Weight-loss temperature data

Vitreous siUca is relatively inert to attack from most acids for temperatures up to 100°C. The weight loss data in acid solutions are summarized in Table 3. The main exceptions are phosphoric acid, which causes some corrosion above approximately 150°C, and hydrofluoric acid, which reacts readily at room temperature (91). This latter dissolution proceeds as follows ... 

Figure 1 applies to pyrolysis in which the wood temperature is raised from 100 C in about 10 h to various final temperatures. The weight losses, depicted as volatiles, and solid residues have been determined after the trials, and originate mainly from Klason, v. Heidenstam, and Norlin (4), under consideration of data published by Goos (18) and Stamm (19). Measurements on small samples by Beall and Eickner (20), LeVan and Schaffer (21), and Elder (22) have been compared. Up to about 275 or 300 C — the temperature range in which cellulose rapidly disintegrates — increased final trial temperatures cause increased increments of volatiles beyond 300 C the increments steadily diminish. 

Table I presents the results of "isothermal" simultaneous thermoanalytical (STA) runs, at 573 K and 773 K, for all three products. Similar data, at a fixed heating rate is shown in Table II. One of the crucial parameters is the temperature of maximum weight loss rate, corresponding to the time when dehydrochlorination of PVC starts becoming important. This temperature is close to 573 K in all cases. In fact, at a relatively fast heating rate, almost no decomposition occurs at temperatures under 563 K. If the materials are heated at 573 K for a prolonged period, complete dehydrochlorination takes place, but no further stages of PVC decomposition occur. None of the three materials investigated decomposes completely until a temperature of ca. 773 K is attained. Even then only a certain fraction of the entire mass of the samples is volatilised, due to the presence of inorganic fillers in their composition.

Polymer films of approximately 1000 microns wet film thickness were laid down with a bar applicator on PTFE coated glass panels and the solvent allowed to evaporate at ambient temperature for a standard period of seven days. A typical plot of solvent weight loss with time is shown in Figure 2. The thickness of the wet film was dictated by the need to have adequate mechanical strength in the dry films in order that they might be suitable for subsequent mechanical test procedures. Dry film thicknesses were approximately 300 microns as measured by micrometer. The dried polymer films were examined by dynamic mechanical thermal analysis (DMTA) (Polymer Laboratories Ltd.). Typical DMTA data for a polymer and paint are... 

According to MS data, HCl does not evolve at any temperature studied. The weight loss due to the thermal treatment at 200°C was 39%. According to our calculation, this percentage corresponds to the elimination of 94% of the theoretically pos-... 

Desmaroux [73a] followed the decomposition of nitrocotton kept at a temperature of 132°C and established that the reaction types (1) and (3) predominated. Only j-j of the substance broke down by the hydrolysis of ester groups. Desmaroux also determined the loss of weight of the sample so as to compare it with the loss of nitrogen. The weight loss of the nitrocellulose calculated on the basis of the nitrogen lost is 3-12 times smaller than the total weight loss, as seen from the data in Table 66. 

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