摘要:

AbstractDeuteration of cellulose in the fiber form has been studied by the new technique developed recently. Infrared spectra in the 3‐μ region were recorded to obtain four well‐resolved bands due to H‐bonded hydroxyl groups in the ordered regions. The peaks at 3298 and 3400 cm−1were assigned to cellulose I, while those at 3445 and 3493 cm−1were assigned to the cellulose II lattice structure. Cotton fibers containing both cellulose I and cellulose II lattice structures (50:50%) gave six bands in the 3‐μ region at 3230, 3298, 3350, 3400, 3445, and 3493 cm−1. Deuteration of swollen and decrystallized cotton fibers revealed that ethylenediamine brings about partial conversion of cellolose I lattice structure to cellulose II lattice structure, giving the characteristic cellulose II band at 3493 cm−1. Swelling mechanism with ethylenediamine to account for formation of cellulose II in cotton fibers has been put forward. Zinc chloride was found to retain the cellulose I structure intact. In both the decrystallized celluloses, the band at 3400 cm−1has been found to be completely wiped out. This band has been assigned to the group of H bonds mainly lying in rather imperfectly ordered crystalline regions in the fiber structure, which are attacked first during swelling treatment by both the swelling agents irrespective of their different mec

ISSN:0021-8995    

DOI:10.1002/app.1976.070200901

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe propagation of sonic pulses through solvent‐swollen polyester yarns has been investigated. A discontinuity is observed in the temperature dependence of the pulse transit time which has been associated with the on set of the glass transition of the polyester–solvent system. Good agreement is reached for several systems with an extrapolated zero shrinkage temperature obtained from dynamic shrinkage determination of the filament in the appropriate solvent. The agreement between the two methods suggests that an interaction parameter for the polyester–solvent system is measured which must ba associated with the onset of its glass trans

ISSN:0021-8995    

DOI:10.1002/app.1976.070200902

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe imbibition of glycerol by cotton has been used as a measure of fiber porosity which includes a major contribution from the fiber lumen. Cotton is swollen in glycerol to saturation and subjected to centrifugation until constant weight is attained. The glycerol retention value (GRV) is calculated from the increase in weight of cotton after swelling and centrifugation. This method is applied to determine GRVs and pore space of 12 American cottons which have different wall thicknesses but more or less the same fiber perimeter. A high negative correlation is obtained between GRV and the percentage of mature fibers for various raw and extracted cottons. Effect of fiber wax content of GRV was studied. It has been shown how the average lumen area in swollen state can be calculated from GRV and gravimetric fineness. The significance of pore space is discussed.

ISSN:0021-8995    

DOI:10.1002/app.1976.070200903

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

年代:1976

数据来源: WILEY

摘要:

AbstractPyromellitic dianhydride was reacted with various substituted aryl amines, under conditions similar to those used for polyimide formation. Yields of model imides have been greatly improved over those found in previous studies. The work has shown that the major impurities formed when the reactions were performed in solutions of N,N‐dimethylformamide or N,N‐dimethylacetamide were adducts containing chemically bound solvent resid

ISSN:0021-8995    

DOI:10.1002/app.1976.070200904

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

年代:1976

数据来源: WILEY

摘要:

AbstractThis paper describes the swelling of cotton fiber in cadoxen containing 4.6% cadmium (w/w) and 30% ethylenediamine (w/w). A special neutral salt technique is described involving the analysis of extract as well as mother liquor which enables the determination of mechanically held liquor and hence the values of true absorption. The percentage true weight swelling values are much lower than the percentage apparent weight swelling as measured by centrifuge technique. The effect of variation in material‐to‐liquor ratio on the true absorption of cadmium and ethylenediamine is also investiga

ISSN:0021-8995    

DOI:10.1002/app.1976.070200905

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe importance of the study of thermal degradation of polymeric fuels arises from their role in the combustion of solid propellants. Estimation of the condensed‐phase heat release during combustion can be facilitated by the knowledge of the enthalpy change associated with the polymer degradation process. Differential scanning calorimetry has been used to obtain enthalpy data. Kinetic studies on the polymeric degradation process have been carried out with the following objectives. The literature values of activation energies are quite diverse and differ from author to author. The present study has tried to locate possible reasons for the divergence in the reported activation energy values. A value of 30 kcal has been obtained and found to be independent of the technique employed. The present data on the kinetics support to chain‐end initiation and unzipping process. The activation energies are further found to be independent of the atmosphere in which the degradation of polymer fuel is carried out. The degradation in air, N2, and O2all yield a value of 30 kcal/mole for the activation energ

ISSN:0021-8995    

DOI:10.1002/app.1976.070200906

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution of two grades of poly(methyl methacrylate) was determined, and the solubility of that polymer in methyl ethyl ketone–2‐propanol mixtures was studied. The effects of the molecular weight distribution of the polymer and the strength of the developing solvent on electron resist sensitivity were studied experimentally and compared with a computer model of the electron exposure process. The molecular weight and the molecular weight distribution were found to have a significant effect on the sensitivity of poly(methyl methacrylate) as an electron resist. Increased sensitivity is predicted for higher molecular weight and narrower molecular weight distribut

ISSN:0021-8995    

DOI:10.1002/app.1976.070200907

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe development of porous polysulfone hollow fibers and the spinning process used are discussed. An analysis is given of the spinning parameters which determine fiber mechanical properties and permeability. Hollow fibers were prepared which display high modulus and high tensile strength. These fibers can withstand hydraulic pressures of more than 1000 psi. They can thus serve as supports for dense, ultrathin membrance coatings, useful in high‐pressure reverse osmosis and ultrafiltration processe

ISSN:0021-8995    

DOI:10.1002/app.1976.070200908

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

年代:1976

数据来源: WILEY

摘要:

AbstractA set of poly(vinyl chloride) samples were investigated with respect to their thermal stability. The dehydrochlorination rates were measured in nitrogen at 190°C by use of a very accurate, conductometric method. For all polymers studied, a significant molecular weight increase was observed after 0.4% conversion. With only one exception, samples exhibiting higher degradation rates showed higher absorptions (350–450 nm) after 0.4% dehydrochlorination. In addition, the relative amount of short polyene sequences was found to be higher for polymers with higher degrees of branching. The dehydrochlorination reaction was predominantly initiated at sites of internal unsaturation (allylic chlorines), but an initiation at tertiary chlorines and unstable end‐groups could not be completely omitted. Head‐to‐head units, extraneous impurities, and syndiotactic sequences were found to be of minor importance in this

ISSN:0021-8995    

DOI:10.1002/app.1976.070200909

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

年代:1976

数据来源: WILEY

摘要:

AbstractViscose rayon fibers modified with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were dyed with some direct and reactive dyes. Exhaustion rate of the dye onto fibers was governed by the amount and nature of the polymer grafted. In general, the dye affinity for cellulose and dye exhaustion onto fibers decreased as the graft yield increased. Dye affinity for the PAN–cellulose graft copolymers was greater than that found with PMMA–cellulose graft copolymers. Except in a few cases, the tendency of cellulose graft copolymers of ca. 13% graft to accept direct dyes was more than that of the untreated cellulose, whereas the affinity of reactive dyes for cellulose graft copolymers of up to ca. 43% polymer was more than that of untreated cellulose. The dye fixation, based on the weight of cellulose component, increased as the graft yield increased. The dyeability of cellulose oxidized with ceric ammonium nitrate was also examined. Oxidation of cellulose prior to dyeing reduced the affinity of the dye for cellul

ISSN:0021-8995    

DOI:10.1002/app.1976.070200910

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

年代:1976

数据来源: WILEY