Preparation and characterization of water‐blown polyurethane foams from liquefied cornstalk polyol

Polyurethane foams were prepared from the liquefied cornstalk polyol, which was obtained by the liquefaction of cornstalk in the presence of polyhydric alcohols using sulfuric acid as catalyst. The advisable liquefaction reaction conditions were selected by investigating their influences on the properties of liquefied cornstalk polyol, taking account of the requirement for the preparation of appropriate polyurethane foams. The influences of the contents of catalysts, water, surfactant, and isocyanate on the properties of polyurethane foams were also discussed, and feasible formulations for preparing cornstalk‐based polyurethane foams were proposed. The results indicated that the foams prepared from such liquefied cornstalk polyol exhibited excellent mechanical properties and thermal properties, and could be used as heat‐insulating materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Biodegradable polyurethane based on random copolymer of L‐lactide and ϵ‐caprolactone and its shape‐memory property

A series of biodegradable polyurethanes (PUs) are synthesized from the copolymer diols prepared from L ‐lactide and ε‐caprolactone (CL), 2,4‐toluene diisocyanate, and 1,4‐butanediol. Their thermal and mechanical properties are characterized via FTIR, DSC, and tensile tests. Their T_gs are in the range of 28–53°C. They have high modulus, tensile strength, and elongation ratio at break. With increasing CL content, the PU changes from semicrystalline to completely amorphous. Thermal mechanical analysis is used to determine their shape‐memory property. When they are deformed and fixed at proper temperatures, their shape‐recovery is almost complete for a tensile elongation of 150% or a compression of 2‐folds. By changing the content of CL and the hard‐to‐soft ratio, their T_gs and their shape‐recovery temperature can be adjusted. Therefore, they may find wide applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4182–4187, 2007     

Polylactides with “green” plasticizers: Influence of isomer composition

Synthesized polylactides (PLA) with different D ‐isomer contents in the polymer chain were melt‐blended with a series of “green” plasticizers by extrusion. Mechanical and thermal properties as well as the morphology of the plasticized materials were characterized to demonstrate how the combination of PLA with different D‐contents and plasticizer controls the material properties. After addition of acetyl tributyl citrate (ATC), the elongation at break for PLA with a low D‐isomer content was twice as high as that for PLAs with high D‐isomer contents. Similar variations in the plasticization effect on the PLAs were also observed with the other plasticizers used, glyceryl triacetate (GTA), glycerol trihexanoate (GTH) and polyethylene glycol (PEG). In order to continue with the development of renewable polymers in packaging applications, the interrelation between a plasticizer and a specific polymer needs to be understood. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2962–2970, 2013     

Phosphorus‐containing silica gel‐coated ammonium polyphosphate: Preparation,characterization, and its effect on the flame retardancy of rigid polyurethane foam

A phosphorus‐containing silica gel was synthesized via a reaction between phenyl dichlorophosphate, poly(ether polyol), and γ‐aminopropyltriethoxysilane. Ammonium polyphosphate (APP) was modified by the synthesized phosphorus‐containing silica gel (MAPP) and then incorporated into the rigid polyurethane foam (PU). Results showed that APP had a smaller particle size, lower initial decomposition temperature, better heat resistance at high temperature, and better compatibility with PU matrix after the modification. The cone calorimeter test results showed that the incorporation of MAPP obviously reduced the values including peak of heat release rate, total heat release, average effective heat of combustion, and total smoke release, and increased the char yield of PU composite comparing with APP. The improved flame retardancy of PU/MAPP composite was attributed to the quenching effect of PO· and PO₂· free radicals released by MAPP in the early stage and the improved thermal stability of phosphorus‐ and silicon‐containing char layer formed in the later stage. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46334.     

Solvent extraction — the challenges of a “mature” technology

The solvent extraction area is perceived by some chemical engineers as being mature and fully developed. The present review shows that this is not the case. Many chemical engineering problems must be solved before equipment can be confidently designed from first principles. The review also outlines progress in extraction process chemistry, and in new techniques such as membrane extraction.     

Curing kinetics of a “green” thiol‐containing resin: Oligo(ethylene‐2‐mercaptosuccinate)

This work focuses on examining the curing process of neat oligo(ethylene‐2‐mercaptosuccinate) using differential scanning calorimetry (DSC), rheology, and Fourier transform infrared (FTIR) spectroscopy. The thiol‐containing resin offers much promise as a bioabsorbable polymer in medical field and as a reusable thermoset in sustainable applications. Although curing between thiol groups has been investigated in solutions, studies of neat materials without solvent are rare. Here, the evolution of glass transition temperature (T_g), complex shear modulus (G*), gelation, and chemical structure are monitored as a function of isothermal curing time and temperature. Both T_g and G* increase with curing, indicating the formation of polymer networks. The conversion of the cure is determined from the DiBenedetto equation and is found to follow a second‐order plus second‐order autocatalytic reaction model. Importantly, the intensity of the S–H bond absorption decreases with the extent of curing, which confirms the curing mechanism, i.e., disulfide formation between the thiol groups. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43205.     

The contributions of “minimum primary emissions” and “new particle formation enhancements” to the particle number concentration in urban air

In an urban site affected by fresh vehicle exhaust emissions, the ambient air number concentrations of particles coarser than 3 nm (N) was split into two components, N=N1+N2. This was done using a method based on the high correlation between black-carbon (BC) and number (N) concentrations which is typically observed in ambient air and is the result of vehicle exhaust emissions. The component N1 accounts for “those aerosol components directly emitted in the particle phase” and “those components nucleating immediately after emission”. The component N2 accounts for the new particle formation enhancements during the “dilution and cooling of the vehicle exhaust” and is also influenced by “in situ new particle formation in ambient air”. The contribution of N1 to N exhibits a maximum of 55% during the morning rush hours (07:00–08:00). The contribution of N2 to N exhibits a daily evolution with a broad maximum during daylight (as solar radiation intensity), while for about 7 h (11:00–17:00) the N2 contribution to N is about 70%. During some “afternoon N2 events”, N2 contributions exceeded 90%. Enhancements in the new particle formation processes may increase the N/BC concentrations ratio in one order of magnitude, from 4.82×10⁶ particles/ng BC to 47×10⁶ particles/ng BC and during some events up to 97×10⁶ particles/ng BC. The results show evidence of the high potential of the vehicle exhausts and of the urban atmosphere to trigger new particle formation if the ambient air conditions are favourable. The method used in this study is useful in assessing future changes in the number to BC relationship due to forthcoming regulations in the vehicle exhaust emissions.     

The effect of “skin-core” morphology on the heat-deflection temperature of polypropylene

The relationship between solid-state morphology and heat-deflection temperature (HDT) of nucleated polypropylenes was studied. Using optical microscopy to characterize the morphology and DMTA to determine the temperature dependence of the tensile modulus, a composite model was adapted to estimate the HDT. Both compression-molded films and injection-molded HDT bars were investigated. Compression-molded films were isotropic except for a thin skin, and the temperature dependence of the tensile modulus was very similar for all compression-molded films regardless of the nucleating agent. Results on isotropic specimens could not account for the higher ASTM HDT of nucleated samples. Injection-molded HDT bars exhibited an anisotropic gradient in both the morphology and the temperature-dependent modulus. A composite model was developed to estimate the HDT. The model successfully predicted the ASTM HDT values relatives to the HDT of unnucleated polypropylene. The increase in HDT was caused by the increased retention of melt orientation, due, in turn, to the higher crystallization temperature of the nucleated samples. © 1996 John Wiley & Sons, Inc.     

Reply to Comment on “Linking Cure Process to Adhesive Bulk Strength by Differential Thermal Analysis”

A Comment published in this issue and authored by B. C. Ennis refers extensively to one of our earlier papers entitled “Linking Cure Process to Adhesive Bulk Strength by Differential Thermal Analysis.” We are delighted to see that our work can capture the attention of scientists working in this area and stimulate them to write lengthy reviews. At the same time, however, we feel that this particular note, in various discussions, misinterprets our paper, and does not seem to contribute any new or substantial scientific information to the literature.     

The role of pore structure in the catalytic behavior of “unaged” and “aged” silica-alumina catalysts

This is a review of research concerning the role played by the porous structure of silica-alumina catalysts on the evolution of organic catalytic processes. A strong effect of the geometrical shape of the pores on catalytic activity and selectivity has been evidenced. The experimental results have also been interpreted by means of a simplified mathematical model, able to relate selectivity for a reaction of the type A → B → C to the geometrical features of macro-microporous catalyst pellets, or granules. The theoretical results are in qualitatively satisfactory agreement with the experimental data.     

Efficient synthesis of zwitterionic sulfobetaine group functional polyurethanes via “click” reaction

A novel polyurethane material containing zwitterionic sulfobetaine groups has been synthesized using the copper‐catalyzed 1,3‐dipolar cycloaddition (azide‐alkyne click chemistry). A standard two‐step polyaddition method was used to produce the well‐defined polyurethane based on polycarbonatediol (PCDL) with alkyne groups. These polyurethanes containing alkyne units were then efficiently clicked using 3‐((2‐azidoethyl)dimethylammonio)propane‐1‐sulfonate (DMPS‐N₃). The novel PU material was characterized by ¹H NMR, Fourier transform infrared (FTIR) spectrometer, gel permeation chromatography (GPC), elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). This facile “click” reaction provides a useful tool for the development of novel functional polyurethanes for biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Flame retardancy of hollow glass microsphere/rigid polyurethane foams in the presence of expandable graphite

Rigid polyurethane foams (RPUF) filled with various loadings of expandable graphite (EG) or/and hollow glass microspheres (HGM) were prepared by cast molding. The flame retardant properties of these composites were investigated by limiting oxygen index (LOI), horizontal and vertical burning tests. The composite with 10 wt % HGM and 20 wt % EG had the best flame retardant properties, and its LOI value reached 30 vol %. The addition of an appropriate loading of HGM improved the compressive strength and modulus of RPUF and EG/RPUF. When the HGM content arrived at 10 wt %, the compressive strength and modulus of the composites reached the maximum value. The dynamical mechanical analysis (DMA) showed that the addition of EG and HGM made the glass transition temperature shift to a higher temperature, and 10 wt % EG and 10 wt % HGM filled RPUF had the highest storage modulus. The scanning electronic microscope (SEM) observation indicates that the additives led to the decrease in the cell size. In addition, the flame retardant mechanism, the thermal properties, the burned surfaces and the interface surfaces were elucidated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Flow of polymer melts in a disc-type extruder and in rotational devices of the “cone-plate” and “plate-plate” type

The flow pattern of a polyethylene melt in the working gap of a disc-type extruder has been visualized. It is shown that there is complex circulating flow in the working gap of the extruder. The flow lines are spirals of Archimedes. An investigation into the qualitative picture of the flow of a polyethylene melt in rotational devices of the “plate-plate” and “cone-plate” type showed that in such devices a complex circulating flow is also realized and the flow lines are spirals of Archimedes.     

Direct formation of “artificial wool” nanofiber via two‐spinneret electrospinning

To reproduce the excellent characteristics of natural fibers like wool and proteins, a novel two‐spinneret electrospinning technology was demonstrated in this communication, which can generate three‐dimensional self‐crimp fibers of HSPET/PTT, HSPET/PAN and PU/PAN directly. In the apparatus, two spinnerets were used to prevent gel formation or precipitation of the polymer, and the voltages of opposite polarities were applied to the spinnerets respectively. And the elecctrospun fibers morphology was observed by using scanning electron microscopy (SEM). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Some new operational modes and parameters of stress relaxation for the viscoelastic characterization of solid polymers. II. The “vertical‐shift” mode and intrinsic “time–strain clock”

As in part I of this study, in the same manner in the present part II as well, by the same modus operandi way, an attempt was made to introduce, by means of a given operational mode, some further practical parameters for a “by‐eye” but well‐proven experimental viscoelastic characterization of a polymeric solid. Thus, through consideration of the peculiar vertical shift behavior of the apparent modulus (?) of isotactic polypropylene (iPP) and based on the KWW model, it is shown that, in an empirical and a formalistic sense, a relevant effective or equivalent (single) characteristic relaxation time can be introduced which can give some new interpretations for the linear and nonlinear viscoelastic behavior of a polymeric material, as that of a “time–strain clock,” which, as an intrinsic function, is responsable for a functional time–strain shift of the relaxation time and, at the same time, for a shift toward to a more linear or to a more nonlinear behavior. In the above context of attempts, another functional relationship was shown, the so‐called spectral shift function and its corresponding parameter of nonlinearity strength, through which some further interpretations and characterizations connected with the existence of the permanent internal stress could be made. Finally, the introduction of the so‐called spectral isostrains and their corresponding “spectral inversion point” complete the “set” of the operative parameters proposed for the above‐mentioned purpose. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 138–148, 2003     

Effect of “glutaraldehyde” functionality on network formation in poly(vinyl alcohol) membranes

The use of higher‐functionality oligomers of glutaraldehyde on network formation was investigated and compared with glutaraldehyde monomer in step‐growth reactions. The effect of using such oligomers in network formation depends on the stoichiometry, which alters either the branching or both the branching and crosslinking of the network. This was demonstrated in the properties of poly(vinyl alcohol) (PVA) networks crosslinked with glutaraldehyde using cryogenic scanning electron microscopy, water swelling studies, and protein transfer across membranes. General guidelines were given for the proper use of glutaraldehyde solutions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 780–792, 2005     

Comment on “Linking Cure Process to Adhesive Bulk Strength by Differential Thermal Analysis” J. Adhesion, 25, 185(1988)

Thermal analysis (TA) is practically indispensable to the study and characterisation of modern structural adhesives, particularly those based on epoxies. Because a recent paper in this journal-“Linking Cure Process to Adhesive Bulk Strength by Differential Thermal Analysis” by Jozavi and Sancaktar¹-advocates TA to those familiar with aspects of adhesion other than analysis and chemistry of adhesives, it is more open to comment than is usual.     

Interrogation of “surface,” “skin,” and “core” orientation in thermotropic liquid‐crystalline copolyester moldings by near‐edge X‐ray absorption fine structure and wide‐angle X‐ray scattering

Injection molding thermotropic liquid‐crystalline polymers (TLCPs) usually results in the fabrication of molded articles that possess complex states of orientation that vary greatly as a function of thickness. “Skin‐core” morphologies are often observed in TLCP moldings. Given that both “core” and “skin” orientation states may often differ both in magnitude and direction, deconvolution of these complex orientation states requires a method to separately characterize molecular orientation in the surface region. A combination of two‐dimensional wide‐angle X‐ray scattering (WAXS) in transmission and near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy is used to probe the molecular orientation in injection molded plaques fabricated from a 4,4′‐dihydroxy‐α‐methylstilbene (DHαMS)‐based thermotropic liquid crystalline copolyester. Partial electron yield (PEY) mode NEXAFS is a noninvasive ex situ characterization tool with exquisite surface sensitivity that samples to a depth of 2 nm. The effects of plaque geometry and injection molding processing conditions on surface orientation in the regions on‐ and off‐ axis to the centerline of injection molded plaques are presented and discussed. Quantitative comparisons are made between orientation parameters obtained by NEXAFS and those from 2D WAXS in transmission, which are dominated by the microstructure in the skin and core regions. Some qualitative comparisons are also made with 2D WAXS results from the literature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007