摘要:

AbstractFilms of nylon 6, polypropylene, and ethylene–vinyl acetate copolymers were graft polymerized with acrylamide or dimethylacrylamide to render the hydrated surfaces slippery. Following UV irradiation in air, the films were placed in the aqueous monomer solution and then either heated to 50°C after degassing or UV‐irradiated in the presence of a small amount of riboflavin without degassing to effect graft polymerization. The graft polymerization altered the films from the hydrophobic and nonlubricating to the hydrophilic and slippery surfaces. To evaluate the surface lubricity, the coefficient of friction (μ) against a glass plate in water was determined with the help of a tensile testing machine. The μ value for the films surface‐grafted with acrylamide up to 30 μ g cm−2was reduced to less than 0.05, regardless of the substra

ISSN:0021-8995    

DOI:10.1002/app.1990.070390301

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

年代:1990

数据来源: WILEY

摘要:

AbstractTensile property data for polystyrene samples of varying polydispersity are correlated with various parametric measures of molecular weight. Traditional measures of molecular weight, such as M̄n, M̄w, and M̄z, are shown to be unable to account for the variation of tensile properties with molecular weight. However, a new molecular weight parameter, termed the failure property parameter, is able to provide a single relationship between tensile strength and the parameter for both the broad and narrow distribution polymers. The form of this parameter is consistent with its having origins in the view that it is the entanglement network in an amorphous polymer that provides the observed strength properties. Specifically for polystyrene, the failure property parameter results indicate that material below 60,000 molecular weight does not contribute to polymer strength. Although the results of this investigation are specifically for polystyrene, the arguments used to develop the failure property parameter are not dependent on polymer chemical structure. Consequently, we believe that both the concepts and definition of this new parameter are applicable to all amorphous polyme

ISSN:0021-8995    

DOI:10.1002/app.1990.070390302

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

年代:1990

数据来源: WILEY

摘要:

AbstractStudies on impact and tensile properties of binary blend of PP and ABS and ternary blend of PP, ABS, and LDPE are presented. Variation of impact strength and the fracture surface morphology with blend composition is examined and interpreted. Tensile behavior in the yield region is studied and the trends of variation of work of yield and impact strength are compared to ascertain the predominent mechanism of impact toughening in these binary and ternary blends. An analysis of yield–stress data in terms of theoretical models is presented to reveal the differences in these binary and ternary blends, attributable to the role of LDPE component in the ternary blen

ISSN:0021-8995    

DOI:10.1002/app.1990.070390303

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

年代:1990

数据来源: WILEY

摘要:

AbstractResole phenolic resins are widely used for gluing wood structures. Solid state13C‐NMR and wide angle X‐ray scattering experiments show that a typical resole adhesive disrupts some of the crystallinity of the cellulose. Several explanations are offered for this observation. It is possible that this effect is connected with the adhesive action of the phenolic polymer. If this is so, then measurements of the type described here could be used to understand the adhesion better and to develop better wood gl

ISSN:0021-8995    

DOI:10.1002/app.1990.070390304

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe low temperature surface and bulk nitration of cellulose has been investigated by electron spectroscopy for chemical analysis (ESCA),13C‐NMR and X‐ray diffraction. Acid mix composition has been probed at room temperature and at low temperatures (0–20°C) by Raman spectroscopy. This multitechnique approach has been employed to elucidate the behavior of surface degree of substitution (DOS) with acid mix composition over a 40°C temperature range. The data obtained have prompted a reinterpretation of previously reported work. Surface “equilibrium DOS” is shown to be established within 1 s at all temperatures investigated. but, at lower temperatures (>5°C) the surface DOS as monitored by ESCA is observed to “dip” after immersion times oft<5 s. This change in DOS is correlated with major structural changes in the fiber as observed by SEM. At low temperatures, e.g., −15°C, nitration is shown to be complete throughout the cellulose fiber after 10 h nitration. Solution state13C‐NMR is used to compare the nitrate ester substitution distribution in cellulose nitrates prepared from acid mixes of the same composition at d

ISSN:0021-8995    

DOI:10.1002/app.1990.070390305

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

年代:1990

数据来源: WILEY

摘要:

AbstractMoisture regain of jute fiber was studied at different alkali concentrations and temperatures. It was found that the moisture regain increased up to 4.5Nalkali treatment and then leveled off. Variation in swelling temperature had no significant effect on moisture regain. Amorphous fraction calculated from Valentine's equation using sorption ratio was compared with infrared crystallinity. The accessibility was increased with decreasing crystallinity in alkali‐treated jute fiber, where as in cyanoethylated jute fiber it increased with increasing the degree of cyanoethylatio

ISSN:0021-8995    

DOI:10.1002/app.1990.070390306

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe sorption behavior of heavy metal thiocyanate complexes was investigated for dibenzo‐18‐crown‐6 (DB18C6) resin and bis[2‐(o‐methoxyphenoxy)ethyl]ether (BMPE) resin. The DB18C6 resin showed a high sorption ability and the degree of zinc sorption increased significantly with thiocyanate concentration. This behavior was not observed for BMPE resin. The sorption behavior was influenced by the countercation species, and the degree of sorption of zinc ions showed the maximum when the potassium thiocyanate was used as a complexing salt. The sorbed species appear to be KZn(SCN)3, K2Zn(SCN)4in the potassium thiocyanate system, and Zn(SCN)2in the lithium thiocyanate system, respectively, according to analysis of the sorption equilibrium. Sodium and ammonium thiocyanate systems show an intermediate behavior of the two. The sorption selectivity for DB18C6 resin depended not only on the hydrophobic nature of heavy metal thiocyanate complexes but also on the stabilization of counter cation species with crown ether matrix, and the sorption selectively was found to be effectively controlled by countercation species according to the cation‐chelatio

ISSN:0021-8995    

DOI:10.1002/app.1990.070390307

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe applicability of high performance size‐exclusion chromatography was tested for anionic polymers with a new type of column. It was found that a solvent salt concentration of 0.1Mand an elevated temperature (60°C) prevented adsorption of the polystyrene sulfonate standards on the column packing. The calibration curve and the effect of the concentration on the retention volume remained, however, colum‐dependent. We concluded also that the use of the column was restricted to the linear range of the calibration curve and to concentrations below 1 mg mL−1for the highest molecular weight standards. The influence of the flow rate (below 1 mL min−1) on the retention volume was negligible. The main cause of errors when the universal calibration technique is used originated in the experimental determination of the intrinsic viscosities of the standards. The combination of the errors on the viscosity and on the experimentally determined retention volume easily introduced an error of 15% on the determined molecular weight of the sulfated polysaccharidek‐carrageenan. The use of the universal calibration method for an exact molecular weight determination of anionic natural polymers is therefore still qu

ISSN:0021-8995    

DOI:10.1002/app.1990.070390308

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new type of solid‐state crystalline photopolymerization is researched in which, different from the topochemical polymerization, vinyl monomers are filmed under the induction of other macromolecular compound, crystallized, and polymerized after photoirradiation. Therefore, it may be also known as induction‐filming polymerization. The crystalline polyacrylamide film with large spherulite structures was obtained from the crystalline acrylamide by this means. Microscopy, differential scanning colorimetry, and infrared measurements were carried out. Mechanism is proposed for the induction‐filming polymerization inv

ISSN:0021-8995    

DOI:10.1002/app.1990.070390309

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

年代:1990

数据来源: WILEY

摘要:

Abstractβ‐Propiolactone was polymerized in bulk at 5°C using pyridine as initiator. The melt spun fibers were drawn at 50°C and subjected to degradation, which was monitored by mechanical, thermal, and molecular weight measurements. The hydrolytic degradation of poly(β‐propiolactone) fibers has been investigated in a buffered salt solution (pH 7.2) maintained at 37°C. The degradation was found to be very rapid during the first 90 days of immersion, with respect to mechanical properties and the weight average molecular weight. Between 90 and 180 days there were no significant changes in the mechanical properties which, however, rapidly decreased thereafter and finally reached zero at 240 days. The crystallinity seemed to increase in a linear fashion, during the same period, from about 5

ISSN:0021-8995    

DOI:10.1002/app.1990.070390310

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

年代:1990

数据来源: WILEY