Polyetherimide PEI Resin

PEI is an amorphous thermoplastic resin with a rated continuous temperature of use up to 170°C. It has an limiting oxygen index (LOI) of 47, one of the highest in the commonly used engineering thermoplastics, coupled with a low smoke emission. PEI retains 41% strength retention at 190°C. Like PES it is a tough resin, but it is sensitive to notches and sharp corners. 

In common with most thermoplastics, PEI should be thoroughly dried before processing. It is more easily processed than PES or PEEK. It has good chemical resistance, but is soluble in partially halogenated solvents like methylene chloride and trichloroethane. 

Solvent induced crystallization [152] and fracture toughness [153] have been studied. 

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Some of the common types of plastics that ate used ate thermoplastics, such as poly(phenylene sulfide) (PPS) (see Polymers containing sulfur), nylons, Hquid crystal polymer (LCP), the polyesters (qv) such as polyesters that ate 30% glass-fiber reinforced, and poly(ethylene terephthalate) (PET), and polyetherimide (PEI) and thermosets such as diaHyl phthalate and phenoHc resins (qv). Because of the wide variety of manufacturing processes and usage requirements, these materials ate available in several variations which have a range of physical properties. 

Diglycidyl ether of bisphenol-A (DGEBA), epoxy resin (YD 128, Kuk Do Chem., Mn = 378), and bisphenol-A dicyanate (BPACY, Arocy B-10, Ciba-Geigy) were used as the thermoset resin. 4,4 -diaminodiphenyl sulfone (DDS, Aldrich Chem. Co.) was used as a curing agent for epoxy. Polyetherimide (PEI, Ultem 1000, General Electric Co., M = 18,000) and 2-methyl imidazole (2MZ, Aldrich Chem. Co.) were used as the thermoplastic modifier and catalyst. 

Matrix materials for commercial composites are mainly liquid thermosetting resins such as polyesters, vinyl esters, epoxy resins and bismaleimide resins. Thermoplastic composites are made from polyamides, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone, polyetherimide (PEI) and polyamide-imide (PAI). 

The PEEK resin is marketed as neat or filled pellets for injection molding, as powder for coatings, or as preimpregnated fiber sheet and tapes. Applications include parts that are exposed to high temperature, radiation, or aggressive chemical environments. Aerospace and military uses are prominent. At present, polyamideimide (PAI) resin and poly(arylene sulfides) are the main competitors for applications requiring service temperatures of 280°C. At lower temperatures, polyethersulfones, amorphous nylons, and polyetherimides (PEI) can be considered. 

TABLE 8.1. Conditions for MNP Synthesis by ion impiantation into Poiyvinyiidene Fiuoride (PVF2), Polyimide (PI), Polymethyl-methacryiate (PMMA), Poiymethyimethacryiate with Phosphorus-Containing Fragments (PMMA -1- PF), Polyethylene (PE), Poly(ethyleneterephthalate) (PET), Silicone Polymer (Phenylmethyl-silane Resin with Tin Diethyidicaprilate), Epoxy Polycarbonate (PC), and Polyetherimide (PEI) ... 

Solution blending (39) has been employed for preparing a polyetherimide (PEI) modified epoxy resin, for which DGEBA was mixed with the PEI and methylenedianiline curing agent in dichloromethane solvent When films were cast fiom the solvent and cured at various reaction times and temperatures, it was found that the mixture had a single which was measured by DSC. increased with increased curing temperature for both the neat and the modified resins, and decreased... 

BPADA is reacted with a more or less equimolar amount of a diamine, for instance, m-phenylene diamine (MPD), to make the polyamide acid. Water is removed by heating to form the polyetherimide (PEI). In this case, after removal of water and solvent, the added flexibility of the polyimide allows the molten resin to be extruded into strands. Strands of the BPADA-MPD polyetherimide [Eq. (8.5)] are cooled and chopped into pellets, which can subsequently be remelted to form parts or film. PEI powder can be made by grinding pellets or through precipitation methods. Special processes have been developed to make small-particle (15- 0,m) PEI powders. 

Combinations of the thermoplastic polyetherimides with 10 to 40 wt% fiberglass reinforcement are very effective for increasing strength and modulus, as shown in Table 8.3. Heat resistance is shghtly increased too. The increase in stiffness is shown in Fig. 8.3, which compares modulus versus temperature for an unfilled BPADA-MPD-based PEI resin and blends with 10 and 30% short-chopped fiberglass. 

Note that due to their high melt-processing temperature, PEI resins are not compatible with many standard polymer additives. Often additives that work well in other, lower-temperature polymers wiU decompose or volatilize in the hot PEI melt. In general, like most amorphous polymers, PEI resins should be processed at least 150°C (270°F) above the polymer s Tg [340 to 400°C (664 to 752°F) for most polyetherimides]. Selection of appropriate additives to blend with PEI is hest handled by the resin manufacturer or those with significant experience in the selection of suitable blending materials. 

There are two different types of performance needs that must be considered when one is discussing melt-processahle polyetherimides. These two types of performance needs are those of the molders or extruders who fabricate the articles and those of the design engineers and the users of the articles made from the PEI resins. 

PEI resins have been used in a variety of applications such as electrical connectors, internal computer parts, printed-circuit boards, flexible circuits, optical fiber connectors, fire helmets, large appliances, aircraft interiors, trays, microwave cookware, reflectors, motor parts, gears, pumps, lubrication systems, wire coating, industrial applications, bearings, small appliances, films, and fibers. Polyetherimides are used in a wide range of applications. A few of the key markets for PEI resins and some of the benefits they bring to the application are summarized below. 

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. 

Polyetherimide (PEI) is an amorphous engineering thermoplastic. Thermoplastic PEIs provide the strength, heat resistance, and flame retardancy of traditional polyimides (Pis) with the ease of simple melt processing seen in standard injection-molding resins such as polycarbonate and acrylonitrile-butadiene-styrene (ABS). 

A wide range of high performance applications have been developed for polyetherimide resins. The main markets for PEI resin and compounds are electrical/electronic applications, aircraft/aerospace interiors, food service (ovenable), high temperature lighting bezels and reflectors, medical instrument trays, institutional kitchenware and under-hood automotive applications. Automotive applications account for around a half of PEI market volume. 

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. 

The most widely used and least expensive polymer resins are the polyesters and vinyl esters. These matrix materials are used primarily for glass fiber-reinforced composites. A large number of resin formulations provide a wide range of properties for these polymers. The epoxies are more expensive and, in addition to commercial applications, are also used extensively in PMCs for aerospace applications they have better mechanical properties and resistance to moisture than the polyesters and vinyl resins. For high-temperature applications, polyimide resins are employed their continuous-use, upper-temperature limit is approximately 230°C (450 F). Finally, high-temperature thermoplastic resins offer the potential to be used in future aerospace applications such materials include polyetheretherketone (PEEK), poly(phenylene sulfide) (PPS), and polyetherimide (PEI). 

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