ISSN:0032-3888    

DOI:10.1002/pen.760040302

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760040303

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractInvestigation of the crystallography of the thin platelike polymer crystals precipitated from dilute solution has led to the concept of chain folding in polymer crystallization. This unexpected and unusual phenomenon has produced much speculation about both its origin and its implications concerning the morphology of the polymer crystals. The theories which have been proposed to account for the observed effects fall into two categories: (a) equilibrium theories; and (b) kinetic theories. At the moment the kinetic theories appear to be the more successful in explaining the observed morphology and behavior of the polymer crystals. Essentially it is proposed that the plate‐like habit of the crystals results from the formation of crystal uncleii from single polymer molecules followed by a growth process whose rate is controlled by nucleation of new crystal layers on existing completed crystal faces. Quantitative observations of crystal growth rates and of the influence of supercooling on the thickness of the crystals are consistent with the predictions of these theorie

ISSN:0032-3888    

DOI:10.1002/pen.760040304

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractThe relationship between crystallization and deformation is two‐fold: (1) deformation or flow in polymers prior to crystallization has an important influence on the resultant crystalline morphology and (2) the morphology in turn largely determines the response of the structure to further deformation after crystallization. Thus, an understanding of deformation processes in crystalline polymers is intimately related to the crystallization processes and vice versa. The crystallization process may be approached by considering the observed morphological structures as being analogous to the usual crystal habits with the addition of various crystal‐defects which add bending and twisting to the more common crystallographic variations. The crystal habit or morphology may be characterized by its surface to volume ratio. Crystallization of polymers may be considered as three steps (1) the formation of primary nuclei (2) crystallographic growth (also a nucleation controlled process) and (3) the introduction of crystal‐defects which cause bending and twi

ISSN:0032-3888    

DOI:10.1002/pen.760040305

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractStudies of polymer morphology under ideal conditions approaching equilibrium structures have been shown to be valuable in the development of an understanding of the relationship of properties to structure. Practical fabrication operations do not permit the achievement of equilibrium structures in commercial products and its is therefore necessary to study the effects of processing on the actual structures that result. In addition, an understanding of the effects of processing variables on properties permits the development of fabrication operations which can be directed toward the improvement of properties. Topics covered include the effects of hydrostatic pressure during processing, effects of combinations of pressure and thermal history, relationships between thermal history and crystallization rates in isotactic polymers and the kinetic and morphological effects of flow deformation on crystallizable plastics.

ISSN:0032-3888    

DOI:10.1002/pen.760040306

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractMechanical and dielectric relaxation as related to the morphology of crystalline polymers is reviewed. The behavior with temperature of the imaginary part of the complex dielectric constant and the mechanical loss factor, tan δ, at constant frequency is discussed in detail for two typical crystalline polymers: poly(chlorotrifluoroethylene) and polypropylene. Three relaxations are typically observed: a low temperature relaxation occurring at temperatures below the dilatometric glass transition temperature; a glass temperature relaxation occurring near the glass transition temperature; and a high temperature relaxation occurring between the glass temperature and the melting point. The activation parameters are given for these relaxations, and the influence of morphology on them is discussed along with possible molecular interpretations

ISSN:0032-3888    

DOI:10.1002/pen.760040307

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractStructural changes are considered in light of the two differing views of the structure of crystalline polymers involving either a two phase structure or a single phase structure involving detects. A compromise picture is proposed which appears consistent with existing experimental evidence. Optical methods are described for analyzing structural changes accompanying deformation of these polymers. These include x‐ray diffraction, static and dynamic birefringence measurements and dynamic light scattering studies. The results are consistent with a two stage deformation process involving first the elastic deformation of a spherulitic or crystalline structure followed by an internal rearrangement of crystals within this structure, taking place by a number of mechanisms such as recrystallization, defect migration, plastic flow and crystal rotation. The time dependence of some of these processes is studied and related to structural feature

ISSN:0032-3888    

DOI:10.1002/pen.760040308

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractOxidation of many polymers occurs by a free‐radical, chain mechanism similar to that developed for the oxidation of volatile hydrocarbons. The rate at which various polymers oxidize and the extent of the reaction is influenced both by the physical and by the chemical structure of the particular polymer. Important morphological changes may also occur as a result of oxidation. Polymer degradation by oxidative reactions can be inhibited effectively at several stages in the over‐all reaction. Synergistic combinations in which each component of a stabilizer system inhibits primarily at one of these stages are particularly effect

ISSN:0032-3888    

DOI:10.1002/pen.760040309

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractThe deterioration of plastics by biological agents of considerable concern not only to the U. S. Department of Defense but to the national economy as a whole. Although the importance of the subject was recognized by some since the early days of the plastics industry, widespread investigation first began during World War II when serious problems were encountered in the tropics with electrical and electronic equipment. In the recent past the great developments in oceanography have emphasized that marine biodeterioration of plastics requires much more investigation. Biodeterioration of plastics is characterized according to that caused by microbiological agents, macrobiological agents, and marine biological agents. the important past and recent knowledge in each category is summarized.

ISSN:0032-3888    

DOI:10.1002/pen.760040310

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractStress‐strain relationships and evaluations thereof at testing and evaluation speeds from 1 to 50 inches per minute are presented. Behavior characteristics at “static” and dynamic strain rates are discussed and a brief reference to lateral critical velocity is

ISSN:0032-3888    

DOI:10.1002/pen.760040311

出版商:Society of Plastics Engineers, Inc.    

年代:1964

数据来源: WILEY