High Performance Polymers polyetherimides

The polyetherimides are competitive not only with other high-performance polymers such as the polysulphones and polyketones but also with polyphenylene sulphides, polyarylates, polyamide-imides and the polycarbonates. 

This review summarizes our work at the University of Bayreuth over the last few years on improving the electret performance of the commodity polymer isotactic polypropylene (Sect. 3) and the commodity polymer blend system polystyrene/polyphenylene ether (Sect. 4) to provide electret materials based on inexpensive and easily processable polymers. To open up polymer materials for electret applications at elevated temperatures we concentrated our research on commercially available high performance thermoplastic polyetherimide resins and synthesized several fluorinaled polyetherimides to identify structure-property relations and to improve further the performance at elevated temperatures (Sect. 5). 

As mentioned in the introduction, the commercial polyetherimide Ultem 1000 reveals the most promising electret behavior among the other high performance polymers investigated. However, a chemically identical polyetherimide synthesized... 

Wirth, J. G., Discovery and Development of Polyetherimides In High Performance Polymers Their Origin and Development, (Seymour, R. B., Kirshenbaum, G. S. eds.), Elsevier, Amsterdam, 1986. 

After 1980 continuous growth was recorded with the development of a number of high performance polymers that could compete with traditional materials such as polyetheretherketone, polyetherimide (1982), polyamide 4,6 (1987), syndiotactic PS (1989), metallocene polyolefins, polyphthalamide (1991), styrene-ethylene copolymer, syndiotactic PP in 1992 and nanocomposites [15]. 

Like the pultrusion process, the selection of a suitable thermoplastic matrix material mainly depends on the desired mechanical properties and the desired long-term service temperature. The range of usable matrix materials starts with standard polymers such as polyethylene (PE) or polypropylene (PP) and ends with high performance polymers such as polyetherimide (PEI) or poyletheretherketone (PEEK). Recent developments have shown that the processing of reactive thermoplastic materials is possible as well (CBT). For some physical properties of common matrix materials see Table 8.2. °... 

Polyetherimides were developed as a result of research interests in aromatic nucleophilic displacement chemistry combined with a perceived marketplace need for high performance polymers which could be readily fabricated by standard plastics extrusion and injection molding processes. 

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. 

D. M. Delozier and D. C. Working. Polyetherimide/montmorillonite nanocomposites via in-situ polymerization followed by melt processing. High Performance Polymers, 16 (2004), 597-609. 

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). 

Polyetherimide is one of the most expensive high performance polymers. At the end of 2000, the average price of PEI was around 9.50-10.5 per kg. PEI prices have been fairly stable in the last... 

Polyetherimide is in competition with other less expensive high performance polymers such as PSU and PES. It is however a very cost effective material and the total systems cost of using PEI compares favourably with competing materials. 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

Both polyamide-imide and polyetherimide have high heat distortion temperature, tensile strength, and modulus. Polyamide-imide is useful from cryogenic temperatures up to 260°C. It is virtually unaffected by aliphatic and aromatic chlorinated and fluorinated hydrocarbons and by most acid and alkali solutions. These polymers are used in high-performance electrical and electronic parts, microwave appliances, and under-the-hood automotive parts. Typical automotive applications include timing gears, rocker arms, electrical connectors, switches, and insulators. 

The electrical properties of the polymer are also exceptional - in many respects comparable to those of typical high performance engineering materials at room temperature, but in addition, changing little over a wide range of elevated temperatures. This is an important property, and of considerable interest when combined with high temperature capability. All of which has led to rapid acceptance of this polyetherimide in both electrical and electronic applications. 

The GE Advanced Materials operation includes high-performance engineered plastics, structured products silicones and high-purity quartzware. The company s range of engineering resins includes Cycolac ABS, Cycoloy PC/ABS blend, Geloy, Lexan PC, Noryl, high temperature Ultem polyetherimide, Valox PBT, Xenoy and Xylex polymer blends. 

In recent years the focus has been on the high performance, specialty resins. For example, polyetherimide, PEI, was commercialized in 1983. In tlie ensuing two years its blends with most engineering and specialty polymers were patented. Since 1990 PEI C blends, Ultem LTX , have been available from GEC. 

The high performance characteristics of polyetherimide polymers and our desire to prepare them by an economically attractive scheme led us to explore several synthetic approaches. The key reaction in all of these was the formation of the diaryl ether linkage by a nucleophilic aromatic displacement reaction on suitably substituted (and activated) phthalic derivatives. Chloride displacement proceeded relatively slowly and gave polymers having only modestly high molecular weights. Fluoride displacement was quite facile, but processes based on the fluoro-deriviatives were economically unattractive. The synthetic and economic accessibility of appropriate nitro-substituted phthalic... 

Polyetherimides are a new family of condensation polymers. The key reaction step in each of their synthetic sequences is an aromatic nitro-displacement reaction which produces the diaryl ether linkages in high yield. Physical properties can be varied over a wide range depending on the choices of bis-phenol, diamine, and positional isomer incorporated into the backbone of the polymer. Our study of these materials has led to the commercial introduction of ULTEM Resin as the first in a series of new high performance engineering thermoplastics. 

High-performance engineering thermoplastics have recently assumed hicteas-ing importance due to their exceptional properties at elevated tenqioatures. A number of such spedalty polymers has been introduced into the market for higili-temperature applications and examples of some of the outstanding ones are poly phenylene oxide (PPO), poly fdienylene sulfide (PPS), polyetlier sulfone ES), polyaryl sulfone (PAS), polyether ether ketone (PEEIQ, polyetherimide (PEl, and polyarylate (PAr). 

The combination of processability and performance provided by these polymers makes them natural candidates for applications such as microelectronics laminates as well as structural and dielectric composites (2). The versatility provided by the use of phenolic feedstocks has allowed the extension of this chemistry into polyesters (i), classical photoresist chemistry (4), and thermally crosslinkable thermoplastics (5). It has also provided a method for thermally processing low molecular weight imide-containing oligomers into high molecular weight polyetherimides (d) In addition, oligomers which are useful as fluorinated lubricant fluids have been prepared (7). 

High-performance engineering thermoplastics Fluoropolymers (PTFE, FEP, PVDF), liquid crystal polymers (LCP), polyphenylene oxides or ethers (PPO, PPE), aromatic polyketones (PEEK, PAEK), polyphenylene sulphides (PPS), polysulphones (PSU), polyether sulphones (PES), polyamideimides (PAI), polyetherimides (PEI), polyimides (TPI). 

Connectors, switches, electric distributors, fuse boxes and other electric fittings need a subtle balance of electrical and mechanical properties, durability, cost and aesthetics. This broad field creates fierce competition not only between engineering thermoplastics and SMC/BMC for the main applications but also with polypropylene and polyethylene or PVC for the lower performance parts and, at the opposite end of the scale, with high-tech plastics such as polyetherketone, polyetherimide, liquid crystal polymers. .. For example, without claiming to be exhaustive ... 

Polyimides (PI) were introduced in 1962 as thermally non-processable Kapton . To improve processability, the main-chain flexibility was enhanced by incorporating segments with higher mobility, viz., polyamide-imide (PAl), polyetherimide (PEI), polyimide-sulfone (PISO), etc. These polymers are characterized by high Tg = 150 20 °C and thermal resistance. They are blended with PPS to enhance its moldabUity, thermal stability, and mechanical performance. 

Owing to their high Tg and the hydrolytic resistance of the aromatic sulfone backbone structure, polysulfones display reliable long-term performance in hot water and steam even under autoclave conditions. Unlike the other high-Tg, transparent polymers, such as polycarbonate (PC), polycarbonate-ester (PCE), and polyetherimides (PEI), the sulfone polymers are not prone to crazing and failure... 

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