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Abstract(s)
Neste trabalho foi realizada a encapsulação de materiais de mudança de fase (PCM), através de polimerização com reticulação em suspensão aquosa, visando a obtenção de produtos úteis no armazenamento/libertação de energia térmica. Foram usados dois tipos de mecanismos de reação: polimerização radicalar clássica (FRP) e polimerização via transferência de cadeia reversível por adição-fragmentação (RAFT). Usaram-se como monómeros metacrilato de metilo (MMA) e dimetacrilato de etilenoglicol (EGDMA), AIBN (2,2’ Azobis (2-metilpropionitrilo)) - como iniciador -, e Poli (álcool vinílico) (PVA) como agente de suspensão. Parafina e octadecano foram considerados como PCM nos estudos de encapsulação realizados.
Relativamente à caracterização, procedeu-se à análise dos produtos por Espectroscopia de Infravermelho com Transformada de Fourier (FTIR) para verificar a presença de PCM nos respetivos espectros. Por Cromatografia de Permeação de Gel (GPC) foi determinado o tamanho e quantidade de moléculas solúveis e a Calorimetria Diferencial de Varrimento (DSC) permitiu avaliar as propriedades térmicas dos produtos sintetizados. Foi ainda realizada a análise Termogravimétrica (TGA) dos materiais para estudo da sua degradação térmica. As partículas de polímero com PCM encapsulado foram ainda analisadas por SEM para avaliação da sua morfologia.
Foi possível concluir que os materiais obtidos armazenam e libertam, de forma eficiente, energia térmica no decorrer das mudanças de fase dos PCM encapsulados (cerca de 28 °C com octadecano e 55 °C com parafina).
Este trabalho é um contributo para o desenvolvimento de técnicas de encapsulação de PCM, materiais que apresentam diversas aplicações, nomeadamente em edifícios para o melhoramento do conforto térmico interior e aumento da eficiência energética.
In this work the encapsulation of phase change materials (PCM) was made by crosslinking polymerization in aqueous suspension, in order to obtain useful products for the storage/release of thermal energy. Classical free radical polymerization (FRP) and polymerization via reversible chain transfer by addition-fragmentation (RAFT) were considered as reactions mechanisms. Methyl methacrylate (MMA) and ethyleneglycol dimethacrylate (EGDMA) were used as monomers, AIBN (2,2'-azobis (2-methylpropionitrile)) - as initiator - and PVA as the suspending agent. Octadecane paraffin were considered as PCM materials in the encapsulation studies performed. For characterization of the products, it was performed the analysis of the materials by Fourier Transform Infrared Spectroscopy (FTIR) to verify the presence of PCM in the respective spectra. By Gel Permeation Chromatography (GPC) was determined the size and the amount of soluble molecules and Differential Scanning Calorimetry (DSC) allowed the evaluation of the thermal properties of the synthesized products. Was also performed the Thermogravimetric analysis (TGA) of materials for study of its thermal degradation. The polymer particles with encapsulated PCM were further analyzed by SEM for evaluation of their morphology. It was concluded that the materials obtained efficiently store and release thermal energy, during the phase changes of the encapsulated PCM (about 28 ° C to octadecano and 55 ° C to paraffin). This work is a contribution to the development of techniques for encapsulation of PCM materials having various applications, e.g., in buildings to improve the interior thermal comfort and to increased energy efficiency.
In this work the encapsulation of phase change materials (PCM) was made by crosslinking polymerization in aqueous suspension, in order to obtain useful products for the storage/release of thermal energy. Classical free radical polymerization (FRP) and polymerization via reversible chain transfer by addition-fragmentation (RAFT) were considered as reactions mechanisms. Methyl methacrylate (MMA) and ethyleneglycol dimethacrylate (EGDMA) were used as monomers, AIBN (2,2'-azobis (2-methylpropionitrile)) - as initiator - and PVA as the suspending agent. Octadecane paraffin were considered as PCM materials in the encapsulation studies performed. For characterization of the products, it was performed the analysis of the materials by Fourier Transform Infrared Spectroscopy (FTIR) to verify the presence of PCM in the respective spectra. By Gel Permeation Chromatography (GPC) was determined the size and the amount of soluble molecules and Differential Scanning Calorimetry (DSC) allowed the evaluation of the thermal properties of the synthesized products. Was also performed the Thermogravimetric analysis (TGA) of materials for study of its thermal degradation. The polymer particles with encapsulated PCM were further analyzed by SEM for evaluation of their morphology. It was concluded that the materials obtained efficiently store and release thermal energy, during the phase changes of the encapsulated PCM (about 28 ° C to octadecano and 55 ° C to paraffin). This work is a contribution to the development of techniques for encapsulation of PCM materials having various applications, e.g., in buildings to improve the interior thermal comfort and to increased energy efficiency.
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Keywords
PCM Encapsulação Armazenamento Libertação Energia térmica Eficiência energética