As compreensões do construtivismo de Ernst Von Glasersfeld e John Fossa: intermediando um diálogo em busca de novas significações

The present thesis, orientated by a letter sent by Ernst von Glasersfeld to John Fossa, is the product of a theoretical investigation of radical constructivism. In this letter, von Glasersfeld made three observations about Fossa’s understanding of radical constructivism. However, we limited our study to the second of these considerations since it de als with some of the core issues of constructivism. Consequently, we investigated what issues are raised by von Glasersfeld’s observation and whether these issues are relevant to a better understanding of constructivism and its implications for the mathema tics classroom . In order to realize the investigation, it was necessary to characterize von Glasersfeld’s epistemological approach to constructivism, to identify which questions about radical constructivism are raised by von Glasersfeld’s observation, to i nvestigate whether these issues are relevant to a better understanding of constructivism and to analyze the implications of these issues for the mathematics classroom. Upon making a hermeneutic study of radical constructivism, we found that what is central to it is its radicalism, in the sense that it breaks with tradition by its absence of an ontology. Thus, we defend the thesis that the absence of an ontology, although it has advantages for radical constructivism, incurs serious problems not only for the theory itself, but also for its implications for the mathematics classroom. The advantages that we were able to identify include a change from the usual philosophical paths to a very different rational view of the world, an overcoming of a naive way of thi nking, an understanding of the subject as active in the construction of his/her experiential reality, an interpretation of cognition as an instrument of adaptation, a new concept of knowledge and a vision of knowledge as fallible (or provisional). The prob lems are associated with the impossibility of radical constructivism to explain adequately why the reality that we build up is regular, stable, non - arbitrary and publicly shared. With regard to the educational implications of radical constructivism, the ab sence of an ontology brings to the mathematics classroom not only certain relevant aspects (or favorable points) that make teaching a process of researching student learning, empowering the student to learn and changing the classroom design, but also certa in weaknesses or limitations. These weaknesses or limitations of constructivism in the classroom are due to its conception of knowledge as being essentially subjective. This requires it to work with one - on - one situations and, likewise, makes the success of teaching dependent on the teacher’s individual skills. Perhaps the most important weakness or limitation, in this sense, is that it makes teaching orientated by constructivist principles unable to reach the goal of the formation of a community. We conclud e that issues raised by von Glasersfeld’s observation are absolutely relevant to the context of a better understanding of radical constructivism and its implications for education, especially for Mathematics Education.

Tratamento de argila montmorilonítica para a produção de nanocompósitos poliméricos com retardo de propagação de chama

Compared to conventional composites, polymer matrix nanocomposites typically exhibit enhanced properties at a significantly lower filler volume fraction. Studies published in the literature indicate t hat the addition of nanosilicate s can increase the resistance to flame propagation in polymers. In this work, a treatment of montmorillonite (MMT) nano clay and the effect of its ad dition o n flame propagation characteristics of vinyl ester were studied. The resea rch was conducted in two stages. The first stage focused on the purification and activation of the MMT clay collected from a natural deposit to improve compatibility with the polymer matrix . Clay modification with sodium acetate was also studied to improve particle dispersion in the polymer. The second step was focused on the effect of the addition of the treated clay on nanocomposites ’ properties. Nanocomposites with clay con tents of 1, 2, 4 wt. % were processed. T he techniques for the characterization of the clay included X - ray fluorescence (XRF), X - r ay d iffraction (XRD), thermogravimetric a nalysis (TGA), d ifferential scanning c alorimetry (DSC) , s urface area (BET) and Fourier transform infrared spectroscopy (FTIR). For t he characterization of the nanocomposites , the techniques used were thermogravimetric a nalysis (TGA) , differential scanning c alorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) , scanning electron mi croscopy (SEM), transmission electron m icroscopy (TEM), and the determination of tensile strength, modulus of elasticity and resistance to flame propagation. According to the results, the purification and activation treatment with freeze - drying used in thi s work for the montmorillonite clay was efficient to promote compatibility and dispersion in the polymer matrix as evidenced by the characterization of the nanocomposite s . It was also observed that the clay modifica tion using sodium acetate did not produce any significant effect to improve compatibilization of the clay with the polymer. The addition of the treated MMT resulted in a reduction of up to 53% in the polymer flame propagation speed and did not affect the mechanical tensile strength and modulus o f elas ticity of the polymer, indicating compatibility between the clay and polymer. The effectiveness in reducing flame propagation speed peaked for nanocomposites with 2 wt. % clay, indicating that this is the optimum clay concentration for this property. T he clay treatment used in this work enables the production of vinylester matrix nanocomposites with flame - retardancy properties .