Modeling ultrafiltration of gelatin–water suspension by computational fluid dynamics

In this paper, principles of computational fluid dynamics (CFD) are used to study ultrafiltration (UF) process. Model has been developed by a new technique in which permeation of solvent molecules is introduced to system via appropriate sink terms in conservation equations for computational domain. Experimental data and fittings are applied in model development. Model results have been compared for two and three-dimensional geometries. Finally a time step and mesh size independent model has been developed in two dimensions for modeling the permeation flux vs. filtration time in a gelatin–water UF system. Final model is able to predict steady-state permeation flux with relative error less than 2%. Accuracy of calculation is investigated through the comparison between mass imbalance and sum of local fluxes. Modeling results show that increase in cross flow velocity (CFV) and trans-membrane pressure (TMP) leads to increase in permeation flux but decrease in solute concentration and rejection of solute particles from membrane surface makes permeation flux increase.     

Recycling by injection and chrome plating of acrylonitrile–butadiene–styrene parts pickled in hydrochloric and nitric acids

Chrome-plated acrylonitrile–butadiene–styrene ( ABS) parts with defects in the metal layer were submitted to pickling with hydrochloric and nitric acids and recycled by injection in different proportions with neat ABS. For comparison, samples with neat ABS (ABSn) and ABS submitted to pickling (ABSp) were also injected. The influence of the pickled material on the samples properties was evaluated by chemical, thermal, and mechanical analysis. The injected samples were chrome by conventional process and evaluated by visual inspection, adhesion test, resistance to corrosion, and accelerated aging test, to evaluate the quality of the chrome finish. A gradual darkening of samples and formation of carbonyl groups with the increase in the pickled ABS concentration and little influence on the melt flow index were observed. The samples exhibited one thermal degradation stage similar to ABSn. The increase in the pickled ABS percentage caused a slight increase in glass-transition temperature of polybutadiene phase, and did not influence the tensile properties and hardness of samples, but decreased the impact resistance. After chrome plating, all samples were approved for visual inspection and metal layer adhesion test. Only the sample injected with pickled ABS was reproved in corrosion test, due to the oxidation of the chrome layer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48372.     

Mechanical and thermal properties of copoly(styrene/acrylonitrile) compatibilised Nylon–thermoplastic elastomer blends

Abstract

The effects of blend compositions on the mechanical and thermal properties of polymer blends containing Nylon 66 and a thermoplastic elastomer (TPE), Santoprene^®, have been studied. A 5% styrene/acrylonitrile copolymer was added to neat Nylon, TPE, and their blends. The blends were injection moulded and the tensile and impact properties were investigated. The morphology and thermal properties of the blends were observed using scanning electron microscopy and differential scanning calorimetry.

The presence of double melting temperatures showed that the Nylon 66 and TPE are immiscible. However, blending produced a modification of mechanical and thermal properties. At TPE/Nylon ratios above 50 : 50 the tensile properties of TPE improved. In addition the impact properties of Nylon improved above the 50 : 50 ratio, i.e. in the TPE rich region. Both the melting temperature and crystallinity were depressed in the region of 50 : 50 blend composition. The presence of two phases, which is evidence of immiscibility of the blends, was confirmed by scanning electron microscopy.     

Study of the phase morphology and toughness in poly (vinyl chloride)/acrylonitrile–styrene-acrylic/styrene–butadiene–styrene ternary blends influenced by interfacial/surface tension

The effect of interfacial interaction on the phase morphology and toughness of poly (vinyl chloride) (PVC)/acrylonitrile–styrene-acrylic (ASA) terpolymer/styrene–butadiene–styrene (SBS) block copolymer ternary blends has been investigated. Water and diiodomethane liquids were used for static contact angle measurements to get surface tension and calculate interfacial tension. A dispersed phase morphology of ASA and SBS in the PVC matrix was predicted by the spreading coefficient theory, which was calculated through interfacial tensions between different polymer pairs. Extraction experiment and scanning electron microscopy were combined to verify this morphology. When the volume fraction of SBS was small, SBS was dispersed in the matrix as droplets and the strong PVC/styrene–acrylonitrile interfacial interaction made up for the poor interfacial adhesion between SBS and PVC. Herein, SBS showed an effective toughening effect on PVC/ASA blends. With the addition of 2.5- and 5-phr SBS, the blends had the highest impact strength of 88.75 kJ/m² at 23 °C and 9.98 kJ/m² at 0 °C, respectively. With the further increase of the SBS content, the diameter of the SBS drops increased largely and the poor interfacial adhesion between SBS and PVC played a leading role, resulting in a sharp decrease in toughness and a sharp ductile–brittle transition. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47721.     

Chemical modification of styrene–butadiene–styrene co-polymer by grafting of N-carbamyl maleamic acid

A styrene–butadiene–styrene (SBS) block co-polymer was functionalized using different amounts of N-carbamyl maleamic acid (NCMA) and benzoyl peroxide as initiator. NCMA, which is a bifunctional monomer, was synthesized in our laboratories. The concentration of NCMA used in the functionalization of SBS ranged from 0.5 to 3% (w/w) based on the co-polymer mass. Benzoyloxy radicals generated from the thermal decomposition of benzoyl peroxide initiated the grafting reaction. The concentration of the initiator was kept constant at 0.076% (w/w). FT-IR spectroscopy was used to determine the amount of NCMA effectively grafted onto the SBS. The maximum amount of monomer grafted was about 0.3% (w/w) when the SBS was modified with 1% (w/w) NCMA. The effect of grafting on the surface properties and the adhesion to polyurethane adhesive of the modified SBS were evaluated. Contact angle values were obtained using liquid droplets. When the concentration of the NCMA used in the grafting reaction was 1% (w/w), the contact angles with water on original and modified SBS were 95° and 77°, respectively. Adhesion properties were evaluated by standard peel tests employing a commercial polyurethane adhesive. The modified SBS having the largest amount of NCMA displayed a T-peel strength value 5-times higher than the corresponding value measured with the original SBS.     

Analysis and modeling of modified styrene–acrylonitrile/carboxylated acrylonitrile butadiene rubber nanocomposites filled with graphene and graphene oxide: Interfacial interaction and nonlinear elastoplastic behavior

Nonlinear elastoplastic behavior of the nanocomposites based on the styrene–acrylonitrile/carboxylated acrylonitrile butadiene rubber (SAN/XNBR) blend was investigated using experimental and theoretical analysis. Graphene, graphene oxide nanoparticles, and glycidyl methacrylate-grafted-XNBR (XNBR-g-GMA) as a compatibilizer were incorporated in the SAN/XNBR blends. In this regard, the focus of this study is on modeling of the stress–strain behavior of these nanocomposites, considering the effect of the interfacial interactions made by compatibilizer. For this purpose, field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) techniques were used to investigate the relationship between microstructure and mechanical properties of nanocomposites. In addition, FESEM and TEM images showed that the presence of a compatibilizer could influence the dispersion and localization of the nanoparticles. According to the tensile test results, the presence of the compatibilizer increased the mechanical properties of the nanocomposites, specifically elongation at break. Considering the nanocomposite containing compatibilizer and graphene oxide, the elongation at break increased about 570% compared with the nanocomposite without compatibilizer. Better dispersion of graphene oxide and the creation of chemical interaction among components in the presence of the XNBR-g-GMA compatibilizer could be the reasons for these improvements, as confirmed by TEM. The usage of the Bergstrom–Boyce model for analyzing the nonlinear elastoplastic behavior of the nanocomposites illustrated proper conformity with the experimental data in the elastic region. However, there are some deviations in the viscoplastic region, particularly close to the breaking elongation region.     

Swelling behaviours of styrene–isoprene–styrene triblock copolymers in supercritical methane

Styrene–isoprene–styrene triblock copolymers (SIS) are representative thermoplastic elastomers possessing both elastomeric and thermoplastic feature. SIS have been used in self-healing cement for natural gas wells, but the mechanism behind the application was not unravelled. We hypothesise such self-repairing function should be associated with the swelling of SIS in natural gas whose main component is methane. It was found that all the four SIS copolymers show similar swelling trend irrespective of their structure difference, and the swelling ratio increases as decreasing the polystyrene block content in SIS. These preliminary pioneering findings show the swelling behaviour of the rubbers displayed quite differently before and after supercritical point, and it is helpful for the further research about the swelling behaviour of rubber in natural gas wells.     

Structural parameter optimization for novel internal-loop iron–carbon micro-electrolysis reactors using computational fluid dynamics

It is generally recognized that internal-loop reactors are well-developed mass and heat-transfer multiphase flow reactors. However, the internal flow field in the internal-loop reactor is influenced by the structure parameter of the reactor, which has a great effect on the reaction efficiency. In this study, the computational fluid dynamics simulation method was used to determine the influence of reactor structure on flow field, and a volume-offluid model was employed to simulate the gas–liquid, two-phase flow of the internal-loop micro-electrolysis reactor. Hydrodynamic factors were optimized when the height-to-diameter ratio was 4:1, diameter ratio was9:1, draft-tube axial height was 90 mm. Three-dimensional simulations for the water distributor were carried out, and the results suggested that the optimal conditions are as follows: the number of water distribution pipes was four, and an inhomogeneous water distribution was used. According to the results of the simulation,the suitable structure can be used to achieve good fluid mechanical properties, such as the good liquid circulation velocity and gas holdup, which provides a good theoretical foundation for the application of the reactor.     

Styrene copolymerization using a metallocenic initiator. Homo- and copolymerization of styrene with isoprene through zirconocene–MAO initiating systems

The copolymerization of styrene with isoprene (Ip) has been tested using combined zirconocene–methylaluminoxane (MAO) initiating system. Both “half-sandwich” and real zirconium-based metallocenes were used. Regardless of the metallocene employed, conversion to copolymer was much influenced by the proportion of Ip in the initial feed. As the proportion of Ip is enriched, conversion to copolymer decreases substantially. Results of NMR and DSC analyses indicate that the products obtained were truly copolymers and not a mixture of both homopolymers. The studied zirconocene–MAO initiating system produces atactic polystyrene. A small amount of Ip in the initial feed substantially diminishes the conversion and at best traces of poly(isoprene) were detected in the homopolymerization of Ip with these initiating systems.     

Melting and crystallization behaviors of compatibilized poly(trimethylene terephthalate)/acrylonitrile–butadiene–styrene blends

The melting and crystallization behaviors of poly(trimethylene terephthalate) (PTT)/acrylonitrile–butadiene–styrene (ABS) blends were investigated with and without epoxy or styrene–butadiene–maleic anhydride copolymer (SBM) as a reactive compatibilizer. The existence of two separate composition-dependent glass-transition temperatures (T_g's) indicated that PTT was partially miscible with ABS over the entire composition range. The melting temperature of the PTT phase in the blends was also composition dependent and shifted to lower temperatures with increasing ABS content. Both the cold crystallization temperature and T_g of the PTT phase moved to higher temperatures in the presence of compatibilizers, which indicated their compatibilization effects on the blends. A crystallization exotherm of the PTT phase was noticed for all of the PTT/ABS blends. The crystallization behaviors were completely different at low and high ABS contents. When ABS was 0–50 wt %, the crystallization process of PTT shifted slightly to higher temperatures as the ABS content was increased. When ABS was 60 wt % or greater, PTT showed fractionated crystallization. The effects of both the epoxy and SBM compatibilizers on the crystallization of PTT were content dependent. At a lower contents of 1–3 wt % epoxy or 1 wt % SBM, the crystallization was retarded, whereas at a higher content of 5 wt %, the crystallization was accelerated. The crystallization kinetics were analyzed with a modified Avrami equation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of acrylonitrile–butadiene–styrene copolymer (ABS) on β-nucleation in β-nucleated polypropylene/ABS blends

β-PP/acrylonitrile–butadiene–styrene (ABS) blends were prepared with PP, ABS and a novel supported β-nucleating agent or β-PP and ABS. The effect of ABS on the β-nucleation of PP and crystallization and melting behavior of β-PP/ABS blends were investigated by differential scanning calorimeter, wide angle X-ray diffraction, and polarized light microscopy. Results suggested that addition of low content of ABS has no effect on the β-nucleation of PP and crystallization behavior, and melting characteristic of β-PP/ABS blends. However, the increasing content of ABS decreases the β-nucleation, crystallization temperatures, and spherulite size of PP in the blends. However, the blends with the β-PP content above 80?% were obtained at the content of ABS below 40?%.     

Computational fluid dynamics study of kaolin–water flow in a T-junction using a novel shear-thinning fluid model

A recently proposed shear-thinning fluid model that mimics the response of seemingly viscoplastic materials is evaluated in computational fluid dynamics simulations by studying the steady flow of a kaolin–water suspension in a 2D T-junction. The velocity profiles for the kaolin–water suspension are reported at the mid-length of the main channel and the root of the bifurcation (where recirculation is expected to appear). The velocity profiles of the proposed model are compared with those from conventional viscoplastic models (Bingham plastic model and the Herschel–Bulkley model) at low (=100) and high Reynolds number (=2000). The new model predicts a recirculation zone (at the inner edge of the bifurcation arm) that conventional models do not. The effect of the variation in the model parameters (α₁ and α₂) on velocity profiles at low (=100) and high Reynolds numbers (=2000) is also documented. These indicate the disappearance of the recirculation zone at low Reynolds number as α₁ (equivalently, viscosity) increases, whereas the recirculation zone persists even for higher values of α₁ at high Reynolds number. Further, at low Reynolds number, the skewing of maximum velocity towards the outer edge of the bifurcation arm disappears as α₂ increases, whereas the skewing persists even at the highest value of α₂ used at the high Reynolds number.     

Computational fluid dynamics for dense gas–solid fluidized beds: a multi-scale modeling strategy

Dense gas–particle flows are encountered in a variety of industrially important processes for large scale production of fuels, fertilizers and base chemicals. The scale-up of these processes is often problematic, which can be related to the intrinsic complexities of these flows which are unfortunately not yet fully understood despite significant efforts made in both academic and industrial research laboratories. In dense gas–particle flows both (effective) fluid–particle and (dissipative) particle–particle interactions need to be accounted for because these phenomena, to a large extent, govern the prevailing flow phenomena, i.e. the formation and evolution of heterogeneous structures. These structures have significant impact on the quality of the gas–solid contact and as a direct consequence thereof strongly affect the performance of the process.Due to the inherent complexity of dense gas-particles flows, we have adopted a multi-scale modeling approach in which both fluid–particle and particle–particle interactions can be properly accounted for. The idea is essentially that fundamental models, taking into account the relevant details of fluid–particle (lattice Boltzmann model (LBM)) and particle–particle (discrete particle model (DPM)) interactions, are used to develop closure laws to feed continuum models which can be used to compute the flow structures on a much larger (industrial) scale. Our multi-scale approach (see Fig. 1) involves the LBM, the DPM, the continuum model based on the kinetic theory of granular flow, and the discrete bubble model. In this paper we give an overview of the multi-scale modeling strategy, accompanied by illustrative computational results for bubble formation. In addition, areas which need substantial further attention will be highlighted.     

Chemical modification of styrene–butadiene–styrene (SBS) rubber by reactive grafting with maleic anhydride

A procedure to increase the adhesion of block styrene-butadiene-styrene (SBS) rubber consisting of the reactive grafting with maleic anhydride (MA) in the presence of an organic peroxide radical initiator is proposed. The influence of the reactive grafting on the surface properties of SBS has been studied with special emphasis on the improvement of the adhesion to polyurethane adhesive. The grafting of MA onto SBS was carried out in the presence of different concentrations of 2,5-dimethyl-2,5-di(tertbutyl peroxy) hexane (DBPH) as initiator to generate oxygen radicals by thermal decomposition, which induce the grafting reaction. The modification process was performed in the molten state using a Brabender mixer to premix the reactants and a hot press to initiate the functionalizing reaction. ATR-IR and XPS spectroscopies were employed to verify the grafting of MA on SBS. The changes in wettability on the modified SBS rubber were determined by contact angle measurements. Adhesion properties were evaluated from T-peel tests of SBS rubber/polyurethane adhesive joints. Reasonable extents of MA grafting on SBS were obtained (evidenced by the presence of a weak carbonyl vibration at 1700 cm^-1 in the ATR-IR spectra and by the carbon- oxygen band at a binding energy of 287.0 eV in the XPS spectra). The higher the DBPH amount, the higher the MA amount grafted onto the SBS surface. The maximum grafting level was obtained using 2 wt% MA. Grafted species seemed to be mainly concentrated on the surface of the SBS-molded sheets. The wettability of the modified rubber increased with respect to the original polymer, new carbon-oxygen moieties were created and the C/O ratio increased. A noticeable enhancement in peel strength values was observed, which was ascribed to the creation of interfacial interactions between the polyurethane and the SBS rubber surfaces.     

An investigation of vinyl–ester?styrene bulk copolymerization cure kinetics using Fourier transform infrared spectroscopy

A Fourier transform infrared (FTIR) spectroscopy technique was developed to investigate the effects of reaction temperature and reactant composition on the isothermal curing kinetics of commercial vinyl nester resins comprised of vinyl–ester monomer (dimethacrylate of diglycidyl ether of bisphenol A DGEBA) and styrene. This technique enables a more complete evaluation of the bulk copolymerization reaction of vinyl–ester styrene systems by monitoring the depletion of vinyl–ester and styrene double bonds independently. The results indicate that the rate of fractional conversion of styrene double bonds is initially less than that of vinyl–ester vinyl groups. However, styrene monomer continues to react after conversion of vinyl–ester double bonds has ceased. In addition, the overall extent of conversion was found to increase with increasing isothermal cure temperature, and it was observed that higher styrene concentration enhances final conversion of vinyl–ester double bonds and not styrene double bonds. Increasing styrene monomer concentration also resulted in lowering the apparent activation energy for the reaction of vinyl groups from both monomers as characterized by an empirical autocatalytic model used to fit the conversion results for styrene and vinyl–ester double bonds independently. The results of this work demonstrate that reaction temperature and resin composition significantly affect the cure behavior of vinyl–ester resins and provide insight into the development of the resulting network structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1572–1582, 2000     

Mechanism of particle formation in radical emulsion copolymerization of styrene with α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer

In the batch emulsion copolymerization of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer, carried out at macromonomer concentrations exceeding the critical micelle concentration (c_mc), particles are formed by a two-step coagulative nucleation mechanism. This mechanism leaves its mark on morphology of particle interface, rate of polymerization and on molecular weight distribution of the obtained polymer. AFM studies revealed that the interface of particles is composed of objects with dimensions close to dimensions of the primary particles. Compartmentalization of styrene in the macromonomer micelles leads to the higher initial rate of styrene conversion than in the similar macromonomer free homopolymerization of styrene. The initial polymerization in the monomer-swollen macromonomer micelles, similar to the microemulsion polymerization, is responsible for the formation of the highest molecular weight component. In the mature particles there are two different polymerization loci: the interfacial layer and the core. This leads to bimodal molecular weight distribution of the formed polymer.     

Effect of drying catalysts on the properties of thermal copolymers from conjugated linseed oil–styrene–divinylbenzene

The effect of addition of a varying concentration of a drying catalyst (cobalt salt as primary drier) and a combination of catalysts such as cobalt, zirconium (secondary drier) and calcium (auxiliary drier) in a fixed concentration (1%) to a 50:20:30 compositions of 87% conjugated linseed oil, styrene (ST), and divinylbenzene (DVB) has been studied by characterizing the resulting polymers from thermal polymerization with various techniques such as soxhlet extraction, ¹H NMR (¹H nuclear magnetic resonance) spectroscopy, dynamic mechanical analysis (DMA), mechanical and thermogravimetric analysis. The thermal polymerization is performed in the temperature range of 85–160 °C. By soxhlet extraction, it is observed that the polymers contain approximately 64–77% crosslinked materials and the crosslinked insoluble fraction increases with an increase in cobalt catalyst concentration. For fixed concentration (1%) of catalysts, the insoluble fraction from the soxhlet extraction is maximum for the cobalt–zirconium mixture and minimum for the cobalt–calcium mixture. The micro-composition of these polymers obtained from the ¹H NMR spectroscopy indicates that the crosslinked materials are composed of both soft oily and hard aromatic phases. The polymers with varying cobalt concentrations up to 0.6 wt% exhibit two separate glass transition temperatures, indicating the presence of two separate phases, one soft rubbery phase with sharp glass transition temperature of −50 °C and a hard brittle plastic phase of broadened glass transition temperature of 70–120 °C. On the other hand, instead of sharp peaks, the polymers with 0.8 and 1.0% cobalt salts exhibit two humps and a distinct peak in between the humps in the tan δ plots, indicating the presence of an additional phase comprised of a copolymer of linseed oil–styrene and DVB. For fixed concentration (1%) of catalysts, the cobalt–calcium combination follows the similar trend in the tan δ as that for the polymers with 0.8–1.0% cobalt whereas other combinations exhibit two phases. These polymers possess crosslink densities of 0.63–0.91 × 10⁴ mol/m³ and compressive strengths of 2.0–26.6 MPa. The catalyzed polymers are thermally stable below 300 °C and exhibit a major thermal degradation with a maximum degradation of 82–88% at a temperature of 500 °C.     

Synthesis of silane monomer-modified styrene–acrylate microemulsion coatings by photopolymerization

A relatively concentrated silane monomer-modified styrene–acrylate microemulsion coating with high monomer to surfactant ratio of 7.5:1 has been prepared by microemulsion photopolymerization. The properties and the structure of the microemulsion coatings were investigated using TEM, FTIR and UV–vis measurements. The microemulsions are transparent with high transmittance in the visible range. The particle sizes of the produced latexes are in the range of 34–52 nm with the number average diameter of 40.9 nm and D_w/D_n of 1.16. FTIR spectrum indicates the possible structure of the silane monomer-modified styrene–acrylate copolymer, and confirms the hydrolysis and condensation resulting in siloxane bonds between polymer particles. The microemulsion coatings show enhanced acid, base and water resistance with decrease of surfactant content and increase of silane coupling agent.     

Enhanced solvent resistance of acrylonitrile–butadiene rubber by electron beam irradiation

In this study, we investigated the effect of electron beam irradiation on NBR (acrylonitrile–butadiene rubber) with TMPTMA (trimethylolpropane trimethacrylate), focusing on the polar and non-polar solvent resistance at different electron beam radiation doses. The electron beam irradiation on NBR containing TMPTMA sheets was performed over a range of absorbed doses from 20 to 200 kGy to make three-dimensional network structures. The solvent resistance was characterized according to ASTM D 471 in benzene and THF solvent. The solvent resistance of NBR was enhanced by the addition of TMPTMA in a dose-dependent manner. In addition, the volume change of immersed NBR in THF solvent was slightly lower than in benzene solvent.