摘要:

AbstractPVC made by suspension and anionic polymerization was partially dehydrochlorinated by three different methods. In the first one, a solution in THF and in the second one, particles swollen by dioxane were treated with alcoholic KOH at low temperatures. In the third method, a solution of PVC in DMF was heated to 130°C or refluxed (153°C). The reactions were followed by UV spectrophotometry and the products analyzed by GPC. Furthermore, the products were ozonolyzed and the molecular weights of the polymeric residues determined by GPC. Treatment with KOH in THF yielded products with randomly distributed polyene sequences. At higher degrees of dehydrochlorination a slight decrease in molecular weight was observed. The polymers were shown to be built up by PVC segments with an average degree of polymerization between 70 and 80, interspaced by polyene segments each with relatively few conjugated double bonds in sequence (fewer than 15). The reaction of KOH with particles swollen in dioxane was slower but yielded products with the same molecular structure. Thermal dehydrochlorination in DMF gave rise to long polyene sequences. They were fewer in number as evidenced by the higher molecular weights of the residues after ozonolysi

ISSN:0021-8995    

DOI:10.1002/app.1978.070221101

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

年代:1978

数据来源: WILEY

摘要:

AbstractA theoretical and experimental study of instability and failure behavior during melt spinning is presented. From an analysis of system dynamics, draw resonance is shown to be a continuous processing analogue of ductile failure. Using viscoelastic fluid mechanics and the White‐Metzner constitutive model, it is shown that melts which exhibit ductile failure in elongational flow tend to show draw resonance in melt spinning. Deformation hardening melts exhibit cohesive fracture in elongational flow and melt‐spinning proces

ISSN:0021-8995    

DOI:10.1002/app.1978.070221102

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

年代:1978

数据来源: WILEY

摘要:

AbstractCyanuric chloride was reacted with polyamines and thiourea, and subsequent hydrolysis of the isothiouronium salt yielded amine polymers with divalent sulfur. The polymers scavenge cupric, cadmium, lead, and mercuric ions from considerably concentrated hydrogen chloride solutions, and they were compared with polystyrene—sulfonic acid resin. Zinc, cobaltous, and nickel ions are adsorbed only at relatively high pH (4.8–6.8). Removal of cupric, cadmium, and mercuric ions is not affected by the addition of sodium chlor

ISSN:0021-8995    

DOI:10.1002/app.1978.070221103

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe thermoluminescence (TL) and thermally stimulated current (TSC) curves observed in styrene—butadiene block copolymers, undoped and doped with different dyes, have been compared in order to test to what extent the thermoluminescence phenomenon can be correlated with intrinsic relaxation properties of the macromolecular chains. Generally, good agreement has been found between the two types of curves. However, the observance of a significant shifting of TL peaks as a function of the nature of the added dye shows that strict correspondence between the kinetics of the two phenomena is unlikely. Consequently, it seems actually dangerous to deduce the characteristic relaxation parameters of the polymer from TL curve

ISSN:0021-8995    

DOI:10.1002/app.1978.070221104

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

年代:1978

数据来源: WILEY

摘要:

AbstractX‐Ray diffraction (XRD) studies were made on native as well as mercerized ramie and cotton fibers after swelling them in ethylenediamine (EDA) solutions and washing out the swelling agent using methyl alcohol (MeOH). These treatments are shown to convert the cellulose I and II lattices into cellulose IIIIand IIIIItype lattices, respectively. Treatment of the IIIIand IIIIIsamples in boiling water or hydrochloric acid results in reconversions of their crystal lattices into the respective parent types. Alkali treatment causes a III → II type conversion. Studies using alkali‐swollen fibers as well as fibers of different lateral order as starting materials indicate the importance of the structural organization in the cellulosic materials in the production of the cellulose III lattices. Possible mechanisms involved in the lattice transformations in cellulose brought about by the EDA and MeOH treatments are disc

ISSN:0021-8995    

DOI:10.1002/app.1978.070221105

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe relationships between the properties and structure of polyurethane elastomers derived from hydroxyl‐terminated liquid polybutadiene (HT‐BD), several low molecular weight aromatic diols, and diisocyanates were studied. The curative effects of the diols were examined by such means as tensile properties, dynamic viscoelasticity, x‐ray diffraction, and others. It was found that the properties of the elastomers derived from HT‐BD were greatly affected by the structure of low molecular weight chain extender diol. These results were interpreted by the steric effect, crystallinity, and the concentration of polar

ISSN:0021-8995    

DOI:10.1002/app.1978.070221106

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

年代:1978

数据来源: WILEY

摘要:

AbstractAn experimental study was carried out on the AIBN‐initiated polymerization of styrene at 60°C. The kinetic rate constants were determined by the method of moments and the MWD method, which was proposed in a previous paper. The results compared favorably with the data in the literature and the MWD method was noted to yield more consistent results than the method of moments, which indicates the importance of considering the whole molecular weight distribution. The theoretical MWD was found to approximate the experimental MWD well. The chain‐transfer constant to AIBN was found to be between 0.09 and

ISSN:0021-8995    

DOI:10.1002/app.1978.070221107

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

年代:1978

数据来源: WILEY

摘要:

AbstractA study has been carried out on the influence of cold drawing (25°C), hot drawing (140°C), and annealing (140°C) on the structure and mechanical properties of a series of four different well‐characterized melt spun polypropylene filaments. The influence of the interaction between melt spinning and drawing variables was given special attention. Cold drawing increased the orientation in the samples, disrupts the initial monoclinic crystal structure and the morphology of the filaments, and it results in extensive fibrillation. Annealing restored the monoclinic structure but eliminated only a small part of the fibrillation. Hot drawing produced changes which were qualitatively similar to the combined effects of cold drawing and annealing. The orientation and morphology of the asspun filaments were found to have major effects on drawing behavior and the mechanical properties of the drawn fibers for a given draw ratio. It was found, however, that the mechanical properties (tensile strength, tangent elastic modulus, and elongation to break) of the melt spun, hot drawn and cold drawn, and annealed fibers could all be correlated with birefringence measurem

ISSN:0021-8995    

DOI:10.1002/app.1978.070221108

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

年代:1978

数据来源: WILEY

摘要:

AbstractDynamic mechanical properties of polystyrene (PS) and polymethylmethacrylate (PMMA) filled with glass beads and mica flakes have been investigated. The α‐dispersion temperature (Tα) increases with filler content in each system. The increase inTαis larger for PMMA than for PS in the case of the same filler; the increase inTαis larger for mica than for glass in the case of the same polymer. Polymer‐filler interaction energies have been estimated from heats of adsorption of the monomers of the filler surfaces determined by solid gas adsorption chromatography. The increase inTαcan be related to the extent of polymer‐filler interaction energy. The thickness of the partially immobilized layer on the filler surface has been estimated to be the orders of 0.1 and 1.0 μm, respectively, for the mica and the glass‐f

ISSN:0021-8995    

DOI:10.1002/app.1978.070221109

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

年代:1978

数据来源: WILEY

摘要:

AbstractA semicontinuous emulsion process was used to polymerize vinyl acetate. The parameters studied were the rate of addition of the various ingredients. The polymerization evolution was followed as samples were taken at regular intervals. These emulsion samples were analyzed for monomer conversion, rate of polymerization as well as for the size and the size distribution of the particles. The molecular weight and molecular weight distribution were obtained by gel permeation chromatography (GPC). Our study showed that the total surface of the particles is an important factor, that the reaction mechanism follows Krackeler's and Wessling's theory, and that the Smith‐Ewart ideal case does not apply her

ISSN:0021-8995    

DOI:10.1002/app.1978.070221110

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

年代:1978

数据来源: WILEY