摘要:

The papers included in this Symposium Issue are part of a continuing experiment that was initiated several years ago by the Polymer Group, Southern California Section of the American Chemical Society. In an effort to bring together the rapidly growing West Coast community of polymer chemists and plastics engineers, a series of symposia on specific polymer subjects was initiated. The first symposium, Adhesives and Adhesion, was held in November 1964; the second, recorded here, High-Temperature Polymers: Synthesis and Degradation, was presented in November 1965; and the third symposium, Block Copolymers, is scheduled for June 5, 1967, at the California Institute of Technology. These one-day symposia have been designed for maximum interplay between the participants. Several general introductory lectures were presented in the morning sessions, and a series of concise papers were given in the afternoons. An extensive discussion period was allowed for each paper and, in the case of the High-Temperature Polymers Symposium, an evening panel discussion was held. Although the quality of such meetings cannot be judged from attendance records, the presence of 250 persons at the first symposium and 400 at the second probably has some significance.

ISSN:0022-233X    

DOI:10.1080/10601326708053914

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

For the past ten years my research group has been interested in preparing polymeric materials that would retain useful properties as films, fibers, rubbers, or plastics at temperatures of 500°C or more. The program has been sponsored by the Materials Laboratory of the Wright Air Development Division, Wright-Patterson Air Force Base. Our early search for heat-stable polymers was in the field of metal chelates, because some of the monomeric materials of this type seemed to show unusual stability at elevated temperatures. We were never able, however, to obtain truly high-molecularweight polymers that had as good tensile property, modulus, and elongation as were needed for useful structural materials. Moreover, the stability of the low polymers that we did obtain was never quite as good as we had hoped for.

ISSN:0022-233X    

DOI:10.1080/10601326708053915

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Inorganic chemistry is to a great extent the chemistry of high polymers. This is not apparent from reading much of the inorganic literature of the last quarter-century, since the research problems described therein have often been carefully selected to avoid complications due to high-polymer formation. Nevertheless, the physical properties of many of the reaction products described in the early inorganic-chemistry literature prior to 1900 clearly show these materials to be macromolecular. In the recent inorganic literature there is a growing trend toward considering the chemistry of the larger molecular structures instead of merely ringing the changes of substituents on a single atom. Thus, we see that inorganic polymers are at once very old and very new.

ISSN:0022-233X    

DOI:10.1080/10601326708053916

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The application of polymers at ever-increasing temperatures has given impetus to research on the chemistry of thermal decomposition. In recent years polymers have been used for a variety of high-temperature applications, such as cooking vessels, motor insulation, and re-entry vehicle heat shields. Interest in chemistry of decomposition has been found in such industries as tobacco and grinding-wheels. Because of the vast number of polymers that are available and the variety of applications thousands of papers have appeared in the literature. Rather than give a complete review the purpose of this paper is to give a brief survey of topics that have been emphasized in the author's research, namely kinetics, mechanisms, and gaseous decomposition products at elevated temperatures.

ISSN:0022-233X    

DOI:10.1080/10601326708053917

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The stability of polymeric substances in oxidizing atmospheres is almost always quite different from that observed in nonoxidizing media. The methods and techniques applicable to studies of the chemical changes taking place in a number of complex condensation polymers have been examined in detail in an effort to draw from the resultant data fundamental information regarding the mechanisms of thermooxidative degradation processes. In general terms, it has been of interest to examine condensation polymers at various stages of curing in both oxidizing and inert atmospheres in order to elucidate the chemical transformations that contribute to the over-all stability of these polymers. The use of structural modifications in specific polymer systems together with model-compound studies, solid-phase monitoring of functional-group changes, and gaseous-product analysis are exemplified as they pertain to an investigation of detailed degradation reactions. The results of these investigations and the mechanistic conclusions that can be drawn offer a ready source of information pertaining to the effects of processing upon the thermal life of particular polymers in oxygen-containing atmospheres and, in addition, they offer data concerning the effect of specific linkages within the polymer unit upon the over-all stability of the polymer. Such information is extremely valuable from a viewpoint of new polymer synthesis and stabilization methods for existing complex polymer systems.

ISSN:0022-233X    

DOI:10.1080/10601326708053918

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Mass spectrometric thermal analysis (MTA), the determination of total ion current as a function of time and temperature, has been employed for investigation of pyrolytic reactions (I). In combination with differential thermal analysis (Ib) it has proved to be very useful for distinguishing between energy changes caused by phase transformations and those caused by decomposition reactions. Determination of total ion current alone is not particularly informative in most cases of polymer degradation, when several products may be formed simultaneously or sequentially. We have modified the usual procedure by repeatedly scanning spectra, as the temperature is raised on a linear program, and then plotting peak height as a function of temperature. MTA determinations conducted in this way have been helpful in several polymer investigations currently in progress in our laboratory. The alternative method, recording of a characteristic peak for each product on an individual channel of the Bendix Time-of-Flight mass spectrometer, was rejected as less reliable and more cumbersome when the number of products exceeds the number of channels on the instrument.

ISSN:0022-233X    

DOI:10.1080/10601326708053919

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The viscoelastic properties of an inorganic anionic polymer were studied as a function of the counterion. It is shown that as the counterion strength (expressed, for instance, by the ratio of charge to internuclear distance between cation and oxygen anion) increases, the distribution of relaxation times narrows in an approximately linear manner. A small effect of the molecular weight is also observed on the narrowing of the relaxation spectrum, but the latter is much smaller than the former.

ISSN:0022-233X    

DOI:10.1080/10601326708053920

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Siloxane and benzimidazole polymers containing carborane groups were synthesized and their thermal stability was measured. The data show the stabilizing effect of the carborane group on the thermal and oxidative stability of the polymer. In many instances the increase in thermal stability has been attributed to the inductive effect of the carborane group. In one case the oxidative stability of a silicone polymer has been increased by a carborane group adjacent to the silicon atom carrying the methyl groups. Carborane in the backbone of a silicone polymer appears to have inhibited rearrangement to cyclic compound. Metal panels coated with carborane polymers appear to have outstanding stability, apparently due to the formation of a protective film during the heating cycle.

ISSN:0022-233X    

DOI:10.1080/10601326708053921

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A wide variety of structurally related Schiff base and acid amide compounds and low-molecular-weight polymers were synthesized. The comparative thermal stabilities of the products in air were investigated by thermogravimetric analysis. Several of the Schiff bases prepared from aromatic diamine compounds and terephthalaldehyde exhibit unusually good resistance to decomposition by heat. The influence of chemical structure on thermal stability is shown, and the important factors that may serve as a guide for the tailor-making of high-molecular-weight polymers with superior heat resistance are discussed.

ISSN:0022-233X    

DOI:10.1080/10601326708053922

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Thermostable polymers and, more particularly, thermostable fibers and films are becoming more and more important as the demands of space-age technology increase. In the preparation of thermostable fibers having good tensile strengths and practical utility the processibility of the polymer is of great importance. Aromatic polyamides meet the two most important requirements: a high degree of thermal stability and an ease of preparation as viscous solutions that can be spun into fibers or cast into films.

ISSN:0022-233X    

DOI:10.1080/10601326708053923

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor