Polyetherimide fibres

The markets for polyetherimides arise to an extent from stricter regulations concerning flammability and smoke evolution coupled with such features as high strength, toughness and heat resistance. Application areas include car under-the-bonnet uses, microwave equipment, printed circuit boards and aerospace (including carbon-fibre-reinforced laminated materials). The polymer is also of interest in flim, fibre and wire insulation form. 

Figure 4.109 displays two examples of tensile strength retention versus temperature for neat and carbon fibre reinforced polyetherimides, showing the steady decay up to 180°C. 

Mat and continuous glass fibre reinforcements theoretically all the thermoplastics are usable in these forms, but up to now developments have concentrated on polypropylenes (PP), polyamides (PA) and thermoplastic polyesters (PET) fibre-reinforced PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. 

Towflex (Hexcel Composites) is based on carbon, glass or aramid fibres impregnated with polypropylene, polyamide, PPS, polyetherimide, PEEK. Product forms include flexible Towpreg, woven fabric, braided sleeving, UD tape, chopped compression moulding compound, moulded plates, thermoformable laminates. 

SUPreM, Plytron, Quadrax (Gurit Suprem) consolidated tapes or fabrics are made from continuous fibres impregnated with thermoplastic powder. The fibres can be glass, aramid, carbon, steel and the matrices are polyethylene, polypropylene, polyamide, PPS, polyetherimide, PEEK, thermoplastic polyimide, or fluorothermo-plastic. High levels of fibres can be obtained, 65% in volume, for example. 

Quantification of residual stresses after manufacture. The build up of thermal stresses starts during fabrication of the laminate when it is cooled from the stress free temperature to room temperature. The stress free temperature in the case of an amorphous thermoplastic as used in this study is taken as the glass transition temperature [1] Tg of the Polyetherimide used is 215°C). On a fibre-matrix scale, the contraction of the matrix ( = 57 x 10 /°C) is constrained by the presence of the fibre (cif = -1 x 10 /°C for the carbon in the fibre direction). This results in residual stresses on a fibre-matrix scale (microscale). On a macroscopic scale, the properties of a unidirectional layer can be considered trans ersally isotropic. This means, in turn, that a multidirectional composite will not only contain stresses on a microscale, but also on a ply-to-ply (macroscopic) scale. 

The effect of adverse environments on the fatigue behaviour of glass fibre reinforced pofymers will be discussed, taking polyetherimide (PEI) as an example [36], PEI is an amorphous thermoplastic, so a low resistance to solvents and similar harsh environments can be expected. Because of its potential applications in aircraft and railways, the hydraulic fluid (Skydrol) and the solvent methyl ethyl ketone (MEK) were chosen. 

These are very demanding end uses with tough standards including lire resistance. National Nonwovens recently launched their Ultra-ProTechtor lire blocker range for aircraft seating applications. These fabrics use fibres made from SABlC s flame-retardant ULTEM resin, a polyetherimide material [14]. 

Many high-performance polymer fibres are used in filter media to meet various specific requirements in diverse filtration applications. Filters made from fluoropol-ymer (Polytetrafluoroethylene (PTFE), Polyvinylidene fluoride (PVDF), and Per-fluoroalkoxy alkane (PFA)) fibres, and membranes have inherent, chemical-resistant, and flame-retardant properties, and they are widely employed to filter aggressive chemicals and acids in the manufacture of wafers and microchips in the microelectronics industry. Ethylene ChloroTriFluoroEthylene (E-CTFE) melt blown fabrics have a unique ability to coalesce difficult liquids and can withstand the piranha effect in filtering ozone enriched ultrapure water. Polyphenylene sulfide (PPS) fibres are also chemical resistant, stand high temperature, and are suitable for making baghouse filters. Eilter media made from other high-performance polymer fibres, such as polyamide-imide, polyetherimide (PEI), Polyimide P84 fibre,polyetheretherke-tone, and liquid crystal polymers also appear in the filtration and separation market. 

Fig. 7.8 Comparison of high-performance thermoplastics PAI, polyamide-imide (30% glass fibre) PEEK, polyetheretherketone (30% glass fibre) PEI, polyetherimide (30% glass fibre) PES, polyethersulphone (30% glass fibre) PPS, polyphenylene sulphide (40% glass fibre) Vectra, A130 (30% glass fibre) Xydar, ECHO (40% glass fibre).

L. Chang, Z. Zhang, H. Zhang, K. Friedrich (2004) Effect of nanoparticles on the tribological behaviour of short carbon fibre reinforced polyetherimide composites, Tribol. Int., submitted. 

Table 3.1 shows continuous use temperatures for engineering and high performance polymers. For comparative purposes, 30% glass fibre-reinforced grades have been selected. PEEK has the highest continuous use temperature of up to 260 C, followed closely by liquid crystal polymers. Other high performance polymers are polyphthalamide (PPA), polyamideimide (PAI), polyarylimide, polyphenylene sulfone (PPSU), polyphenylene sulfide (PPS), polyetherimide (PEI), polysulfone (PSU), polyethersulfone (PES). 

Table 3.10 presents a comparison of the performance properties for unfilled polyetherimide and 30% glass fibre-reinforced grades. 

Polyetherimide resins are inherently flame resistant with low smoke emission which makes PEI suited to a variety of applications in the fields of electrical equipment and electronics. In the telecommunications maiket, there is an increasing need for high heat resistant materials, especially for high-end connectors in the fibre optics segment. PEI resin offers high heat resistance as well as great flow for thin wall design. Other applications include electrical switches and controls, electrical motor parts, printed circuit boards and coimectors. 

Comments GF = glass fibre, PEI/PC = blend, SILTEM = coatings. flexibie siloxane-polyetherimide copolymer for cable and wire ... 

Hou, M., L. Ye, and Y.-W. Mai, An experimental study of resistance welding of carbon fibre fabric reinforced polyetherimide (CF Fabric/PEI) composite material, Appl Compos Mater, 6, 35-49,1999. 

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