摘要:

AbstractThe interest of the Air Force and other military organizations in high temperature fibers spans a broad range of fiber types and applications. Fibers and yarns with a high degree of flexibility and good thermal capabilities are required for flexible fibrous materials for use in decelerators and expandable and/or rigidizable structures. High temperature fibers with outstanding modulus‐to‐weight ratio are needed for reinforcement of composite structural materials. In most instances, a high strength‐to‐weight ratio, at temperature, is desirable. To meet these space‐age requirements, research is being conducted by the Air Force Materials Laboratory on a wide variety of fiber types, including polymeric, metallic, graphite, glass, and ceramic. The results of this, and similar research being conducted by industry, while maintaining our military superiority, will, in many instances, also be felt in the commerc

ISSN:0449-2994    

DOI:10.1002/polc.5070190103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractFibers were spun from five different wholly aromatic ordered copolyamides. Each polymer contained units derived from aminobenzoic acids, arylene diamines, and arylene diacids. Structural differences in the ordered copolyamides were made by variations in combinations ofpara‐ andmeta‐phenylene units, 2,6‐naphthalene units, and 4,4′‐bi‐phenylene units. Tensile properties of the fibers were obtained at standard conditions, at elevated temperatures, and after heating at 300°C. in air. All of the fibers had tenacities of about 6 g./den. and all were crystalline after drawing. Easy of crystallization, initial modulus, elongation, and retention of tensile properties at elevated temperatures in air were, in general, consistent with variations in the structure of the polymers. Fiber properties were retained to a high degree at temperatures up to 400°C., and fibers heat aged at 300°C. showed remarkable retention of tensile properties. Radiation resistance (γ source, 2.92 × 105rads/hr.) of these fibers was good and resistance to ultraviolet light appeared to be better than that of unsta

ISSN:0449-2994    

DOI:10.1002/polc.5070190104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThermostable fibers were spun from several ordered heterocycle‐amide copolymers. Tenacities up to 8 g./den. at standard conditions were obtained. The polymers were prepared by condensation of arylene diacid chlorides with aromatic diamines containing preformed heterocyclic units of types known to be thermally stable (oxadiazole, thiazole, and bithiazole). Fiber tensile properties were determined at temperatures up to that at which the fiber failed. Each fiber had a zero strength temperature of over 515°C. in nitrogen, and each had appreciable strength at 400°C. In general, the fiber showed excellent retention of tenacity after heat aging for long periods of time at 300°C. in air. An oxadiazole‐amide fiber retained three‐fourths of its original tenacity after 168 hr. under these co

ISSN:0449-2994    

DOI:10.1002/polc.5070190105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractFibers of ordered aromatic copolyamides have been found to be exceptionally resistant to degradation at high temperatures. A typical member of this class of fibers has been selected for presentation to illustrate the high performance characteristics of these fibers. The selected polymer, containing ordered aromatic components withmeta‐ andpara‐benzanilide linkages, was spun into fibers from solution. The excellent heat stability of the fiber is demonstrated by its retention of strength at high temperatures and after prolonged exposures to elevated temperatures. Among other outstanding properties are its balance of tensile properties, resistance to hydrolysis and chemical degradation, high dielectric strength, and stability in ionizing radiation. Fabrics constructed from this fiber have good flexibility and abrasion resistance at elevated temperatures. The combination of high strength and durability at high temperatures should gain acceptance for this fiber in a variety of industrial and military applications including hot gas filter bags, belting, heat resistance clothing, electrical insulation in motors and transformers, and fabrics for parachute packs and harnes

ISSN:0449-2994    

DOI:10.1002/polc.5070190106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe excellent high temperature properties of aromatic polyimides, well known in films and enamels, have also been demonstrated in fibers. Current investigations show that experimental aromatic polyimide fibers have a very high level of thermal and dimensional stability and property retention at high temperatures, as well as a good, all‐round level of other fiber propertie

ISSN:0449-2994    

DOI:10.1002/polc.5070190107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe polybenzimidazole polymer prepared by Vogel and Marvel from diaminobenzidine and diphenyl isophthalate has been scaled up and dry spun from DMAc for a full‐scale evaluation of the fiber for end uses requiring thermal stability. A process has been developed for the purification of diaminobenzidine suitable for making high molecular weight PBI. A nitrogen sweep process run at atmospheric pressure was substituted for the difficult vacuum cycle of the literature polymerization. Polymers prepared by this process had equivalent molecular weight, better solubility in DMAc, and less gel structure than those prepared in vacuum. Inherent viscosities of 0.75–0.85 and plugging values>1.0 in 97% sulfuric acid have been obtained consistently. An increase in the temperature of solutioning in DMAc was required to dissolve the higher molecular weight fractions of the polymer. Solutioning at 230°C. under pressure dissolved 95–100% of the polymer. 1–2% lithium chloride was required to prevent solution instability or “phasing‐out” of the polymer in DMAc. PBI fiber was dry spun from DMAc into a hot nitrogen atmosphere and steam stretched in tandem with spinning. Yarn was pressure washed on perforated bobbins with hot water, air dried, and oven dried prior to drawing. Drawing was performed at 520°C. and a 2:1 draw ratio. Final physical properties average 5.0 g./den. tenacity, 23% elongation, and 115 g./den. initial modulus. Small‐scale spinning of a high molecular weight fraction of polymer (ηinh= 1.2) gave fiber properties superior to those obtained from the same whole polymer (ηinh= 0.72). The bulk polymer and amorphous fiber were crystallized with phenol under pressure. An oriented and crystalline fiber was obtained by treatment of oriented fiber under pressure wi

ISSN:0449-2994    

DOI:10.1002/polc.5070190108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThe only improvement seen in increasing the molecular orientation of PBI fiber over that exhibited by presently defined target property material is the improvement seen in the strength and stiffness of the material at high strain rates. This improvement, however, cannot be extrapolated to a good impact performance. No advantage of fiber crystallization was detected in the properties measured in this evaluation conducted in accordance with the current state of the art of testing of high temperature fibers. However, as the testing of high temperature performance fibers becomes more sophisticated, advantages of crystallization undetectable in this investigation may appear. Should this occur, it would then be advisable to explore the crystallization of PBI further in an attempt to induce a higher degree of crystallinity than accomplished in this work while maintaining adequate tensile properties.

ISSN:0449-2994    

DOI:10.1002/polc.5070190109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractA chemical cyclocondensation reaction process has been developed to convert the easily prepared poly(phenylene)hydrazide to the corresponding high molecular weight poly‐3,5‐(m‐,p‐phenylene)‐4‐phenyl‐1,2,4‐triazole. Polytriazole fibers have been spun from formic acid solutions utilizing both wet and dry spinning techniques. These fibers develop a high degree of orientation and crystallinity on stretching at temperatures of 300°C. and higher. Such fibers retain approximately 30% of their initial breaking strength at a temperature of 300°C. and are not seriously degraded on exposure to elevated temperatures for prolonged periods. The fiber dimensional stability at temperatures above the glass transition temperature of 260°C. for the amorphous polymer was found to be directly related to the fiber orientation and crystallinity. The ease of fabrication and thermal stability of the phenylene triazole polymer makes this material potentially attractive for other end‐use applications such as films, protective coatings, and e

ISSN:0449-2994    

DOI:10.1002/polc.5070190110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractThis work has demonstrated the preparation of aromatic poly‐1,3,4‐oxadiazole fibers with a high level of physical properties by the cyclodehydration of undrawn high molecular weight copolyhydrazide fibers and subsequent drawing of the converted fiber to high orientation. The fibers have a high level of thermal stability, good property retention at high temperature testing, and excellent resistance to hydrolytic degradat

ISSN:0449-2994    

DOI:10.1002/polc.5070190111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY

摘要:

AbstractIt has been shown that aromatic poly‐1,3,4‐thiadiazole fibers can be prepared in a manner analogous to that of the aromatic poly‐1,3,4‐oxadiazole via the thermal cyclode‐hydration of an aromatic polyoxathiahydrazide fiber. These fibers exhibited the same high level of thermal and hydrolytic stability observed for the aromatic poly‐1,3,4‐oxadiazole fibers. The oxathiahydrazide‐thiadiazole conversion was found to occur at lower temperatures and much faster rates than the hydrazide‐oxad

ISSN:0449-2994    

DOI:10.1002/polc.5070190112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1967

数据来源: WILEY