Thermoplastic polyimide chemical resistance

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... 

Third 1965 PPS, polyimides, aromatic polyesters, aromatic polyamides, fluoropolymers, thermoplastic elastomers High mechanical strength, very high melting point, superior chemical resistance... 

Polyesters in wire and cable apphcations include Hytrel (Du Pont), a thermoplastic polyester elastomer for the offshore industry Kapton (Du Pont), a polyimide film offering weight saving and chemical resistance and Mylar (Du Pont), used in primary insulation, shield isolation, chemical barrier, and... 

Hot-melt-type (thermoplastic) polyimide films have been developed as high-heat-resistant adhesive materials. Mitsui Chemical s TPI, DuPont s Kapton KJ, Ube s Upicel, and Kaneka s Pixeo are typical examples. These are coated on dimensionally stable polyimide films to ensure good physical performance. 

Engineering thermoplastics are a class of thermoplastic materials that have exceptionally high temperature and chemical resistance. They have properties very similar to those of thermoset plastics and metals. As a result, they are not as easy to weld thermally or to solvent cement as are tbe more conventional thermoplastics. Typical engineering thermoplastics are polysulfone, acetal, amide-imide, and thermoplastic polyimide. 

PAIs are unique materials that have elements of PA (aka nylon) chemistry, as well as aromatic polyimide chemistry. They have exceptional mechanical, chemical, and thermal properties and are considered by some to be at the top of the thermoplastic performance chart. They have high strength, exceptional high heat capability, and broad chemical resistance. Polyamide-imide polymers are melt processible and can be processed into a wide variety of forms—from injection- or compression-molded parts and ingots— to coatings, films, fibers, and adhesives. PAI is often lower in cost than TPI. 

The primary resin of interest is epoxy. Carbon-fiber-epoxy composites represent about 90% of CFRP production. The attractions of epoxy resins are that they polymerize without the generation of condensation products that can cause porosity, they exhibit little volumetric shrinkage during cure which reduces internal stresses, and they are resistant to most chemical environments. Other matrix resins of interest for carbon fibers include the thermosetting phenolics, polyimides, and polybismaleimides, as well as high-temperature thermoplastics such as polyether ether ketone (PEEK), polyethersulfone (PES), and polyphenylene sulfide. 

In this discussion we deal with the resistance of polymers to various chemicals, (mainly water, acids, bases or organic solvents) as well as with their endurance after being exposed to climatic conditions or to fire. Most polymers show very low water absorbency, except for Nylon and cellulose derivatives that are sensitive to humidity. Most polymers also withstand mild inorganic chemicals at ambient temperatures. Excelling at this are the fluoro compoimds, Noryl, polyimide and polysulfone while polypropylene, PVC and epoxy are considered fair. Polyester and polycarbonate are sensitive to bases, while Nylon is affected by acids. Detailed tables of data exist, describing the resistance of plastics to many chemicals at specific temperatures. Most thermoplastics have a tendency to dissolve in specific organic solvents. 

In 1908, aromatic polyimides were first reported by Bogert and Renstiaw [1]. Aromatic polyimides became well-known in 1950, after successful development of two-step polyimide synthesis by DuPont [2]. This class of polymers possesses a number of outstanding properties such as excellent thermal stability, mechanical strength, and electrical properties that have led to application in several fields from engineering thermoplastics to the aerospace and electronics industries, as well as for fibers and adhesives and in matrices for composite materials [3-5]. In addition, polyimides have high thermo-oxidative stability and chemical- and solvent-resistive properties, leading to many membrane-based applications... 

Polyamide-imides are thermoplastic amorphous polymers that possess exceptional mechanical, thermal, and chemical- and wear-resistant properties. They are inherently nonflammable, have outstanding electrical properties, and possess enormous temperature stability from cryogenic to 300°C. These properties place polyamide-imides at the top of the price and performance pyramid with polyketones and polyimides. 

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