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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1325-1330 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effectiveness of applying silent discharge plasmas (SDP) for destroying and removing volatile organic compounds (VOCs) from gas streams is experimentally evaluated with a laboratory-scale reactor. The VOCs selected for study include toluene and methyl ethyl ketone (MEK). Direct collision with energetic electrons and reaction with generated gas-phase radicals are two major mechanisms responsible for destruction and removal of VOCs from gas streams. Operating parameters investigated include applied voltage, gas residence time, and temperature and composition of the gas stream. Experimental results indicate that the removal efficiency of toluene and MEK achieved with SDP can be enhanced by operating the system at a higher gas temperature and applied voltage due to the generation of more energetic electrons and radicals. O2 is essential for removing VOCs from gas streams with SDP. More than 80% removal efficiencies were achieved with this system for both toluene and MEK. SDP can potentially serve as an alternative control technology for removing VOCs from gas streams.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 792-803 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The J-integral method to determine the fracture toughness of tough and ductile polymeric materials previously developed has been applied to the elastomer-modified polycarbonates. This investigation compares three different methods to obtain Jc: the conventional crack growth length, the stress whitening zone, and the newly developed hysteresis method. Jc values obtained from these three comparative methods are fairly close. The hysteresis method has the advantage over the other two methods of obtaining Jc without requiring the measurement of the crack growth length or the stress whitening zone, therefore avoiding the controversy in defining crack blunting. Results also indicate that the effect of elastomer quantity in polycarbonate on Jc is insignificant as long as the crack is in a stable condition. Higher elastomer contents in polycarbonate result in higher dJ/dΔa, dJ/dΔl, and tearing modulus (Tm). This indicates that the elastomer toughening mechanism is due to the increase of the energy required for crack growth extension. The hysteresis loss energy is directly related to the size of the crack tip plastic zone, and the presence of more elastomer indeed increases the crack tip plastic zone, thus making the polycarbonate tougher. Besides, the presence of elastomer tends to increase the crack initiation displacement and shift the failure modes from an unstable fracture. Jc and the criterion for crack initiation based on rate change of hysteresis energy are discussed in detail.
    Additional Material: 19 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1433-1439 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J1c values, whereas the ASTM E813-87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J1c obtained from the E813-81 or the hysteresis method.
    Additional Material: 9 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 190-194 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of physical aging on the penetration impact toughness and Mode I interlaminar fracture toughness of continuous carbon fiber (C.F.) reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites has been investigated by using an instrumented falling weight impact (IFWI) technique and a double cantilever beam (DCB) test. Composite materials studied are aged below their glass transition temperature (Tg) at various periods. Initiation force and energy of damage, failure propagation energy, impact energy and ductility index (D.I.) are reported. The Mode I critical value of strain energy release rate (GIC) of the unidirectional carbon fiber-reinforced PEEK (APC-2) composites is obtained. Results show that aging has a significant effect on the toughness of both composite materials. Energy absorbed during impact decreases with the increase of aging temperature and period. The PEEK/C.F. composites exhibit a higher retention of impact toughness than that of the PPS/C.F. composites after aging; however, the PPS/C.F. composites show a much higher ductility index. The Mode I fracture mechanism of the APC-2 composite is a combination of stable and unstable failure and shows a “stick-slip” behavior. Owing to the formation of a relative rigid structure, the fracture toughness (GIC) of APC-2 decreased with the increase of aging temperature and period.
    Additional Material: 13 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 13 (1992), S. 448-453 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The hygrothermal behavior of carbon fiber-reinforced poly(ether ether ketone) (PEEK) and poly(phenylene sulfide) (PPS) composites subjected to moisture and temperature is investigated in this study. The properties of both composites exposed to temperature/humidity and immersed in water for extended periods are studied. Properties studied include moisture sorption, crystallinity, dynamic mechanical response, tensile strength, and flexural strength. Both the PEEK/C.F. and the PPS/C.F. composites exhibit good moisture/temperature resistance and property retention after hygrothermal exposure. The diffusivities and the equilibrium moisture absorption are measured at 60, 70, 80°C with 85% R.H. (relative humidity). A Fickian type diffusion is observed at all exposures. Crystallinity increase of the composites is found for the PPS/C.F. composites exposed to 80°C with 85% R.H. environment and is correlated with the damping properties in the dynamic mechanical study. However, the hygrothermal effect on the crystallinity and the glass transition temperature of the PEEK/C.F. composites is negligible. Mechanical properties of the PEEK/C.F. composites decrease slightly with the increase of temperature/moisture and exposure period. Mechanical property reductions of the PPS/C.F. composites decrease with the increase in exposure temperature when subjected to a similar environment; this is due to the relatively complete molecular relaxation and additional crystallization at higher temperatures.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1167-1172 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon-13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solution.
    Additional Material: 4 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1198-1202 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The energy stored in polystyrene after plastic deformation is measured by the differential scanning calorimetry (DSC) technique. Similar to metals, the stored energy increases with plastic straining, first rapidly, and then more slowly, and finally the stored energy seems to approach a saturation value (about 1 cal/gram). By comparing to the plastic work done, the fraction stored ranges from 30 percent after 10 percent compression to 10 percent after 60 percent compression. The fraction is about twice as large as that of copper. The release of stored energy has two distinct parts, one below Tg and the other above Tg. Most of the strain recovery seems to accompany the second part. By using the Kissinger plot, the second part has an activation energy, of 142 kcal/mole which is about 10 percent larger than that of compressive strain recovery.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1173-1181 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chlorination of high density; polyethylene results in polymers which consist of unmodified methylene units and chlorinated methylene co-units. The effect of the concentration and distribution of chlorinated units on the solid state structure has been examined by thermal, wide angle X-ray diffraction and dynamic mechanical analysis. As the substitution becomes more random, the crystallinity, crystallite size, and crystalline perfection decrease for a given chlorine content. The chlorinated units are shown to be capable of co-crystallizing, and the concentration of chlorine in the crystalline phase increases as the distribution is made more random. Concurrently, the chlorine concentration of the amorphous phase decreases. Segregation of chlorine into the amorphous regions is most efficient when the substitution is blocky.
    Additional Material: 13 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 1616-1627 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Bubble nucleation in a mixture of volatile liquid and polymer melt under shear flow conditions was investigated, using a light scattering technique. In the study, a mixture of polystyrene and trichlorofluoromethane was extruded through a slit die having glass windows and bubble nucleation in the flow channel was observed optically. A He-Ne laser was used to illuminate the nucleating and growing bubbles. The light flux scattered by the growing bubbles at a fixed angle was detected by a photomultiplier with the aid of a high-voltage power supply. The bubble nucleating site in the flow channel was located using a computer controlled tracking system, which was designed to move the entire optical system automatically in the three dimensional space, and also had the ability to follow the software control command and cooperate with the data acquisition system. When the site of bubble nucleation was located, the coordinates of this site in the flow channel and the experimental conditions were automatically recorded on a floppy diskette by entering a software command. The pressure profile along the flow channel was measured by pressure transducers, with the aid of a microprocessor-based pressure reading system. It has been found that the site of bubble nucleation varies with the position in the direction perpendicular to the flow direction, which is attributed to the nonuniform velocity and stress distributions in the slit flow channel. The present investigation suggests that bubble nucleation can be induced either by flow and/or shear stress; specifically, flow-induced bubble nucleation is the dominant mechanism at positions near the center of the die opening, and shear-induced bubble nucleation is the dominant mechanism at positions near the die wall. It should be mentioned that the bubble near the die wall may also be generated by cavitation brought about by the surface roughness of the wall and also by thermal fluctuations due to the heat transfer between the metal (die wall) and the mixture of polymer and volatile component. The present study indicates that bubble nucleation in a shear flow field can occur at an unsaturated condition. This is in contrast to bubble nucleation under static conditions, where supersaturation is necessary.
    Additional Material: 17 Ill.
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