Effect of screw rotation speed on the properties of polystyrene/organoclay nanocomposites prepared by a twin‐screw extruder

We discuss the effect of screw rotation speed on the mechanical and rheological properties and clay dispersion state of polystyrene (PS)/organoclay (clay) nanocomposites prepared by melt compounding with a counterrotating‐type twin‐screw extruder. Poly(styrene‐co‐vinyloxazolin) (OPS) was used as an additional material. The Young's modulus of the PS/OPS/clay nanocomposites showed the maximum value at a screw rotation speed of 70 rpm in this study. This implied the existence of an optimized screw rotation speed for the melt compounding of the polymer/clay nanocomposites. For PS/clay systems without the addition of OPS, the peak intensity from clay increased and the distance between clay platelets in the nanocomposites decreased with the screw rotation speed. On the other hand, inverse results were obtained for PS/OPS/clay systems. According to the transmission electron microscopy photographs, the PS/OPS/clay nanocomposite at 70 and 100 rpm had fully exfoliated clay platelets. The dynamic rheological properties of the PS/clay nanocomposites were almost the same as those of neat PS. On the other hand, the storage and loss moduli of the PS/OPS/clay nanocomposites at the same frequency were larger than those of the PS/clay system. On the whole, the bonding between clay platelets and PS was important for increasing the viscosity and elasticity in the melts of the PS/clay system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1165–1173, 2006     

Separation of Zinc by a Non‐dispersion Solvent Extraction Process in a Hollow Fiber Contactor

Abstract

A process for recovery of zinc from acid solution with di(2‐ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso‐dodecane was carried out at 20°C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1–1.0 g/L), pH 0.1–2.1, and D2EHPA concentrations (2–8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38–0.80 L/min) and organic flow rate (0.22–0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2×10^?6 m/s to 25.3×10^?6 m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer.     

不同方法提取罗汉果种籽油脂的研究

文章采用了回流提取、索氏提取法、超声波提取、压榨法提取、二氧化碳超临界提取、水酶等方法提取罗汉果种籽油,以出油率、酸价、碘价、角鲨烯含量为指标,比较不同方法的差异性,结果表明：使用石油醚作为溶剂,采取索氏提取法、回流提取、超声波提取出油率、角鲨烯含量较高;水酶法提取油脂样品的酸价最高。     

Synergistic flame‐retarded effect between carbon nanotubes and ammonium polyphosphate in Nylon6 and Nylon6/polystyrene blends

The association of carbon nanotubes (CNTs) and ammonium polyphosphate (APP) as flame retardants was utilized for improving the flame retardancy of nylon6 (PA6) and blends of PA6/Polystyrene (PS). A remarkable synergistic effect between APP and CNTs was observed in PA6 at 1‐wt% CNTs loading. Rheological tests showed that 1‐wt% CNTs formed a network structure. Morphology of residue char indicated that a network enhanced synergistic effect. A synergy between APP and CNTs in blends of PA6/PS (56/24) was also investigated. APP and CNTs exhibited a remarkable synergistic effect at 0.25‐wt% CNTs loading, but the antagonistic effect on flame retardancy of blends was observed at 1‐wt% CNTs loading. Transmission electron microscopy showed that CNTs were exclusively dispersed in the PA6 phase of blends. The selective dispersion of CNTs caused the formation of a network at 0.25‐wt% CNTs loading. Morphology of residue char indicated that 0.25‐wt% CNTs were benefited by the formation of a continuous and well‐swollen residue char that enhanced the synergistic effect in blends. However, the aggregation of 1‐wt% CNTs in PA6 phase caused high viscosity of PA6 phase, resulting in a poor expansion of the residue char. Consequently, the antagonism was exhibited.     

Experimental study of the rheological,mechanical, and dielectric properties of MgO/LDPE nanocomposites

The properties of the polymer nanocomposites (PNCs), consisting low density polyethylene (LDPE) and magnesium oxide nanoparticles (MgO‐NPs), were systematically discussed in this paper. The shear mixing time and MgO concentration were considered as the two factors affecting the dispersion state, which was found to be effective to change the crystallinity and the mechanical performance of MgO/LDPE PNCs. A reduction in the dynamic shear viscosity was observed when the concentration of MgO‐NPs at a relative low level, which was also dominant by the dispersion states of MgO‐NPs. Evident enhancement of the static yield stress was revealed only by introducing a minute amount of MgO‐NPs (0.25 wt %). Meanwhile, the elastic and loss modulus were also found to be dependent on the dispersion state of MgO‐NPs. A positive increase in dielectric permittivity was identified by uniaxial stretching the MgO/LDPE PNCs strips owing to the orientation enhancement of internal microstructure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43038.     

超声辅助萃取沙棘黄酮工艺研究

探索超声波萃取法浸提沙棘黄酮最优工艺条件;通过单因素和正交实验法与微波法、索氏浸提法作了对比研究;超声萃取法优化条件为:浸提温度为60℃,功率70W,时间45min,固液比1∶10为佳,在最优条件下浸提沙棘叶中的黄酮,两种方法的产量分别为:超声波3.867mg/g,索氏浸提法3.697mg/g;电磁强化分离沙棘黄酮具有产量高、省时、溶剂用量少、耗能低等优点。     

非共价改性法制备聚苯乙烯/高分散石墨烯复合材料

以工业化石墨烯粉体(IGN)与苯乙烯为原料,聚乙烯醇、磷酸三钙为分散剂,过氧化苯甲酰为引发剂,聚苯乙烯(PS)树脂作为非共价改性组分,通过超声分散、悬浮聚合法制备了聚苯乙烯/高分散石墨烯复合材料,探究了超声分散时间与PS含量对IGN在复合材料中的分散性影响机理。结果表明,PS可提高IGN在苯乙烯(St)单体中的相容性;超声时间30 min,PS添加量为St单体质量的3 %时,复合材料微观形貌较好,IGN分散性较佳;随着PS/IGN中IGN含量的增加,复合材料的外延起始降解温度逐渐提高40 ℃,玻璃化转变温度最大提升7.3 ℃,拉伸强度由43.5 MPa增强至68.3 MPa,提升近65 %。     

Formation of bead‐free and core–shell superfine electrospinning fibers under the assistance of another polymer and an interfacial compatibilizer

This work presents a new way of preparing bead‐free and core–shell superfine polymer electrospinning fibers under the assistance of another polymer and an interfacial compatibilizer. For the electrospinning of polystyrene (PS)/CHCl₃ solution, the bead‐free fiber cannot be obtained until the PS concentration is above 0.25 g/mL but its average diameter is above 10 μm. Using polyamide 6 (PA6) as an additive, the critical concentration capable of forming bead‐free fiber greatly decreased and core–shell fibers with PA6 as the core and PS as the shell were obtained due to the driving effect of high spinability of PA6. The introduction of a copolymer (PS‐co‐TMI) of styrene (St) and 3‐isopropenyl‐α,α‐dimethylbenzene isocyanate (TMI) can react with amine of PA6 to form the copolymer of PS and PA6 as an interfacial compatibilizer. As a result, it can further enhance the dispersion and deformation of minor component PA6 into uniform microfiber core, and drive PS to uniformly cover the surface of PA6 fibers, and finally form bead‐free and core–shell superfine fibers. POLYM. ENG. SCI., 59:1437–1444 2019. © 2019 Society of Plastics Engineers     

Ultrasonic improvement of the compatibility and rheological behavior of high‐density polyethylene/polystyrene blends

The effects of ultrasonic oscillations on the rheological behavior, mechanical properties, and morphology of high‐density polyethylene (HDPE)/polystyrene (PS) blends were studied. The experimental results show that the die pressure and apparent viscosity of HDPE/PS blends are remarkably reduced in the presence of ultrasonic oscillations and that mechanical properties of the blends are improved. The particle size of the dispersed phase in HDPE/PS blends becomes smaller, its distribution becomes narrower, and the interfacial interaction of the blends becomes stronger if the blends are extruded in the presence of ultrasonic oscillations. Ultraviolet spectra and Soxhlet extraction results show the formation of a polyethylene‐PS copolymer during extrusion in the presence of ultrasonic oscillations, which improves the compatibility of HDPE/PS blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 23–32, 2002     

Preparation and characterization of composite membranes of polysulfone and microcrystalline cellulose

Physical and chemical modifications of polymeric ultrafiltration membranes are necessary to improve their hydrophilic properties, strength, and other characteristics. Microcrystalline cellulose (MCC) was prepared from cellulose pulp by acid‐catalyzed hydrolysis in the presence of ultrasonic radiation, and the properties of MCC were evaluated. Through the addition of MCC to a polysulfone (PS) membrane solution, a casting solution of a PS/MCC blend was obtained. Subsequently, the ultrafiltration membrane from the blend was further developed in a phase‐inversion process comprising immersion and deposition. The capacity for ultrafiltration was better with increasing MCC content. When the ratio of MCC to PS was 0.3, the pure water flux of the composite membrane reached 234.2 L/m²/h, and the retention of a bovine serum albumin solution (1 g/L) was as high as 93.4%. The membranes were also observed with scanning electron microscopy and atomic force microscopy to study their microstructures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mini Liquid‐Liquid Extractor without Moving Parts Based on the Coanda Effect

A mini liquid‐liquid extractor was designed based on a feedback fluidic oscillator. According to the Coanda effect, the designed oscillator with two feedback channels enables good mixing of the aqueous and organic phases. Co‐current liquid‐liquid extraction was performed in the mini extractor, and it was visually observed that the aqueous phase was dispersed into small droplets because of fluidic oscillation and vortex formation. The aqueous phase was more effectively dispersed at the stage near the outlet and with increasing flow. Several tests were performed for evaluating the extraction performance of the extractor using 30 % tributyl phosphate‐kerosene and 3 M HNO₃ solutions as the organic and aqueous phases, respectively. The obtained extraction efficiency was close to the equilibrium efficiency, indicating that this extractor has the potential for liquid‐liquid extraction of hazardous liquids.     

Compounding of MWCNTs with PS in a Twin‐Screw Extruder with Varying Process Parameters: Morphology,Interfacial Behavior,Thermal Stability,Rheology, and Volume Resistivity

1, 2, 3, 5, and 7.5 wt% MWCNTs are incorporated into PS in a twin‐screw extruder at varying speeds, throughputs and extruder barrel temperatures. Increased SME at enhanced processing speeds seems to have the single largest effect in enhancing dispersion. A relative evaluation of PS/MWCNT interactions indicate an interfacial layer growth of 24% for 2 wt% MWCNT at 1100 rpm compared to 18% growth at 500 rpm. Raman analysis does not show an MWCNT peak shift but a constant increase in FWHM is observed irrespective of the MWCNT content. A significant enhancement of thermal stability occurs up to 2 wt% MWCNT loading while 1–2 wt% shows the rheological threshold. The volume resistivity decreases dramatically in a 2 wt% sample processed at 1100 rpm compared to those processed at 500 rpm.

     

高浓度超高相对分子质量聚乙烯冻胶纤维的萃取工艺

以超高相对分子质量聚乙烯(UHMWPE)放流冻胶丝为原料,经过切粒机切碎和静置脱油,得到UHMWPE质量分数15%、20%、25%的冻胶颗粒,经纺丝机纺丝制得相应UHMWPE质量分数的冻胶丝。通过对UHMWPE质量分数不同的3种冻胶纺纤维的萃取温度、萃取时间、超声波功率和预拉伸倍数等影响因素进行研究,发现冻胶纤维萃取后残余含油率随萃取温度升高而减少,温度升高至40℃时,残余含油率变化减缓。随着冻胶纤维UHMWPE质量分数的提高,其结构更加紧密,包含在其中的白油溶剂更加难以去除,需要更高的萃取温度或者更长的萃取时间。此外,加大萃取时施加的超声波功率、预拉伸倍数或者加大萃取液新液补充流量,可以明显提高萃取效果。     

Optimization of extraction of bulk enzymes from spent mushroom compost

The profiling of ligninase, hemicellulase and cellulase of Pleurotus sajor‐caju after inoculation of spawn in bags containing sawdust was done at monthly intervals for a period of 6 months. Xylanase (EC 3.2.1.8) was produced throughout the 6 months studied with the productivity range from 5.60 to 7.51 U g^?1. Cellulase (EC 3.2.1.4) and β‐glucosidase (EC 3.2.1.21) productivities were highest at 4 months, producing 3.31 U g^?1 and 121.13 U g^?1 respectively. Laccase (EC 1.10.3.2) productivity was highest at 2 months with a value of 7.59 U g^?1. Lignin peroxidase (EC 1.11.1.14) productivity was highest at 5 months with a value of 206.20 U g^?1. Total soluble proteins were highest at 4 months with a value of 0.139 mg cm^?3. The profiling of lignin peroxidase in 5‐month‐old spent mushroom compost was monitored over a period of 10 months. It was observed that lignin peroxidase was produced throughout the period but productivity was variable. The average lignin peroxidase productivity ranged from 30 to 110 U g^?1. The activities of the enzymes extracted in tap water at pH 8.4 were comparable to that extracted in 50 mmol sodium citrate buffer at pH 4.8 and distilled water at pH 5.2 at 4 °C using an incubator shaker at 200 rpm for 18 h. The optimum extraction time was 1 h using an incubator shaker at 4 °C. When an incubator shaker was used, there was no significant difference in the recovery of xylanase, cellulase and laccase at different pH values at 4 °C and 28 °C. No significant difference was observed in the recovery of β‐glucosidase using an incubator shaker at different pH values at 4 °C although the enzyme recovery was slightly higher at pH 8.12, with a value of 29.27 U g^?1. The optimum extraction of β‐glucosidase was at pH 4 at room temperature using an incubator shaker. For the lignin peroxidase enzyme, the optimum pH for extraction was 6 at 4 °C and pH 7 at room temperature using an incubator shaker at 200 rpm for 1 h. Homogenization for 8 min at 8000 rpm using tap water at pH 4 had an advantage over the use of the incubator shaker for the extraction as high titers of enzymes were recovered. Copyright © 2003 Society of Chemical Industry     

Mass Transfer in Molybdenum Extraction from Aqueous Solutions Using Nanoporous Membranes

Modeling of non‐disperse solvent extraction of molybdenum(VI) with PC‐88A as extractant and a nanoporous hollow‐fiber membrane contactor as extractor was performed. Computational fluid dynamics was applied for modeling and simulation of molybdenum extraction. Concentration, pressure, and velocity distributions for molybdenum were determined. The extraction of Mo⁶⁺ was greatly influenced by the flow rate of feed solution. The extraction efficiency was reduced with higher feed flow rate and increased with the molybdenum content in the feed. The pressure drop along the shell side of the membrane extractor was found to be not significant, being one of the advantages of membrane extractors which assist in reducing the operational costs. The proposed simulation method is capable to prognosticate the performance of solvent extraction of molybdenum in membrane extractors.     

湍流旋液萃取器萃取性能的研究

描述了新型萃取设备—湍流旋液萃取器的原理和结构。应用磷酸三丁酯-煤油-ZnCl_2水溶液这一萃取体系对该设备的萃取性能进行了实验测定,并与传统的混合澄清槽作了比较,结果表明该萃取设备具有处理量大,萃取效率高以及分相能力强的优点,适于工业化生产应用。     

Pilot‐scale Ultrasonic Assisted Cloud Point Extraction of Polycyclic Aromatic Hydrocarbons from Polluted Water

Abstract

Cloud point extraction (CPE) has been proved to be an efficient and environment‐friendly separation technology for polycyclic aromatic hydrocarbons from polluted water in many related researches. However, its traditional phase separation process, based on throughput‐limited centrifugation or low‐efficient heating, limited the scaling up and continuous operation of CPE process to a large extent. In our previous study, an efficient and easy‐scaling up CPE process, namely ultrasonic assisted cloud point extraction (Us‐CPE), was developed by performing the CPE process in an ultrasonic environment. The introduction of an ultrasonic environment successfully accelerated the phase separation; and due to that the ultrasonic effect was free from throughput limitation, the process was of a good potential in the scaling up and continuous operation. In this paper, a pilot‐scale Us‐CPE process of three polycyclic aromatic hydrocarbons (PAHs), anthracene, phenanthrene, and pyrene from polluted water was performed in a pilot‐scale extraction column with a volume up to 500 mL, and the treatment was operated continuously with pumps. The steady state time of the continuous system was determined, and the influence of operation parameters including ultrasonic power, temperature, extraction column volume, flow rate, and PAHs initial concentration, were evaluated by determining the PAHs concentrations in the treated water and the corresponding distribution coefficients. Comparing with the batch operation in our previous study, a comparable high performance was able to be obtained by the continuous process in a PAHs initial concentration range lower than 20 mg/L, which means that the continuous process was feasible in the treatment of common PAHs polluted water. And the results that the extractability of the system increased with the ultrasonic power and system volume indicated that a high performance was expectable in a further scaling up process with a higher column volume, given a suitable ultrasonic power.     

Mathematical Modeling of Supercritical Extraction of Valerenic Acid from Valeriana officinalis L.

The dynamic behavior of supercritical fluid extraction (SFE) of valerenic acid (VA) from valerian (Valeriana officinalis L.) roots was studied by mathematical modeling. The extraction yield of VA was considered as the most desirable compound among the other extracted constituents. A two‐phase desorption model was developed by considering a diffusion controlled regime in the particle and axial dispersion in the bed. The mass transfer parameters, i.e., pore diffusivity, film mass transfer coefficient and axial dispersion, along with the solubility parameters were chosen as the model parameters. The first three mass transfer parameters were predicted using nondimensional equations from the literature. The solubility equation and the parameters were studied using different equilibrium models, i.e., Henry, Langmuir, Freundlich, Langmuir‐Freundlich (L‐F) and Toth isotherms. The equilibrium parameters were correlated by comparing the outlet results of the dynamic SFE model with experiments. The experimental yield of the VA extraction was obtained at a pressure of 15.0–36.0 MPa, temperature of 310–334 K, solvent flow rate of 0.50–1.10 · 10^–6 m³/min and different particle sizes ranging from 0.18–2.00 · 10^–3 m in diameter, at a 20 min constant static period, in the presence of 46.9 μL/g ethanol as the co‐solvent, followed by dynamic time extraction for up to 50 min. From the results, the mathematical model using the L‐F equation exhibited the best agreement with the experimental yield of VA extraction in the range of studied conditions. The present model can be applied to design and scale up the SFE process of VA from Valeriana officinalis L. roots.     

Rheology,morphology, and mechanical properties of reactive compatibilized polypropylene/polystyrene blends via Friedel–Crafts alkylation reaction in the presence of clay

Attempts were made to study the effect of reactive compatibilization via Friedel–Crafts alkylation reaction, using AlCl₃ as a catalyst, on rheology, morphology, and mechanical properties of polypropylene/polystyrene ( PP/PS) blends in the presence of an organoclay (Cloisite 15A). During the reactive compatibilization process, PS showed much more degradation than that of PP in the presence of AlCl₃. It was found that the effect of generation of PP‐g‐PS copolymer at the interface of the PP/PS blend dominates the effects of degradation of PS and PP phases, which manifested itself by increased toughness as well as uniform dispersion of the dispersed PS particles in the PP matrix. Generation of PP‐g‐PS copolymer was confirmed by using Fourier‐transform infrared analysis. By using rheological and X‐ray diffraction analyses, it was shown that the clay had higher affinity to PS than that of PP. It was also shown that the clay located at the interface of PP and PS phases, leading to increased relaxation time of the deformed PS dispersed particles, exhibited higher dispersion in PP/PS blend, which resulted in higher ductility of the blend. By using the results of rheological studies, it was concluded that during reactive compatibilization of the blend nanocomposite, the clay migrated into the dispersed PS phase, which was confirmed by scanning electron microscopy analysis. It was demonstrated that the rheological studies have a reliable sensitivity to the clay partitioning and phase morphology of the studied blends and blend nanocomposites . J. VINYL ADDIT. TECHNOL., 24:18–26, 2018. © 2015 Society of Plastics Engineers     

Scaling‐up of the dispersion process of nanoparticle‐agglomerates in epoxy resin with an innovative continuous ultrasonic flow‐through‐cell dispersion system

Thermosets reinforced with inorganic nanoparticles show numerous benefits over the unreinforced polymer. However, to achieve reinforcement the nanoparticles have to be well separated and distributed homogeneously within the matrix. In the present study the laboratory scale discontinuous ultrasonic dispersion process was scaled up to a continuous ultrasonic dispersion process of agglomerated nanoparticles in epoxy resin (EP). Exemplarily, the dispersion experiments were carried out for a 4‐l suspension volume consisting of epoxy resin and 14 vol% TiO₂‐nanoparticles was carried out as a function of the dispersion time and the amplitude of the ultrasonic cell. Following, nanocomposites were manufactured with particle contents of 2, 5, and 10 vol%. For the verification of the manufactured nanocomposites quality, particle sizes analysis and mechanical characterization were undertaken. The obtained results were compared with those of the discontinuous dispersion at laboratory scale. It has been found that comparable particle sizes and mechanical properties could be achieved, although, the volume of the suspension was 10 times higher as that one of the batchwise dispersion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers