Polybenzimidazole

Moulded polybenzimidazole has the highest compressive strength of any unfilled resin (400 MPa), of 427 C and HDT of 435 °C. It can withstand temperatures of 700 °C for several minutes. The LOI is 58%. However, it is degraded in hot aqueous acids. Poly benzimidazole can be solution spun into fibre and is extensively nsed in fightfighters clothing and other fire blocking applications. 

Kemmish, High Performance Engineering Plastics, Rapra Review Report No.86, Rapra Technology, Shrewsbury, Shawbury, UK, 1995. 

Odle and R. Galluci, Gallucci in Proceedings of the 61st SPE Antec Conference, Nashville, TN, USA, p.l853. 

Rulkens and R. Crombach, inventors DSM IP Assets BV, assignee US6747120, 2002. 

Marrocco, R. Gagne and M. Trimmer, inventors Maxdem Inc., assignee US5227457, 1989. 

PBl has no known melting point and a glass-transition temperature of 427 C (800 F). It has an ultrahigh heat-distortion temperature of 435 C (815 F), retards flame, and will not bum in air. The material can withstand steady temperatures up to 427°C (800 F) and short bursts up to 760°C (1,400°F)- This material is reported to resist steam at 343 C (650°F) and 15 MPa (2,200 psi) pressure. When exposed to saturated steam, PBI absorbs only 0.4 percent moisture. It resists a wide range of chemicals, including harsh ones. 

This plastic has high mechanical and physical strength properties including a high compression strength. PBI can bear loads for short periods at temperatures up to 650°C (1,200 F). When reinforced with silicon-carbide fibers, it can thwart an attack even from laser weapons. It has a low coefficient both of friction and of thermal expansion (0.000013 in./in./T). 

PBI has been targeted to replace metals, ceramics, carbon, and other materials where an industry needs materials that are highly resistant to heat and corrosion, as in the chemicals and oil processing, aerospace, and transportation. PBI s main commercial applications include use as valve seats, seals, electrical connections, thrust washers. 

---

A number of thermally stable polymers have been synthesized, but in general the types of stmctures that impart thermal resistance also result in poor processing characteristics. Attempts to overcome this problem have largely been concentrated on the incorporation of flexible groups into the backbone or the attachment of stable pendent groups. Among the class of polymers claimed to be thermally stable only a few have achieved technological importance, some of which are polyamides, polyimides, polyquin oxalines, polyquinolines, and polybenzimidazoles. Of these, polyimides have been the most widely explored. 

Polybenzimidazole (PBI) Fibers. Poly(2,2 -(y -phenylene)-5,5 -bisbenzimidazole) [25734-65-0] is a textile fiber marketed by Hoechst-Celanese (11) which does not form Hquid crystalline solutions due to its bent meta backbone monomeric component. PBI has exceUent resistance to high temperature and chemicals. 

PBI is being marketed as a replacement for asbestos and as a high temperature filtration fabric with exceUent textile apparel properties. The synthesis of whoUy aromatic polybenzimidazoles with improved thermal stabUities was reported in 1961 (12). The Non-MetaUic Materials and Manufacturing Technology Division of the U.S. Air Force Materials Laboratory, Wright-Patterson Air Force Base, awarded a contract to the Narmco Research and Development Division of the Whittaker Corp. for development of these materials into high temperature adhesives and laminates. 

Polymerization Solvent. Sulfolane can be used alone or in combination with a cosolvent as a polymerization solvent for polyureas, polysulfones, polysUoxanes, polyether polyols, polybenzimidazoles, polyphenylene ethers, poly(l,4-benzamide) (poly(imino-l,4-phenylenecarbonyl)), sUylated poly(amides), poly(arylene ether ketones), polythioamides, and poly(vinylnaphthalene/fumaronitrile) initiated by laser (134—144). Advantages of using sulfolane as a polymerization solvent include increased polymerization rate, ease of polymer purification, better solubilizing characteristics, and improved thermal stabUity. The increased polymerization rate has been attributed not only to an increase in the reaction temperature because of the higher boiling point of sulfolane, but also to a decrease in the activation energy of polymerization as a result of the contribution from the sulfonic group of the solvent. 

PolybenZimidaZoles. The polyben2imida2oles (PBIs) are generally produced by the high temperature, melt polycondensation reaction of aromatic bis-ortho-diamines and aromatic dicarboxylates (acids, esters, or amides) in a reaction such as that shown in equation 11 to form ben2imida2ole [51-17-2] as the repeating unit. 

A considerable number of non-cross-linked aromatic and heterocyclic polymers has been produced. These include polyaromatic ketones, aromatic and heterocyclic polyanhydrides, polythiazoles, polypyrazoles, polytriazoles, poly-quinoxalines, polyketoquinolines, polybenzimidazoles, polyhydantoins, and polyimides. Of these the last two have achieved some technical significance, and have already been considered in Chapters 21 and 18 respectively. The most important polyimides are obtained by reacting pyromellitic dianhydride with an aromatic diamine to give a product of general structure (Figure 29.17). 

If one amino group in o-phenylenediamine is converted to an amide group by formic acid, the intermediate benzimidazole is formed. This reaction, conducted with a wide range of reactants, produces resins (polybenzimidazoles) used as high-temperature adhesives for laminates in the aerospace industry. Heat insulation is made by including tiny bubbles of silica and all... 

Polybenzimidazoles Developmental laminating resin, fiber, film stable 24 hours at 300°C (572°F) in air. 

Neuse, E. Aromatic Polybenzimidazoles. Syntheses, Properties, and Applications. Vol. 47, pp. 1-42. 

A report130 of DSC measurements on polybenzimidazole fibers describes important differences for the glass transition temperature depending on die mechanical treatment of the fiber. An as-spun fiber exhibits a Tg at 387°C instead of 401°C for a drawn fiber free to shrink or 435°C for a drawn fiber widi fixed length. 

Falling-ball rebound test, 244 Ferrocene-containing polybenzimidazole, 315... 

PA-4,6 synthesis from, 171-172 PA-6,6 polymerization from, 169-170 PA-6,1 synthesis from, 181 PA salt solution, polymerization from, 164 Pawlow, James H., 431 PBIs. See Polybenzimidazoles (PBIs)... 

Poly(arylene thioether)s, 363-364 Poly(arylene thioether sulfone)s, 364 Poly(aryl sulfone) derivatives, 354 Poly(p-benzamide), synthesis of, 188-189 Polybenzimidazoles (PBIs), 265 ferrocene-containing, 315 synthesis of, 313... 

Staudt, R. and J. Boyer, Development of polybenzimidazole-based, high temperature membrane and electrode assemblies for stationary and automotive applications, U.S. DOE 2004 Annual Program Review Proceedings, Philadelphia, PA, May 2004. 

Polyazo dyes, 9 363—361 Polybenzamide, 15 109-110 Poly(p-benzamide) (PBA), 10 212 19 714 crystal lattice parameters of, 19 728t laboratory synthesis of, 19 719 Polybenzimidazole (PBI), asbestos substitute, 3 3141 Polybenzimidazole (PBI) fibers,... 

Other Reactive Oligomers - In the mid 1960 s, a reactive oligomeric precursor to a polybenzimidazole (PBI) was available as... 

---