Avaliação de propriedades mecânicas e térmicas de compósito à base de polietileno de alta densidade e hidroxiapatita deficiente de cálcio

• Autor(a) principal: Colonese, André
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/8014
• topic: High density polyethylene; Calcium-deficient hydroxyapatite; Kinetics; Crystallization; Non-isothermal; Osawa method; Mo method; Polietileno; Hidroxiapatita; Materiais; Polimeros - Propriedades mecânicas; Cristalização; Compositos poliméricos; Cinética; Não isotérmico; Método de Osawa; Método de Mo; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

In this work, composites of high density polyethylene HDPE with calciumdeficient hydroxyapatite were synthesized in order to obtain materials with good mechanical properties and bioactivity. The addition of calcium-deficient hydroxyapatite resulted in an increase in elastic modulus (high rigidity), lower impact resistance and lower HDPE crystallinity degree, promoting, in these materials, a higher bioactivity. Scanning thermal analysis (non-isothermal system) was carried out by differential scanning calorimetry (DSC), and it was evaluated the calcium phosphate content added and the screw speed in the processing. In non-isothermal crystallization studies it was observed a decrease in crystallization temperature as the cooling rate was increased for all produced materials. The activation energy of crystallization was evaluated by Kissinger and Ozawa methods. The sample with 5 wt.% of calcium-deficient hydroxyapatite and processed at 200 rpm screw speed showed the lower value of activation energy (262 kJ/mol) and the lower deviation from linearity. Calcium-deficient hydroxyapatite does not promote the crystallization process due to the high activation energy determined by the described methods. Probably the screw speed promotes the dispersion of the filler in the HDPE matrix and hinders the crystallization process. Correlation coefficients in Osawa-Avrami method indicated loss in the linear correlation. These losses might be associated with a small percentage of secundary crystallization and/or the temperatures chosen to determine the crystallization rate. The parameters obteined from Mo method, the lower percentages of crystallization showed a great deviation from linearity, with correlation coefficient much smaller than 1, when increasing the percentage of crystallization, the deviation from linearity decreases, getting closer to 1.The results of Mo and Osawa-Avrami models were not able to set the kinetic behavior of the materials produced in this study.