摘要:

AbstractThe effects of gas plasma generated by electrodeless (inductive coupling) glow discharge on polymers were investigated as functions of gas pressure, discharge power, exposure time, and type of plasma gas. A remarkable similarity between the plasma susceptibilities of low molecular weight organic compounds and polymers was observed; i.e., polymers which have ether, carbonyl, ester, or carboxylic acid attached to a nonaromatic structure are very susceptible to plasma. The weight loss was proportional to the exposure time and exposed area. The discharge power and type of gas were found to have a great influence on both the rate of weight loss and the morphology of the exposed surface. The predominant effect of plasma on polymers was found to be degradation (manifested by weight loss). The crosslinking effect was found to be marginal with many polymers; however, significant crosslinking was observed with double bond‐containing polymers. The crosslinking was examined by swelling the treated films. With copolymers of styrene–butadiene, 4‐vinylpyridine–butadiene, methacrylic acid‐butadiene, and acrylic acid–butadiene, the crosslinking was greatly dependent on the discharge power, the butadiene content of the copolymers, and the exposure time. Both degradation and crosslinking by gas plasma were generally limited to the exposed surface; however, the propagation of crosslinking in the direction of thickness was observed with copolymers of styrene–butadiene. The plasma of organic vapor also cause degradation of plasma‐susceptible polymers, particularly at high wattage, although the deposition of polymer occurs

ISSN:0021-8995    

DOI:10.1002/app.1973.070170111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractMelt flow behavior was examined using “as polymerized,” mechanically intact polypropylene, and the same polymer after pelletization in a screw extruder. In addition, the polymers were extruded through different capillaries and subsequently tested for melt flow characteristics. Significant differences in shear stress at a given shear rate and shear rate critical to the onset of extrudate roughness were found and compared with the previous shearing history. Both shearing intensity and mode of flow were found to impart long‐lasting and short‐term effects to the melt flow properties of the polymer. These differences were not explainable on the basis of changed molecular weights, since no significant differences were observed in the molecular weights as a result of the shearing treatments used in thi

ISSN:0021-8995    

DOI:10.1002/app.1973.070170112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe flow pattern of molten polymer through capillaries was studied by using a tracing method. An incompatible polymer was added to polypropylene as a tracer, and the influence of shear in a capillary rheometer on the tracer particle size as well as on the distribution of the particles in the extrudate in relation to flow was studied. It was found that the particle size varied inversely with shear rate of extrusion, capillary aspect ratio, polymer viscosity, and extrusion temperature. The flow was found to be of the telescopic type, and the tracer particle size was independent of position along the radius of the cylindrical extrudate. It is assumed that the supermolecular structure of a polymer melt is of the cluster type suggested by Busse, and it is postulated that spherical clusters of molecules in the melt are modified by shear analogously to the spherical particles of the incompatible tracer polymer. The large spectrum of melt properties obtainable, by various shearing treatments, from a polymer of constant molecular structure suggests that a wide range of supermolecular structures must be possible in the polymer melt.

ISSN:0021-8995    

DOI:10.1002/app.1973.070170113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractAs a continuation of the investigation of the effects of shearing history on the subsequent properties of polypropylene, the changes of crystalline structure induced by differences in shearing history were examined. It was found that even extremely high shear in a capillary does not increase the crystal orientation in the extrudate. Such orientation is increased by either extremely high rates of extension of the molten extrudate or by slight plastic deformation occurring in the solidified extrudate as a result of imposed stress. The size of crystallites was found to decrease with increasing shear rate experienced by the polymer prior to the crystallization process. A possible explanation for these changes in polymer properties related to shearing history is proposed as an extension of the cluster flow theory of Busse. This explanation takes into account the size of the ball‐like clusters, their internal structure, as well as the type, number, and length of the intercluster connections. The changes induced in a polymer by shearing are of technologic importance in connection with both melt flow characteristics and solid‐state properties subsequently develo

ISSN:0021-8995    

DOI:10.1002/app.1973.070170114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractAn experimental study has been carried out to investigate the effects of spinning conditions on the shape of fibers spun through noncircular spinnerette holes, namely, rectangular holes, trilobal holes, and round holes with lugs. For the study, bench‐scale apparatuses of wet spinning and melt spinning were used which had been constructed in connection with an earlier study by Han. In the wet‐spinning experiment, the spin dope used was an aqueous solution of polyacrylonitrile (PAN) consisting of approximately 10% polymer and 40% sodium thiocyanate (NaSCN), and the spin dope was spun into aqueous solutions of NaSCN. In the melt‐spinning experiment, polystyrene was used. The variables investigated were: size and shape of the spinnerette hole, coagulating bath concentration, throughput rate, and jet stretch. It has been found in wet spinning that, for a given shape of spinnerette hole, the fiber shape is most strongly affected by jet stretch and relatively little by the bath concentration and throughput rate. Also determined in the wet‐spinning experiment was the maximum jet stretch at which thread breakage occurs. It has been found that the maximum jet stretch decreases as bath concentration is in

ISSN:0021-8995    

DOI:10.1002/app.1973.070170115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe plasma polymerization of organic compounds was used to prepare a composite reverse osmosis membrane which consists of an ultrathin semipermeable membrane formed by plasma polymerization of an organic compound or compounds and a porous substrate. Many nitrogen‐containing compounds (aromatic amines, heteroaromatic compounds, aliphatic amines, and nitriles) were found to yield excellent reverse osmosis membranes by plasma polymerization directly onto porous substrates such as Millipore filters, porous polysulfone filters, and porous glass tubes. Factors involved in the preparation of reverse osmosis membranes by plasma polymerization were investigated and discussed. The plasma polymerized membranes have the following unique features: (1) very stable performance independent of salt concentration and applied pressure (practically no water flux decline was observed with many membranes): (2) salt rejection and water flux both increase with time in the initial stage of reverse osmosis (consequently, the performance of the membrane improves with time of operation); (3) very high salt rejection (over 99%) with high water flux (up to 38 gfd) can be obtained with 3.5% NaCl at 1500 psi (membranes perform equally well under conditions of sea water conversion and brakish water treatment

ISSN:0021-8995    

DOI:10.1002/app.1973.070170116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe dielectric properties of partially sulfonated polystyrene films (15% degree of sulfonation) in their dry and slightly wet (4.7% by weight of water content) states were measured over the frequency range between 102and 105Hz with temperature as a parameter. Loosely crosslinked (1% divinyl benzene) polystyrene films were synthesized and sulfonated with chlorosulfonic acid to a 15% degree of sulfonation. Films containing more than 15% sulfonation were very brittle. Dielectric constant and loss data of these sulfonic acid films are presented at various temperatures and are correlated in terms of Cole‐Cole plots. The dielectric response characteristics of these films find application in the electroformation of sulfonated polymer electrets, which have been shown to possess a high degree of polarizability and are capable of storing large amounts of electric charg

ISSN:0021-8995    

DOI:10.1002/app.1973.070170117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractThe d.c. electrical conductivity of 14% (by weight) sulfonated polystyrene films was measured as a function of temperature from 20° to 60°C in a 25‐micron vacuum. Sulfonated films in the silver, cadmium, and methylene blue sorbed forms were prepared for these electrical measurements. Plots of log specific conductance versus reciprocal temperature gave straight lines with activation energies of 0.49 eV for methylene blue, 0.60 eV for Ag, and 0.98 eV for Cd. Large conductivity ansiotropies were also measured for the sulfonated polystyrene films in the Ag and methylene blue forms. Attempts with Hall‐effect measurements to determine the sign and concentration of the charge carriers were unsuccessful. Photoconduction studies were also carried out with Ag‐, Cd‐, and methylene blue‐doped sulfonated polystyrene films in the film lateral direction of highest photocurrent. Rise of photocurrent under d.c. illumination was found to be exponential with time constants of 29, 3.5, and 1.0 sec for Ag‐, Cd‐, and methylene blue‐doped samples. The rise and decay of photocurrent in these films exhibited similar responses. Photocurrent was ohmic up to 400 V and varied linearly with light intensity up

ISSN:0021-8995    

DOI:10.1002/app.1973.070170118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractA calorimeter has been designed, calibrated, and tested to measure the total amount of heat released and the rate of heat released from the combustion of fabrics in air. Calibration of the calorimeter gave a reproducibility of ±3% for total heat measurements and ±5% on rate measurements. Consideration of systematic errors gives an expected accuracy of ±7% for total heat and ±10% for combustion rate measurements. Measurements on cotton show that 90% of the standard heat of combustion is released when cotton is burned in air. The rate of heat release for cotton is independent of fabric weight. The constancy of rate of heat release as determined calorimetrically confirmed the result implied by the 45° test measurements on flame spread rate. The rate and amount of heat release of other commercial fabrics and blends were also meas

ISSN:0021-8995    

DOI:10.1002/app.1973.070170119

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY

摘要:

AbstractEfficiencies of three flame retardants for cellulose, phosphoric acid, diammonium phosphate, and THPOH ammonia finish, have been evaluated based on the heat release value and the rate of heat release of treated fabrics burning in air measured with the isoperibol calorimeter. The results were compared and correlated with those obtained previously with the bomb‐calorimetric technique. Complete heat balances were obtained for the systems studied by correlation of the calorimetric data and the measurement of combustible gases evolved from the fabric burning in air. The rate of heat release was found to correlate with the flame propagation rate measured at a 45° angle. The results from the heat, rate, and combustible gas measurements were interpretable in terms of existing mechanisms of flame‐retardant ac

ISSN:0021-8995    

DOI:10.1002/app.1973.070170120

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1973

数据来源: WILEY