摘要:

AbstractThe surface composition of TiCl3‐based Ziegler—Natta catalysts prepared by various methods was analyzed by ESCA to correlate the total amount of surface titanium with the catalyst activity in propylene polymerization. The ESCA peak ratio (Ti 2P3/2/Cl 2P) of the catalysts was measured to estimate the surface composition. The titanium index defined as the product of the (Ti/Cl peak ratio and surface area) was closely correlated with the catalyst activity in polymerization. This indicates that surface titanium concentration and surface area determine the catalyst activity. It was also found that removal of surface aluminum and chlorine at the catalyst preparation stage results in concentration of titanium at the surface and an increase in surface a

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190111

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractDielectric relaxation spectra of a series of polyhydroxyether copolymers have been obtained. It has been shown that the systems exhibit very similar relaxation spectra with the α(Tg) process a function of molecular weight. All systems exhibit two secondary relaxations: β (ca. 240 K) and γ (ca. 180 K). These have been assigned as hydroxyl motion and main‐chain motion, respectively. The peak positions are not functions of composition in the ranges studied. The effect of sorbed water on the relaxation spectra is discu

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190112

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe rheological behavior of an uncrosslinked polybutadiene on sudden application of finite strain was examined. The shear stress σ, two components of birefringence, and the extinction angle were measured in shear (magnitude of shear γ ≤ 3.5) and tensile stress and the birefringence were measured in uniaxial elongation (elongation ratio λ ≤ 3.8). Measurements were performed at 30°C with a tensile tester equipped with appropriate sample holders. The stress‐optical coefficient was 3.01 × 10−9Pa−1. The first and second normal‐stress differencesv1andv2were separately evaluated with the use of stress‐optical law. The Lodge—Meissner relationv1= γσ held good. The ratiov2/v1was independent of time and varied from about −0.3 to −0.2 with increasing γ in the range of measurements. Each of the stress components was factored into a function of strain and one of time, and the latter was common to all the stress components. Simple formulas were proposed to represent stress comp

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190113

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractMonolayers of certain surface‐active diacetylene compounds were polymerized at the gas—water interface and collapsed to self‐supporting fibers. The monolayer fibers were found to have an unusual morphology in that while the polymeric backbones have a random orientation, the hydrocarbon side chains are all perpendicular to the fiber axis. The fiberdspacings determined from x‐ray diffraction agree well with electron diffraction data from unperturbed polymeric monolayers. Tensile tests of the monolayer fibers indicate average strength and high

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190114

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe results of an initial study of the microwave properties of low‐density foamlike (CH)xare reported for intermediate dopant levels. The electrical conductivity and dielectric constant are obtained at microwave frequencies, and the results are analyzed in terms of effective medium theory. The possibility of utilizing the doped foamlike (CH)xas an efficient microwave absorber is discusse

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190115

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190116

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1981.180190117

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY