Polybenzimidazole plastic

Fiber, polybenzimidazole High strength, heat resistance fiber made from polybenzimidazole plastic... 

A number of plastics are condensation polymers and include polyesters and nylons that are not as highly oriented as the same materials but in fiber form. Other plastics have been developed that have outstanding heat stability, strength, and other properties that allow their wide use. These plastics include polycarbonates, polyimides, polybenzimidazoles, polysulfides, polyethers, polysulfones, and polyketones. 

As aromatic compounds have been exhausted as building blocks for life science products, A-heterocyclic structures prevail nowadays. They are found in many natural products, such as chlorophyll hemoglobin and the vitamins biotin (H), folic acid, niacin (PP), pyridoxine HCl (Be), riboflavine (B2), and thiamine (Bi). In life sciences 9 of the top 10 proprietary drugs and 5 of the top 10 agrochemicals contain A-heterocycIic moieties (see Tables 11.4 and 11.7). Even modern pigments, such as diphenylpyrazolopyrazoles, quinacri-dones, and engineering plastics, such as polybenzimidazoles, polyimides, and triazine resins, exhibit an A-heterocydic structure. 

More recently, we have seen other new plastics arrive, including such exotic, high performance materials as the polybenzimidazoles, polyoxadiazoles, polyperfluorotriazines, polyphenylenes, and such inorganic materials as the boron polymers, the metalloxanes, and the polysilazanes, to name only a few. These exotic materials are mostly development products today, they are very expensive and will undoubtedly find their first uses, if any, in the aerospace industry which requires the high performance offered by these materials and can afford to pay for them. Some of these new materials will become commercial successes, others will not. 

Syntactic materials based on polybenzimidazole and glass or phenolic microspheres (y = 40-500 kg/m3) have been described in the literature109 nl). They have been used as ablation materials that consist of two layers, one of which is a monolithic carbon plastic. Carbon fiber was added to the polyimide binder to improve the mechanical properties of the material. 

These plastics, also known as pyrrones, are experimental materials prepared from aromatic dianhydrides and aromatic tetraamines. The polymer syntheses provide soluble prepolymers that are converted to the pyrrone structures by thermal or chemical dehydration. The precursors can be used to cast films or coatings, or can be molded under very high pressures into filled or unfilled forms. The pyrrones combine some of the best properties of the polybenzimidazoles and polyimides. The pyrrone films are exceptionally radiation resistant and retain their strength properties after 10,000 megarads of 1-MeV electrons. 

In summary of this section, it must noted that, in spite of numerous studies, nowdays we know very little about carbonyl hydrides and other substituted (mixed) carbonyls thermolysis in polymeric systems, as well as in reactive plastics. For example, in some experiments the decomposing metal carbonyls were placed into an epoxide resin heated up to the nanoparticles deposition on the forming polymer surface [121]. It is possible that the highly reactive metal particles in such systems can initiate the epoxy cycle cleavages followed by a three-dimensional space structure formation. Iron carbonyl being decomposed into polybenzimidazole suspension (in transformer oil at 473 K) forms the ferrum nanoparticles (1-11 nm) capable of polymer thermostabization [122]. 

Cold wall heats of ablation values ranged between 7700 and 13,800 Btu/lb. The best performance was obtained with the heterocyclic polyimide and polybenzimidazole and the aromatic polyphenylene resins, all of which exceed the heat of ablation for the widely used phenol formaldehyde (phenolic) resin. The superior charring characteristics of these polymers contributed greatly to their high heats of ablation. The various plastic materials, with their inherently low thermal conductivities, greatly restricted the flow of heat from the surface region into the specimen substrate. 

These new types and forms of fiber provided the industry with more freedom to select the most appropriate type of fiber reinforcement for a given application. Newly developed, high modulus plastics, such as cycloaliphatic epoxies and new-generation high-temperature plastics, such as polybenzimidazole and nylon plastics, offer another degree of fi-eedom in terms of material matrix selection. 

DiSano, L., Polybenzimidazole, in Modem Plastics Encyclopedia Handbook, McGraw-Hill, New York, 1994, p. 16. 

Figure 6-61. Heat-resistance properties of resins retaining 50 percent of properties obtainable at room temperature with resin exposure and testing at elevated temperature. Zone 1 Acrylics, cellulose esters, LDPE, PS, PVC, SAN, SBR, UF, etc. Zone 2 Acetals, ABS, chlorinated polyether, ethyl cellulose, EVA, ionomer, PA, PC, HDPE, PET, PP, PVC, PUR, etc. Zone 3 PCTFE, PVDF, etc. Zone 4 Alkyds, fluorinated ethylene-propylene, MF, polysulfone, etc. Zone 5 TS acrylic, DAP, epoxy, PF, TS polyester, PTFE, etc. Zone 6 Parylene, polybenzimidazole, silicone, etc. Zone 7 PAI, PI, etc. Zone 8 Plastics in R D etc. Since plastics compounding is rather extensive, certain basic resins can be modified to meet different heat-resistance properties.

PAA polyaryl amide PAI polyamide-imide PAN polyacrylonitrile PB polybutylene PBA physical blowing agent PBI polybenzimidazole PBNA phenyl- -naphthylamine PBT polybutylene terephthalate PC permeability coefficient PC personal computer PC plastic composite PC plastic compKJunding PC plastic-concrete PC polycarbonate PC printed circuit PC process control PC programmable circuit PC programmable controller PCB polychlorinated biphenyl PCB printed circuit board PCE perchloroethene PCR post-consumer resin pcf pounds per cubic foot... 

The sandwich construction method mentioned above involves joining metals to other materials by bonding. Further examples include the bonding of brake linings (phenolic adhesives) and compound materials in ski manufacture, where aluminum is bonded to plastics, wood, etc. (phenolic and epoxy adhesives). Highly alloyed steels, beryllium and titanium alloys, and other special metals can be bonded with adhesives (e.g., polyi-mides, polybenzimidazoles) that have comparable high-temperature resistance. 

These materials also command premium prices and some require special processing. Examples are polyimides, polyetheretherketone, liquid-crystal polymers, polytetra-fluoroethylene, and polybenzimidazole (Odian GC (2004) Principles of polymerization. Wiley, New York Modern plastics encyclopedia, McGraw-Hill/Modern Plastics, New York). 

---