Kinetic aspects of concentration of solid nanoparticles at the interface in polystyrene–polyethylene mixtures

The effect of several mixing process parameters on the concentration of carbon black particles at the interface between the polymer components in polyethylene–polystyrene mixtures was studied. It was established that the process of particle transport from the polymer phase to the interface happens only under the action of shear deformation, but simultaneously acting shear stresses prevent particle concentration. The nanoparticle accumulation at the interface is determined not only by how favored this process is thermodynamically, but also by the parameters of the mixing process. The filler concentration at the interface is facilitated by a reduction in the shear stress, polymer viscosity, filler particle size, and preliminary injection of filler into the polymer component that is less effective at wetting the filler surface. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48585.     

Kinetic and thermochemical study of the oxidative polymerization of α-substituted styrenes

This article reports a systematic kinetic study on the oxidative polymerization of ??-substituted styrene monomers such as styrene (St), ??-methylstyrene (AMS), 4-chloro ??-methylstyrene (CAMS), and ??-phenylstyrene (APS) in the presence of 2,2??-azobisisobutyronitrile as a free radical initiator at 100?psi oxygen pressure and 40-50?°C in toluene. The rate of oxidative polymerization follows the order: APS?>?CAMS?>?AMS?>?St. Theoretical calculations have been performed using density functional theory to support the order of oxidative polymerization rates. In addition, the synthesis and characterization of poly(4-chloro ??-methylstyrene peroxide) (PCAMSP) is reported here for the first time. Elemental analysis and nuclear magnetic resonance spectroscopy confirm the alternating copolymer structure of PCAMSP with ?CO?CO?C bonds in the main chain. Thermal degradation studies using differential scanning calorimeter and thermogravimetric analysis reveal that PCAMSP degrades highly exothermically and the average enthalpy of degradation at various heating rates is found to be 48.7?±?0.6?kcal/mol, which is of the same order reported for other vinyl polyperoxides.     

Preparation and characterization of the halogen-free,smoke suppression,organic–inorganic hybrid flame-retardant expandable polystyrene materials

Expandable polystyrene (EPS) is a plastic widely used in the field of construction, but it is flammable. This work provided a novel strategy for flame-retardant modification of EPS. A kind of polyester polyol (JZP) with the high content of phosphorus and nitrogen was synthesized. Then, intrinsic flame-retardant polyurethane (PFWPU) with the high content of phosphorus and nitrogen was synthesized by JZP acted as soft segment chain extender. Finally, a high-efficiency flame-retardant expandable polystyrene thermal insulation material (AF-EPS) was prepared by the organic–inorganic hybrid flame-retardant synergistic action of PFWPU and ammonium polyphosphate. The effects of different contents of inorganic flame retardants on flame retardancy of materials were studied by limiting oxygen index (LOI), cone calorimetry, thermogravimetric analysis/infrared spectrometry , scanning electron microscopy, and so on. The test results showed that the carbon residue rate of the modified material increased from 0 to 28.5%, the LOI increased from 17 to 35.8%, and the vertical combustion test reached the highest grade V-0. In addition, the total smoke production of AF-EPS samples decreased from 2.33 m² to 0.57 m², the time to ignition was increased to 41 s, and the peak heat release rate and the total heat release were decreased by 90.2 and 62.7%, respectively.     

Low-temperature combustion synthesis of nanocrystalline HoFeO3 powders via a sol–gel method using glycin

Single phase nanocrystalline HoFeO₃ powders were successfully synthesized by the sol–gel self-propagation combustion method using glycin (C₂H₅NO₂) as the chelating reagent at a low combustion temperature. Four different mole ratios of glycin to metal nitrate (G/M) were used to prepare HoFeO₃ powders in the experiment. The XRD patterns indicate monophasic HoFeO₃ powders can be formed by further calcination, the SEM micrographs show that the nano-sized grains with distinguishable boundaries had been obtained. The M–H curves show HoFeO₃ powders had the characteristic of antiferromagnetism at 50 K, while the powders had the characteristic of paramagnetism as the ambient temperature reached 100 K or 300 K. The FC/ZFC magnetic measurement results demonstrate that there was a transition from antiferromagnetism to paramagnetism in HoFeO₃ nanopowders as the temperature was increased.     

“One pot” synthesis of fluorinated block copolymers using a surface-active ATRP initiator under emulsion polymerization conditions

Three fluorinated block copolymers have been prepared successfully in emulsion system using a surface-active atom transfer radical polymerization (ATRP) initiator disodium 4-(10-(2-bromo-2-methylpropanoyloxy)decyloxy)-4-oxo-2-sulfonatobutanoate (1). The copolymerization can be conducted in “one pot” under activator generated by electron transfer (AGET) ATRP in emulsion conditions, thus greatly simplifying the operations and workup. The anionic surface-active ATRP initiator (1) and nonionic surfactant OP-10 may form synergistic stabilizers that effectively guarantee stability of the final latex. The ATRP follows first-order kinetics and has living/controlled characteristics based on the researching results of polymerization of trifluoroethyl methacrylate (TFEMA). Surface studies indicate that the fluorinated block copolymers reveal lower surface energy and stronger hydrophobic property compared with those non-fluorinated polymers. The decreasing order of surface energy of the polymers is: polystyrene (PS) > polytrifluoroethyl methacrylate-block-polystyrene (PTFEMA-b-PS) > polyhexafluorobutyl methacrylate-block-polystyrene (PHFBMA-b-PS) > polydodecafluoroheptyl methacrylate-block-polystyrene (PDFHMA-b-PS) > polydodecafluoroheptyl methacrylate (PDFHMA). Fluorinated homopolymer PDFHMA and copolymer PDFHMA-b-PS exhibits relatively low-surface energy, which is ascribed to the long and flexible DFHMA units containing in the polymers.     

Size-controlled synthesis of nano α-alumina particles through the sol–gel method

Nano α-alumina particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 M aluminum nitrate. 1/3-benzened disoulfonic acid disodium salt (SDBS) and sodium bis-2-ethylhexyl sulfosuccinate (Na(AOT)) were used as surfactant stabilizing agents. Solution was stirred for different periods (24, 36, 48 and 60 h) at 60 °C. The samples were then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Introduction of surfactant stabilizing agents and different stirring times will affect the size and shape of particle formed and also the degree of aggregation. SDBS, however, produced better dispersion, finer particles and spherical shape nanoparticles, compared to Na(AOT). The finest particle size (20–30 nm) was obtained at 48 h stirring time with SDBS surfactant.     

High-efficiency synthesis of dendrimer-like poly(ethylene oxide) via “arm-first” approach

In this study, a dendrimer-like polymer based on poly(ethylene oxide) (PEO) was synthesized through a combination of anionic ring-opening polymerization (AROP) and click reaction via arm-first method. Firstly, the polymeric arm, a linear PEO with one alkynyl group and two bromo groups, was synthesized by AROP of ethylene oxide followed by functionalization with propargyl bromide and esterified with 2-bromopropionic bromide. Second, a star PEO carrying three azide groups was synthesized though AROP of ethylene oxide used 1,1,1-tris(hydrosymethyl) ethane as initiator followed esterificated with 2-bromopropionic acid and azidation. By azide–alkyne click reactions between the azide-terminated PEO star polymer and linear PEO with functionalization alkynyl group, a three generation dendrimer-like PEO, G3-PEO-24Br, was successfully synthesized. The resulting polymers were observed to have precisely controlled molecular weights and compositions with narrow molecular weight distributions.     

Numerical–experimental method to study the viscous behaviour of ceramic materials

The aim of the work deals with the development of a numerical–experimental method to study the viscous behaviour of ceramic materials and to estimate the viscosity evolution as a function of temperature.The current state of the art regarding the study of viscous behaviour of ceramic materials is carried out by using optical methods able to perform measurements without contact with the sample to be analyzed. The two point bending configuration is the conventional test currently used. Despite the use of the optical technology, the test specimen, because of its viscous behaviour, interferes with the measuring device. The experimental test results are inevitably compromised.The developed numerical–experimental method aims at overcoming the drawbacks of the conventional experimental test configuration and at determining the material viscosity. This method consists of an ad hoc developed experimental test configuration and of a numeric simulation of the experimental test.     

Microwave-assisted sol–gel synthesis of alpha alumina nanopowder and study of the rheological behavior

In the present work, alpha alumina nanopowder was synthesized via a sol–gel route. After preparation of bohemite (AlOOH) sol, carbon black was added and the resultant sol was dried and calcined in microwave furnace for 10 min. XRD results showed that alpha alumina was the only crystalline phase with specific surface area, mean diameter and crystallite size of 51 m² g^?1, 100 and 25 nm, respectively. Rheological measurements revealed that the optimal content of Tiron at pH=10 is 1 and 0.1 g per 100 g nano- and micron-alumina (1.5 m² g^?1), respectively. Furthermore, the optimum solid content of the slips was determined as 35–45 and 70 wt.% for nano- and micron-alumina, respectively.     

In situ synthesis of Al2O3–SiC powders via molten-salt-assisted aluminum/carbothermal reduction method

Al₂O₃–SiC composite powder (ASCP) was successfully synthesized using a novel molten-salt-assisted aluminum/carbothermal reduction (MS-ACTR) method with silica fume, aluminum powder, and carbon black as raw materials; NaCl–KCl was used as the molten salt medium. The effects of the synthesis temperature and salt-reactant ratio on the phase composition and microstructure were investigated. The results showed that the Al₂O₃–SiC content increased with an increase in molten salt temperature, and the salt–reactant ratio in the range of 1.5:1–2.5:1 had an impact on the fabrication of ASCP. The optimum condition for synthesizing ASCP from NaCl–KCl molten salt consisted of maintaining the temperature at 1573 K for 4 h. The chemical reaction thermodynamics and growth mechanism indicate that the molten salt plays an important role in the formation of SiC whiskers by following the vapor-solid growth mode in the MS-ACTR treatment. This study demonstrates that the addition of molten salt as a reaction medium is a promising approach for synthesizing high-melting-point composite powders at low temperatures.     

An electrochemical alternative strategy to the synthesis of β-lactams via NC4 bond formation

A simple electrochemical synthesis of β-lactams has been developed using constant current electrolysis in a suitable solvent-supporting electrolyte solutions, with subsequent addition of bromoamides. The regio- and stereo-selectivity of the electrochemically-induced cyclization of bromoamides to β-lactams, via NC4 bond formation, has been evidenced. This synthesis avoids any addition of bases and probases and gives β-lactams in high yields.     

Styrenated urethane oil synthesis via CuAAC “click” chemistry approach

In this study, a novel route for the modification of sunflower oil-based partial triglycerides with styrene (St) was described. For this purpose, in the first step, copolymers of St and 4-chloromethyl styrene (P(St-co-CMS)) were synthesized by free radical polymerization (FRP) and controlled/living radical polymerization (nitroxide mediated radical polymerization (NMRP)) methods. In the second step, chloro groups of these samples were transformed into azido groups by using NaN₃/DMF and then azido groups were coupled with propargyl alcohol to achieve hydroxyl functional polystyrene chain (PSt-OH) via Cu(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) “click” chemistry approach. Finally, alcohol groups of PSt-OH and the partial glyceride (PG) were combined by the reaction with toluene 2,4-diisocyanate (TDI). As a result, styrenated urethane oil (PG-TDI-PSt) was obtained as an oil-based binder. The structures were determined by FT-IR, ¹H NMR and GPC analyses, and film properties of the products were examined according to the related standards. (PG-TDI-PSt) gave good film properties, and therefore could be considered as an applicable oil-based binder.     

Novel method for the synthesis of a β-tricalcium phosphate coating on a zirconia implant

A novel method for the synthesis of a thin β-tricalcium phosphate (β-TCP) coating on zirconia implants has been developed. The synthesis procedure involves two steps: (i) rapid wet-chemical deposition of a biomimetic CaP coating and (ii) subsequent post-deposition processing of the biomimetic CaP coating, which includes a heat treatment at 900 °C followed by a short sonication in a water bath. The obtained β-TCP coating showed a uniform and dense morphology with a thickness of ≈500 nm and displayed a roughness in the nanometre range (R_a = 28 nm). The β-TCP coating demonstrated an apatite-mineralization ability in a simulated body fluid and enhanced the adsorption of serum proteins on the zirconia. Moreover, the β-TCP coating adhered firmly to the zirconia substrate, developing a notable scratch resistance (L_c = 97 N) and tensile strength (52 MPa) and showed strong resistance towards mechanical forces present during implantation of the coated zirconia implant into the artificial bone.     

Effect of p-aminobenzoic acid on synthesizing ordered mesoporous alumina via the sol–gel method

Ordered mesoporous alumina (OMA) samples were prepared via the sol–gel method. The triblock copolymer P123 and aluminum isopropoxide were chose as the template and aluminum source, respectively. The p-aminobenzoic acid (PABA) worked as both the interfacial protector and the assisted template. Different techniques, including X-ray diffractions, N₂ physisorption measurement and transmission electron microscope, were employed to study the structural properties of the prepared samples. The results showed that the mesostructure ordering and specific surface area of the samples highly depend on the quantity of the added PABA. The samples after calcinated at 800 °C with the n(PABA)/n(Al³⁺) molar ratio lying in 0.30 exhibited high specific surface areas (301 m² g^?1) and retained an ordered mesostructures. It was indicated that the carboxyl groups of PABA have multiple functions in the formation of OMA with a long-range ordering and high specific surface area. The carboxyl groups of PABA can slow down the hydrolysis-condensation reaction of aluminum isopropoxide, reduce the influence of chloride ions on self-assembly process. The amino groups of PABA can also react with the hydrogen ions to form quaternary ammonium salt, which can neutralize the charges of the chloride ions, protect the balance of inorganic–organic interface, further to improve the mesostructure ordering and specific surface area of the prepared OMA.     

Investigation of the formation process of highly porous α-Al2O3 via citric acid-assisted sol-gel synthesis

Macroporous α-alumina can be obtained by polymer-induced phase separation during the sol-gel process based on dissolved aluminum salts. Polyethylene oxide (PEO) acts as phase separating agent, propylene oxide as proton scavenger. Calcination at 1200 °C yields the thermodynamically stable α-Al₂O₃. It usually exhibits little to no porosity, with internal surface areas below 5 m²/g. We report on the successful establishment of citric acid as a novel phase separating agent in this process. Macropores ranging from 115 nm up to several μm have been successfully introduced in α-Al₂O₃. Compared to the PEO-route, BET surface areas doubled, going up to 12 m²/g. The materials prepared via the new method also exhibit a significantly different microstructural habitus.¹³C-NMR studies and TG/DTA measurements revealed a complete incorporation of citric acid into the gel network. This implies a change in phase separation mechanism, giving rise to a more particulate structure and hence the formation of larger macropores.     

Grafting of polystyrene “from” and “through” surface modified titania nanoparticles

We report the surface modification of titania (TiO₂) nanoparticles with azo-based radical initiator and vinyl (acrylate) polymerizable groups. This is achieved through the reaction of the surface hydroxyl groups of the titania with acid halides. Polymer (specifically, polystyrene) was grafted “from” the surface using the azo-modified titania, and “through” the surface of the vinyl-modified surface. Both conventional radical and reversible addition-fragmentation chain transfer (RAFT) polymerizations were performed. The surface-modified titania and the polystyrene-titania nanocomposites were characterized using IR spectroscopy, thermogravimetric analysis and gel permeation chromatography.     

One-step synthesis of ?-caprolactam via the liquid phase catalytic nitrosation of cyclohexane in the presence of concentrated sulfuric acid

A simple and efficient approach for the synthesis of ?-caprolactam via the liquid phase nitrosation of cyclohexane and nitrosyl sulfuric acid in the presence of concentrated sulfuric acid has been developed. A series of novel AlVPO composites were prepared by an impregnation method and the composites were then employed to catalyze the nitrosation reaction of cyclohexane and nitrosyl sulfuric acid. Compared to the reaction using fuming sulfuric acid, the selectivity for the desired product was significantly improved using this one-step catalytic process. This method affords a shortcut to prepare ?-caprolactam and its analogs from cyclohexane.     

Box–Behnken response surface method for the synthesis of high-temperature- and salt-resistant filter loss reducers

Wellbores are destabilized by the immersion of a formation in drilling fluid during deep well drilling. To address this issue, in the present study, trimethylolethane triallyl ether (TMETE), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), acrylamide, and N-vinylpyrrolidone undergo free radical copolymerization to produce a PTAAN filter loss reducer. The Box–Behnken response surface method is used to optimize the synthesis of PTAAN; the optimal conditions are 1 wt% TMETE and 0.1111 wt% initiator at 60°C. Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis are used to characterize the composition, micromorphology, and thermal stability of the PTAAN product, respectively. The synthesized product is resistant to high temperatures and salt under the optimal synthesis conditions. It has an API filtration loss of 8.2 mL for freshwater-based mud, an API filtration loss of 13.8 mL for 20% by weight brine mud after aging at 220°C, and an API filtration loss of 29.5 mL at 150°C under high temperatures and pressures. Incorporating PTAAN into the base slurry prevents clay particle agglomeration at elevated temperatures and high mineralization, resulting in a broader clay particle size distribution and ultimately leading to the formation of a thin and compact filter cake.