摘要:

AbstractThe polymerization of β‐propiolactone (βPL) by sodium acetate catalyst has been investigated. The polymerization behavior with monomer purified with calcium chloride was found to be a little different from that previously reported for this monomer. That is, poly‐β‐propiolactone (PβPL) obtained from βPL dried with CaCl2has a higher degree of polymerization than that obtained from conventionally treated βPL, and its infrared spectrum shows type II configuration, which differs from that reported in previous papers. Some chain transfer reaction is observed even for the polymerization of the CaCl2–dried βPL; however, this is less important in toluene. The electronegativity of the anion or cation in catalyst greatly influences the rate of

ISSN:0021-8995    

DOI:10.1002/app.1967.070110601

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

年代:1967

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile–β‐propiolactone (βPL) graft copolymer was synthesized by means of ionic polymerization, in which polymerization of βPL was initiated by polyacrylonitrile containing a small amount of some reactive groups such as COOK, COONa, COOLi, and COOH. Lower electronegativity of the countercation favored higher total conversion and higher grafting percentage. The grafting percentage increased with the reaction time and concentration of reactive groups in the trunk polymer, but grafting efficiency varied very little under these conditions. In the bulk polymerization at 60°C., grafting efficiency was about 60%, but in the solution polymerization in toluene or dioxane, grafting efficiency was higher than in bulk

ISSN:0021-8995    

DOI:10.1002/app.1967.070110602

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

年代:1967

数据来源: WILEY

摘要:

AbstractPolyacrylonitrile (PAN)–β‐propiolactone (βPL) graft copolymer was synthesized by means of the ionic polymerization of βPL in the presence of polyacrylonitrile containing diketene units by using basic catalysts. A graft copolymer was produced by the copolymerization of βPL with the lactone ring in the trunk polymer. In this graft copolymerization method, the grafting efficiency was low. However, grafting efficiency increased with the mole ratio of polymeric lactone to βPL; also higher molecular weight of PβPL favored higher grafting efficiency. The reactivity ratio of polymeric lactone to βPL was estimated to be in the range

ISSN:0021-8995    

DOI:10.1002/app.1967.070110603

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe preparation of polyisocyanurates by the polytrimerization of isocyanate prepolymers in the presence of organometallic catalysts leads to an increase in adhesive strength at 400°F. for bonding aluminum‐to‐aluminum. The trimerization efficiency of several other catalysts is briefly descr

ISSN:0021-8995    

DOI:10.1002/app.1967.070110604

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe present paper describes the results of a preliminary study of certain physical and thermal properties of benzhydrylated cotton yarns. The 200‐yd. lengths of 7/2 yarn consisting of purified mercerized cellulose were reacted in a special reactor to various degrees of substitution from DS 0.31 to DS 1.22 with benzhydryl bromide in a mixture of equal volumes of 2,6‐lutidine and dimethylformamide. The products were examined for tensile strength at break, which decreased only slightly with substitution; ultimate elongation, which was relatively uniform at 60–70% of the control yarn; and tenacity, which decreased with substitution largely due to added weight. The energy of rupture remained relatively constant at about 50% above the control. Tensile stiffness decreased progressively with substitution to about 25% of the control. Density decreased 10–11% with substitution. Crystallinity of the cellulose largely disappeared with substitutions above DS 1, and the lattice of benzhydryl cellulose began to appear. Stiffness, elastic recovery and work recovery were measured on 5‐in. specimens of the yarn in an oven while they were subjected to repeated extension to about 1–2% and relaxed as the temperature was raised twice to 200°C. and lowered. During the heating phase of the first cycle the yarn underwent considerable heat adaptation. However, during the cooling phase and during both heating and cooling phases of the second cycle, the yarns showed generally favorable behavior. Attempts are made to interpret the results in terms of molecular m

ISSN:0021-8995    

DOI:10.1002/app.1967.070110605

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe membrane potentials of thin (300–1300 A.) nitrocellulose (Parlodion) membranes have been investigated. Measurements were made in a Lucite cell by use of calomel electrodes with 0.05NKCl and 0.1NKCl. Variables having an influence on membrane structure, such as solvent polarity, temperature, and thickness, have been studied in relation to membrane potential. The range of potentials observed for Parlodion (2.1–9.2 mv.) is believed to be the result of differences in the orientation of the nitrocellulose molecules (and their accompanying electrochemically active carboxyl groups) in the membrane struct

ISSN:0021-8995    

DOI:10.1002/app.1967.070110606

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe radiation‐induced grafting to cellulose of styrene, methyl methacrylate, vinyl acetate, 2‐vinylpyridine, and 4‐vinylpyridine in methanol has been studied. All monomers exhibit appreciable grafting at room temperature in either vacuum or air for total doses up to 10 Mrad and at dose rates as high as 1.4 Mrad/hr. in a spent fuel or60Co facility. The magnitude of the grafting depends upon both the total dose and dose rate. Under certain experimental conditions, the grafting experiences a maximum which has been attributed to the Trommsdorff effect. A novel mechanism involving charge‐transfer bond formation is proposed to account for the observed data in the grafting re

ISSN:0021-8995    

DOI:10.1002/app.1967.070110607

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe kinetics of the radiation‐induced grafting of styrene to cellulose in methanol have been studied in air at dose rates of 0.007, 0.014, and 0.078 Mrad/hr. in60Co and spent fuel element facilities. The variables affecting rate of grafting include monomer concentration, radiation dose rate, and total dose. Grafting reaches a maximum at 60–70% by volume methanol in styrene. The results have been interpreted in terms of possible grafting mechanisms, including charge‐transfer intermediates; however, a complete mathematical treatment of the data is not possible at present because of the absence of appropriate swelling data for cellulose in mixtures of styrene and methanol. Poor grafting observed in solutions of up to 10% monomer is attributed to radical scavenging (predominantly from the solvent) by the monomer leading to the formation of scavenged products including homopolymer. Rate of grafting falls off for solutions above 80–90% monomer concentration and radical scavenging by monomer radicals is again postulated to account for the observed b

ISSN:0021-8995    

DOI:10.1002/app.1967.070110608

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe cold drawing of synthetic polymers is generally carried out through necking at a short collar between the drawn part and the undrawn part of the fiber; if the drawing is carried out in certain organic liquids, the lengthening is realized through thousands of simultaneous necks which permit the fiber to be penetrated by a dye dissolved in the liquid. The stress–strain curves for the drawing in liquid show an important decrease in the force at the time the multiple necking are produced. This decrease is the result of an increase in the mobility of the macromolecular chains through the penetration of the organic liquid to the level of the shoulder of the necks. A morphological study has been carried out through the observation of cuts by optical microscopy, along with a utilization of the techniques of x‐ray diffraction, IR spectroscopy, and electron microscopy. It was found that the liquid penetrates t̀he fiber to the level of the necking via a rupture of the interchain bonds which takes place during the change of structural following the drawing. The bonds are maintained ruptured as long as the liquid is not squeezed out by the aligning of the chains; they reform later to produce a new highly crystalline struc

ISSN:0021-8995    

DOI:10.1002/app.1967.070110609

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

年代:1967

数据来源: WILEY

摘要:

AbstractInfrared spectral analysis has been applied for the study of cotton–polyacrylonitrile copolymers prepared by using the preirradiation method. The degree of grafting was determined from the absorption at 2249 cm.−1, which is characteristic of the polyacrylonitrile spectrum, with an accuracy of ±

ISSN:0021-8995    

DOI:10.1002/app.1967.070110610

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

年代:1967

数据来源: WILEY