Effect of incorporation of 2-tert-butylaminoethyl methacrylate on flexural strength of a denture base acrylic resin

Polymethyl methacrylate (PMMA) resins have commonly been used as a denture base material. However, denture bases may act as a reservoir for microorganisms and contribute to oral diseases in denture wearers. It is hypothesized that the 2-tert-butylaminoethyl methacrylate (TBAEMA) incorporated to acrylic resins should have antimicrobial activity related to the presence of amino groups on acrylic resin surface. OBJECTIVES: The objectives of this study were to evaluate the presence of amino groups on acrylic resin surface and the influence on flexural strength after incorporation of TBAEMA. MATERIAL AND METHODS: Six groups were divided according to the concentration of TBAEMA incorporated to acrylic resin (Lucitone 550): 0, 0.5, 1.0, 1.5, 1.75 and 2%. Specimens surface were evaluated by Electron Spectroscopy for Chemical Analysis (ESCA) to detect the presence of amino groups, represented by nitrogen ratios. Flexural strength of the specimens was tested and results were analyzed by ANOVA and Tukey's test (α=0.05). RESULTS: Different nitrogen ratios were observed on specimen surfaces: 0, 0.13, 0.74, 0.66, 0.92 and 0.33% for groups 0, 0.5, 1.0, 1.5, 1.75, and 2%, respectively. Significant differences were found for flexural strength (

Análise termodinâmica do comportamento mecânico na região elástica de blendas de poli (tereftalato de etileno) reciclado e poliolefinas recicladas Thermodynamic analysis of mechanical behaviour in the elastic region of blends of recycled poly (ethylene terephthalate) and recycled polyolefins

Este trabalho descreve o estudo de blendas de poli(tereftalato de etileno) reciclado e poliolefinas recicladas, com e sem adição de polipropileno funcionalizado com anidrido maleico e poli(etileno-co-octeno-1) utilizando ensaios mecânicos e microscopia eletrônica de varredura. Foi aplicado um formalismo termodinâmico com base na função trabalho de Helmholtz para o comportamento mecânico na região elástica, correlacionando-se com o armazenamento de energia elástica para os materiais estudados. Também foi analisada a dissipação de energia relativa ao fenômeno elasto-plástico na região de baixas deformações. Para as blendas estudadas, observou-se que o armazenamento de energia e o efeito do compatibilizante são muito mais acentuados na região rica em poliolefinas, corroborando com as imagens da morfologia observadas via microscopia eletrônica. A análise termodinâmica apresentada mostrou-se uma ferramenta útil e confiável e de baixo custo, para avaliar o efeito de compatibilização de sistemas poliméricos imiscíveis. No presente trabalho, particularmente para a avaliação do comportamento mecânico de misturas de materiais "commodities" reciclados.This work describes the study using mechanical tests with the blend of recycled poly(ethylene terephthalate) (PET) and recycled polyolefin with and without the addition of polypropylene grafted with maleic anhydride and poly(ethylene-co-octene-1). A thermodynamic approach based on the Helmholtz work function was applied in the analysis of mechanical tests, correlating the effects of energy storage and from the compatibilizer on the elastic region of the materials. For the system studied, the polyolefin-rich region shows higher storage of elastic energy corroborating the morphology images obtained from SEM analysis. The thermodynamic analysis seems a useful tool to evaluate the compatibilizer effect in polymeric immiscible blends. In this work, more specifically, this method was used to analyze the mechanical behavior of different compositions of recycled polymeric commodity materials

Estudo do efeito do envelhecimento sob radiação UV no transporte de água em filmes de PET reciclados de bebidas carbonatadas Study of the UV ageing effect on water transport through PET films recycled from beverage bottles

Este trabalho descreve um estudo sobre o efeito do envelhecimento sob radiação UV no transporte de água em filmes planos de PET reciclados de garrafas de bebidas carbonatadas. A partir do formalismo termodinâmico utilizando a relação de Eyring e os resultados de coeficientes de permeabilidade, foram determinadas a entropia e a entalpia de ativação para o transporte da água. Estas funções representadas num gráfico de efeito de compensação termodinâmica permitiram correlacionar a degradação do material, avaliada via espectroscopia na região do infravermelho com transformada de Fourier, com o transporte de água. Foram analisados os possíveis efeitos da presença de estabilizantes, pigmentos e história de processamento.This work describes a study about the UV ageing effect on water transport through PET film sheets recycled from beverage bottles. Using a thermodynamic formalism based on the Eyring relationship and results of water permeability coefficient, it is possible to determine the entropy and enthalpy of activation for the water transport process. These functions were correlated using the compensation thermodynamic plot and correlations were made between the degradation of the PET samples, measured by FTIR, and transport properties. Also, possible effects from the presence of stabilizers, pigments and processing history were analyzed

Correlation between Onset Oxidation Temperature (OOT) and Fourier Transform Infrared Spectroscopy (FTIR) for monitoring the restabilization of Recycled Low-density Polyethylene (LDPE)

In this work a new method was developed for monitoring the oxidative stability of restabilized and non-restabilized low-density polyethylene (LDPE) during multiple extrusion cycles. The method is based on correlations between Fourier Transform Infrared spectroscopy (FTIR) and Onset Oxidation Temperature (OOT). Non-linear calibration curves correlating the concentration of primary or secondary antioxidants and the OOT values were obtained