Effect of heat treatment temperature and surface roughness to the PDMS-FR4 adhesive bonding

The current work investigates the use of liquid polydimethylsiloxane (PDMS), with a 10:1 ratio of prepolymer:curing agent?=?10:1 as the intermediate layer for adhesive bonding with Flame Retardant 4 (FR4). The spin coating of liquid PDMS on FR4 allows irreversible adhesive bonding with the solid PDMS. The strength of the proposed adhesive bonding technique has been investigated under different treatment temperatures: oven-heated at 60?°C, 70?°C, and 80?°C, cooled down in the room temperature of 25?°C, and exposed to direct sunlight at 35?°C. All the samples were left for 6?h. Investigations were conducted to analyze the effect of FR4 surface roughness on the strength and quality of the adhesive bonding. The standard procedure of American Standard Test Measurement (ASTM) D1002 was followed to verify the strength of PDMS-FR4 adhesive bonding. Strongest adhesive bonding, free from air bubbles, was obtained from a sample with smooth surface of FR4 that has undergone a cooling down treatment in the room temperature of 25?°C. FR4 was coated by solder mask to obtain smooth surface. The techniques reported in this paper are simple, straightforward, and effective to be implemented with FR4 as a base material for adhesive bonding with PDMS, thus eliminating expensive and complicated operating equipment as widely used in the oxygen plasma-assisted bonding treatment. Another benefit from this adhesive bonding technique is the fact that it avoids the use of expensive oven or hot plate.     

The influence of temperature and cyclic loading on adhesion in polycarbonate-polyurethane-glass adhesive joint

The paper deals with the influence of temperature and cyclic loading on adhesion and transparency of the adhesive joint consisting of soda-lime-silica glass and polycarbonate (PC) bonded with polyurethane (PU) adhesive film. The tested joint represents critical part of transparent armored glass used in vehicles. Dynamic tension creep tests were performed at temperatures to which armored glass is commonly exposed (25, 50, 60, 70, and 80?°C). Sawtooth loading mode was performed to 650?N and the sine loading in the force range 0–1550?N. The aim of the paper was to discover conditions causing delamination of the adhesive joint and glass milky appearance during the use. Delamination of soda-lime-silica glass/PU adhesive interface occurred at 25?°C after load to 1550?N without the change of transparency. Both dynamic and static tension creep tests performed to 400?N led to plastic deformation of PU adhesive at and above 70?°C, in preference at both ends and circumference edges of adhesive joint, and thus, to loss of transparency, but extent of deformation differed. Milky maps observed after sawtooth load to 650?N at 80?°C reflected delaminated areas of highly deformed PU adhesive. Temperature of 70?°C was found out to be the critical parameter being in synergy effect with different thermal expansion of PC and PU adhesive.     

Nanogels of poly-N-isopropylacrylamide,poly-N,N-diethylacrylamide and acrylic acid for controlled release of thymol

Synthesis of new nanogels composed of poly N-isopropylacrylamide (PNIPAM) and poly N,N-diethylacrylamide (PNDEA) at different mole ratios of 100:0–50:50 were performed with constant acrylic acid (AA) content (NIPAM:AA mole ratio of 10:1) by free radical polymerization. The obtained nanogels were loaded with thymol and self-assembled on the surface of chitosan films to evaluate control release of the antimicrobial. The effect of temperature (8–35 °C), pH (2–8), and ions were evaluated on particle size (100–200 nm) and charge (?25--40 mv). With the increasing ratio of PNDEA in the copolymers, the lower critical solution temperature shifted gradually from 33 °C to <10 °C. When pH value decreased from 8 to 2, nanogel shrink occurred. Different ions influenced the hydrodynamic diameters of particles, causing salting out effect that followed the order of Hofmeister series. Thymol loaded within mole ratios of 50:50 of NIPAM/NDEA nanogels had longer release time (>24 h) at 4 °C than that at 25 °C (around 6 h). All thymol loaded nanogels exhibited antimicrobial activity against E. coli and B. subtilis.     

EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON THE DRYING RATES AND DRYING TIMES OF GREEN BELL PEPPERS (CAPSICUM ANNUUM L)

ABSTRACT

Green bell pepper dices were dehydrated at different dry bulb air temperatures (55°, 60°, 65°, 70° and 75°C) and relative humidities (15, 20, 25, 30, 35 and 40%). The effects of temperature and relative humidity (RH) on the drying rates and drying period of diced green bell peppers were determined. Drying rate curves were characterized by a short induction (heating) phase followed by a falling rate period. Near constant rate drying was observed only at 55°C at 15% RH and at 65°C (15% RH). Drying rates generally increased with increasing temperatures and decreasing RH. The effect of temperature on the drying rates became less pronounced with increasing RH Drying rate maxima at 70°C and RH of 15, 20 25 and 40% exceeded those at 75°C, possibly due to case-hardening.     

Column Fractionation of Canola Oil Deodorizer Distillate Using Supercritical Carbon Dioxide

Semi-continuous column fractionation of canola oil deodorizer distillate using supercritical CO₂ (SCCO₂) was carried out to determine the feasibility of value-added processing of this feed material for the recovery of bioactive components such as sterols and tocopherols and to determine the effect of operating conditions [pressure (20, 25 MPa using a temperature gradient of 70–100 °C), temperature (70, 100 °C) and a linear temperature gradient (70–100 °C at 25 MPa)] on extract yield and separation efficiency. Total extract yield increased significantly (p ≤ 0.05) with pressure, whereas at isobaric conditions (25 MPa) the highest yield was obtained at the lowest temperature tested (70 °C). Fractionation efficiency was reflected in the composition of fractions and was affected by operating conditions. Residue composition was determined by extract yield in addition to selectivity. Use of the thermal gradient (70–100 °C) decreased the content of volatiles, free fatty acids and tocopherols while increasing sterol content significantly (p ≤ 0.05) to a level of 40% (GC area %) in the residue obtained at 25 MPa. The findings indicate the potential of canola oil deodorizer distillate as a source of sterols and warrant further research on the countercurrent column fractionation to improve the separation efficiency.     

Dielectric stability in the relaxor: Na0.5Bi0.5TiO3-Ba0.8Ca0.2TiO3-Bi(Mg0.5Ti0.5)O3- NaNbO3 ceramic system

Ceramics with temperature-stable dielectric characteristics have been developed in the system: 0.6[0.85Na_0.5Bi_0.5TiO₃-(0.15-x)Ba_0.8Ca_0.2TiO₃-xBi(Mg_0.5Ti_0.5)O₃]?0.4NaNbO₃, x ≤ 0.15. Dielectric measurements exhibited relaxor ferroelectric characteristics with temperature-stable relative permittivity from ε_r~1330 ± 15% in the temperature range from ?70?°C to 215?°C and tanδ ≤ 0.02 from ?20?°C to 380?°C for x = 0 compositions. For the Bi(Mg_0.5Ti_0.5)O₃ modified compositions the temperature range of stable relative permittivity extended from ?70?°C to 400?°C, with ε_r ~ 950 ± 15% and tanδ ≤ 0.02 from ?70?°C to 260?°C. Values of dc resistivity were ~ 10⁸ Ω?m at a temperature of 300?°C and the corresponding RC constant values were in the range from 0.40 ? 0.78?s at 300?°C. All ceramic samples exhibited a linear polarisation-electric field response at maximum applied electric field of 5?kV/cm (1?kHz).     

Studies on Ozone Bleaching. I. The Effect of PH,Temperature, Buffer Systems and Heavy Metal-Ions on Stability of Ozone in Aqueous Solution

Ozone was found to be reasonably stable at moderately low pH (～pH 3) and ambient temperature in acetic, sulfuric and nitric acid solutions. In these cases, the exact kinetic order of ozone decomposition could not be established. However, second order with respect to ozone was preferred on the basis of statistical analysis of the data. At pH 3, the ozone decomposition rate was found to be slightly higher at 15°C and moderately higher at 35°C than at 25°C for all three buffer systems. At lower concentration level (～ 0.5 ppm), only Co(II) ion enhanced decomposition of ozone in sulfuric acid solution at pH 3 and 25°C. In contrast, at the higher concentration level (～ 3.0 ppm), Ca(II), Cr(III), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) ions were found to contribute the decomposition of ozone; the effect of Co(II) and Fe(II) ions was very pronounced as compared to the other ions. Using acetic acid instead of sulfuric acid as buffer reagent resulted in drastic and moderate reductions of the ozone decomposition catalyzed by Co(II) and Fe(II) ions, respectively. These indicate that acetic acid acts as radical scavenger for hydroxyl radical as postulated by Walling et al. Thus, the drastic increase in the ozone decomposition in the sulfuric acid solution with the presence of Co(II) or Fe(II) ion is caused by free radical chain reactions initiated by free radicals produced in the process.     

Toughening effect of CPE on ASA/SAN binary blends at different temperatures

The effect of chlorinated polyethylene (CPE) on the impact toughness of acrylonitrile–styrene–acrylic (ASA) terpolymer/styrene–acrylonitrile copolymer (SAN) binary blends (25/75, w/w) was systematically investigated at three different temperatures (?30 °C, 0 °C, and 23 °C). With the addition of 60 phr CPE, the impact strength increased by 11 times at 23 °C and 10 times at 0 °C. However, the toughening effect was not obvious when the testing temperature was ?30 °C. Since the glass‐transition temperature (T_g) of CPE was about ?18.3 °C as measured with dynamic mechanical analysis tests, the polymeric chains of CPE have been “frozen out” at ?30 °C. As a result, CPE evidently cannot improve the toughness of the blend system. The morphology of impact‐fractured surfaces observed by scanning electron microscopy also confirmed the effect of CPE on the impact toughness of ASA/SAN binary blends. The heat distortion temperature remained almost unchanged, indicating that the improvement in toughness did not sacrifice heat resistance. Furthermore, other mechanical properties were evaluated, and the possible interactions among components of the blends were also analyzed by Fourier transform infrared spectra. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43353.     

Effect of temperature on the joint strength of a silyl-modified polymer-based adhesive

Temperature is a very important factor that must be fully considered in the study on the adhesive joint strength. In this paper, a silyl-modified polymer-based adhesive ISR 70-08 which is widely used in engineering was studied. Dog-bone specimens were fabricated and tested at ?40°C, room temperature (RT), and 90°C. Results show a decrease in the main mechanical properties with increasing temperature. Butt joints (BJs), single-lap joints (SLJs), and Scarf joints (SJs) were fabricated and tested at different temperatures. A quadratic polynomial expression was an ideal choice to express the joint strength as a function of temperature which was obtained using the least-squares method. Temperature combinations of ?40°C, 0°C, and 90°C were obtained to study the effect of temperature on the joint strength more easily for this adhesive. A three-dimensional surface, consisting of temperature, adhesive angle, and joint strength was presented to facilitate the application of bonding structures in engineering     

The solubility of hydrogen in aliphatic amines

The solubility of hydrogen in ammonia, monomethylamine, monoethylamine and n-propylamine was determined at temperatures from ?70°C to 25°C and in 1,2-propanediamine and 1,2-ethanediamine over the temperature ranges ?25°C to 11°C and 25°C to 34°C respectively. Measurements were made at total pressures up to 300 psig. The solubility data were correlated in terms of Henry's law and the solubilities are in the range 1 × 10^?5 to 3 × 10^?4 mole fraction at a hydrogen partial pressure of 1 atmosphere. The measured solubility data were used to extend a correlation proposed by Yen and McKetta. This revised correlation may be used to estimate the solubility of hydrogen in polar, associated amines.     

Effects of TMPTMA and silane on the compressive strength of low‐temperature cured acrylic polymer concrete

This study addresses the effects of additives on the compressive strength of low‐temperature cured acrylic polymer concrete (PC). Three curing temperatures (0°C, ?10°C, and ?20°C) and five ages (6, 12, 24, 72, and 168 h) with two different types of additives [trimethylolpropane trimethacrylate (TMPTMA) and silane] were investigated. As a result, the compressive strength tended to decrease as the curing temperature decreased. The compressive strengths at 24 h were approximately 90% of those at 168 h at both curing temperatures of 0°C and ?20°C, indicating that the rate of early age strength development was quite high even at a very low curing temperature range. The results of two‐way variance analysis revealed that silane had a greater impact on the compressive strength than TMPTMA. About 13%–23% strength improvements with a 168‐h compressive strength of over 80 MPa could be obtained at ?20°C by adding silane. Furthermore, this study proposed optimum mixture proportions of acrylic PC that generate a working life of 50–70 minutes with a compressive strength of 80 MPa at subzero temperatures. The findings of this study are expected to be effectively used in field applications of acrylic PC, especially in the cold regions during winter season. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40939.     

MgO calcination for easy direct coagulation casting of aqueous alumina slurries

The reactivity of MgO with ammonium poly(acrylate) and diammonium hydrogen citrate dispersants was decreased by high-temperature calcination which enabled easy preparation of direct coagulation casting slurries without cooling. The decrease in reactivity of MgO with an increase of calcination temperature (30–1200?°C) was due to the decrease of surface area (52.7–0.7?m²/g) as a result of an increase of average particle size (285–2075?nm) as well as a change of particle morphology from flaky to near spherical. The MgO calcined at a temperature of 1000?°C and above provided sufficient time for mixing with aqueous alumina slurries by ball milling at room temperature (~30?°C) without producing an adverse increase in viscosity before casting. The setting time of 55?vol% alumina slurries was in the ranges of 260–1070 and 10–50?min at room temperature and at 70?°C, respectively, at MgO concentrations in the range of 0.1123–1.2?wt%. The faster setting at 70?°C was due to a combination of faster dispersant-MgO reaction, faster hydration of MgO and high valance counter ion effect.     

Application of the Conant-Finkelstein Reaction to the Modification of PVC: Iodinated PVC

The Conant-Finkelstein reaction was applied to PVC with the aiming of replacing the chlorine atoms with iodine ones. The effect of reaction temperature with regard to the characteristics of the modified PVC was significant. Formation of a gel and degraded polymeric materials was observed when working at temperatures higher than 60 °C. The degraded polymer formed at 70 °C was insoluble and gave rise to a polyacetylene-like chain with a melting point of 60 °C. However, the reaction on PVC at lower temperatures resulted in soluble polymers which were easily amenable to spectral characterization. The molecular weights of the iodine-modified PVCs were temperature-dependent. At 40, 45, 50 and 60 °C, molecular weights lower than that of the initial PVC were measured; however, at 35, 30 and 25 °C, a gain of about 9% in molecular weight was seen. Substitution and elimination reactions occurred to different extents depending mostly on temperature. Optimal substitution was obtained at 50 °C for a reaction time of 20 h.     

Structure and properties of ultraviolet‐irradiated high density polyethylene at different environmental temperatures

C? O, C?O, and C(?O)O oxygen‐containing groups were introduced onto the molecular chain of high‐density polyethylene (HDPE) through ultraviolet irradiation in air. The introduction rate of the oxygen‐containing groups onto HDPE increased with increasing environmental temperature. After ultraviolet irradiation, the molecular weight of HDPE decreased, and its distribution became wider; the melting temperature, contact angle with water, and impact strength decreased; the degree of crystallinity and yield strength increased; and their variation amplitude increased with environmental temperature. The environmental temperature had an effect on the gel content of irradiated HDPE. HDPE‐irradiated for 48 h at 35° and 50°C were not crosslinked. However, gelation took place in HDPE irradiated for 24 h at 70°C. HDPE irradiated at a high environmental temperature was more effective than that irradiated at a low environmental temperature in compatibilizing HDPE with PVA. Compared with the 83/17 HDPE/PVA blend, the yield and notched impact strength of the 73/17 HDPE/PVA blend compatibilized with 10% HDPE irradiated for 24 h at an environmental temperature of 70°C increased from 30.8 MPa and 110 J/m to 34.9 MPa and 142 J/m, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2966–2969, 2003     

Dynamic mechanical and impact properties of PP/SEBS blend

Studies on impact behaviour of the blend of isotactic polypropylene (PP) with styrene-b-ethylene-co-butylene–b-styrene triblock copolymer (SEBS) in the composition range 0–25 wt % SEBS at three temperatures, viz., ambient, ?30°C, and ?190°C, are presented. Dynamic mechanical properties on a torsion pendulum in the temperature range ?100?100°C are also studied for this blend at various compositions. Scanning electron microscopic studies of the impact-fractured surfaces are presented to illustrate the differences in the mode of fracture at the three temperatures of impact tests. Choice of the three temperatures for impact tests was such that the effect of shear yielding mechanism of toughening of PP at ambient temperature remains suppressed at ?30°C, whereas at the lowest temperature (i.e., ?190°C) the elastomeric role of the inclusion SEBS is suppressed. The observed considerably large difference in impact toughening at ambient temperature and at ?;30°C seems not entirely accountable by the prevalence of shear yielding or crazing mechanisms in the respective temperature regions. A third mechanism, viz., viscoelastic energy dissipation, is invoked to account for the observed large difference of impact toughening at these two upper temperatures. Correlation of peak area of dynamic mechanical loss peaks occurring below the impact test temperature with the impact strength is also shown. This suggests greater significance of viscoelastic energy dissipation mechanism in the toughening of this blend at ambient temperature than at ?30°C.     

Effect of shade and thermo-mechanical viscosity stimulation methods on the rheological properties of nanohybrid resin composite

The aim of the present study is to measure the rheological properties of nanohybrid resin composite of three shades in pre-polymerized phase using different thermomechanical stimulations. Nanohybrid composite (Kerr Herculite XRV Ultra) in enamel, dentin, and incisal shades was included. Rheological measurements were made with a rotational rheometer in dynamic oscillation mode using three methods: (a) Strain Sweep test explored a range of deformation γ₀ from 0.025 to 3% with a frequency ω = 1 Hz (temperature set at 25 and 65?°C), (b) Frequency Sweep test explored frequencies between 1 and 100 rad/s applying a deformation γ₀ = 0.5% (temperature set at 25; 45; 65?°C), and (c) Ramp Temperature test explored a heating phase from 25 to 75?°C then a cooling phase back to 25?°C applying a γ₀ = 0.5% and a ω = 10 rad/s. Data were analyzed using a three-way ANOVA and Tukey’s test (α = 0.05). Viscosity measurement (p < 0.05) and shade of the composites (p < 0.05) significantly affected the results. Viscosity turned out to be subordinate to strain amplitude, frequency, temperature, and axial force applied during each test. Enamel shade was the most viscous whereas dentin shade was 8% less viscous (p < 0.05). The incisal shade was significantly less viscous (70%) than enamel (p < 0.05). Pre-heating decreased viscosity of incisal shade (30%) above 50?°C but this value was 90 and 98%, respectively, for strain and frequency sweep test. Preheating had a side effect as in the cooling phase, viscosity increased from 66 to 450% exceeding the value recorded at the beginning of the test. Preheating was not effective to reduce viscosity, and may reveal some side effects. The composite tested might not be pre-heated above 45?°C.     

Damage microstructure evolution of helium ion irradiated SiC under fusion relevant temperatures

In-situ transmission electron microscopy (TEM) with ion irradiation has been used to study the damage microstructure evolution of He ion irradiated 4-H SiC at nuclear fusion relevant temperatures. The SiC samples were irradiated with 20?keV He ions at 25, 400, 800 and 1200?°C to a dose of 5.0 displacements per atom (DPA). At 25?°C, the material fully amorphises at 1.5 DPA and no He bubble nucleation occurs up to the doses studied. At 400 and 800?°C, He bubble nucleation occurs and the material remains crystalline. Bubble nucleation occurs at 2.0?DPA at 400?°C but occurs at only 0.5?DPA at 1200?°C. This is attributed the He atoms de-trapping from vacancies and migrating interstitially to larger He-vacancy clusters at higher temperatures, leading to faster nucleation of observable He bubbles. Helium platelets form at an irradiation temperature of 1200?°C at 0.5?DPA showing a preference for nucleation between the {0001} basal planes.     

Effect of curing and heat treatment history on the dynamic mechanical response and the pore structure of hardened cement paste

Results for the dynamic mechanical response of hcp (hardened cement paste) specimens as a function of the curing-heat treatment history are reported. The temperature range investigated is from ?160°C to +100°C. In the temperature range from +25°C to +100°C, specimens cured at room temperature (R-cured) show a partially irreversible transition (reduction) in E. There are two low temperature transitions: the “adsorbate transition” between ?160°C and ?6-°C, and the “capillary transition” between ?50°C and 0°C. Both of these transitions are significantly affected by the curing-heat treatment history. Furthermore, both the E-modulus and the BET (water) surface area decrease as the severity of heat treatment increases.     

Anodic bondable Li-Na-Al-B-Si-O glass-ceramics for Si - ULTCC heterogeneous integration

In this paper, we report an anodic bondable Li-Na-Al-B-Si-O (LNABS) glass-ceramic system with a low temperautre (150 °C) and voltage (200 V) for Si - ULTCC (Ultra-Low Temperature Co-fired Ceramics) heterougeneous integration. The ULTCC materials are predominantly composed of multicrystalline LiAlSi₂O₆ with a small amount of glass phase. The coefficient of thermal expansion (CTE) of LNABS is 3.27 ppm/°C (25–300 °C) leading to excellent theraml compatibility with silicon wafer over a wide temperature range from 60 °C to 300 °C. To demonstrate the utility of this system, a silicon micro-electro-mechanical (MEMS) systems pressure sensor is encapsulated between silicon and ULTCC substrates. This sensor exhibits high accuracy and good stability in the temperature range from ?40 °C to 120 °C. The bonding current, cross section and alkali ions concentration were investigated, and the anodic bonding mechanism at low temperature and voltage was revealed. The alkali ions migrate through the glass phase due to its lower activation energy, which also forms a high space-charge electric field at the bonding interface. The non-bridge oxygen (NBO) drifts towards silicon and oxidized silicon under high space-charge electric field. The calculated diffusion coefficient of NBO indicates that the elevated temperature and voltage both benefit the migration of NBO. These finding illustrate the great potential of LNABS glass-ceramic for high quality microelectronic and MEMS packaging technology with advantages of multilayer structure, low anodic bonding temperature and voltage, as well as the excellent theraml compatibility with Si wafers.     

Composition-dependent xBa(Zr0.2Ti0.8)O3-(1-x)(Ba0.7Ca0.3)TiO3 bulk ceramics for high energy storage applications

This work reports the composition dependent microstructure, dielectric, ferroelectric and energy storage properties, and the phase transitions sequence of lead free xBa(Zr_0.2Ti_0.8)O₃-(1-x)(Ba_0.7Ca_0.3)TiO₃ [xBZT-(1-x)BCT] ceramics, with x?=?0.4, 0.5 and 0.6, prepared by solid state reaction method. The XRD and Raman scattering results confirm the coexistence of rhombohedral and tetragonal phases at room temperature (RT). The temperature dependence of Raman scattering spectra, dielectric permittivity and polarization points a first phase transition from ferroelectric rhombohedral phase to ferroelectric tetragonal phase at a temperature (T_R-T) of 40?°C and a second phase transition from ferroelectric tetragonal phase - paraelectric pseudocubic phase at a temperature (T_T-C) of 110?°C. The dielectric analysis suggests that the phase transition at T_T-C is of diffusive type and the BZT-BCT ceramics are a relaxor type ferroelectric materials. The composition induced variation in the temperature dependence of dielectric losses was correlated with full width half maxima (FWHM) of A₁, E(LO) Raman mode. The saturation polarization (P_s) ≈8.3?μC/cm² and coercive fields ≈2.9?kV/cm were found to be optimum at composition x?=?0.6 and is attributed to grain size effect. It is also shown that BZT-BCT ceramics exhibit a fatigue free response up to 10⁵ cycles. The effect of a.c. electric field amplitude and temperature on energy storage density and storage efficiency is also discussed. The presence of high T_T-C (110?°C), a high dielectric constant (ε_r ≈?12,285) with low dielectric loss (0.03), good polarization (P_s ≈?8.3?μC/cm²) and large recoverable energy density (W?=?121?mJ/cm³) with an energy storage efficiency (η) of 70% at an electric field of 25?kV/cm in 0.6BZT-0.4BCT ceramics make them suitable candidates for energy storage capacitor applications.