Thermoset plastics polyimides

The Kinel materials produced by Rhone-Poulenc are polybismaleinimides of the type shown in Figure 4.22. These materials have chain-end double bonds, as explained previously, can be processed like conventional thermosetting plastics. The properties of the cured polymers are broadly similar to the polyimides and polyamide-imides. Molding temperatures are usually from 200°C to 260°C. Post-curing at 250°C for about 8 h is necessary to obtain the optimum mechanical properties. 

The major thermosetting plastics, in order of decreasing market volume, are polyurethanes, phenol-formaldehyde, urea-formaldehyde, and polyesters. More specialized thermosets include melamine-formaldehyde, furans, vinyl esters, aUyls, epoxy resins, silicones, and polyimides. While they may sometimes compete with each other and with thermoplastics, for the most part, each of them has unique properties and fills unique markets and applications. 

For bulk materials, Jin et al fabricated poly (methylmethacrylate) (PMMA)/MWNT nanocomposites by melt mixing. MWNTs were well dispersed in the matrix [90]. Melt compounding is also widely used for the fabrication of composite fibers. Sandler et al mixed polyamide-12 pellets and CNTs in a twin-screw micro-extruder and then the extrudate was chopped and fed into a capillary rheometer with 1 mm die. The CNTs in the spun fibers were uniformly dispersed [91]. Not only can thermoplastic polymers be melt-compounded, polyimide, a thermoset plastic, can be also prepared by mixing the imide oligomer at 320 °C on a steel plate and then cured at 370°C. It was found that the dispersion of CNTs in... 

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. 

Plastics. Almost all commercial plastics find some use both dry and lubricated for sliding at low speeds and light loads the most commonly used thermoplastics are nylon, acetal resins, and polytetrafluoroethylene (PTFE). Typical thermosetting resins for bearing appHcations are phenoHcs, polyesters, and polyimides. Table 8 compares the characteristics of plastic bearing materials with those of graphite, wood, and mbber which find use in somewhat similar appHcations. 

Commonly accepted practice restricts the term to plastics that serve engineering purposes and can be processed and reprocessed by injection and extmsion methods. This excludes the so-called specialty plastics, eg, fluorocarbon polymers and infusible film products such as Kapton and Updex polyimide film, and thermosets including phenoHcs, epoxies, urea—formaldehydes, and sdicones, some of which have been termed engineering plastics by other authors (4) (see Elastol rs, synthetic-fluorocarbon elastol rs Eluorine compounds, organic-tdtrafluoroethylenecopolyt rs with ethylene Phenolic resins Epoxy resins Amino resins and plastics). 

The resin matrix can be either thermosetting or thermoplastic. Thermosetting resins such as epoxy, polyimide, polyester, and phenolic are used in applications where physical properties are important. Polyester and epoxy composites make up the bulk of the thermoset composite market. Of these two, polyesters dominate by far. Reinforced with glass fiber, these are known as fiberglass-reinforced plastics (FRPs). FRPs are molded by layup and spray-up methods or by compression molding either a preform or sheet molding compound (SMC). 

Some examples of both types of plastics material are given in Table 1.1. Note that polyimides are unusual since the ones made by the addition polymerization process are thermosetting resins, but others are formally thermoplastics the difference depends on their detailed synthesis and structure. Very high temperature thermoplastics are not easily processed by conventional thermoplastics methods. 

There are of course many plastics materials which have better high temperature performances than the polysulphones, for example the polyimides and fluorocarbon polymers, but most of these materials are thermosetting resins and all require somewhat specialised techniques for handling eg sintering or thin layer coating techniques (12). 

Thermosetting polyimides are one of the highest performing engineering plastics, exhibiting superior performance in applications requiring low wear and long life in severe environments. Polyimide materials feature ... 

Polymer composites are plastics within which fibres are embedded. The plastic is known as the matrix (resin) and the fibres dispersed witbin it are known as the reinforcement Thermosetting matrix materials include polyester, vinyl ester and epoxy resins. For higher temperature and extreme environments, bismaleimlde, polyimide and phenolic resins are used. Composites can be used to replace metal parts but care must be taken during design. Most engineering materials have similar properties in any direction (called isotropic) where composites have not This can however be offset by arranging the reinforcement layers in varying directions. 

Toxicology Nuisance dust Uses Constituent of cement in refractories anticaking agent in table salt, vanilla powd. filler-reinforcement for plastics, phenolic, epoxy, melamine, nylon, polyimide, PBT, PVC, PC, DAP, polybutadiene, thermoset polyester, polyolefin, and urethane polymers provides friction and wear props, in brake and clutch iTidtoridls... 

Polyimide parts can be joined with mechanical fasteners. Self-tapping screws must be strong enough to withstand distortion when they are inserted into the polyimide resin which is very hard. Polyimide parts can be bonded with epo adhesives. Only abrasion and solvent cleaning is necessary to treat the substrate prior to bonding. Tbe plastic part will usually have a hi er thermal rating than the adhesive. Thermosetting polyimides carmot be heat welded or solvent cemented. 

Dimer acid-based polyesters being used as thermoplasts, thermoset, and elastomers are used in large quantities as adhesives and coatings. The polyesters, as we have reported herein, may have various commercial applications. Owing to the flexural properties, these low molecular weight linear polyesters of dimer acid may be used as plasticizers providing internal lubrication for various polymers, such as polyimides and inorganic coordination polymers, which may have very poor processibility. 

Thermosetting polyimides are one of the highest performing engineering plastics, exhibiting... 

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