Custodio Vásquez Quintero

OBTENCIÓN, ELECTRODEPOSICIÓN Y CARACTERIZACIÓN DE UN RECUBRIMIENTO POLIMÉRICO BIOABSORBIBLE A PARTIR DE ÁCIDO L-LÁCTICO PARA APLICACIONES BIOMÉDICAS

espanolEl acido poli (L-lactico) (APL) ha sido usado ampliamente en aplicaciones biomedicas como suturas e implantes bioabsorbibles debido a su capacidad para permitir el crecimiento controlado de tejido biologico durante su biodegradacion controlada. En este trabajo se obtuvo APL a partir de la policondensacion de acido lactico en presencia de un catalizador de zinc metalico en condiciones de vacio y atmosfera inerte. Se variaron las concentraciones de Zn++ y el tiempo de polimerizacion con el fin de obtener varias muestras que fueron caracterizadas mediante espectroscopia infrarroja (IR), calorimetria diferencial de barrido (DSC), analisis termogravimetrico (TGA) y microscopia electronica de barrido (SEM). Se obtuvieron recubrimientos polimericos por electrodeposicion catodica sobre sustratos de Ti6Al4V, usando una celda electrolitica con capacidad de 200ml y dos anodos de grafito cuya area expuesta fue de 12,57 cm2. El electrolito consistio en una disolucion 30:70 v/v de APL y acetona. Las variables involucradas fueron: voltaje, tiempo, temperatura, velocidad de agitacion y las condiciones de preparacion del polimero. Los recubrimientos obtenidos se caracterizaron mediante microscopia optica y ataque quimico. Los resultados revelaron la obtencion de APL y la influencia del iniciador de Zn++, el cual promovio la migracion y formacion de grupos cationicos que lograron neutralizarse y condensarse sobre Ti6Al4V bajo cargas catodicas. El analisis termico mostro que en el rango de temperatura, entre 25 °C - 50 °C, no hubo variaciones importantes en la degradacion termica, indicando que el material podria ser utilizado para recubrir implantes ortopedicos. EnglishPoli (L-lactic) (PLA) has been used broadly in biomedical applications, such as sutures and bioadsorbable implant due to its capacity to allow the controlled growth of the biological tissue during their controlled biodegradation. In this work, a material polymeric PLA starting from the polycondensation in vacuum and inert atmosphere of lactic acid in presence of a catalyst of metallic zinc was obtained. In order to obtain different samples, both the Zn catalyst content and time of polycondensation were varied. Analysis of Infrared Spectroscopy, TGA, DSC, SEM and chemical etching were used to characterize the samples. Through a method of cathodic electrodeposition, a polymeric film was obtained on Ti6Al4V, by using an electrolytic cell with capacity of 200 ml and two graphite anodes whose exposed area was 12,57cm2. The electrolyte was a PLA-acetone dissolution 30:70 v /v. For this process, the variables were: voltage, time, temperature, stirring and the preparation conditions of polymer. Optical microscopy and etching techniques were used to characterize the resulting polymeric film. It was evidenced the PLA formation using a metallic initiator Zn which has provided migration and formation of cationic groups. These were efficiently neutralized and clustered on the Ti6Al4V substrate due to cathodic current application. In a range between 25 to 50 °C, considerable variations of thermal degradation were observed which induces that the material can potentially be used as a coating in orthopedic implantations.

Método electroquímico para evaluar el efecto de la contaminación por CO2 sobre el deterioro de estructuras de concreto reforzado en la costa del Pacífico colombiano

A electrochemical method to evaluate the carbonatation effect from CO2 atmospheric on degradation of concrete structures in Colombian pacific coast, mainly, on the penetration and the effective diffusion coefficient of chloride ion in concrete specimens made with Portland cement type I, with water/cement relationships: 0.4, 0.5 and 0.6. Samples with 28 days of curing were exposed to accelerated carbonation for two different fronts of carbonation: 5 mm (Face A) and 10 mm (Face B). The tests were carried out in an atmosphere of 25% CO2 and relative humidity between 55-65%. The penetration depth of the front was determined with phenolphthalein and carbonated and non carbonated samples, were characterized by XRD and SEM. Accelerated Chloride Migration test (ACMT), Rapid Chlorides Penetration Test (RCPT) and penetration chlorides tests by immersion, in order to determine the income of the Clion through the cement matrix and determine the effective diffusion coefficient of this type of concrete. Beside, colorimetric and potentiometric titration tests were carried out. There was a marked influence on the ability of chloride ion penetration through the cement matrix, in relation to passing current charge. It was corroborated by comparison of current charges calculated of the methods RCPT and ACMT, the influence of temperature on the diffusive capacity of the ions. Key woRds: Carbonation, effective diffusion coefficient, chloride ion, concrete, CO2, electromechanical method, ACMt, RCPt. Boletín Científico CCCP (2008), No. 15: 23-31