A mathematical model for the kinetics, composition and molar mass development of the bulk reversible addition-fragmentation chain transfer (RAFT) copolymerization of glycidyl methacrylate (GMA) and styrene (St), at several GMA molar feed fractions at 103 °C, in the presence of 2-cyano isopropyl dodecyl trithiocarbonate as the RAFT agent and 1,1′-azobis(cyclohexane carbonitrile), as the initiator, is presented. The copolymerization proceeded in a controlled manner and dispersities of the copolymers remained narrow even at high conversions. Experimental data and calculated profiles of conversion versus time, composition versus conversion and molar mass development for the RAFT copolymerization of St and GMA agreed well for all conditions tested, including high-conversion regions. The kinetic rate constants associated with the RAFT- related reactions and diffusion-controlled parameters were properly estimated using a weighted nonlinear multivariable regression procedure. The mathematical model developed in this study may be used as an aid in the design and upscaling of industrial RAFT polymerization processes.
The problems of learning mathematics are a particularly important field in the educational relationship. In the degree of any engineering and specifically in Chemical Engineering (IQ) requires a series of mathematical skills for learning and problem solving. By virtue of having made a revision on the indices of failure in the educational experiences of the IQ program, it was detected that the highest values were precisely the basic mathematics, this led to propose the solution proposing a change in the teaching with the objective of improve learning and with it, reduce failure rates from the use of a didactic model. The didactic model is based on 3 stages that include bibliographic, documentary and statistical information, for the intervention part, framed within the quantitative field research modality of descriptive type, with characteristics of participant observation. When implemented, it allowed to observe some significant changes in reference to the habits of study and attitude that the students present before the mathematics and on the styles adopted by the professors for this chair, with which finally it was evaluated concluding that it effectively improves the indexes of approval and meaningful learning.
Magnesium and its alloys have been of scientific interest in bone regeneration due to its resorbable, biocompatible and mechanical characteristics. However, its electrochemical activity is a challenge; surface modification treatments are sought through biopolymers or conversion treatments to reduce its corrosion rate. The objective of this research was to evaluate the corrosive behavior of magnesium in simulated physiological solution through electrochemical techniques through a phosphating interface and a chitosan-grenetine film. The phosphating treatment was carried out by chemical conversion pH 10, 11 and 12 and a film was prepared by polymer solution and convective drying. The surfaces were characterized by DRX, RAMAN, SEM-EDS. Combined phases of phosphates with rugose and porous morphology with non-conductive properties were obtained to relate to the electrochemical response of the phosphate interface with different areas of pure magnesium, estimating the actual phosphated area. The biopolymeric film induces the corrosion process at a rate of approximately a quarter of magnesium phosphate during 4 weeks of exposure in the physiological medium. Improving the adhesion properties of the biopolymer film and the porosity could contribute to bone regeneration during this corrosive process.
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