepared by free radical solution polymerization in aqueous solutions of AAm with AMPS as co‐monomer and two multifunctional crosslinkers such as ethylene glycol dimethacrylate (EGDMA) and 1,4 butanediol dimethacrylate (BDMA). Swelling experiments were performed in water at 25°C, gravimetrically. The influence of AMPS content in hydrogels was examined. Uranyl ion adsorption from aqueous solutions was studied by batch sorption technique at 25°C. The effect of uranyl ion concentration and mass of AMPS on the uranyl ion adsorption were examined. Finally, adsorption capacity (the amount of sorbed uranyl ion per gram of dry hydrogel) (q) was calculated to be 0.67 × 10⁻³–2.11 × 10⁻³ mol uranyl ion per gram for the hydrogels. Removal effiency of uranyl ions (RE%) was changed range 9.05–29.92%. The values of partition ratio (K_d) of uranyl ions was calculated to be 0.10–0.43 for AAm/AMPS hydrogels and AAm/AMPS/Bent composite hydrogels, respectively. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Micromechanics for fiber volume percent with a photocure vinyl ester composite

Micromechanics for fiber volume percent (V_f) from 0.0V_f to 54.0 V_f were conducted using (3 mm long × 9 μm diameter) high‐purity quartz fibers in a visible‐light vinyl ester particulate‐filled photocure resin. MTS fully articulated four‐point bend fixtures were used with a 40 mm test span and 50 × 2 × 2 mm³ sample dimensions. Specimens were tested following the combined modified ASTM standards for advanced ceramics ASTM‐C‐1161–94 and polymers ASTM‐D‐6272–00 for modulus, flexural strength, and yield strength. Experimental data provided reliable statistical support for the dominant fiber contribution expressed through the rule‐of‐mixtures theory as a valid representation of micromechanical physics. The rule‐of‐mixtures micromechanics described by V_f could explain 92, 85, and 78% of the variability related to modulus, flexural strength, and yield strength respectively. Statistically significant improvements with fiber addition began at 10.3V_f for modulus, 5.4V_f for flexural strength, and 10.3V_f for yield strength, p < 0.05. In addition, correlation matrix analysis was performed for all mechanical test data. An increase in V_f correlated significantly with increases in modulus, flexural strength, and yield strength as measured by the four‐point bending test, p < 10⁻¹⁰. All mechanical properties in turn correlated highly significantly with one another, p < 10⁻⁹. POLYM. COMPOS., 28:294–310, 2007. © 2007 Society of Plastics Engineers     

Influence of silicoating,etching and heated glaze treatment on the surface of Y-TZP and its impact on bonding with veneering ceramic

The study aimed to investigate the influence of surface treatments of Y-TZP on its topography and their impact on shear bond strength (SBS) of Y-TZP to veneering porcelain. Thirty-four zirconia cubes (Cercon) (10 × 10 × 10 mm³) were divided randomly into 3 groups (n = 11) according to the different surface treatments, Silica Coating (SC); Hot Solution Etching (HE); and Heat Treatment after porcelain glaze and powder application (GP). Porcelain application (IPs e.max) was performed after surface treatment using a standardized technique. Porcelain application (Ceramco-3) was also performed on 10 metal cubes (I BOND 2) as controls (MC). Specimens were subjected to thermocycling (5–55 °C, 20,000 cycles) followed by SBS testing in a universal testing machine. Surface topography was assessed by scanning electron microscopy and surface roughness (Image J). SC developed significantly higher SBS (42.10 ± 5.84 MPa) of Y-TZP to veneering ceramics compared to treatment by HE (24.0 ± 6.4 MPa), GP (23.30 ± 4.72), and the MC (29.3 ± 5.4 MPa) control (p < 0.05). SBS among HE, GP and MC specimens was comparable (p > 0.05). Y-TZP specimens treated with SC and HE showed high surface roughness compared to GP. Silicoating of Y-TZP prior to veneering can potentially reduce the high failure rates of zirconia-based restorations by enhancing the chemical bond between the core and the veneer materials.     

Influence of molar mass on the thermal properties,conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

The sample preparation pathway of solid polymer electrolytes (SPEs ) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 10⁴ g mol^?1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (M _η = 3 × 10⁵, 6 × 10⁵, 1 × 10⁶, 4 × 10⁶ g mol^?1) and LiClO₄ salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σ _DC ～ 10^?6 S cm^?1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion ? dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry     

Improvement of microwave absorption for PAni/HA/TiO2/Fe3O4 nanocomposite after chemical treatment

In order to obtain efficient microwave absorbers that possess high conductivity, dielectric and magnetic properties, hexanoic acid doped polyaniline (PAni) nanocomposites which contain different ratios of ferum (II) oxide (Fe₃O₄) and titanium dioxide (TiO₂) nanoparticles were successfully prepared by in situ chemical polymerization through template free method. Chemical structure, conductivity, morphology, thermal stability, magnetic properties, and amorphous/crystalline behavior of PAni nanocomposites were characterized by Fourier transform infrared spectrometer (FTIR), four point probe, field emission scanning electron microscope (FESEM), thermal gravimetric analysis (TGA), vibrating samples magnetometer (VSM), and X‐ray diffractometer (XRD), respectively. From this study, conductivity was significantly improved from 8.48 × 10⁻⁴−1.23 × 10⁻² S/cm for PAni nanocomposites without any chemical treatment (during addition of Fe₃O₄) to 3.58 × 10⁻²−4.77 × 10⁻² S/cm for those with chemical treatment. PAni nanocomposites with chemical treatment show a narrow sharp reflection loss (RL) peak with high absorption (−48.9 dB) at lower frequency due to the limited individual Fe₃O₄ nanoparticles outside the nanorods/nanotubes as proved by the new proposed mechanism (Fig. 5 ), while it shows a broad RL peak with poor absorption (−13 dB) at higher frequency for those without chemical treatment. The novelty of this research has been focused on PAni with chemical treatment which yield better microwave absorption property (99.999% absorption), combination of high conductivity (3.58 × 10⁻²−4.77 × 10⁻² S/cm), high heterogeneity and moderate magnetization (Ms = 8.87–28.49 emu/g) compare to the PAni without chemical treatment. POLYM. COMPOS., 34:1186–1194, 2013. © 2013 Society of Plastics Engineers