Polyimides thermal weight loss

A representative sample of many of the polyimide films that were produced were subjected to thermo-mechanical analysis (TMA), torsional braid analysis (TBA), thermal gravimetric analysis (TGA), infrared spectral analysis and weight loss on prolonged heating (e.g. isothermal studies), TABLE II. The softening temperature as measured by TMA and TBA are in general... 

The approximately 100 °C increase in Tg in comparison to the PEI, allows the blend composition to be shifted to 90% polyimide, keeping a blend Tg in the range of 350 °C, but now showing a greatly reduced thermal-oxidative weight loss after a 1000 h exposure to air at 315 °C, as illustrated in Fig. 6. The excellent mechanical properties listed in Table 3 indicate that the 10/90 PBI/6FC0PI is a matrix candidate for use at temperatures up to about 315 °C. 

Examination of the thermal stability of the polyimides synthesised, carried out using differential thermogravimetric analysis (air, AT = 4.5 °C/min), revealed that, under the conditions specified, the 10% weight loss (used as a criterion of thermal stability) is almost independent of the structure of the polyimides (Table 5.1). For all polyimides examined, the 10% weight loss temperature was 400 °C. The relatively low thermal stability of these polyimides may be related to the presence of the methoxy groups. 

The glass transition temperatures ofthe polyimides are 195-250 °C their 10% weight loss temperamres (dynamic thermogravimetric analysis, air, AT = 4.5 °C/min) are 390-422 °C. Of particular interest are the dielectric constants of these polyimides. At a relative humidity of 50% these constants are 2.70-2.90 and are comparable with constants of the best fluorinated polyimides [21, 50-55]. The lowest dielectric constant (2.70) was observed for polyimide based on 6F dianhydride, containing the highest amount of fluorine. Thermal treatment of this polymer film at 280-290 °C for 1 hour led to a decrease (2.45) of dielectric constant due to the possible formation of nanofoams [56]. 

The thermal properties of the polyimide film were evaluated by the 5 % weight loss (T5), 10 % weight loss (T10), the decomposition temperatures... 

Bismaleimides have excellent thermal stability, comparable with the better condensation polyimides mentioned above, although they are also intrinsically brittle. Weight losses frequently start at 350°C or higher. As with many other resins, the use of solvent varnishes to prepare prepregs can... 

Representative TG curves of polymer BAPDM/BPDA in nitrogen and air atmosphere are shown in Fig. 2.9. In the figure it is apparent that the polymer possesses excellent thermal stability with decomposition temperature in excess of 500 °C. Decomposition temperatures at 10% weight loss of these polyimides reach 542-564 °C and 549-572 °C in nitrogen and air, respectively. It was... 

Thermal ageing in air at 371°C shows that polybenzimidazole 29 is completely degraded after 100 h at that temperature [curve (a)]. Poly(A-phenylbenzimidazole) in which aU N-H groups are replaced by N-C Hs substituents exhibits better resistance to air oxidation with 70% weight loss after 200 h at 371°C [curve (b)], while both polyimide 4 and polyphenylquinoxaline 15 [curve (c)] are more stable with only 30% weight loss under the same time-temperature conditions. 

In the initial stage of decomposition, according to the initial decomposition temperature, the polyimide Af-(3-(2-5-dioxo-2,5-hydro-l-l-l-pyrrole-l-yl)phenylacet-amide bonded with 4(-4-aminocyclohexyl-)methyl-cyclohexan amine has the best thermal stability (initial decomposition temperature T of 250°C) the corresponding temperatures for 10% and 30% weight loss are 406°C and 457°C, respectively. 

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