Boron-Containing Non-Flammable Polyurethane Foams

Boron-containing oligoetherol was synthesized from melamine diborate (MDB) with ethylene carbonate. The oligoetherol was then used to obtain polyurethane foams. Additional amount of MDB was also used as additive flame retardant added at the foaming step into foaming composition. Obtained PUFs were non-flammable as demonstrated by vertical and horizontal flaming tests. The products has also high thermal resistance and can be exposed to long term heating at 175°C. Fire properties of the obtained foams were compared with the properties of foams obtained from melamine and propylene carbonate and from MDB and ethylene carbonate.     

Rigid polyurethane foams derived from cork liquefied at atmospheric pressure

The aim of this study was to evaluate the possibility of using polyols derived from liquefied cork in the production of novel bio‐based polyurethane foams (PUFs). For that purpose, different liquefaction conditions were used at atmospheric pressure and moderate temperature where poly(ethylene glycol) and glycerol were used as solvents and sulfuric acid as catalyst. The ensuing polyols were used to produce foams which were characterized using structural, morphological, thermal and mechanical analyses to demonstrate that liquefaction conditions play a crucial role in the properties of the foams. The resulting foams exhibited the typical cellular structure of PUFs with low densities (57.4–70.7 kg m^?3) and low thermal conductivities (0.038–0.040 W m^?1 K^?1). However, the mechanical properties differed significantly depending on the liquefaction conditions. The best stress–strain results were obtained for PUFs prepared using the polyol with lowest I_OH and water content (Young's modulus of 475.0 kPa, compressive stress (σ_10%) of 34.6 kPa and toughness of 7397.1 J m^?3). This PUF was thermally stable up to 200 °C and presented a glass transition temperature of around 27 °C. The results obtained demonstrate that these polyols from liquefied cork yield PUFs that are adequate materials for insulation applications. © 2014 Society of Chemical Industry     

Preparation and performance of crosslinked poly(arylene ether)s containing azobenzene chromophores

A series of novel poly(arylene ether)s with crosslinked groups and different azobenzene chromophores contents (azo-CPAEs: PAE-allyl20%-azo20%, PAE-allyl20%-azo40%, PAE-allyl20%-azo60%) were synthesized from a new bisfluoro monomer, (2,6-difluorophenyl)-(4-hydroxyphenyl)methanone. Their chemical structures were characterized by means of UV-vis and FI-IR. The thermal properties of the polymers were investigated by TGA and DSC, indicating the polymers had high glass transition temperatures (T_g > 147 °C) and good thermal stability (T_d5 > 360 °C) even when the contents of azobenzene chromophores was high to 60%. And the influence of thermal crosslinking on the performance of PAE-allyl20%-azo20%, a typical one of the series, was investigated. T_g of PAE-allyl20%-azo20% increased with the increase of heating time when heat-treated at 250 °C for 20, 40 and 60 min, indicating the crosslink degree of the polymer increased. After heat-treated for 60 min, T_g of PAE-allyl20%-azo20% increased to 175 °C from 147 °C before thermal crosslinking. Upon irradiation with a 532 nm neodymium doped yttrium aluminum garnet (Nd:YAG) laser beam, the remnant value of the polymer PAE-allyl20%-azo20% before and after the thermal crosslinking were 81 and 96%, respectively, meaning that the PAE-allyl20%-azo20% after thermal crosslink showed more stable photoinduced alignment than that before thermal crosslinking.     

Capabilities of different cooking oils in prevention of cholesterol oxidation during heating

The potential of various cooking oils to prevent cholesterol degradation and/or oxidation, as measured by the production of 7-ketocholesterol during heating at different temperatures, was studied using a cholesterol model system. In the control group (without cooking oil), cholesterol was relatively stable, and 73% of its initial concentration was present after 30 min of heating at 125°C. Less than 30 and 10% of cholesterol remained at 150 and 175°C after 30 min, respectively, and 10% at 200°C after 10 min. In the treatment group, cholesterol mixed with corn, canola, soybean, or olive oil had significantly improved thermal stability. More than 60 and 40% of cholesterol remained at 150 and 175°C after 30 min, respectively. In the control group, 7-ketocholesterol was produced when samples were heated above 150°C, and levels increased consistently during 30 min of heating. At 175 or 200°C, the level of 7-ketocholesterol did not increase further after reaching the highest level after 10 min of heating. 7-Ketocholesterol is not stable above 175°C, and its degradation rate could be much faster than its production at 200°C. 7-Ketocholesterol was not found in samples of cholesterol mixed with corn oil or laboratory-prepared soybean and rice bran oils until the heating temperature was raised to 175°C for 20 min. The levels of 7-ketocholesterol in those treatment groups were greater than that in the control group at 175°C for 30 min. These oils may increase the thermal stability of 7-ketocholesterol and retard its degradation rate.     

The effect of synthesis conditions on the physicochemical properties of magnesium aluminate materials

Magnesium aluminate-based materials were prepared by applying different methods: (i) mechanochemical milling of the initial mixture of magnesium and aluminium nitrate powders (in appropriate stoichiometric amounts) followed by heat treatment at temperatures of 650 °C and 850 °C and (ii) melting of the mixture of nitrate precursors at 240 °C followed by thermal treatment at 650 °C, 750 °C and 850 °C. The effect of synthesis method on the structure and morphology of the obtained solids was studied by using various techniques such as: nitrogen adsorption-desorption isotherms, powder XRD, IR spectroscopy and SEM. It was shown that the mechanochemical milling performed before calcination procedure leads to obtaining of nanocrystalline magnesium aluminate spinel phase at lower temperature of 650 °C in comparison with the method using thermal treatment only (at 750 °C). The obtained nanomaterials exhibit mesoporous structure.     

Effect of short thermal treatment on cotton degradation

Cotton fabric was subjected to thermal treatment for durations ranging from 0.5 to 5 min at a temperature range of 160°C. In comparison with the untreated cotton, the copper number (measure of the aldehyde content) decreased after heating cotton for up to 3 min at 160°, 180°, and 190°C but increased when heating was prolonged to 5 min. Thermal treatment at 200°C or above caused an appreciable increase in the copper number. The carboxyl content increased with time of heating, attained a maximum, and then fell down to reach values which in some cases were lower than that of untreated cotton. Thermal treatment at 180°C caused a substantial reduction in the D. P.; this reduction increased with time of treatment. At the other temperatures there was no significant decrease in D. P. when cotton was heated up to 3 min. The D. P. decreased in these cases only when the thermal treatment was conducted for 5 min. The tensile strength remained practically unimpaired after thermal treatment of the cotton for up to 2 min, regardless of the temperature used within the range studied. A loss in tensile strength of ca. 9% and 13% was observed with fabrics treated for 5 min at 160° and 180°C, respectively. This contrasts with a loss of ca. 4% at 190°C, 7% at 200°C, and 8% at 220°C. The highest dye exhaustion was obtained on cotton which was thermally treated at 180°C prior to dyeing, while the lowest dye exhaustion was obtained on cotton heated at 220°C. Thermal treatment at 160°C left the susceptibility of cotton toward the dyestuff practically unaltered.     

Crosslinking benzotriazolylimides and polymeric materials on base of them

A new kind of crosslinking oligobenzotriazolylimides with terminal maleimide groups has been synthesized via an interaction of an excess of bismaleimides with 5,5′‐bisbenzotriazoles in melt. Conditions of obtaining these oligomers were optimized via the syntheses of model compounds. Oligomers, according to dynamic thermogravimetric analysis (DTGA), fuse at 135–160°C, crosslink at 175–250°C, and possess the high thermal stability in air up to 410°C. Using these oligomers as thermosetting binders or crosslinking agents, tough laminate plastics reinforced by a glass‐fiber cloth as well as crosslinked films on base of a linear polybenzimidazole (PBI) matrix were obtained. The plastics and the crosslinked films possess high mechanical characteristics. It has been proved that the crosslinked films on base of the PBI matrix are perspective precursors to design the phosphoric acid electrolyte membranes for the medium temperature fuel cells. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of paraffin-based phase-change microcapsules and application in geopolymer coating

A type of paraffin phase-change microcapsule for thermal insulation of exterior walls was prepared by in situ polymerization of low-softening-point paraffin (46°C) as core material and acrylic copolymer as shell. The surface morphology, phase-change thermal properties, and thermal stability were characterized by scanning electron microscopy, laser particle size distribution analysis, differential scanning calorimetry, and thermogravimetric analysis, respectively. The results showed that, for polymerization reaction temperature of 75°C and paraffin/acrylic copolymer mass ratio of 1.8, the microcapsules prepared at rotation speed of 1600 r/min with 8% emulsifiers were spherical particles with smooth surface and average particle size of 0.68 μm. The phase-change temperature and latent heat storage capacity of the microcapsules were 47.8°C and 174 J/g, respectively. The paraffin phase-change microcapsules obtained using the optimum synthesis condition were mixed in a metakaolin-based geopolymer coating at different proportions, and the thermal insulation ability of the resulting phase-change thermal energy storage coating characterized.     

Thermal Decomposition of Diammonium Tetrachloroplatinate to form Platinum Nanoparticles and its Application as Electrodes

Pt nanoparticles were obtained via the thermal decomposition of (NH₄)₂[PtCl₄] (diammonium tetrachloroplatinate) by heating from room temperature to 760 °C. The thermal decomposition process was analyzed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), X-ray thermodiffraction and infrared spectroscopy. The size and structure of the platinum particles were analyzed using transmission electron microscopy (TEM). The electrochemical activity of Pt particles was assessed by cyclic voltammetry in 0.5 M H₂SO₄. The TGA and DTA results suggested that the thermal decomposition of the precursor proceeded in two stages: loss of NH₄Cl at ~300 °C, followed by loss of NH₄Cl and Cl₂ at ~372 °C. Metallic Pt particles were then produced at temperatures of 372 °C and above. At 760 °C, the mean ± SD size of the Pt particles was (4.1 ± 1.6) nm, as determined from TEM measurements. In cyclic voltammetry (CV) measurements, an electrode comprised of glassy carbon and Pt particles in 0.5 M H₂SO₄ exhibited behavior similar to that observed using a polycrystalline Pt electrode.     

Effect of the thermal treatment on microstructure and physical properties of low-density and high transparency silica aerogels via acetonitrile supercritical drying

In this paper, we reported the experimental results about the effect of the thermal treatment on microstructure and physical properties of low-density and high transparent silica aerogels. From our results, with tetramethyl orthosilicate as precursor and via acetonitrile supercritical drying process, silica aerogel monolith was obtained possessing the properties as low-density (0.018 g/cm³), high surface area (923 m²/g), high optical transparency (87.9 %, 800 nm). It should be noted that high transparency of silica aerogel can be maintained up to 600 °C (91.5 %, 800 nm). The mechanical properties of silica aerogel decreased with increasing heat treated temperature to 600 °C, and silica aerogels still maintained crack-free monoliths completely and possessed high homogeneous density even after 600 °C thermal treatment. Furthermore, thermal conductivity of the monoliths at desired temperatures was analyzed by the transient plane heat source method. When the temperature flowed from 25 to 600 °C, thermal conductivity coefficients of silica aerogels changed from 0.021 to 0.065 W (m K)^?1, revealed an excellent heat insulation effect in high-temperature area. Currently, the specific process developed for low-density aerogels affected by thermal treatment has not been reported in previous literature.     

Sodium Humate as a Promising Coating Material for Microencapsulation of Beauveria bassiana Conidia Through Spray Drying

Microencapsulation of Beauveria bassiana (Bb) conidia with sodium humate (SH) was undertaken successfully through spray drying at a high inlet air temperature of 175°C with corresponding outlet air temperature of 86.5 ± 1.3°C using 0.2% SH. The obtained product was a free-flowing, dark-brown powder containing microcapsules of Bb conidia coated with sodium humate (Bb-SH). These microcapsules measured 2.47–3.57 µm and possessed an uneven, fluffy surface. The colony-forming units (CFU) of Bb-SH microcapsules spray-dried at 175°C were 21.54 LCFUg^?1, on par with 21.59 LCFUg^?1 for Bb conidial powder not subjected to spray drying. Bb-SH microcapsules resulted in a high mortality of 93.0% against six-day-old Helicoverpa armigera larvae within five days after treatment. Bb-SH microcapsules readily dispersed in water, releasing sodium humate from the conidial surface. Germination of conidia was not affected by sodium humate as visualized by scanning electron microscopy of the cuticular surface of treated larvae. Bb-SH microcapsules showed good viability (21.11 LCFUg^?1) at the end of six months of storage at room temperature (～30°). Thus, sodium humate is a promising biopolymer for encapsulation of Bb conidia for extended shelf-life at room temperature.     

Preparation of poly (vinyl alcohol)/gelatin composites via in-situ thermal/mechanochemical degradation of collagen fibers during melt extrusion: effect of extrusion temperature

By in-situ degradation of collagen fibers into gelatin under the thermal/mechanochemical effects of the extruder, PVA/gelatin composites were successfully prepared using PVA and collagen fibers derived from cattle hide limed split wastes as raw materials. The effect of extrusion temperature on the degradation of collagen fibers and the thermal processability and mechanical properties of the composites were studied. The results showed that the controllable degradation of collagen fibers in extruder could be realized by adjusting the extrusion temperature. Particularly, high extrusion temperature promoted the generation of low-molecular-weight gelatin and the esterification between the hydroxyl of PVA and the carboxyl of gelatin, as well as the hydrogen bonding between O-H, C = O, N-H in gelatin and water or O-H in PVA, thus endowing gelatin with the good compatibility with PVA, and significantly increasing the content of non-freezable bound water in system. Ascribing to the plasticization of the gelatin with lower molecular weight and more non-freezable bound water, PVA/gelatin composites exhibited the improved thermal processability and the decreased mechanical properties with the increase of extrusion temperature. Even so, the tensile strength and Young’s modulus of the composite obtained at 175 °C still above 40 MPa and 1.0 GPa respectively, satisfying some practical applications.     

Branched polyols based on oleic acid for production of polyurethane foams reinforced with bamboo fiber

Fatty acids and bamboo fiber (BF) are abundant and renewable materials that have great potential application in the production of high-valued chemical products. In this work, polyurethane foams (PUFs) with remarkable mechanical and thermal properties were synthesized using OAPs (polyols-based on oleic acid (OA), an important fatty acid) and polymeric isocyanates. PUFs were reinforced with BF. Novel OAPs were prepared from OA through a process consisting of hydroxylation, carboxylation, and esterification. The strategy afforded branched polyols with high content of primary hydroxyls. Phthalic anhydride was used as a modifying agent to improve the properties of OAPs. Physicochemical properties of the polyols were characterized by standard methods (analyses of hydroxyl number, viscosity, acid value, density, and water content) and instrumental analysis (gel permeation chromatography, Fourier transform infrared spectroscopy, and thermogravimetry). The mechanical properties of polyurethane foams made from the OAPs were improved by applying modified BF as filler. With BF having particle sizes of 250–500 μm, the compressive strength of composite foams increased from 0.45 to 0.66 MPa, and the flexural strength increased from 0.66 to 0.77 MPa. Surface modification of BF by alkali could enhance the interfacial interaction between the reinforcing fibers and foam matrix, resulting in greater mechanical strength of the PUFs. It also improved the thermal stability and dynamic thermomechanical properties of PUFs.     

Solvent Extraction of Fucoxanthin from Phaeodactylum tricornutum

The extraction yield of fucoxanthin from Phaeodactylum tricornutum, a marine diatom, was investigated for 16 h as the functions of the kind of solvent, temperature, and solvent/diatom weight ratio. Acetone, ethanol, and ethyl acetate were used as solvents for the extractions. The extraction yield increased in a saturation manner with the extraction time when the extraction temperatures were 30°C and 40°C. However, the extraction yield increased with time in the early stage of the extraction; thereafter, it was stagnant or decreased with time in the late stage at 50°C, 75°C, and 85°C. The thermal deterioration would suppress the extraction yield in the late stage at those higher temperatures. The maximum extraction yield was obtained at 40°C and no significant benefit in the extraction yield was obtained when the extraction period was extended over 12 h. The extraction yield markedly increased when the solvent/diatom ratio increased from 3/1 to 6/1, but no marked benefit was obtained when the amount of solvent increased over the ratio of 6/1. Ethanol was the most effective solvent in the extraction of fucoxanthin, and the extraction yield was greater in the order of ethanol > acetone > ethyl acetate.     

Effect of γ-radiation on the thermal conductivity of polypropylene

The effect of ⁶⁰Co γ-radiation on the thermal conductivity of polypropylene (PP) has been studied over the temperature range 0–160°C. for radiation doses of 600 and 1800 Mrad. The conductivity of unirradiated specimens rises from 4.5 × 10^?4 cgs units (cal./cm.-sec.-°C.) at 0°C. to 4.8 × 10^?4cgs units at 80°C. and subsequently decreases with temperature to a value of about 3.1 × 10^?4cgs units at 160°C. Upon irradiation to 600 Mrad the thermal conductivity is lowered over the 0–150°C. temperature range. Above 90°C. the conductivity decreases with temperature and becomes relatively constant at 3.4 × 10^?4 cgs units from 120 to 160°C. Differential scanning calorimeter (DCS) measurements from 30 to 200°C. show that irradiation to 600 Mrad lowers the energy associated with crystalline melting and shifts the endotherm melting peak from about 160 to 105°C. Irradiation to 1800 Mrad results in additional lowering of the thermal conductivity over the 50–160°C. range, a further decrease in area of the endothermic peak and a shift of its maximum peak position to about 75°C. The effects of radiation on the thermal conductivity of polypropylene are compared and correlated with the observed effects of radiation on the dynamic mechanical behavior.     

Determination of Optimum Drying Condition of VIP Core Material by Wet Method

Vacuum insulation panel (VIP) core materials were successfully fabricated by wet method. The phase composition, microstructure, and thermal conductivity of VIP core materials were investigated. The density of VIP core materials was 176 kg/m³, while the mean thermal conductivity of VIP core materials was about 31 mW/(m · K). The mean thermal conductivities of VIPs were 2.78 mW/(m · K), 2.62 mW/(m · K), 2.47 mW/(m · K), 2.5 mW/(m · K), and 2.4 mW/(m · K), which correlated to VIP core materials that had been dried at 150°C for 30 min, 60 min, 90 min, and at 170°C for 30 min and 60 min, respectively. However, the mean thermal conductivity evaluated for VIPs with core material that had not been dried was 3.0 mW/(m · K). The thermal conductivity of VIPs with core material that had been dried reached a maximum on the third day and tended to be a steady value with time, whereas the one with core material that had not been dried recorded a high thermal conductivity value and continued to rise in a fluctuating pattern with time. According to the result of the thermogravimetric curve, drying at 150°C for 60 min showed characteristics of complete drying. In addition, the thermal conductivity of VIPs at this drying condition was low and stable. Theoretical and experimental analysis showed that the optimum drying condition for fiberglass VIP core materials was drying at 150°C for 60 min.     

Oilseed Meal Based Plastics from Plasticized, Hot Pressed Crambe abyssinica and Brassica carinata Residuals

With the increased use of plant oils as sustainable feedstocks, industrial oilseed meal from Crambe abyssinica (crambe) and Brassica carinata (carinata) can become a potential source for oilseed meal based plastics. In this study, crambe and carinata oilseed meal plastics were produced with 10–30 % glycerol and compression molding at 100–180 °C. Size exclusion HPLC was used to relate tensile properties to changes in protein solubility and molecular weight distribution. By combining glycerol and thermal processing, increased flexibility has been observed compared to previous work on unplasticized oilseed meal. Tensile results varied from a brittle crambe based material (10 % glycerol, 130 °C), Young’s modulus 240 MPa, strain at maximum stress of 2 %, to a soft and flexible carinata based material (30 % glycerol, 100 °C), Young’s modulus 6.5 MPa, strain at maximum stress of 13 %. Strength and stiffness development with increasing molding temperature is in agreement with the protein profiles obtained. Thus, the highest mechanical parameters were obtained at the protein solubility minimum at 140 °C. Higher temperatures caused protein degradation, increasing the level of low molecular weight extractable proteins. In carinata based materials the strain at maximum stress decreased as the protein aggregation developed. Results presented indicate that both crambe and carinata oilseed meal based materials can have their properties modulated through thermal treatment and the addition of plasticizers.     

Highly soluble phenylethynyl terminated oligoimides derived from 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane, 4,4′-oxydianiline and mixed thioetherdiphthalic anhydride isomers

Novel highly soluble phenylethynyl-endcapped oligoimides derived from mixed thioetherdiphthalic anhydride isomers (m-TDPA) and 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (DAPI), 4,4′-oxydianiline (4,4’-ODA) with 4-phenylethynylphthalic anhydride (PEPA) as a reactive endcapping agent were synthesized. The calculated molecular weights of all the oligoimides were 2500 g·mol^?1.The effect of the mole ratio of DAPI/4,4’-ODA on solubility and melt viscosity of oligoimides as well as the thermal and mechanical properties of cured polyimide films was investigated. Experimental results indicated that DAPI greatly improved the solubility (>30 wt.%) of the oligoimides in low boiling points solvents when the content of DAPI was more than 10 mol% per total diamine. All the oligoimides exhibited very good processability with minimum melt viscosity lower than 60 Pa·s at about 330 °C. Tough and brown films were obtained after thermally cured at 370 °C for 1 h and dynamic mechanical analysis (DMA) showed that glass transition temperatures of the cured films increased up to 340 °C with the increasing content of DAPI. However, the thermal stability and mechanical properties decreased with the increase of DAPI content. The temperature of 5% weight loss was higher than 470 °C in both air and N₂ atmosphere obtained by thermogravimetric analysis (TGA). And the tensile strengths of the cured films were about 60 MPa.     

Sintering behavior,microstructure and thermoelectric properties of calcium cobaltite thick films for transversal thermoelectric multilayer generators

The sintering behavior and the thermoelectric performance of Ca₃Co₄O₉ multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A transversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca₃Co₄O₉ green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT = 200 K in the temperature interval of 25 °C to 300 °C.     

Response Surface Methodology to Supercritical Carbon Dioxide Extraction of Essential Oil from Amormum krevanh Pierre

Abstract

Response surface methodology was employed to investigate the effects of operating conditions and predict the optimal conditions for supercritical carbon dioxide extraction of essential oil from Amomum krevanh Pierre. The factors investigated were operating temperature (33–67°C), the operating pressure (91–259 bar), and the extraction time (20–70 min). The main effect of the operating pressure and the interaction effect between the operating temperature and the extraction time were found to be significant factors. From the response surface model, an optimal condition for essential oil content within the range of experimental study was found to be at 33°C, 175 bar, and 70 min, which gave the oil yield of 17.3 mg/g dry wt. The essential oil yield obtained at all conditions were higher than that obtained by organic solvent extraction (9.74 mg/g dry wt.) while the composition of the extract was similar, which were 1,8-cineole (70.87%), β-pinene (8.89%), and limonene (4.81%).