A quartz spoon gauge, recording pressures automatically, is described. The gauge, representing a closed reaction system, can be used for investigations of the degradation of polymers. I t has been tested by degrading polymethylmethacrylate over a temperature range of 300 to 400" C. The important features of the gauge are as follows: (I) The pressure exerted by gases during degradation is continuously recorded a t appropriate chart speeds via an electrical transducer (maximum displacement 4~0.038 csn; spoon gauges used in this work had sensitivities in the region of 0.035 cm/atm). (2) Only small quantities of polymers are needed; 20 to 40 mg of polymer in the form of filsns was deposited on the walls of the reaction vessels; however, much smaller samples could be used, the limit being given by mechanical vibrations set up in the system. (3) Temperature equilibrium between the reaction vessels and a thermostated bath is reached within about 30 seconds.Useful results for polymethylmethacrylate were obtained up to 400°C, which is a temperature about 100" higher than that reached by previous workers, not neglecting the initial parts of the reactions. The reproducibility of the results has been indicated by average curves obtained from several runs a t any one particular temperature and their standard deviations.The new technique for the study of polymer degradation reactions consists essentially of an automatic recording quartz spoon gauge, which can be used for thermal reactions or any other reactions such as photodegradation as long as volatiles are produced. T h e present paper deals with this technique as applied t o thermal degradation processes. These reactions can be studied with this apparatus a t higher temperatures than before because of the short time needed to reach temperature equilibrium between the reaction vessel and a thermostated bath. The method should in principle also be useful for the study of ceiling temperatures. Only small quantities of polymer are required; the smallest amount employed in this work was 20 mg but there is no reason why smaller quantities (ca. 1 mg) could not be used. The lower limit would essentially be given by mechanical vibrations set up in the system. Thermal degradation of high polymers is quite well understood a t relatively low temperatures where the rates of degradation are slow enough to be measured by instruments such as a thermobalance ; but, once the rates become appreciable, different methods are needed. One attempt in this direction is reported in the present paper. There is scarcely any kinetic data in the literature for degradation reactions whose rates are high, although there is quite substantial information available from analytical experiments on the degradation of polymers a t high temperatures (1).The new apparatus described here has been evaluated using polymethyllnethacrylate, which is known to degrade primarily into monomer. Useful rate measurements were obtained up to 400" C, which is about 100" C higher than the temperature used by other aut...
Two brothers with the X-linked disorder, dyskeratosis congenita, are described. They showed the dermatologic triad of reticular hyperpigmentation, dystrophic nails, and leukoplakia oris as well as the other major feature of this disorder, aplastic anemia. Less common features observed included prenatal and postnatal growth retardation, mental retardation, elevated immunoglobulin levels, and gastrointestinal hemorrhage from mucosal ulceration. Previously unreported findings were intracranial calcifications and nutmeg-like cirrhotic changes of the liver. These brothers demonstrated that skeletal changes and bony fragility may predate anemia or steroid therapy. Although a DNA repair defect is postulated as a possible primary defect, cytogenetic studies revealed no evidence of increased chromosomal breakage.
The thermal degradation of poly(methyl methacrylate) has been studied with unfractionated and fractionated polymer samples over a temperature range of 275–400°C. in a closed system by a new technique. Kinetic data have been obtained at temperatures about 100°C. higher than was possible previously. The results are compared with those obtained in open systems. Two main degradation reactions are operative. It is shown that the energies of activation for these reactions do not vary with polymer chain length in accordance with what is to be expected from the usually assumed depolymerization mechanisms. The termination reactions are diffusion‐controlled. Hydrogenation by Adam's catalyst and bromination of the polymers have only moderate effects on the rate of degradation.
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