ISSN:0007-1641    

DOI:10.1002/pi.4980150102

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980150103

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractPolycondensation of terephthalic aldehyde with 2,4 — or 2,6‐dimethyl ‐, or 2,4,6 — trimethylpyridine leads to a new kind of heat‐resistant resin with aromatic‐heterocyclic structure.These resins are mixtures of thermosetting oligomers. A few components have been identified after separation by size‐exclusion chromatography. Although infrared spectroscopy sheds some light on certain aspects of their heat‐curing mechanism, this has not yet been fully elucidated.Derivatives of trimethylpyridine (symmetrical collidine) appear to be particularly interesting in view of their possible use with reinforcing fibre materials for prepreg fabrication. These derivatives lead to composite materials whose high mechanical properties remain unaffected for several thousand hours at 250°C and a few hours at 350°C.These products are being developed on an industrial scale under the n

ISSN:0007-1641    

DOI:10.1002/pi.4980150104

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractN,N‐Bis (2, 3‐epoxypropyl) aniline and 4,4′‐methylenebis‐[N,N‐bis (2,3‐epoxypropyl) aniline] containing bromo, chloro, trifluoromethyl or polyfluoroalkoxy substituents were synthesised and cured with aromatic diamines in order to investigate the effect of substituted halogen on water absorption. Significant improvements were achieved: thus use of 4,4′‐methylenebis‐[N, N‐bis (2, 3‐epoxypropyl)‐3, 5‐dichloroaniline] and 4,4′‐methylenebis‐[N,N‐bis (2,3‐epoxypropyl)‐3‐(trifluoromethyl) aniline] instead of 4,4′‐methylenebis‐[N,N‐bis (2,3‐epoxypropyl) aniline] reduced the water absorption by about a half. Departures from Fickian behaviour were observed during water immersion ageing at room temperature and were a general feature of the epoxy systems examined. Plots of water absorption against the Fickian parameter (√t/d) usually showed at least mild sigmoid character and were not independent of specimen thickness. Further, slow continued uptake of water occurred during long‐term ageing, and evidence is provided

ISSN:0007-1641    

DOI:10.1002/pi.4980150105

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe water absorption at 50°C and dynamic and isothermal thermogravimetric properties were studied for a series of resins made from the same maleic/phthalic anhydride‐based unsaturated polyester cross‐linked with each of styrene, 4‐methyl styrene, 4‐ethyl styrene, 4‐n‐butyl styrene, 4‐isopropyl styrene, tertiary butyl styrene, 4‐chlorostyrene and 3,4‐dichlorostyrene. Chloro substituents and most alkyl groups give rise to a loss of water resistence. However, the tertiary butyl group leads to a decrease in both water absorption and water damage. The thermal stability of the resin is decreased by chloro substituents and increased by n‐alkyl groups, and the results suggest that the main degradation step involves styrene residues, but that the initial decompos

ISSN:0007-1641    

DOI:10.1002/pi.4980150106

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractTwo general approaches in the development of light‐crosslinkable resin systems with very good end‐properties are summarised: (1) photoinitiation of the cationic polymerisation of epoxy resins, and (2)‘dual‐functionality’ epoxies. The major known photoinitiators for epoxy cure are surveyed, and in particular various sulphonium salt types. Recent observations on sulphoxonium salts of different kinds, as new catalysts for the photo‐cure of epoxy resins, ar

ISSN:0007-1641    

DOI:10.1002/pi.4980150107

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractRadiation curing of unsaturated polyester resin‐based compositions offers a number of significant advantages over the use of peroxides and similar free‐radical polymerisation initiators; the cure process can be closely controlled, is usually much faster, and the fabricator is not required to measure out, add, and blend‐in small quantities of catalyst. However most forms of radiation including ultra violet (UV) involve heavy initial expense and the need to provide shielding to protect personnel. Furthermore UV radiation will not usually penetrate deeply into thick glassfibre‐containing compositions owing to the absorption of UV light by both resin and glass.Photoinitiator systems which need only visible light have now been developed however. Using these systems almost any available light source including fluorescent tubes, tungsten filament bulbs and of course natural sunlight and daylight will cause the resin to cure rapidly and completely. By controlling the intensity of the incident light continuous close control of the cure process is easily achieved.The advantages of reduced energy requirements, fast cure,‘one pot’ chemistry and built‐in indicators of degree of cure have already led to a number of special applications for visible light curable pol

ISSN:0007-1641    

DOI:10.1002/pi.4980150108

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractDuring the past 20 years the usage of anaerobic‐curing sealants and adhesives has grown rapidly from almost nothing to an estimated 1500 tonnes per annum. An annual growth rate in excess of 10% is predicted throughout the present decade.In this paper, the gradual improvement in the performance characteristics of these systems is traced, from the somewhat uncommercial earliest formulations which required air or oxygen to be bubbled continuously through the system in order to prevent premature gelation, to the present day systems which cure rapidly on most metallic substrates yet possess shelf lives in excess of twelve months.Reaction mechanisms are postulated for the ever‐more efficient curing systems being developed and also for the extremely delicate balance between high reactivity and extended storage stability in commercially available produ

ISSN:0007-1641    

DOI:10.1002/pi.4980150109

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

摘要:

AbstractThe use of torsional braid analysis (TBA) for the dynamic mechanical characterisation of polymers in composites has been inhibited to some degree by difficulties associated with both the measurement and processing of data. Methods for overcoming difficulties associated with spurious motions of the TBA pendulum and for the rapid and optimum processing of raw output data are outlined. A description follows of the application of the modified TBA technique to the analysis of six nominally similar epoxy resins systems. It is shown, by the presentation of comparative data, that the TBA method gives highly reproducible results, with little scatter, in studies both of gelation and vitrification times over a wide range of isothermal temperatures, and of activation energies for the processes involved, and also in studies of dynamic mechanical behaviour over a wide temperature range.

ISSN:0007-1641    

DOI:10.1002/pi.4980150110

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980150111

出版商:John Wiley&Sons, Ltd    

年代:1983

数据来源: WILEY