Isothermal ageing

LARC-TPI is a linear thermoplastic PI which can be processed ia the imide form to produce large-area, void-free adhesive bonds. Mitsui Toatsu Chemicals, Inc., has obtained Hcense to produce this product commercially for appHcations such as adhesives, films, mol ding compounds, etc. These are thermooxidatively stable and show essentially no loss ia weight at 300°C ia air. Weight loss does not exceed 2—3% after isothermal aging ia air at 300°C for 550 h. 

Use isothermal aging tests to monitor stability at desired drying temperature... 

Co-distillation leads to long period of time under heat resulting in exceeding the isothermal aging characteristics for a thermally unstable material which leads to thermal decomposition and overpressure of the vessel. 

Evaluate isothermal aging characteristics of thermally unstable components at the maximum expected utility temperature... 

Elevated drum Evaluate thermal stability parameters of material temperatures (isothermal aging tests, SADT, etc.) reaching Self, Keep drums away from source of heat Accelerating Decomposition store at required temperature Temperature (SADT). CCPS G-15 CCPS G-22 CCPS G-29 CCPS G-30... 

Figure 2 Time sequence of th< spin configuration on a (100) plane at 50% when the system at T=2.5 (snapshot a) is quenched down to T—1.7 and is subject to an isothermal aging. Snapshots demonstrated in figs, b, c and d correspond to time t=20,000, 43,000 and 50,000. The long range and short range order parameters input from the PPM calculations and resultant ones in the simulated lattice are also demonstrated [22, 24, 28]. ...

The calculated results are demonstrated in Figs. 7a and 7b [25, 33). The system maintained at T—1.85 is subject to down quenching with a temperature step AT = 0.05 and isothermal aging is followed at each temperature to equilibrate the system. After reaching the equilibrium at T =1.5, the operation is reversed up to T =1.85. In Fig. 7a, one sees that the resultant relaxation time is shortened with decreasing temperature and... 

Figure 7 Relative change of electrical resistivity during isothermal aging condition with falling and rising temperatures obtained by PPM calculations [25, 33] without (a) and with (b) incorporating thermal activation process in the spin flip probability 6. The assumed temperature dependency of 6 is indicated in figure c.

Figure 36. Stored negative space charge (a), coupled electric field (b), and internal voltage (c) in anodic oxide during anodization (curve 1) and during isothermal aging at various times (curves 2-7).61...

Characterization. Differential scanning calorimetry and thermal mechanical analysis data were obtained on a DuPont 990 thermal analyzer coupled with a DuPont DSC or TMA cell. Isothermal aging studies were carried out with an automatic multisample apparatus. 

Figure 4. Isothermal aging studies of the thermosetting resins derived from the mixtures of BCB and K-353, in comparison with those derived from pure BCB and K-353.

For comparative isothermal aging studies, all the samples of pure BCB and dlcyanate monomers, as well as their 1 1 molar mixtures, were cured in a single batch at 200-220°C for 40 hours under nitrogen atmosphere. The cured samples of BADCy, METHYLCy, and THIOCy were all transparent and yellow/amber, and their blends with BCB were also transparent but dark red in color. The cured sample of BCB was translucent and yellow. The Tg s (cure) of the thermosets derived from the dlcyanate monomers are relatively high, 224°-261°C as determined by thermomechanical analysis (TMA). There Is an increase of 10-31°C in Tg (cure) values in their blends with BCB. The ITGA results of the cured samples of BCB,... 

Based on the assumption that there is no chemical interaction or any synergistic effect caused by physical changes in the blends, theoretical weight losses of the blends can be calculated, using the isothermal aging data of the individual components as well as their weight percents in the blends. The results are compared with the experimental data in Table IV (BCB/K-353) and Table V (BCB/Dicyanate). 

Fig. 31. KINPTR isothermal aging predictions at 794 K, 928 kPa H2 pressure, C6- 416 K Mid-Continent (P, paraffins A, aromatics C, Cs-).

Fig. 26. Isothermal aging study on various mole ratio copolymers of...

The enhancement of thermal stability as measured by these isothermal aging experiments by the addition of bisbenzocyclobutenes to dienophilic thermosetting monomers has also been observed with bis activated acetylenes and dicyanates. The isothermal weight loss results obtained on a one to one mole... 

Diels-Alder mechanism. It was found that those polymers which had the least weight loss in the isothermal aging study were derived from those monomers which by DSC polymerized to the greatest extent by a Diels-Alder mechanism. It was inferred therefore that if similar considerations apply to the copolymers of bismaleimides and bisbenzocyclobutenes then these materials too might be the result of predominantly Diels-Alder type polymerizations. To the extent to which these conclusions are correct, the enhanced thermal stability of the bisbenzocyclobutene/bismaleimide copolymers is likely to be due to their being Diels-Alder polymers of some sort. 

Of all the high temperature, high performance polymers, the benzobisazole rigid-rod polymers are one of the most thermally stable systems known. A variety of thermal techniques have been used to investigate their stability such as thermal gravimetric analysis (TGA), thermal gravimetric-mass spectrometry (TG-MS) and isothermal aging studies. A TGA plot shown in Fig. 4 is indicative... 

A PFMB-based polyimide (BPDA-PFMB) can be used to prepare fibers with mechanical properties comparable to those of commercial PPTA fibers. However, owing to superior thermooxidative stability, the fibers retain their properties for much longer periods of time when subjected to isothermal aging in air at elevated temperatures. In fact, BPDA-PFMB fibers retain their properties under these conditions better than any other available high-performance fiber. 

Isothermal age mode The sample is directly heated to the desired initial temperature. At this temperature, the instrument seeks for an exothermal effect as above. 

An autocatalytic decomposition can be followed by isothermal aging and periodic sampling for a chemical analysis of the substance. The reactant concentration first remains constant and decreases after an induction period (Figure 12.7). This is characteristic for self-accelerating or autocatalytic behavior. The chemical analysis may also be replaced by a thermal analysis using dynamic DSC or other calorimetric methods, following the decrease of the thermal potential as a function of the aging time. 

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