摘要:

The mechanism for heat rejection of char-forming, ablative heat shields is well known [1]. However, the data needed by the engineer to design heat shields have often been determined by laboratory experiments [2–4]. The fraction of heat shield which remains as char after pyrolysis and the thermokinetic parameters for thepyrolysis process have been estimated from thermogravimetric measurements [5,6]. This empirical approach to determining the char yield of phenolic heat shields and the fraction of polymer involved in the pyrolysis reactions has been the result of lack of definitive information on the mechanism of high-temperature decomposition of the polymers used in compounding the heat shield.

ISSN:1532-1797    

DOI:10.1080/15583727108085368

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

This, or any modern review cannot be expected to detail every existing work relevant to a given subject. Restrictions must be made, both to hold the subject matter within manageable limits and to in-crease value by allowing more than cursory treatment. In this particular field, the number of contributions is not overwhelming, so many of the papers can be discussed in depth, but, unavoidably, some will simply be footnoted. This discrimination is made primarily so that specific lines of inquiry can be developed with reasonable continuity.

ISSN:1532-1797    

DOI:10.1080/15583727108085369

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

Numerous reactions have been developed over the years which lead to products containing coupled aromatic nuclei. These methods involve many different types of starting materials as well as a variety of mechanisms. Earlier work was concerned mainly with the lower members of the biphenyl series, but the increasing demand for thermally stable materials has resulted in the development of numerous methods for preparation of the higher molecular weight polyphenyls or poly(phenylene)s. Indeed, research into the preparation and properties of these materials has expanded at a remarkable rate during the last decade and is emphasized by the fact that almost 50% of the references cited herein are the results of work carried out since the last major review on this subject was published in 1960 [1]. Less comprehensive reviews [2–4] have since appeared.

ISSN:1532-1797    

DOI:10.1080/15583727108085370

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

An abundance of experimental and theoretical information has been published on the flow of linear amorphous polymers. The most comprehensive set of studies available involve well-characterized polystyrenes. These are linear, high molecular weight polymers anionically polymerized to narrow distributions. Most of the studies on these polystyrenes have been designed to develop and to improve general interrelationships between molecular and shear variables. The former include polymer molecular weight, distribution, and concentration; the latter include shear rate, frequency, and test temperature. Each of these studies has been reported, however, with virtually no intercomparison with related rheological results reported by others on equivalent polystyrenes.

ISSN:1532-1797    

DOI:10.1080/15583727108085371

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

摘要:

There is an acute demand for thermally and heat-stable materials in modern technology. Of great interest are also polymers resistant to chemicals, particularly to oils, organic solvents, and mineral acids, as well as those possessing stability to light and radiation, and electroinsulating, semiconductive, and catalytic properties. These polymeric materials must have good mechanical properties and be suitable for existing industrial processing and synthesis techniques if they are to be useful technologically. Polymers containing various heterocycles in the chain attract, therefore, the increasing attention of polymer chemists, as it is known that many 5and 6 membered heterocycles are stable to high temperatures and have some specific useful properties. Of the heterocycle-containing polymers, polyazoles, the polymers with azole cycles in the chains, are exceptionally interesting and have been studied adequately. Some polyazoles are described in a number of reviews and monographs dealing mainly with the synthesis of thermally stable polymers [1–101].

ISSN:1532-1797    

DOI:10.1080/15583727108085372

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor

ISSN:1532-1797    

DOI:10.1080/15583727108085373

出版商:Taylor & Francis Group    

年代:1971

数据来源: Taylor