摘要:

AbstractResins having different rubber particle sizes were prepared by polymerizing impact polystyrene using different agitation rates but keeping all other parameters constant. Also, samples were made varying the amount and type of rubber and type of agitation. The impact and tensile properties of the prepared resins are studied in relation to existing theories of rubber particle reinforcement. The particle size dependence of energy absorption in impact (high intensity) and tensile (low intensity) testing appear to be opposite in nature. Energy absorption increases with increasing particle size in the high‐intensity mode and decreases in low‐intensity testing. Different mechanisms are, therefore, postulated to be operative in each of these two test meth

ISSN:0021-8995    

DOI:10.1002/app.1978.070220301

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

年代:1978

数据来源: WILEY

ISSN:0021-8995    

DOI:10.1002/app.1978.070220302

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

年代:1978

数据来源: WILEY

摘要:

AbstractDeterminations of individual terminal carboxylic acid endgroups and terminal reducing sugar moieties together with analysis of spent liquor revealed that the same reactions occur during treatment of hydrocellulose with hot sodium bicarbonate as with sodium hydroxide solution. Some fragmentation reactions, of little importance in the presence of sodium hydroxide, are favored in bicarbonate medium while benzilic acid rearrangements are less favored. Hence, the formation of 2‐dieoxyerythropentonic acid endgroups is more important. Among the soluble reaction products, 3,4‐dideoxypentonic acid formed via 3‐deoxypentulose and cyclic compounds formed via the same precursor are much more abundant in bicarbonate medium while 3‐deoxy‐2‐hydroxymethylpentonic (isosaccharinic) acids are le

ISSN:0021-8995    

DOI:10.1002/app.1978.070220303

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe fluorescence and phosphorescence excitation and emission spectra of commercial poly(4‐methylpent‐1‐ene) are examined using a fully compensated spectrofluorometer. The excitation spectra of the polymer are compared with the absorption spectra of model chromophores of those believed to be present in the polymer. The fluorescence emission is primarily associated with the presence of enone and the phosphorescence with dienone impurity chromophoric units. Bromination of cold hexane extracts of the polymer significantly reduces the intensity of the fluorescence, confirming the presence of ethylenic unsaturation. The behavior of the luminescent enone and dienone groups during irradiation under sunlight‐simulated conditions is also examined. Possible mechanisms for the participation of these chromophoric units in the photo‐oxidation of poly(4‐methylpent‐1‐ene

ISSN:0021-8995    

DOI:10.1002/app.1978.070220304

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

年代:1978

数据来源: WILEY

摘要:

AbstractExperimental data on the specific volume of a 50% crystalline sample of poly(tetrafluorethylene) are presented and discussed. Data points were taken along 22 isotherms spaced 5 to 30°C apart (up to 372°C) in pressure increments of 100 kg/cm2up to 2000 kg/cm2. In addition to the melting transition and the first‐order solid–solid transition near room temperature, a previously reported second‐order transition near 140°C atP= 0 is observed. This transition shifts to higher temperatures with increasing pressure by about 0.015°C per kg/cm2. The melt data are discussed in detail. They can be fitted to both the empirical Tait equation, with the usual exponential temperature dependence of the Tait parameter, and to the Simha‐Somcynsky hole theory (with the reducing parametersV*= 0.424 cm3/g,T*= 7906°K, andP*= 7100 kg/cm2= 6960 bars), thus providing a test for this theory at high reduced temperatures

ISSN:0021-8995    

DOI:10.1002/app.1978.070220305

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

年代:1978

数据来源: WILEY

摘要:

AbstractElectron spectroscopy for chemical analysis (ESCA) was used to study the surface composition of several radiation‐grafted polymers in both the dry and hydrated (frozen at 160°K) states. Poly(2‐hydroxyethyl methacrylate) (HEMA) and polyacrylamide, both hydrophilic polymers, were readily detected in the hydrated or dehydrated states when grafted to polyethylene substrates. For silicone rubber substrates, both grafts were observed on the hydrated surface but were significantly decreased in surface concentration upon dehydration. For grafts on a polyester‐urethane, acrylamide was not a major constituent of either the dry or hydrated surface, while HEMA appeared to increase in abundance upon drying. The amount of the hydrophobic poly(ethyl methacrylate) found on the graft surface depended upon the substrate polymer used, but the surface abundance of poly(ethyl methacrylate) was not affected by drying. These results were considered in terms of polar group orientation, polymer chain mobility, substrate permeability, and the limitations of the ESCA technique. The implications of these results with respect to the use of radiation‐grafted hydrophilic polymers for biomedical applications are also d

ISSN:0021-8995    

DOI:10.1002/app.1978.070220306

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe relationship was investigated between birefringence and oscillatory shear deformation of linear high molecular mass polymers exemplified by narrow‐ and broad‐distribution polybutadienes and polyisoprenes. Polymer deformation at different frequencies and amplitudes was carried out in an annular gap. The stress field uniformity was not below 95%. It was shown that in oscillatory deformation of polymers in the fluid and high‐elastic states, birefringence contains a time‐independent steady component and an oscillatory component with a frequency equal to that of the assigned oscillation. A linear interrelation was found to exist between the amplitude of the oscillatory component of birefringence and that of the shear stresses, with a proportionality factor equal to the stress‐optical coefficient of the polymers. The phase of the oscillatory component of birefringence coincides with that of the shear stresses. Measurements of the steady component of the birefringence make it possible to find the steady component of the first normal stress difference resulting from the assignment of shear oscillations to the polymer. On the basis of the experimental data obtained for polybutadienes and polyisoprenes, and the literature data for polystyrene solutions, a master curve was constructed that generalizes the dependence of the steady component of the first normal stress difference in the linear and nonlinear deformation regimes on the product of the square of the deformation amplitude and the storage modulus measured at low amplitudes. This dependence is valid in the linear and nonlinear deformation regimes. It is invariant with frequency, amplitude deformation, molecular mass, and molecular mass distribution of the polymers. It is shown by visual observation of deformation that the abrupt drop in resistance of polymer to shear in large‐amplitude deformation is due to polymer rupture near the surface of the inner cylinder and is accompanied by a slip‐stick process. This is the phenomenon of spurt early observed in capillary viscometers at high shear stresses and recently investigated in coaxial cylinder devices at large amplitud

ISSN:0021-8995    

DOI:10.1002/app.1978.070220307

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe effects of sulfur atoms on the thermal degradation and flammability of cellulose phenylthiophosphonate were investigated using thermogravimetry, IR spectrometry, and limiting oxygen index flammability tester. Introduction of sulfur atoms instead of oxygen atoms in the phosphonyl groups had little influence on the thermal degradation of cellulose. The thermal reactions were altered by ion exchange with sodium ions, and degradation of the cellulose chains was retarded. Cellulose phenylthiophosphonate was self‐extinguishing above 4.64% phosphorus content. The flame‐retardant properties remained when the cellulose phosphorus ester was ion exchanged with sodium ions. It was concluded that introduction of sulfur atoms into phosphorus esters of cellulose was effective in preventing the decrease in flame‐retardant properties by ion exchange in laund

ISSN:0021-8995    

DOI:10.1002/app.1978.070220308

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

年代:1978

数据来源: WILEY

摘要:

AbstractMutual diffusion coefficients are measured for the ethylbenzene‐polystyrene system for the temperature range of 115.5°–178°C and for concentrations as high as 70 wt‐% ethylbenzene. Experiments were carried out using a quartz spring sorption apparatus which was modified for high‐temperature measurements. The diffusivity data are compared with the predictions of a recently developed free‐volume theory of polymer‐solv

ISSN:0021-8995    

DOI:10.1002/app.1978.070220309

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

年代:1978

数据来源: WILEY

摘要:

AbstractTwo black yeast polysaccharides show similar non‐Newtonian behavior when the effects of polysaccharide concentration, shear rate, pH, salt, and temperature on the viscosity of dispersions are examined. Both polysaccharides readily form viscous aqueous dispersions and can be cast into flexible films, and both stabilize oil–water emulsions. Each of these two polysaccharides occurs extracellularly in the culture fluids of two different black yeast‐like fungi—Rhinocladiella elatiorMangenot (strain NRRL YB‐4163) andRhinocladiella mansonii(Castellani) Schol‐Schwarz (strain NRRL Y‐6272). This report appears to be the first on the rheology of an extracellular polysaccharide which contains the unusual sugar N‐acetyl‐D‐gl

ISSN:0021-8995    

DOI:10.1002/app.1978.070220310

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

年代:1978

数据来源: WILEY