Physical characteristics of sweet potato pulp/polycaprolactone blends

Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004     

Performance of fluorine-added CoMoS/Al2O3 prepared by sonochemical and chemical vapor deposition methods in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

The performance of a new type of CoMoS/Al₂O₃ catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS₂ crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS₂ crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS.     

Application of combined coagulation-ultrafiltration membrane process for water treatment

The objectives of this research are to identify the membrane fouling potential due to different fractions of NOM and correlate the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane and investigate the mechanism of coagulation affecting UF, and find the optimum conditions of the combined of coagulation with UF membrane filtration for NOM removal. For Nakdong river water, the humic acid fraction was the most reactive precursor fraction for the formation of the ratio of THMFP/DOC (STHMFP) and TOXFP/DOC (STOXFP). The result of adsorption kinetics tests showed that hydrophobic organics adsorbed much more quickly than hydrophilic organics on both membranes. Thus, hydrophobic compounds exhibited a preferential adsorption onto membrane. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption ratio (C₁/C_e) was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions. For combined coagulation with membrane process, flux reduction rate showed lower than the UF process alone. Also, the rate of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying the coagulation process before membrane filtration showed not only reduced membrane fouling, but also improved removal of dissolved organic materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle size distribution occurred under rapid and slow mixing conditions due to the simultaneous formation of microflocs and NOM precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved not only dissolved organic removal efficiency but also DBP (Disinfection By-Product) precursor's removal efficiency.     

Polymerization of styrene in a continuous filled tubular reactor

Free radical solution polymerization of styrene has been studied using a binary mixture of symmetrical bifunctional initiators in a filled tubular reactor packed with static mixers. Owing to intensive radial mixing induced by the static mixers, a near plug flow pattern was obtained in the reactor with some axial dispersion effect. The axial mass dispersion coefficient was determined from the residence time distribution experiment and a dynamic axial dispersion model has been developed and solved to investigate steady state and transient behavior of the filled tubular reactor. With a solvent volume fraction of 0.3, the monomer conversion up to 70% was obtained without fouling problems in the temperature range 90 to 120°C. The experimental filled tubular reactor was operated under various reaction conditions and a reasonably good agreement between the model and the experimental data was obtained without using any adjustable parameters.     

Quantitative Analysis of Zinc Vaporization from Manganese Zinc Ferrites

Zinc vaporization of Mn-Zn ferrites was quantitatively characterized in terms of oxygen partial pressure P _O2, temperature, grain size and sample geometry. The amount of zinc loss was measured as a function of time at various temperatures by a thermogravimetric method. The weight loss due to irreversible zinc vaporization showed a linear behavior with time and increased exponentially with temperature. The observed weight loss due to zinc evaporation at 1100°C was small, whereas a significant weight change was detected at 1200°C. The weight loss was even greater in a reducing atmosphere ( P _O2= 5 × 10⁻⁵). Below 1300°C, the diffusion of elemental zinc was sufficiently fast to compensate the zinc loss at the interface region, resulting in a linear dependence on time. At temperatures ≥1400°C, the weight change no longer followed the linear dependence and showed a rather parabolic behavior with a concave upward slope. The core shape and the gas flow around ferrite cores were important factors that affected the rate of zinc vaporization, but not the grain size.     

Thermal and thermomechanical properties of poly(ethylene oxide) networks produced with silica and organic crosslinking agents

The thermal and thermomechanical properties of two series of poly(ethylene oxide) networks (NPEOs) were investigated as a function of the chain length between crosslink sites (M_c) and the concentration of LiClO₄ (C_L) in the NPEOs. The two series of networks were produced with silica and organic crosslinking agents and, therefore, had crosslink sites of different natures: one was an inorganic silicate network (silica NPEO), and the other was an organic polar group (organic NPEO). The crosslink sites in both series of networks were commonly covalently bonded to the poly(ethylene oxide) (PEO) phase through a urethane group in the NPEOs. The glass‐transition temperatures (T_g's) of the PEO phases in the NPEOs, according to differential scanning calorimetry, increased with a decrease in M_c and were higher in the silica NPEOs than in the organic NPEOs under the same M_c conditions. The difference in T_g between the two series of networks with the same M_c values increased with decreasing M_c. These results suggested that the interaction of crosslink sites with the PEO phase was stronger in the silica NPEOs than in the organic NPEOs. The addition of LiClO₄ to the NPEOs resulted in T_g of the PEO phase in the NPEOs being elevated and increased according to the increase in C_L. The increase of T_g of the PEO phase according to the increase of C_L in the NPEOs was retarded or saturated at high values of C_L, and this indicated that the limit of solubility of the salt in the polymer was attained. The retardation or saturation of the increase of T_g was also observed in dynamic mechanical analyses. The curves of the loss factor tan δ and temperatures from the dynamic mechanical analyses for the NPEOs with high values of C_L showed shoulders or double peaks indicating the existence of the second phase in the polymer networks. In the curves of tan δ for salt‐complexed NPEOs with high values of C_L, silica NPEOs showed a shoulder of low intensity, but organic NPEOs showed a distinguished second peak becoming stronger with increasing C_L. The results of the T_g behavior and tan δ curves suggested that the salt solubility in the NPEOs was limited and that the salt solubility of PEO in the silica NPEOs was higher than that in the organic NPEOs. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 270–277, 2003     

Effect of TiO2 thin film thickness and specific surface area by low-pressure metal–organic chemical vapor deposition on photocatalytic activities

TiO₂ photocatalyst films having an anatase crystal structure with different thickness were prepared by the low-pressure metal–organic chemical vapor deposition (LPMOCVD) to examine the effect of growth conditions on photocatalytic activity. Film thickness was linearly proportional to the deposition time. Structure of the film was strongly dependent on the deposition time. In early stage of deposition, fine particles deposit on the substrate. As increasing the deposition time, crystal orientation is gradually selected following the Kolmogorov model and c-axis oriented columnar crystals become dominant. The photocatalytic activity strongly depends on the film deposition time (or film thickness) in nonlinear way. The optimum thickness of TiO₂ catalyst film grown by LPMOCVD may locate between 3 and 5 μm.     

Blends of chlorinated isotactic polypropylene with poly(ethylene-co-vinyl acetate) I. Effect of component polymers composition on the blend miscibility

Chlorinated isotactic polypropylenes (CPP) having various chlorine contents were blended with poly(ethylene-co-vinyl acetate)s (EVA) having various vinyl acetate (VA) contents. The blends were made by casting films from dilute THF solutions and miscibility of the blends was identified by single glass transition temperature, which was confirmed by DSC and dynamic mechanical measurements. Based on the miscibility data from a large number of CPP/EVA combinations, a miscibility map was depicted where CO equivalent weight (CO-EQW) of EVA was plotted against chlorine equivalent weight (Cl-EQW) of CPP. Though an attractive interaction between CPP and EVA could be detected in all the miscible and immiscible blend pairs, miscibility of the CPP/EVA blends could solely be observed in a relatively narrow range of Cl-EQW ca. 65–100 and CO-EQW ca. 170–230.     

Improved mechanical properties of shape‐memory polyurethane block copolymers through the control of the soft‐segment arrangement

High‐performance shape‐memory polyurethane block copolymers, prepared with two types of poly(tetramethylene glycol) (PTMG) used as soft segments, were investigated for their mechanical properties. Copolymers with a random or block soft‐segment arrangement had higher stresses at break and elongations at break than those with only one kind of PTMG. Random copolymers with fewer interchain interactions showed higher elongation than block copolymers. All the copolymers had shape‐recovery ratios higher than 80%. In dynamic mechanical testing, the glass‐transition behavior clearly depended on the soft‐segment arrangement: random copolymers had only one glass‐transition peak, whereas block copolymers showed two separate glass‐transition peaks. Overall, the control of the soft‐segment arrangement plays a vital role in the development of high‐performance shape‐memory polyurethane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2410–2415, 2004     

Kinetics of cellobiose decomposition under subcritical and supercritical water in continuous flow system

The effects of reaction temperature, pressure and residence time were investigated with a flow apparatus. Cellobiose decomposition kinetics and products in suband supercritical water were examined at temperatures from 320 to 420 °C at pressures from 25 to 40 MPa, and at residence times within 3 sec. Cellobiose was found to decompose via hydrolysis and pyrolysis. The yield of desired hydrolysis product, glucose, was the maximum value of 36.8% at 320 °C, 35 MPa, but the amount of 5-(hydroxymethyl)furfural (HMF), fermentation inhibitor increased too because residence time increased in the subcritical region owing to decrease of reaction rate. Meanwhile, though the yield of glucose is low in the supercritical region, the yield of HMF decreased compared with the subcritical region; and at the minimum yield of HMF (380 °C, 25 MPa), the yield of glucose was 21.4%. The decomposition of cellobiose followed first-order kinetics and the activation energy for the decomposition of cellobiose was 51.05 kJ/mol at 40MPa.