Biomaterials must meet certain fundamental requirements for their usage in living beings, such as biocompatibility, bifunctionality, and sterilizability, without having chemical and structural changes. The biocompatibility of poly(lactic acid) (PLA) films, shaped by compression, was evaluated after sterilization by ethylene oxide by a histological in vivo test with Wistar rats and cytotoxicity in cell adhesion in vitro. The cytotoxicity test was performed by the reduction of tetrazolium salt (MTT). Thermal and chemical changes in PLA films concerning the proposed sterilization process and characteristics were not observed to evidence polymer degradation due to sterilization. The analysis of the cytotoxicity by the MTT method has shown that the sterilized PLA films are not cytotoxic. The adhesion and proliferation of fibroblasts on PLA films were homogeneously distributed over the evaluation period, showing an elongated appearance with unnumbered cytoplasmic extensions and cell-cell interactions. By examining the biocompatibility in a histological study, a mild tissue inflammation was observed with the presence of fibrosis in the samples that had been exposed for 21 days in the rats' bodies. PLA films sterilized with ethylene oxide did not exhibit cell adhesion in vitro and toxicity to the surrounding tissue in vivo and they may be used in future in vivo testing, according to histological findings in Wistar rats in the present study.
RESUMONeste trabalho, foi estudado o efeito da composição de diferentes misturas de polietileno de alta densidade (HDPE) virgem, HDPE reciclado e serragem de Pinus sp., nas propriedades físico-mecânicas de placas confeccionadas pelo processo de compressão. As misturas foram homogeneizadas em um misturador tipo Drais, sem controle de temperatura e moldadas por compressão em prensa hidráulica a 150 o C. Partindo das placas, foram confeccionados corpos-de-prova para ensaios de tração, flexão, impacto e dureza, segundo normas ASTM, e também foram determinadas as densidades médias das placas. A modelagem estatística foi realizada segundo o planejamento centróide simplex, utilizando sete misturas dos três componentes e três repetições de cada mistura. Os resultados mostraram que a resistência à tração, a resistência à flexão, a dureza e a densidade das placas, são explicadas pelo modelo linear, enquanto a resistência ao impacto é explicada pelo modelo quadrático. Não houve diferença significativa nas propriedades físico-mecânicas dos compósitos confeccionados com HDPE virgem, daqueles confeccionados com HDPE reciclado, exceto para resistência ao impacto, no qual o HDPE virgem apresentou maiores valores.Palavras-chave: compósitos; polietileno; serragem. ABSTRACTIn this work, the effect of different compositions of virgin and recycled high density polyethylene/Pinus sp. on physical-mechanical properties of sheets made by compression molding was studied. The compositions were blended in a thermokinetic mixer (Draiss) and compression molded at 150 o C. ASTM samples for tensile, flexural, impact and hardness tests were taken from the sheets. The density of the sheets were determined. The statistical model used was a centroid simplex with seven compositions and three repetitions. Results showed that tensile and flexural strength as well as hardness and density followed a linear model, while impact strength is explained by a quadratic model. Physicalmechanical properties of compositions using virgin and recycled HDPE did not show significative changes, except for impact strength, when virgin HDPE showed higher numerical results.Keywords: composites; polyethylene; sawdust. Segundo Rowell (1994), uma emergente preocupação ambiental no que diz respeito à reciclagem de materiais e os constantes aumentos do preço do petróleo tem incentivado a utilização de fibras naturais em compósitos. Tita (1999) considera um compósito como sendo qualquer material multifásico que exiba uma proporção significativa das propriedades de ambas as fases que o constituem, obtendo-se assim, uma melhor combinação de propriedades. INTRODUÇÃONos compósitos poliméricos, geralmente o polímero é o componente contínuo, responsável pela transferência de um esforço sofrido para outro componente descontínuo que fornece a resistência ao esforço. A matriz polimérica, portanto, é o principal suporte constituinte que governa as propriedades mecânicas do material (Bittencourt, 2001). Novos compósitos, que podem oferecer benefícios sociais e ambientais, estão
Many polymers have been used as biomaterials due to their physicochemical characteristics and structural versatility. However, usage on the human body requires sterilization in order to prevent microbial contamination and diminish the risk of rejection or inflammation. This study presents the use of thermogravimetric analysis (TGA) as an alternative to monitor the presence of residual ethylene oxide from polymers sterilization processes. This is a simple technique and does not require sample preparation stages which can imply in some ethylene oxide loss. Ethylene oxide has been used to sterilize polymeric biomaterials, but with restrictions in the amount used due to the difficulty in removing the toxic waste after the sterilization procedure. Samples of commercial (PEEKc) and medical (PEEKm) grade poly(ether ether ketone) (PEEK) were manufactured in the form of cylindrical tubes, hygienized and sterilized with ethylene oxide. PEEKs showed no chemical changes, but exhibited thermal changes by TGA, which evidenced weight loss between 100 and 500°C that was attributed to the removal of residual ethylene oxide, so this technique, at a 10°C•min -1 heating rate, can be used to monitor the sterilization processes.
A low-cost and easy-to-handle manufacturing procedure for urban trash containers, made of recycled plastic lumber, was developed focusing on the following aspects: materials selection, materials compounding, plastic sheet manufacturing and mechanical testing, urban trash container design and assembly, and a pilot test. The material, a composite of polyethylene (PE) urban waste, ethylene-vinyl acetate copolymer (EVA) industrial waste and calcium carbonate, was prepared in a Drais batch mixer. The mixture was hot compression molded as rectangular-shaped sheets of 900 mm length, 600 mm width and 12 mm or 7 mm thickness. These sheets were characterized with regard to mechanical properties, microstructure and UV resistance. An urban trash container prototype was prepared from the plastic sheets and a hundred trash containers were submitted to a pilot test. All the steps, material compounding, plastic sheet processing, and trash container design and manufacturing were optimized in order to give the required physico-mechanical properties, functional characteristics and finish of the urban trash containers.
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