Visualization of hydrolysis in polylactide using near‐infrared hyperspectral imaging and chemometrics

The hydrolysis of polylactide (PLA) occurs during melt processing, leading to product defects in, for example, appearance and mechanical properties. Hydrolyzed PLA products, whose mechanical properties were deteriorated, must be detected during processing to ensure the quality control of PLA products. In this study, near‐infrared (NIR) hyperspectral imaging was applied for evaluating the extent of hydrolysis. NIR spectra in the wavelength range from 1200 to 1600 nm were changed by (1) hydrolysis induced by molding and (2) crystallization induced by annealing. The changes in the NIR spectra mediated by these two factors were distinctly different but overlapping, leading to difficulty in evaluating PLA at only a single wavelength. Partial least squares regression was introduced for detecting the hydrolyzed PLA. NIR imaging combined with the constructed partial least square models clearly visualized the differences in the extent of hydrolysis in hydrolyzed PLA under varying degrees of crystallization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45898.     

Replication of sub‐micron features using amorphous thermoplastics

A comprehensive experimental study was carried out to replicate sub‐micron features using the injection molding technique. For the experiments, five different plastic materials were selected according to their flow properties. The materials were polycarbonate (PC), styrene‐butadiene block copolymer (SBS), impact modified poly(methyl methacrylate), methyl methacrylate‐acrylonitrile‐butadiene‐styrene polymer (MABS), and cyclic olefin copolymer (COC). Nanofeatures down to 200‐nm line width and with aspect ratios (aspect ratio = depth/width) of 1:1 could be replicated. In all selected materials, the greatest differences between the materials emerged when the aspect ratio increased to 2:1. The most favorable results were obtained with the use of high flow polycarbonate as the molding material. The best replication results were achieved when melt and mold temperatures were higher than normal values.     

Lasting high surface energy co‐polyester ionomer and its application in laminated tin‐free steel

A lasting high surface energy co‐polyester poly[ethylene terephthalate‐co‐ethylene isophthalate sodiosulfonate‐co‐poly(ethylene glycol)] polyester (PEPST) was synthesized and applied in laminated tin‐free steel (TFS). The structures and properties of the co‐polyester were characterized by nuclear magnetic spectra (¹H‐NMR), thermogravimetry, differential scanning calorimetry, polarized optical microscopy, and surface energy tests. Meanwhile, the peel strength and corrosion resistance of the co‐polyester film were also measured. The results confirm that an improvement in the lamination temperature leads to PEPST film peel strength increases, and crystalline and corrosion resistance decrease. Based on the purpose of reducing a detrimental effect on corrosion resistance, a reasonable lamination temperature was determined. Scanning electron microscope and energy dispersive X‐ray analysis prove the interface combination morphology of laminated TFS. Anticorrosion property analysis shows PEPST film has good anticorrosion performance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45174.     

Epoxy curing reaction studied by using two‐dimensional correlation infrared and near‐infrared spectroscopy

The isothermal curing process of bisphenol A epoxy resin with polyamine reagent (1,6‐diaminohexane) was monitored in situ by using temperature‐controlled Fourier‐transform infrared (FTIR) and Fourier‐transform near infrared (FTNIR) spectroscopy to elucidate the relative changes in functional groups during the curing reaction. It was shown that generalized two‐dimensional correlation spectroscopy can provide new information about the mechanisms and kinetics of the curing process, and the band assignments for complex NIR spectrum associated with this system. The sequential order of relative changes in functional groups during the curing process was examined by generalized 2D correlation spectroscopy and NIR‐IR hetero‐correlation spectroscopy, and the details of the complex epoxy curing reaction involving both primary and secondary amino group were revealed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhancement of petroleum coke thermal reactivity using Oxy‐cracking technique

Petroleum coke (petcoke) is a challenging fuel in terms of its complexity, high sulphur and nitrogen content, low volatile content, and undesirable emissions of SOx and NOx when used for power generation. To overcome these challenges, the oxy‐cracking process was recently proposed to convert the petcoke into a clean combustion fuel by reducing its sulphur and nitrogen contents, and consequently increasing its reactivity and combustibility. This work aimed to study the heating values and thermo‐oxidative behaviour of the oxy‐cracked petcoke, virgin petcoke, and their blends using thermogravimetric analysis (TGA). The results showed that the oxy‐cracked petcoke is oxidized at a temperature of 475 °C, which is easier and faster than the virgin petcoke, which is usually oxidized at around 540 °C. The heating value of the oxy‐cracked petcoke was not impacted and maintained constant ~30 MJ/kg, which is relatively similar to the virgin petcoke. The nitrogen and sulphur content in the oxy‐cracked petcoke is much lower than that of virgin petcoke. A significant improvement in the combustion performance parameters of the oxy‐cracked petcoke and their blends with virgin petcoke was achieved. For instance, the ignition temperature of the proposed fuel is reduced to 13 % compared to the virgin petcoke, which led to increasing the ignition index by two‐folds. Therefore, this approach might help in improving the thermal efficiency of petcoke by using oxy‐cracked products as an initiator in the combustion process.     

Improvement in the bonding strength of laminated composites by using air‐textured core‐and‐effect glass yarns

Delamination is the most common failure mode in laminated composites due to the reduced strength in the through‐the‐thickness direction. Air‐jet texturing was used to produce bulk and loops in the yarn, which provides more surface contact between the fibers and the resin. The development of core‐and‐effect textured glass yarns and the effect of texturing parameters were presented in the previous article. This article describes the effect of texturing on the mechanical properties including tensile properties, flexure properties, interlaminar shear strength (ILSS) and fracture toughness (Mode I) of glass laminated composites. The composites of plain and twill weave fabrics were developed from both the textured and nontextured yarns. It was observed that the tensile properties decreased and the flexure properties remained unchanged after texturing. However, significant improvement was observed in ILSS and the Mode I fracture toughness of the composites after texturing. The bulkier, loopy structure of the textured yarn provided more surface contact between the fiber and the resin and significantly improved the bonding strength. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Study nonlinear vibration of cross‐ply laminated plates using scale models

This article describes the establishment of necessary similarity conditions for geometrically nonlinear vibrations of thin cross‐ply laminated plates. The Von‐karman's strain‐displacement relations have been employed to model structural nonlinearity of the system. The Galerkin procedure is used to reduce the nonlinear partial differential equations to a nonlinearly second‐order ordinary differential equation. An analytical investigation based on the direct use of the governing equations of the systems is undertaken to derive the necessary scaling laws and similarity conditions. In this study, a set of scaling laws are introduced that can predict the nonlinear free vibration frequency of the prototypes by projecting the frequency of the model, accurately. The effects of distorted models with relaxations in the number of plies, stacking sequence, and different vibration amplitudes are studied. The results presented herein indicate that models with different relaxations can predict the nonlinear vibration frequency of prototypes with good accuracy. POLYM. COMPOS., 35:752–758, 2014. © 2013 Society of Plastics Engineers     

Shrinkage cracking of styrene butadiene polymeric emulsion‐modified concrete using rapid‐hardening cement

This study was performed to resolve the problem of cracks caused by the rapid hydration heat produced during the early setting stages of rapid‐hardening cement. To address the hydration heat of rapid‐hardening cement, we prepared a modified rapid‐hardening cement using calcium sulfoaluminate clinker combined with a styrene butadiene (SB) polymer. The performance of SB polymeric emulsion‐modified concrete made from modified rapid‐hardening cement was assessed by determining shrinkage (change in length, and plastic and autogenous shrinkage). The modified rapid‐hardening cement in combination with SB polymeric emulsion effectively reduced cracking. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dehydration of THF‐water mixtures using zeolite‐incorporated polymeric membranes

Using a solution technique, polymeric composite membranes were prepared by the incorporation of NaY zeolite into chitosan. The resulting membranes were tested for pervaporation separation of water–tetrahydrofuran mixtures in a temperature range of 30–50°C. The effect of membrane swelling on the separation performance was studied by varying the water composition in the feed from 5 to 30 mass %. Pervaporation data demonstrated that both flux and selectivity increased simultaneously with increasing zeolite content in the membrane. This was explained on the basis of enhancement of hydrophilicity, selective adsorption, and establishment of molecular sieving action. It was found that both total flux and flux of water are close to each other, suggesting that the developed membranes are highly selective toward water. The membrane containing the highest loading of zeolite exhibited the highest separation selectivity of 2140 with a substantial water flux of 16.88 × 10^?2 kg/(m² h) at 30°C for 5 mass % of water in the feed. From the temperature dependency of diffusion and permeation data, the Arrhenius activation parameters were estimated. A significant difference was noticed between E_pw and E_pTHF, E_Dw and E_DTHF values, signifying that membranes developed with higher loading of zeolite exhibited remarkable separation selectivity toward water. The E_p and E_D values ranged between 11.69 and 21.23, and 11.21 and 20.72 kJ/mol, respectively. All the membranes exhibited positive ΔH_s values, suggesting that the heat of sorption is still dominated by Henry's mode of sorption. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ethanol purification using polyamide‐carbon nanotube composite membranes

This work presents synthesis and characterization of polyamide‐carbon nanotube (CNT) composite membranes for purification of ethanol. The solution‐casting method was applied for preparation of nanocomposite membranes. The nanocomposite membranes were characterized using scanning electron microscopy to ensure the fine dispersion of nanoparticles in polymer matrix. The effect of CNT loading on membrane performance was investigated. The separation performance of synthesized membranes was evaluated in separation of ethanol from ethanol/water mixture using pervaporation. Effect of feed temperature and feed concentration on separation of ethanol was investigated. The results showed that increasing temperature increases flux of ethanol through the membrane, but decreases separation factor. The results also confirmed that the best separation performance can be obtained at CNT loading of 0.5 wt%. Furthermore, a mathematical model was developed to simulate the separation process. The model was based on solving the continuity equation for ethanol in the feed side and membrane. The simulation results were compared with the experimental data and were in good agreement. POLYM. ENG. SCI., 54:961–968, 2014. © 2013 Society of Plastics Engineers     

In‐line and in situ monitoring of semi‐batch emulsion copolymerizations using near‐infrared spectroscopy

This article shows that near‐infrared spectroscopy (NIRS) can be used efficiently for the simultaneous in‐line and in situ monitoring of monomer (methyl methacrylate, MMA, and butyl acrylate, BuA) and polymer concentrations in the reaction medium during seeded semibatch emulsion copolymerizations. A series of actual reaction experiments was planned to allow the proper obtainment and selection of calibrating samples. Partial least squares (PLS) was used to build three independent calibration equations in the range of 1100–1900 nm, which were used to successfully monitor some disturbed reactions in‐line. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2670–2682, 2002     

A multidimensional model for simulating vegetation fire spread using a porous media sub‐model

An unsteady multidimensional model is reported with the objective of studying wildfires. The present work aims to validate the modelling assumptions against reported experiments of a lab‐scale line fire through a vegetation fuel bed. In this model the fuel bed is assumed to be a porous medium with a randomly orientated discrete solid matrix. A set of time dependent equations of mass, momentum, species and energy are obtained for the gas and solid phase. The hydrodynamic turbulence model is based on a k‐ϵ eddy viscosity model extended to buoyancy effects and to flow through vegetation. The effects of devolatilization of cellulose material, combustion of gas and heat transfer between gas and solid matrix are simulated. The radiative heat transfer equation in the fuel bed is solved using the discrete ordinates method developed for a porous medium. Soot formation and its impact on radiation are accounted for. The solution is performed numerically by a finite volume method. This model has been applied for the prediction of fire spreading through a litter of pine needles. The predicted rates of fire spread and fuel mass consumption for two cross wind velocities are presented and compared with measurements showing a satisfactory agreement. Copyright © 2000 John Wiley & Sons, Ltd.     

Surface‐enhanced infrared absorption (SEIRA) and its use in analysis of plasma‐modified surface

A thin film (<10 nm) of fine metal clusters (silver or gold) with an island form was deposited on a CaF₂ salt plate by slow vacuum thermal evaporation. Molecular layers of stearic acid, p‐nitrobenzoic acid, and m‐nitrobenzoic acid (p‐ and m‐NBA) were prepared on the thin metal film. The system was then examined by infrared spectroscopy attenuated total reflection (IR–ATR). It was found that through the interaction between the metal islands film and the electric field of the incident IR beam the infrared absorption of the molecule layers adsorbed on the islands was enhanced by a factor of 17. The surface‐enhanced IR absorption (SEIRA) also presents a selection rule. This method was then used to study the surface modification with O₂ and NH₃ plasma and the plasma polymerization of allylamine. This is the first time that SEIRA has been used in plasma investigations. A model is provided to explain the interactions between the metal islands film and the electric field of the incident IR beam in the SEIRA. The in‐plasma‐built functional groups can be further used to graft biofunctional molecules for the biomedical industry. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1231–1237, 1999     

Characterization of mechanically reinforced electrospun dextrin‐polyethylene oxide sub‐microfiber mats

Dextrin and dextrin‐polyethylene oxide (DEX/PEO) fibers in the submicron range were produced by electrospinning of single and blend polymer solutions. The morphology, intermolecular interactions, and mechanical properties of dextrin microfibers with and without PEO were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray diffraction, nuclear magnetic resonance spectroscopy, and uniaxial tensile testing. Spectroscopic results confirmed hydrogen bond formation, evidencing dextrin as a molecular entanglement source for fiber mechanical reinforcement. The uniaxial tensile tests demonstrated a synergistic mechanical reinforcement effect that varied with blend composition. Equal weight ratio blends supported a maximum tensile strength with a high elastic modulus and demonstrated to be more elastic and resistant to breaking, even than pristine PEO fibers. Moreover, elastic moduli of blend fiber mats were found to lie within the value range for human skin, thus providing the DEX/PEO meshes with potential applicability as skin tissue scaffolds. This synthesis approach proved the feasible and inexpensive fabrication process of natural‐synthetic polymer hybrid fibers that combine the biocompatibility, biodegradability, and encapsulating capability of dextrin with the mechanical strength and flexibility of PEO for the development of scaffolds for tissue engineering and topical drug delivery applications in skin wound healing. POLYM. ENG. SCI., 59:1778–1786, 2019. © 2019 Society of Plastics Engineers     

Characterization of vegetable oils‐alumina membranes interactions by diffuse reflectance Fourier transform infrared spectroscopy

Adsorption of vegetable oil components, either as pure molecules or as mixtures, on alumina membranes was investigated by diffuse reflectance Fourier transform infrared spectroscopy. All tested compounds displayed very similar spectra. Triolein and diolein physically adsorb onto alumina by hydrogen bonding with the carbonyl groups of the carboxylic ester and surface hydroxyls. Monolein most likely interacts with glycerol hydroxyls, while phospholipids appear to adsorb either by the ester carbonyl or charged phosphate group. Due to the catalytic properties of alumina some hydrolysis takes place during treatments. The resulting oleic acid, most likely chemisorbs by ionic interactions with the carboxylic C=O bond of the alumina. The fact that no change in the symmetric and asymmetric CH₂ stretches is noticed in comparison with the free (unbound) form indicates that the molecules are not parallel, but at an angle to the surface. When alumina comes into contact with increasing amounts of crude vegetable oils a broadening of the band at 3280 cm^‐1 indicates an increasing adsorption of molecules with free hydroxyls, such as mono‐ and di‐acylglycerols or phospholipids. Among all oil components, sodium oleate seems to adsorb preferentially to alumina. However, a subsequent adsorption of a lipidic monolayer at the membrane surface or even inside the pores, is not consistent with the drastic flux reduction observed in previous studies during microfiltration, and could only initiate formation or/and deposition of macromolecular structures inside membrane pores.     

Solubilities of sub‐ and supercritical carbon dioxide in polyester resins

In supercritical carbon dioxide (CO₂) assisted polymer processes the solubility of CO₂ in a polymer plays a vital role. The higher the amount of CO₂ dissolved in a polymer the higher is the viscosity reduction of the polymer. Solubilities of CO₂ in polyester resins based on propoxylated bisphenol (PPB) and ethoxylated bisphenol (PEB) have been measured using a magnetic suspension balance at temperatures ranging from 333 to 420 K and pressures up to 30 MPa. An optical cell has been used to independently determine the swelling of the polymers, which has been incorporated in the buoyancy correction. In both polyester resins, the solubility of CO₂ increases with increasing pressure and decreasing temperature as a result of variations in CO₂ density. The experimental solubility has been correlated to the Sanchez–Lacombe equation of state. POLYM. ENG. SCI. 46:643–649, 2006. © 2006 Society of Plastics Engineers     

Computational fluid dynamics‐based steam cracking furnace optimization using feedstock flow distribution

Nonuniform temperature fields in steam cracking furnaces caused by geometry factors such as burner positions, shadow effects, and asymmetry of the reactor coil layout are detrimental for product yields and run lengths. The techniques of adjusting burner firing (zone firing) and feedstock mass flow rate (pass balancing) have been practiced industrially to mitigate these effects but could only reduce the nonuniformities between the so‐called modules (a group of many coils). An extension of the pass balancing methodology is presented to further minimize the intra‐module nonuniformities, that is, variation between the coils within a module, in floor fired furnaces. Coupled furnace‐reactor computational fluid dynamics‐based simulations of an industrial ultraselective conversion (USC) furnace were performed to evaluate four different feedstock flow distribution schemes, realizing equal values for coil outlet temperature, propene/ethene mass ratio, maximum coking rate and maximum tube metal temperature (TMT), respectively, over all the reactor coils. It is shown that feedstock flow distribution creates a larger operating window and extends the run length. Out of the four cases, the coking rate as criterion leads to the highest yearly production capacity for ethene and propene. Uniform maximum coking rates boost the annual production capacity of the USC furnace with a nameplate ethene capacity of 130 10³ metric tons per year with 1000 metric tons for ethene and 730 metric tons for propene. For industrial application, achieving uniform maximum TMT is more practical due to its measurability by advanced laser‐based techniques. Most steam cracking furnaces can be retrofitted by optimizing the dimensions of venturi nozzles that regulate the feedstock flow to the coils. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3199–3213, 2017     

Analysis of a crease‐resisting finish on linen fabrics using Fourier transform infrared spectroscopy and visible and near‐infrared spectroscopy

A wide range of chemical reagents are capable of producing a satisfactory crease‐resisting finish for cellulosic fabrics and are currently available on the market. However, these agents do not work as efficiently on linen relative to cotton or rayon. Untreated linen controls and samples treated with a N‐methylol reagent were investigated for physical and chemical changes, and an attempt was made to quantify the crosslinking bonds formed and assess other changes in the treated fabrics using Fourier transform infrared spectroscopy (FTIR) and visible and near‐infrared spectroscopy (NIR). The results were compared with nitrogen analysis data, crease‐recovery angle measurements, and abrasion‐resistance tests in an attempt to assess the effectiveness of the treatment relative to the responses of the instrumental techniques. This study shows correlations between the visible and NIR and FTIR spectra and the crease‐recovery angle and abrasion resistance. The study also indicates that FTIR may be useful in assessing the crosslinking bonding changes associated with the dimethylol urea treatment of linen to achieve improved crease recovery. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1886–1896, 2001     

Pervaporation of methanol/dimethyl carbonate using SiO2 membranes with nano‐tuned pore sizes and surface chemistry

Porous silica membranes with different pore sizes (average pore size: 0.3–1.2 nm) and surface chemistry were prepared from SiO₂, steam‐treated SiO₂, SiO₂? ZrO₂, and SiO₂? TiO₂ by sol‐gel processing, and were applied to the pervaporation (PV) separation of methanol (MeOH) /dimethyl carbonate (DMC) mixtures at 50°C. Although SiO₂? ZrO₂ membranes demonstrated a separation factor of <10, the SiO₂ porous membranes had an increased separation factor from 10–160. Silica membranes with an average pore size of 0.3 nm showed the highest permselectivity of methanol with a separation factor of 140 and a methanol flux of 180 mol/(m²h) for MeOH 50 mol% at 50°C. To characterize the surface property of SiO₂ membranes, SiO₂ powdered samples were used for an adsorption experiment of vapor (MeOH, DMC) in single and mixed systems, revealing increased MeOH selective adsorption for SiO₂ powders with hydrophilic and small pores, which was consistent with PV performance. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Production of bio‐crude from forestry waste by hydro‐liquefaction in sub‐/super‐critical methanol

Hydro‐liquefaction of a woody biomass (birch powder) in sub‐/super‐critical methanol without and with catalysts was investigated with an autoclave reactor at temperatures of 473–673 K and an initial pressure of hydrogen varying from 2.0 to 10.0 MPa. The liquid products were separated into water soluble oil and heavy oil (as bio‐crude) by extraction with water and acetone. Without catalyst, the yields of heavy oil and water soluble oil were in the ranges of 2.4–25.5 wt % and 1.2–17.0 wt %, respectively, depending strongly on reaction temperature, reaction time, and initial pressure of hydrogen. The optimum temperature for the production of heavy oil and water soluble oil was found to be at around 623 K, whereas a longer residence time and a lower initial H₂ pressure were found to be favorite conditions for the oil production. Addition of a basic catalyst, such as NaOH, K₂CO₃, and Rb₂CO₃, could significantly promote biomass conversion and increase yields of oily products in the treatments at temperatures less than 573 K. The yield of heavy oil attained about 30 wt % for the liquefaction operation in the presence of 5 wt % Rb₂CO₃ at 573 K and 2 MPa of H₂ for 60 min. The obtained heavy oil products consisted of a high concentration of phenol derivatives, esters, and benzene derivatives, and they also contained a higher concentration of carbon, a much lower concentration of oxygen, and a significantly increased heating value (>30 MJ/kg) when compared with the raw woody biomass. © 2009 American Institute of Chemical Engineers AIChE J, 2009