Frontiers of Chemical Science and Engineering (v.2, #1)
Studies on the liquid-liquid interfacial mass transfer process using holographic interferometry by Chaofan Zhao; Youguang Ma; Chunying Zhu (1-4).
This paper aims at the interfacial phenomena of liquid-liquid mass transfer and its characteristic. By using the real-time holographic technique, the concentration distributions on the aqueous side were obtained according to holographic diagrams of mass transfer of ethanol through the interface of oil and water at different initial concentrations. Furthermore, the concentrations near the interface and the mass transfer coefficients were attained. A correlation of concentration near the interface to the concentration of the solute in the oil side was proposed. An approach of interfacial energy with solute concentration was established, and the calculated results are at good agreement with the experimental data. It is indicated that the liquid-liquid mass transfer process is approximately in accordance with two-film theory, the interfacial performance may be changed by the addition of the solute, and the interface of liquid-liquid is nonequilibrium thermodynamically during the mass transfer process.
Keywords: liquid-liquid mass transfer; holographic interferometry; concentration profile; concentration near the interface; mass transfer coefficient; interfacial nonequilibrium
Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method by Yongzhi Zhao; Yi Cheng; Maoqiang Jiang; Yong Jin (5-9).
A discrete element method (DEM)-computational fluid dynamics (CFD) two-way coupling method was employed to simulate the hydrodynamics in a two-dimensional spouted bed with draft plates. The motion of particles was modeled by the DEM and the gas flow was modeled by the Navier-Stokes equation. The interactions between gas and particles were considered using a twoway coupling method. The motion of particles in the spouted bed with complex geometry was solved by combining DEM and boundary element method (BEM). The minimal spouted velocity was obtained by the BEMDEM-CFD simulation and the variation of the flow pattern in the bed with different superficial gas velocity was studied. The relationship between the pressure drop of the spouted bed and the superficial gas velocity was achieved from the simulations. The radial profile of the averaged vertical velocities of particles and the profile of the averaged void fraction in the spout and the annulus were statistically analyzed. The flow characteristics of the gas-solid system in the two-dimensional spouted bed were clearly described by the simulation results.
Keywords: discrete element method; computational fluid dynamics; spouted bed; boundary element method
Kinetic model for hydroisomerization reaction of C8-aromatics by Ouguan Xu; Hongye Su; Xiaoming Jin; Jian Chu (10-16).
Based on the reported reaction networks, a novel six-component hydroisomerization reaction network with a new lumped species including C8-naphthenes and C8-paraffins is proposed and a kinetic model for a commercial unit is also developed. An empirical catalyst deactivation function is incorporated into the model accounting for the loss in activity because of coke formation on the catalyst surface during the long-term operation. The Runge-Kutta method is used to solve the ordinary differential equations of the model. The reaction kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimization method (BFGS). The kinetic model is validated by an industrial unit with sets of plant data under different operating conditions and simulation results show a good agreement between the model predictions and the plant observations.
Keywords: C8-aromatics; hydroisomerization; reaction network; kinetic model; catalyst deactivation function; parameter estimation
Formation of coke in thermal cracking of jet fuel under supercritical conditions by Yuhong Zhu; Caixiang Yu; Zimu Li; Zhentao Mi; Xiangwen Zhang (17-21).
Continuous-flow reactor experiments were carried out to study coke formation from thermal cracking of home-made jet fuel RP-3 under supercritical conditions. The mechanism and precursor of coke forming were analyzed. The starting cracking temperature of RP-3 fuel was determined to be 471.8°C by differential scanning calorimetry (DSC). Temperature-programmed oxidation and scanning electron microscopy (SEM) characterizations of the stressed tubes showed that there are three different coke species including chemisorbed carbon, amorphous carbon and filamentous coke in the solid deposits. More than 90% of coke deposits are carried away by the supercritical fluid, which has strong capabilities of extraction for coke deposits and their precursors. There were 17.1 wt-% of iron and 11.1 wt-% of chromium found on the coke surface detected by energy dispersive spectroscopy (EDS) which suggests carburetionon alloy. RP-3 fuel and its cracking liquids were analyzed by GC-MS,which showed that the content of alkyl benzene and alkyl naphthalene increased evidently in cracking liquids.
Keywords: coke; jet fuel; thermal cracking; supercritical; extraction
Study on enzymatic hydrolysis of steam exploded straw by using shaking ball by Zhanwei Sun; Xiaoguo Fu; Hongzhang Chen; Yanhui Wang; Runyu Ma (22-27).
A novel method of enzymatic hydrolysis was developed in this paper to produce a high conversion yield and hydrolysis rate. A comparison was described by using three methods of enzymatic hydrolysis and adsorption of steam exploded straw (SEWS): shaking ball in the regime, shaking with stirrer bed, and static state. The most adequate filter-paper activity, speed and reaction time were 3.6 × 10−27 mol/(s·mL), 150 r/min and 24 h, respectively, with the reducing sugar yield of 0.43. The results showed that the method of shaking ball produced the highest adsorption, conversion yields and hydrolysis rate of the enzyme. This might be due to the continuous frequency increase of enzyme adsorption and desorption on the substrate surface as well as the relieved end-product inhibition. The morphological variation of SEWS was characterized by environmental scanning electron microscopy (ESEM).
Keywords: cellulose; cellulase; stainless ball; ESEM
Bio-modification of eucalyptus chemithermomechanical pulp by Qifeng Yang; Huaiyu Zhan; Shuangfei Wang; Kecheng Li; Shiyu Fu (28-33).
Eucalyptus chemithermomechanical pulp (CTMP) was modified with the white-rot fungus 19-6 in a stationary culture condition. Different factors that influence the effect of white-rot fungus treatment, including additional nutrition, pH value, temperature, treatment time and oxygen input were investigated. The results show that the energy consumption of post refining of CTMP treated by white-rot fungus 19-6 was lower than that of untreated pulp and the strength properties also obviously improved. At a freeness level of about 330 mL, compared to the untreated pulp, the tensile index, tear index and internal bonding strength increased by 21.3%, 27.4% and 33.1%, respectively. Unfortunately, the treatment with white-rot fungus substantially decreased all optical properties except for opacity, which was essentially unchanged. Brightness and light scattering coefficient were reduced to as much as 25% and 21% compared to the untreated pulps. However, after a towstage “Na2S2O4-H2O2” bleaching, the final brightness can reach 70.3% ISO, which is similar to that of the untreated CTMP.
Keywords: eucalyptus CTMP; white-rot fungus19-6; bio-modification
Cell carrier function of hollow-fiber membrane in rotating wall vessel bioreactor by Kedong Song; Tianqing Liu; Hu Zhao; Xiangqin Li; Zhanfeng Cui; Xuehu Ma (34-39).
Large-scale expansion of the osteoblasts of a Sprague-Dawley (SD) rat was studied in a rotating wall hollow-fiber membrane bioreactor (RWHMB) by using hollow-fiber membrane as the carrier. For the sake of contrast, cells were also expanded in a T-flask using a hollow-fiber membrane as carrier and in a rotating wall vessel bioreactor (RWVB) using a microcarrier. During the culture period, the cells were sampled every 12 h, and after 5 days, the cells were harvested and evaluated with scanning electron microscopy (SEM), hematoxylin-eosin (HE) staining and alkaline phosphatase (ALP) staining. Moreover, von-Kossa staining and Alizarin Red S staining were carried out for mineralized nodules formation. The results show that in RWHMB, the cells present better morphology and vitality and secrete much more extracellular matrix. It is concluded that the RWHMB combines the advantages of the rotating wall vessel and hollow-fiber membrane bioreactors. The hydrodynamic stimulation within it accelerates the metabolism of the osteoblast and mass transfer, which is propitious to cell differentiation and proliferation.
Keywords: hollow-fiber membrane; microcarrier; bioreactor; osteoblast; expansion
Preparation of D-lysine by chemical reaction and microbial asymmetric transformation by Yi Liu; Qingcai Jiao; Xiaoxing Yin (40-43).
The DL-lysine crystals from the racemization of L-lysine was treated as substrate with Hafnia alvei AS1.1009 intact cells as biocatalysts to produce crystalline D-lysine with a yield of 56.6% from the reaction mixture after simple purification. In the presence of 0.10 molar equivalent of salicylaldehyde, L-lysine racemization can be completed within 4 h in 1.0 mol/L of NaOH at 100°C. The activation energy of the processes was 62187.86 J/mol. The characteristics of Hafnia alvei AS1.1009 decarboxylase were studied. Under the conditions of pH 8.0, temperature 37°C, cell concentration 10 g/L, tween-80 0.5 g/L, substrate concentration 30 g/L, and the specific activity of up to 3840 U, L-lysine can be completely degraded by the decarboxylase for 12 h under the optimal conditions.
Keywords: D-lysine; decarboxylase; racemization; biotransformation
Fabrication of titania thin film with composite nanostructure and its ability to photodegrade rhodamine B in water by Gaojie Zhang; Jinming Wu; Shaoguang Liu; Mi Yan (44-48).
A titania nanorod filmwas synthesized by direct oxidation of metallic Ti with hydrogen peroxide solution under a low temperature. Titania nanoparticles were then filled into the gaps among the nanorods through an infiltration sol-gel procedure to form a composite titania film with an ordered nanostructure. X-ray diffraction spectra indicate that the composite film was a mixture of anatase and rutile while the titania film obtained by only using a sol-gel procedure was pure anatase. Field emission scanning electron microscopy observations show that titania nanoparticles were embedded into the titania nanorod film. Photoluminescence spectra suggest the enhanced separation of electron and hole pairs for the obtained composite titania film over the corresponding titania nanorod film. The composite titania film exhibited improved ability to photodegrade rhodamine B in water compared with the titania nanorod film. The apparent photodegradation rate constant, fitting a pseudo-firstorder, was 3 times of that obtained by the sol-gel derived titania film at the same weight. The improved photocatalytic activity for the composite titania film could be attributed to the enhanced separation of electron and hole pairs due to the embedding of the titania nanoparticles within the titania nanorods.
Keywords: titania; composite catalyst film; sol-gel; nanorod; photoluminescence spectra
Preparation and property of porous hydroxyapatite as an inorganic dispersant used in suspension polymerization by Kaqiu Xu; Jiale Xu; Yuhong Wang (49-54).
The porous hydroxyapatite (HAP) for suspension polymerization dispersant was prepared using calcium carbonate and phosphoric acid as raw materials. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET nitrogen adsorption. The results show that the prepared HAP has a porous structure, low particle density, large specific surface area, uniform particle size and does not agglomerate easily between the particles. The preparation conditions for the HAP were optimized as follows: solid content of calcium carbonate aqueous suspension 90 g/L, concentration of phosphoric acid 1.0 mol/L, reaction/aging temperature 50°C, and aging time 3 h. The HAP prepared under optimal preparation conditions has 106.8 m2·g−1 of specific surface area, which is about 1.5–1.8 times asmuch as that of Japanese HAP or commercial HAP. Its application result in the suspension polymerization of styrene show that the porous HAP dispersant has high surface activity, excellent suspension dispersibility and stability and can markedly improve the quality of polystyrene beads.
Keywords: hydroxyapatite; porous structure; inorganic dispersant; suspension polymerization
Modification of acidity of Mo-Fe/HZSM-5 zeolite via argon plasma treatment by Xinli Zhu; Kailu Yu; Dangguo Cheng; Yueping Zhang; Qing Xia; Changjun Liu (55-58).
The NH3-TPD characterization was conducted to confirm that the acidity of Mo-Fe/HZSM-5 zeolite could be selectively modified via the glow discharge plasma treatment. The plasma catalyst treatment could totally change the distribution of aromatic products with higher methane conversion compared to the untreated catalyst. Some polycyclic aromatics such as anthracene, pyrene and phenanthrene were also produced over the plasma treated catalyst, in addition to benzene, toluene and naphthalene, which were normally obtained over the untreated catalyst.
Keywords: methane; aromatization; plasma; acidity; Mo-Fe/HZSM-5 zeolite
Kinetics of halogen-exchange fluorination of 2,6-dichlorobenzaldehyde by Zhengyong Liang; Bindong Li; Chunxu Lü; Chao Feng (59-62).
Under the conditions of phase transfer catalysis and nitrobenzene as the solvent, the halogen-exchange fluorination of 2,6-dichlorobenzaldehyde using KF as fluorinating agent was studied. The kinetics was investigated and the reaction rate constants were obtained under the optimum conditions of n(KF):n(2,6-dichlorobenzaldehyde): n(Ph4PBr):n(acetone-furan crown ether) = 4:1:0.1:0.05 and temperatures of 433 K, 443 K, 453 K and 463 K. The results illustrated the activation energy of the first and the second step is 4.57 × 104 J·mol−1 and 3.53 × 104 J·mol−1, respectively. The pre-exponential factor is 4.50 × 105 h−1 and 1.08 × 104 h−1, respectively. Thus a reliable kinetics data could be obtained for further research.
Keywords: 2,6-dichlorobenzaldehyde; halogen-exchange fluorination; phase transfer catalysis; kinetics
Preparation of Ni/SiO2 catalyst in ionic liquids for hydrogenation by Qingming Fan; Yingxin Liu; Yifan Zheng; Wei Yan (63-68).
A series of silica supported nickel catalysts were prepared from nickel nitrate and tetraethyl orthosilicate by the sol-gel method with the imidazolium type ionic liquids as solvents. The catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Their catalytic performances for the selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde were investigated. The results show that the Ni/SiO2 catalyst prepared with 1-(2-hydroxyethyl)-3-methylimidazole tetrafluoroborate ionic liquid as solvent exhibits the highest catalytic activity for the reaction. Under the optimal conditions of catalyst dosage (based on the mass of cinnamaldehyde used) 10%, reaction pressure 2 MPa, temperature 373 K and reaction time 2 h, the conversion of cinnamaldehyde and the selectivity to hydrocinnamaldehyde can reach 97.6% and 98.8%, respectively.
Keywords: nickel catalyst; ionic liquid; sol-gel method; selective hydrogenation; cinnamaldehyde; hydrocinnamaldehyde
Continuous reaction performances of benzene alkylation with long chain olefins catalyzed by ionic liquid by Congzhen Qiao; Chengyue Li (69-73).
Based on a compulsive mixing-reacting-separating-recycling small experimental setup,the continuous reaction performances of benzene alkylation with long chain olefins catalyzed by [BMIM]Cl-AlCl3 ionic liquid were investigated. Three different situations including normal continuous operation mode (reagent materials), sidetrack feeding from different axial positions along the static mixing reactor (reagent materials) and normal continuous alkylation using industrial paraffin and olefins materials were examined. Even under the relatively hypecritical reaction conditions, the single pass conversion of pure 1-dodecene could reach to nearly 100.0%, and the selectivity of 2-phenyl isomer was higher than 37.7%. Although the positions along the reactor for sidetrack feeding were different, the 100.0% single pass conversion of 1-dodecene was also attained before the outlet of the reactor. The refined industrial olefins as raw material could meet with the requirements of continuous alkylation. The influences of impurities such as di-olefins and non-benzene aromatics on the catalytic activity and stability should be studied further.
Keywords: ionic liquid; alkylation; benzene; 1-dodecene; recycling; continuous operation mode
Study on reformulation of fluid catalytic cracking gasoline and increasing production of light olefins by Pingxiang Yan; Xianghai Meng; Jinsen Gao; Chunming Xu; Zhiyu Sui (74-79).
The effects of reaction temperature, mass ratio of catalyst to oil, space velocity, and mass ratio of water to oil on the product distribution, the yields of light olefins (light olefins including ethylene, propylene and butylene) and the composition of the fluid catalytic cracking (FCC) gasoline upgraded over the self-made catalyst GL in a confined fluidized bed reactor were investigated. The experimental results showed that FCC gasoline was obviously reformulated under appropriate reaction conditions. The olefins (olefins with C atom number above 4) content of FCC gasoline was markedly reduced, and the aromatics content and octane number were increased. The upgraded gasoline met the new standard of gasoline, and meanwhile, higher yields of light olefins were obtained. Furthermore, higher reaction temperature, higher mass ratio of catalyst to oil, higher mass ratio of water to oil, and lower space velocity were found to be beneficial to FCC gasoline reformulation and light olefins production.
Keywords: fluid catalytic cracking gasoline; catalytic reformulation; light olefins
Improvement in the synthesis of 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester by Shihao Gao; Changquan Gao; Chenghui Sun; Xinqi Zhao (80-84).
2-(5-Amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester(III), an important intermediate of the fourth generation cephalosporins, was efficiently synthesized by reacting 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid (I) with 2,2′-dibenzothiazole disulfide (II) in the presence of triphenylphosphine. Effects of reaction time, temperature, solvents, catalysts and feeding molar ratio on the yield and quality of products were investigated, and an improved procedure suitable for industrial production was established. Using 1,2-dichloroethane as solvent, triphenylphosphine as reducer, and triethylamine as catalyst, n(I): n(II): n(triphenylphosphine)51.0: 1.0: 1.0, the product was obtained at room temperature in 98.1% yield. The purity of the product without further purification is 98.7% determined by HPLC method. This procedure could be a suitable alternative to the traditional processes because of its easy handling, high yield and low cost.
Keywords: pharmaceutical engineering, 2-(5-amino-1,2,4-thiadiazol-3-yl)-2-(Z)-methoxyiminoacetic acid 2-benzothiazolyl thioester; cephalosporin; thioesterification
Control on self-assembly structures of rod-coil-rod (PANI)98−(PEG)136−(PANI)98 triblock copolymer by Zhifang Yang; Jingao Wu; Yingkui Yang; Xingping Zhou; Xiaolin Xie (85-88).
The self-assembly behaviors of the rod-coil-rod (PANI)98−(PEG)136−(PANI)98 triblock copolymer are investigated in different solvents, such as N-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF), ethanol and water. The effects of solvents, concentration and ultrasonic irradiation on self-assembly are discussed. The results indicate that the triblock copolymer forms particles, rods, fiber, networks and fiber bands in the above solvents, respectively. Especially, the triblock copolymer can form a multi-layer, tri-dimensional fibrous network and a petaline structure from the mono-layer fibrous network with the increase of its concentration in ethanol. Also, the ultrasonic irradiation has a great effect on the self-assembly of the triblock copolymer.
Keywords: block copolymer; self-assembly; selective solvent
Preparation and properties of gel membrane containing porous PVDF-HFP matrix and cross-linked PEG for lithium ion conduction by Mei Zhang; Aiqing Zhang; Zhenyu Cui; Baoku Zhu; Gaige Han; Youyi Xu (89-94).
Lithium ion conducting membranes are the key materials for lithium batteries. The lithium ion conducting gel polymer electrolyte membrane (Li-GPEM) based on porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix and cross-linked PEG network is prepared by a typical phase inversion process. By immersing the porous PVDF-HFPmembrane in liquid electrolyte containing poly(ethylene glycol) diacrylate (PEGDA) and an initiator to absorb the liquid electrolyte at 25°C, and then thermally cross-linking at 60°C, the Li-GPEMis fabricated successfully. The measurements on its weight loss, mechanical and electrochemical properties reveal that the obtained Li-GPEM has better overall performance than the liquid and blend gel systems used as conductive media in lithium batteries. The ionic conductivity of the fabricated Li-GPEM can reach as high as 2.25 × 10−3 S/cm at 25°C.
Keywords: poly(vinylidene fluoride-co-hexafluoropropylene); lithium ion; polyethylene glycol; gel electrolyte; porous membrane
Sulfonated poly(ether ether ketone)/zirconium tricarboxybutylphosphonate composite proton-exchange membranes for direct methanol fuel cells by Qijun Gao; Mianyan Huang; Yuxin Wang; Yuquan Cai; Li Xu (95-101).
Sulfonated poly(ether ether ketone) (SPEEK) is a very promising alternative membrane material for direct methanol fuel cells. However, with a fairly high degree of sulfonation (DS), SPEEK membranes can swell excessively and even dissolve at high temperature. This restricts membranes from working above a high tolerable temperature to get high proton conductivity. To deal with this contradictory situation, insolvable zirconium tricarboxybutylphosphonate (Zr(PBTC)) powder was employed to make a composite with SPEEK polymer in an attempt to improve temperature tolerance of the membranes. SPEEK/Zr(PBTC) composite membranes were obtained by casting a homogeneous mixture of Zr(PBTC) and SPEEK in N,N-dimethylacetamide on a glass plate and then evaporating the solvent at 60°C. Many characteristics were investigated, including thermal stability, liquid uptake, methanol permeability and proton conductivity. Results showed significant improvement not only in temperature tolerance, but also in methanol resistance of the SPEEK/Zr(PBTC) composite membranes. The membranes containing 30 wt-% ∼ 40 wt-% of Zr(PBTC) had their methanol permeability around 10−7 cm2·s−1 at room temperature to 80°C, which was one order of magnitude lower than that of Nafion®115. High proton conductivity of the composite membranes, however, could also be achieved from higher temperature applied. At 100% relative humidity, above 90°C the conductivity of the composite membrane containing 40 wt-% of Zr(PBTC) exceeded that of the Nafion®115 membrane and even reached a high value of 0.36 S·cm−1 at 160°C. Improved applicable temperature and high conductivity of the compositemembrane indicated its promising application inDMFC operations at high temperature.
Keywords: sulfonated poly(ether ether ketone); zirconium phosphonate; composite membrane; direct methanol fuel cell
Synthesis and characterization of macromolecular surface modifier PP-g-PEG for polypropylene by Hanjia Chen; Xuhua Shi; Yafei Zhu; Yi Zhang; Jiarui Xu (102-108).
A novel macromolecular surface modifier, polypropylene-grafted-poly(ethylene glycol) copolymer (PP-g-PEG), was synthesized by coupling polypropylene containing maleic anhydride with monohydroxyl-terminated poly(ethylene glycol). The effects of the reaction condition on the graft reactions were studied. The copolymers were characterized by IR, 1H NMR, thermogravimetry (TG) and differential scanning calorimetry (DSC). The results indicated that the graft reactions were hindered by increasing the molecular weight of PP or PEG. The graft copolymer was found to have a higher initial thermal degradation temperature and lower crystallization capacity as compared with pure PP, and the side chain of PEG hindered the PP chain from forming a perfect β crystal. The thermal stability of PP-g-PEG decreased with the increasing content or molecular weight of PEG. The copolymers were blended with polypropylene to modify the surface hydrophilicity of the products. The results of attenuated total reflectance FTIR spectroscopy (ATR-FTIR) showed that PP-g-PEG could diffuse preferably onto the surface of the blends and be suitable as an effectual macromolecular surface modifier for PP.
Keywords: surface modification; polypropylene; graft copolymers; ATR-FTIR
Selective removal of Cu(II) from contaminated water using molecularly imprinted polymer by Jingyao Qi; Xin Li; Ying Li; Jianhua Zhu; Liangsheng Qiang (109-114).
A synthetic molecularly imprinted polymer (MIP) was prepared by noncovalent imprinting technique for the selective removal of Cu2+ from aqueous solutions. In the preparation of imprinted polymer, Cu2+ was used as the template, oleic acid as the functional monomer and divinylbenzene as the cross-linker. The surface morphologies and characteristics of the MIP were determined by BET, scanning electron microscopy (SEM), FTIR and energy dispersive X-ray spectrometer (EDS). The proper adsorption and selective recognition ability of the MIP were studied by an equilibrium-adsorption method. In general, the removal efficiency of Cu2+ increased rapidly with pH from 2 to 7 and decreased at a pH 8. The removal efficiency of Cu2+ increased with temperature from 25°C to 50°C. Competitive adsorption studies showed that the coexisting cations have no obvious influence on the adsorption of Cu2+. In addition, the variation in the adsorption ability of the MIP that was repeatedly used was investigated, and it showed excellent reproducibility.
Keywords: copper; molecularly imprinted polymer; water treatment; removal
A novel approach in preparing polymer/nano-CaCO3 composites by Zhengying Liu; Runze Yu; Mingbo Yang; Jianmin Feng; Wei Yang; Bo Yin (115-122).
An novel compounding process using nano-CaCO3 aqueous suspension for preparing polymer/nano-CaCO3 composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO3 in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO3 improve slightly. It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers.
Keywords: nanoparticles; mild mixing; polar and nonpolar polymer; dispersion
Hyperbranched azo polyurethane synthesized through A2+B3 scheme by Pengchao Che; Yaning He; Xiaogong Wang (123-126).
A hyperbranched azo polyurethane was synthesized by one-step polymerization of an A2 type monomer diphenylmethane-4,4′-diisocyanate and a B3 type monomer 4-(N,N′-bis(2-hydroxyethyl))amino-2′-hydroxyethoxyl-4′-nitro-azobenzene. The azo polymer was characterized by 1H nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) spectrum and thermal analysis. The λmax of the polymer in dimethylformamide (DMF) solution is 488 nm. The number average molecular weight (Mn) determined by GPC is 9,300 with a polydispersion index 1.9. The glass transition temperature (T g) of the polymer is 131°C observed from DSC thermogram. The results show that the azo polyurethane has been successfully synthesized through this scheme. Surface-relief-gratings (SRGs) were fabricated on the polymer film after being irradiated by interference pattern of Ar+ laser beams for 1,000 s. The surface modulation depth and the grating space period measured by AMF are 67 and 770 nm, respectively.
Keywords: Hyperbranched; Azo polyurethane; A2+B3 ; Surface-relief-gratings