A New Technique for the Study of High-Polymer Degradation Reactions

Abstract

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...

Review on Chemical Reactions of Burning Poly(methyl methacrylate) PMMA

“…Besides the above two main decomposition processes, there are other termination reactions that compete with the decomposition reaction. This is demonstrated by forming products such as CO, CO 2 , OH, CH 4 , and char [5,[10][11][12], other than the monomer.…”

Coupled matrix-based Monte Carlo modeling for a mechanistic understanding of poly (methyl methacrylate) thermochemical recycling kinetics

“…Termination reactions involving MCRs are although not taken into account, as this termination type is less likely with low kinetic significance, as supported by acrylate radical polymerization studies [48]. Also the further decomposition of the small radical species in Figure 3, which can be linked to the formation of MMA derivates such as methyl 2-methylbutanoate, methanol, carbon oxide (CO) and carbon dioxide (CO2), is not taken into account [27,[49][50][51]. It is simply assumed that all small radicals are removed together with MMA to the gas phase, not affecting the further polymer degradation kinetics.…”

“…Model validation is for such models only performed based on (apparent) overall pre-exponential factors and activation energies with raw data typically coming from thermogravimetric analysis (TGA) [16,23,[25][26][27][28][29]. More desired is to develop and apply kinetic models driven by elementary reactions, as their predictive power for varying reaction conditions is much larger, and both main and side products can be better accounted better defining the overall quality of the recycling product [29][30][31][32][33][34][35][36][37][38][39][40].…”

Progress in Reaction Mechanisms and Reactor Technologies for Thermochemical Recycling of Poly(methyl methacrylate)

“…It is interesting to note that methanol and methane have been experimentally observed in the product spectrum from the thermal degradation of PMMA [75][76][77]. Hence, reactions also occur that block eventual MMA formation and must be seen as side reactions.…”