摘要:

Macroscopic particles of various morphological forms are created by the crystallization of isotactic polystyrene from rapidly stirred solutions. Crystallization from trimethylbenzene over a 150° C temperature range produced spherical particles, globules, fibers, and rings depending upon the growth temperature. Crystallization from cyclohexanol (θ = 83.5°C) produced fibers in the temperature range of 85° to 140° C. Globular structures, similar to those formed by stirrer crystallization in trimethylbenzene developed during the Ziegler-Natta polymerization of styrene in trimethylbenzene between 25° and 75°C. Highly birefringent conical appendages appeared on many of the globules and fibers. The fibers often exhibited a skin-core effect with an average longitudinal and transverse orientation of the chain molecules in the skin and core, respectively. The skin frequently displayed periodic banded extinctions. All of these macrostructures consisted of a highly porous assembly of constituent microfibrillar units. It is believed that the morphogenesis of these structures involves the gradual aggregation of microfibrils under the influence of the flow patterns of the system.

ISSN:0022-2348    

DOI:10.1080/00222347008212511

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

In expressing the results of particle size analysis from micrographs, i t is customary to report statistics of the distribution such as mean diameter and standard deviation, together with various weighted average diameters. Each of these values represents one or more moments of the distribution, as do the various average particle sizes which are determined by different experimental methods. An analogous situation prevails in the reporting of molecular weights of heterogeneous polymers. During recent extensive work in this laboratory on lattices of very narrow-size distributions, correlations among the various statistics became apparent; this led us to consider the narrow distribution as a special limiting case.

ISSN:0022-2348    

DOI:10.1080/00222347008212512

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.

ISSN:0022-2348    

DOI:10.1080/00222347008212513

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

It has been found that commercial poly(ethylene terephthalate) film exhibits current glow curves which have maxima at 73.5 ± 3.4°C and at 105.3 ± 3.4°C. These current glow curves were obtained by measuring the current flowing under zero bias as the temperature was raised 1°C/min. A typical curve, for untreated 1-mil du Pont Mylar A, is seen in Fig. 1. Although a paper on this study will shortly be submitted for publication, some conclusions of that paper may be stated here.

ISSN:0022-2348    

DOI:10.1080/00222347008212514

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

In an earlier note [1], the results of an investigation on the orientation distribution of crystallites in polyethylene films having different degrees of orientation and fiber symmetry were described and, from visual inspection of the intensity of the 002 reflection, a qualitative comparison with the mechanical data was made. Quantitative measurements of intensity distribution have now been made and from these the orientation distribution of crystallites and their effect on mechanical anisotropy have been evaluated.

ISSN:0022-2348    

DOI:10.1080/00222347008212515

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor