Thermoplastic polyimide

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Alloys containing styrenics Alloys containing thermoplastic polyimide... 

Aerospace, top-of-the-range sports and leisure the core is generally made of honeycombs or high-performance foams and the skins can be made of carbon fibre reinforced thermoplastic polyimides. 

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. 

TABLE 2. Bonding Strength of Selected Thermoplastic Polyimides after Exposing Surfaces to Plasma Treatment or Heating Material to 380°C... 

Adhesive films consisting of thermoplastic polyimides were prepared by Yanagida et al. (3) consisting of 4,4 -oxydianiline, p-phenylenedi amine, and... 

Poly[2,2 -(m-phenylene-5,5 -benzimidazole)] (PBI) is a very high glass transition temperature (Tg 430°C), commercially available material. It possesses excellent mechanical properties, but is difficult to process into large parts and has high moisture regain and poor thermo-oxidative stability at temperatures above approximately 260 °C. Polyimides, especially the thermoplastic polyimides, offer attractive thermo-oxidative stability and processibility, but often lack the thermal and mechanical characteristics necessary to perform in applications such as the matrix for high use-temperature (over 300 °C) structural composites (for example, carbon fiber reinforced) for aerospace use. The attempt to mitigate... 

Certain thermoplastic polyimides possess excellent resistances to high temperatures and chemicals, with Tgs ranging from 217 to 371 °C. Certain polyimides also exhibit excellent toughness and dielectric properties. The melt blending process of polyimides with other thermoplastic polymers is difficult due to polyimides high Tg, high melt viscosities, and incompatibility. A solution process is used, therefore, to achieve a semi-interpenetrating polyimide network... 

St. Clair [36] synthesized and evaluated the properties of a semi-2-IPN comprising Thermid 600 (an acetylene terminated imide oligomer from National Starch and Chemical Company) and LaRC-TPI (a thermoplastic polyimide with a Tg of 257 °C). The composition having the ratio of 65 35 of thermosetting Thermid 600 to LaRC-TPI showed the best flexural strength at ambient temperature [36]. 

Pascal et al. [49-50] studied semi-2-IPN derived from linear thermoplastic polyimides and thermosetting bismaleimides from the same type of starting... 

Not only do the chemical structure and the molecular weight affect the processability but also the method of synthesis, in particular the imidation step. Thermally imidized polyimides are always less tractable than solution imidized polyimides. That is because thermally imidized polyimides can undergo cross-linking, and because thermal treatment (about 300 °C) favour chains packing and provide higher molecular order than that achievable by solution imidation. Therefore, solution imidation is always preferable when thermoplastic polyimides are to be developed. 

A list of commercial thermoplastic polyimides is given in Table 7, along with the name of the manufacturer and indicative information on the chemical composition. 

US 5,204,399 (American) 1991 Thermally conductive thermoplastic polyimide film die attach adhesives and their preparation National Starch and Chemical Investment Holding Corp. R Edelman Adhesive formulations having excellent die shear strength A polyimide-siloxane was prepared from aromatic amines, bis aminophe-noxybutylsiloxane and aromatic dianhydrides... 

Maudgal S, St Clair TL (1984) Preparation and characterization of siloxane-containing thermoplastic polyimides. Int J Adhes 4 2 87... 

Yoon TH, Arnold-McKenna CA, McGrath JE (1992) Adhesion behavior of thermoplastic polyimides and poly(imide siloxane) segmented copolymers influence of test temperatures J Adhes 39(100) 15... 

Furukawa N, Yamada Y, Kimura Y (1997) Lap shear bond strength of thermoplastic polyimides and copolyimides. High Perform Polym 9(1) 17... 

Ying L, Edelman R (1986) A novel thermoplastic polyimide for composite matrix applications. 31st International SAMPE Symposium 1131... 

McGrath JE, Rogers ME, Arnold CA, Kim YJ and Hedrick JC (1991) Synthesis and blend behavior of high performance homo- and segmented thermoplastic polyimides Makromol Chem Macromol Symp 51 103... 

LARC TPI Langley Research Center Thermoplastic Polyimide... 

Goodwin AA, Whittaker AK, Jack KS, Hay JN, Forsythe J (2000) Absorption of low molecular weight penetrants by a thermoplastic polyimide. Polymer 41(19) 7263-7271... 

Polyimides for microelectronics use are of two basic types. The most commonly used commercial materials (for example, from Dupont and Hitachi) are condensation polyimides, formed from imidization of a spin-cast film of soluble polyamic acid precursor to create an intractable solid film. Fully imidized thermoplastic polyimides are also available for use as adhesives (for example, the LARC-TPI material), and when thermally or photo-crosslink able, also as passivants and interlevel insulators, and as matrix resins for fiber-reinforced-composites, such as in circuit boards. Flexible circuits are made from Kapton polyimide film laminated with copper. The diversity of materials is very large readers seeking additional information are referred to the cited review articles [1-3,6] and to the proceedings of the two International Conferences on Polyimides [4,5]. 

Substrates used included fiber-reinforced epoxy base polymer [FRP], nylon 66, polytetrafluoroethylene [Teflon], poly(ethylene terephthalate) [PET], phenolic resin, and thermoplastic polyimide [ULTEM, GE]. FRPs were the primary substrates used. Initially, they were cleaned with detergent in an ultrasonic bath followed by rinsing with deionized water and alcohol. For further cleaning, they were treated with oxygen plasma (1.33 seem, 60 W, 5 min) followed by a hydrogen plasma treatment (3 seem, 60 W, 5 min). 

The first reported (8) siloxane-polyimide polymer was synthesized from l,3-bis(aminopropyl)-l,l,3,3-tetramethyldisiloxane and pyromellitic dianhydride. This material was described as a soluble, thermoplastic polyimide. Many other siloxane-polyimide polymers have been prepared via similar methodology using other dianhydrides and diamines (9). 

Heat resistant Intractable thermoset polylmides (Vespel, Kinel, Kapton) have been supplemented by injection moldable polyamlde-lmides (Torlon) and modified polylmides (Kanox, Toramid).( Thermoplastic polyimide adhesives were cited as one of the top 100 Inventions in 1981. Polyimide foam does not Ignite at temperatures below 4300C and is being considered as a cushioning material in public conveyances. 

NASA-Langley provided a further improvement in processibility by replacing the methylenedianiline with a commercial aromatic diamine mixture that afforded even better handling characteristics (17). This type of product is formed by the reaction of formaldehyde with aniline as a precursor in isocyanate manufacture. Fluorine-containing thermoplastic polyimides and polyimides end capped with acetylene groups for cross-linking are also available as potential commercial high-temperature resins. 

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