摘要:

AbstractThe development of gel permeation chromatography (GPC) has provided a convenient tool for the rapid determination of molecular weight distribution. The question has arisen as to the suitability of the method for specification purposes. The present work, suggested by the Naval Air Systems Command, represents an attempt to assess the precision of the method through a series of tests carried out by a number of laboratories using identical procedures on the same samples. Ten laboratories agreed to take part. Naval Ordnance Station, Indian Head, worked out standard conditions for operation of the chromatograph, for calibration of the columns, and for analysis of the GPC curves. Two samples of polystyrene were used by the various organizations for calibration of their instruments. Number‐average molecular weight, heterogeneity index, and cumulative molecular weight distribution curves were determined on four samples of carboxyl‐terminated polybutadiene (CTPB) and two samples of hydroxyl‐terminated polybutadiene (HTPB), all unidentified except by letter code. All laboratories used identical directions for setting up CTPB and HTPB calibration curves which were based on curves determined from vapor‐pressure osmometer molecular weights and GPC count numbers of fractionated material. Variation among the different laboratories was 0.15 in heterogeneity index, and a maximum of 1200 in molecular weight provided one aberrant set of values was eliminated. The six samples had heterogeneity indices from 1.15 to 1.54, while molecular weight varied from approximately 3000 to 6000. The average coefficient of variation of the molecular weight values was 6.2 ± 0.7%, which is quite acceptable. Variation in heterogeneity index was too great for specification purposes when considered among the different laboratories, but may be sufficiently good when measured by any one la

ISSN:0021-8995    

DOI:10.1002/app.1973.070170121

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe reaction of methyl iodide with cellulose β‐mercaptoethylaminocarboxylate (RDTC) made from cotton was investigated. The product was found to contain dimethyl sulfonium groups in addition to S‐methyl groups, with accompanying hydrolytic cleavage of some of urethane linkages. The iodide counterions could be easily exchanged with hydroxide and chloride ions. The dyeabilty of RDTC and its sulfonium derivatives toward Direct Sky Blue A was studied. The equilibrium uptake of the dye by RDTC decreased with increasing sulfur content, while the uptake by the sulfonium derivatives was higher than that of control cotton and increased with increasing sulfonium content. The counterions did not affect the dyeability. The dye adsorbed onto the sulfonium derivatives was very fast against solvent extraction, and could be extracted only with Cadoxen containing 0.5% sodium hydroxide. The equilibrium uptake of the dye was much more than the amount calculated on basis of the 1 : 1 ionic bonding between the sulfonic acid group in the dye molecule and the sulfonium group in the modified cotton. The spatial effect in the dye–sulfonium bonding is dis

ISSN:0021-8995    

DOI:10.1002/app.1973.070170122

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

年代:1973

数据来源: WILEY

摘要:

AbstractBei genügend asymmetrischen Reaktionsverhältnissen war es möglich, dieSchwär‐zungsgrade eines Phasenfrontphotos mit Mikrohärtemessungen zu vergleichen. Mit Hilfe der Äquidensitendarstellung konnte die Auswertung polarisationsoptischer Aufnahmen von Vernetzungsfronten verbessert

ISSN:0021-8995    

DOI:10.1002/app.1973.070170123

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

年代:1973

数据来源: WILEY

摘要:

AbstractA theory of the kinetics of consective second‐order reactions has been generalized and used to interpret observations of toluene‐2,4‐diisocyanate reacting with polyoxypropylene glycol without diluent or catalyst to form a urethane prepolymer. The first reaction in the sequence has a second‐order rate constant of 1.2 × 10−7m3mole−1sec−1at 303°K with an activation energy of 3.5 × 104J mole−1. The rate constant of the second reaction appears to be one half of this. Deviations from the theoretical kinetics and an increase in the viscosity of the prepolymer product above 1.9 kg m−1s−1(measured at 313°K) when the temperature of reaction exceeds about 360°K show that above this temperature, undesirable side

ISSN:0021-8995    

DOI:10.1002/app.1973.070170124

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

年代:1973

数据来源: WILEY

ISSN:0021-8995    

DOI:10.1002/app.1973.070170125

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

年代:1973

数据来源: WILEY

ISSN:0021-8995    

DOI:10.1002/app.1973.070170126

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

年代:1973

数据来源: WILEY