ISSN:0007-1641    

DOI:10.1002/pi.4980200502

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractAddition type imide resins are finding increased use as matrix resins for advanced composites. Many different chemical approaches have been used to synthesize imide resins which are easy to process (similar to epoxies) but higher in temperature resistance. This paper outlines recent advances in thermosetting imide resin chemistry; however, only those concepts which have been accepted by the industry and the most promising research concepts are discussed, such as:endomethylenetetrahydrophthalimidesacetylene terminated polyimidesbismaleimidesbenzocyclobutenes.Of these, the bismaleimides are easiest to process. When used in combination with comonomers such as bisallylphenyl compounds, bis‐o‐(propenylphenoxy)‐benzophenones, benzocyclobutenes, etc., their toughness can be improved significantly to make them prime candidates as matrices for advanced composites and adhe

ISSN:0007-1641    

DOI:10.1002/pi.4980200503

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThere has been considerable research into high temperature polymers in recent years and many novel systems have been synthesised. The requirements of high temperature resistance, resistance to moisture, and mechanical strength vie with each other in the selection of materials. In the defence field there are many applications for high temperature polymers, one of which is as high temperature adhesives. A particular problem with adhesives for defence use is that they need to withstand wide operating extremes both of temperature and humidity. A particular class of material that is suitable for high temperature adhesive application is the bismaleimides. The thermal resistance and strength of these materials has been established in previous studies. However, the effect of moisture upon these compositions has not been addressed. This paper covers aspects of diffusion of water into bismaleimide resin systems and is part of an ongoing research programme into high temperature polymers.

ISSN:0007-1641    

DOI:10.1002/pi.4980200504

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe frontrunner in the race to develop a high temperature resin for use in advanced composites intended for high temperature applications is the NASA developed polyimide PMR‐15. One of the key factors in the success of the material is the relatively easy processing which is due mainly to the use of the PMR approach (Polymerisation of Monomeric Reactants). Prepreg and high quality composite laminates (glass or carbon) can be prepared with ease. Laminate properties compare well with conventional epoxy based systems but thermal stability is much greater. Continuous use temperatures are in the range 280‐300°C, some 150‐170°C higher than epoxy systems. Applications of PMR‐15 composites include aero‐engines, missiles, spacecraft and military aircraft. Despite being the leading system available today PMR‐15, like all materials, has a number of limitations affecting its widespread use. Included in these are reliable methods of quality control, prepreg batch to batch variability, microcracking from thermal cycling, health and safety hazards and high temperature processing. This paper reviews the present status of PMR‐15 development and outlines work designed to identify and where possible overcome th

ISSN:0007-1641    

DOI:10.1002/pi.4980200505

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractConsiderable work has been carried out on the development of resin transfer moulding (RTM) as a viable processing alternative to conventional autoclave and compression techniques. RTM has the capability of producing high quality components of complex shape with tight tolerances.This paper reviews recent advances in materials suitable for the process of RTM and production of aerospace components. Three main areas are covered:(1)a general description of the process of RTM,(2)resin systems which have been used for RTM (epoxy, bismaleimides and polystyrylpyridines) of aerospace components,(3)high temperature resin systems which have the main processing attributes for RTM but have yet to be used in this area.

ISSN:0007-1641    

DOI:10.1002/pi.4980200506

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe approach to obtaining fully cyclised polyimides is based on the interactions between a benzhydrol group carried in the polyimide main chain and the solvent. The CH of the benzhydrol function is an efficient1H‐NMR probe in order to follow the extent of imide cyclisation, as shown using benzhydrol tetracarboxylic dimethylester (5.95 ppm), the corresponding diamide diacid (6.20 ppm) and the final imide (6.35 ppm).Three types of polybenzhydrolimides are described. A linear AABB polymide was prepared from benzhydrol tetracarboxylic dimethylester obtained by hydrogenation of the corresponding industrial ketonic tetraacid diester. The solution properties of the polyimide and the extent of imide cyclisation are discussed.The synthesis of a linear AB polymer from (3‐aminophenyl)‐4‐hydroxymethyl monomethylphthalate is described. This product is used as silver filled adhesive for electronic applications.A cyclised nadimide end‐capped benzhydrolimide oligomer (Mw=1940,Mn= 1370) is soluble in diglyme. The crosslinking of this oligomer starts at 275°C and the properties of the network according to the curing cycle are

ISSN:0007-1641    

DOI:10.1002/pi.4980200507

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractFor olefins containing aromatic groups such as naphthyl, monomer reactivities have been evaluated on the basis of the absolute rate constants and relative equilibrium constants which were determined by the flash photolysis method using phenylthiyl radicals as attacking radicals. The rate constant for addition of α‐methyl‐1‐vinylnaphthalene is lower than that of α‐methyl‐2‐vinylnaphthalene. This suggests that the aromatic π‐orbital; of the 1‐naphthalene derivative are twisted away from the olefinic π‐orbital; in the transition state, the delocalization of the unpaired electron on the olefinic carbon into the naphthyl group is reduced by the angular structure. For such twisted monomers, the dihedral angles between the aromatic π‐orbitals and the olefinic π‐orbital have been estimated by comparing the observed rate constants with the reactivity indexes calculated by the molecular orbital method. In the case of α,β‐disubstituted olefins, the rate constants are lower than those of α,α‐disubstituted ones; this suggests that the approach of the phenylthiyl radical is impeded. New reactivity parameters were evaluated

ISSN:0007-1641    

DOI:10.1002/pi.4980200508

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980200510

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980200514

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980200516

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY