18 High Performance Thermoplastic Resins and Their Composites (mainly manufacturers'datasheets)could be lower.Many of the thermoplastics listed in Table 4 have Tg greater than 200 C and then have use temperatures in the 170C-180 C range required for applications on supersonic fighter and supersonic commercial aircraft [1,74]. Figure 3 presents the average Tg found in Table 4 for a number of thermoplastics. Except Phillips Petroleum's polyphenylene sulfide (PPS).a member of the polyarylene sulfide family,all Tg's are over 140 C.The polyimide family.Amoco's polyamideimide Torlon and polybenzimidazole(PBI)exhibit very high Tg's.Among them,N-polymer and PBI have the highest Tgs,both higher than 300 C and higher than 400 C in the case of PBI.It can also be observed that the latest compositions within the polyketone and polyarylene sulfide families have higher Tg's than their predecessors(Dupont's polyetherketoneketone(PEKK),ICI's polyetherketone (PEK).BASF's polyetherketoneetherketoneketone(PEKEKK)versus ICI's polyetheretherketone (PEEK)and Phillips Petroleum's polyarylene sulfide(PAS-2)and polypherylene sulnde sulfone(PPSS)versus PPS)[31.Unfortunately,as mentioned earlier,the desired high Tg of a high performance thermoplastic is generally associated with a high melt viscosity and a high processing temperature.often close to the decomposition temperature.As shown in Table 4,processing temperatures for thermoplastics vary from 290 to 470C compared to 177C for Hercules 3501-6 epoxy.In general.amorphous thermoplastics exhibit higher Tg values than the semi-crystalline polymers but fortunately they are processed in the same temperature range as semi-crystalline thermoplastics [77].Processing temperature must exceed Tg in the case of an amorphous thermoplastic while it has to exceed Tm in the case of a semi-crystalline thermoplastic in order to achieve a low melt viscosity.good consolidation and proper morphology [1]. The thermal stabilities of different thermosets inchiding epoxy and polyimide thermoset resin formulations as well as the thermoplastic resins PEEK and PPS have been measured and compared by Knight and Wright [78].They have rated the relative thermal stabilities of these polymers in a decreasing order as follows:PEEK and PPS polyimides epoxies.Scola[79]examined the thermal-oxidative stability of polymer materials which are candidates for application in advanced composites in the temperature region of 287-343C. Among these polymers were N-polymer,PPQ,Durimid(Larc-TPI produced by Rogers),Larc-TPI (produced by Mitsul Toatsu Chemcals(MTC)),Ethyl Corporauon's Eymyd L-30N(based on the same resin formulation of Eymyd U-35).Ethyl Corporation's Eymyd L-20N (based on the same resin formulation to Eymyd U-25)and PBI.Figure 4 shows the thermo-oxidative stability of some of these polymers at 316C.In terms of their thermo-oxidative stability in air for 1500 hours at 316C,the author has rated the polymers as follows:N-polymer >>>PPQ Durimid Eymyd L-20N Larc-TPI>>>Eymyd L-30N PBI.18 High Performance Thermoplastic Resins and Their Composites (mainly manufacturers’ datasheets) could be lower. Many of the thermoplastics listed in Table 4 have Tg greater than 200’ C and then have use temperatures in the 170’ C - 180” C range required for applications on supersonic fighter and supersonic commercial aircraft [ 1, 741. Figure 3 presents the average Tg found in Table 4 for a number of thermoplastics. Except Phillips Petroleum’s polyphenylene sulfide (PPS), a member of the polyarylene sulfide family, all Tg’s are over 140’ C. The polyimide family, Amoco’s polyamideimide Torlon and polybenzhnidazole (PBI) exhibit very high Tg’s. Among them, N-polymer and PBI have the highest Tgs, both higher than 300” C and higher than 400” C in the case of PBI. It can also be observed that the latest compositions within the polyketone and polyaxylene sulfide families have higher Tg’s than their predecessors (Dupont’s polyetherketoneketone (PEKK), ICI’s polyetherketone (PEK). BASF’s polyetherketoneetherketoneketone (PEKEKK) versus ICI’s polyetheretherketone (PEEK) and Phillips Petroleum’s polyarylene sulfide (PAS-2) and polyphenylene sulfide sulfone (PPSS) versus PPS) (31. Unfortunately, as mentioned earlier, the desired high Tg of a high performance thermoplastic is generally associated with a high melt viscosity and a high processing temperature, often close to the decomposition temperature. As shown in Table 4, processing temperatures for thermoplastics vary from 290 to 470” C compared to 177” C for Hercules 3501-6 epoxy. In general, amorphous thermoplastics exhibit higher Tg values than the semi-crystalline polymers but fortunately they are processed in the same temperature range as semi-crystalline thermoplastics [77]. Processing temperature must exceed Tg in the case of an amorphous thermoplastic while it has to exceed Tm in the case of a semi-crystalline thermoplastic in order to achieve a low melt viscosity, good consolidation and proper morphology [ 11. The thermal stabilities of different thermosets including epoxy and polyimide thermoset resin formulations as well as the thermoplastic resins PEEK and PPS have been measured and compared by Knight and Wright [78]. They have rated the relative thermal stabilities of these polymers in a decreasing order as follows: PEEK and PPS z polyimides > epoxies. Scala [79] examined the thermal-oxidative stability of polymer materials which are candidates for application in advanced composites in the temperature region of 287 - 343” C. Among these polymers were N-polymer. PPQ, Durimid (Larc-TPI produced by Rogers), Larc-TPI (produced by Mitsui Toatsu Chemicals (MTC) ), Ethyl Corporation’s Eymyd L-30N (based on the same resin formulation of Eymyd U-35). Ethyl Corporation’s Eymyd L-20N (based on the same resin formulation to Eymyd U-25) and PBI. Figure 4 shows the thermo-oxidative stability of some of these polymers at 316” C. In terms of their thermo-oxidative stability in air for 1500 hours at 316’ C, the author has rated the polymers as follows: N-polymer >>> PPQ > Durimid > Eymyd L-20N > Larc-TPI >>> Eymyd L-30N > PBI