ESTUDIO DEL EFECTO DE ADITIVOS PRO-OXIDANTES “OXO” EN EL PROCESO ABIÓTICO DE OXODEGRADACIÓN DE PELÍCULAS DE POLIPROPILENO Y POLIESTIRENO DE ALTO IMPACTO ( STUDY OF THE INFLUENCE OF PRO-OXIDANT ADDITIVES DURING THE OXODEGRADATION OF POLYPROPYLENE AND HIGH IMPACT POLYSTYRENE FILMS )

En este trabajo se presenta la influencia de aditivos pro-oxidantes en la degradacion acelerada de muestras de polipropileno homopolimero (PPh), polipropileno copolimero (PPc) y poliestireno alto impacto (PSAI). Se prepararon peliculas por extrusion y con contenidos de aditivo de 0 y 3% w/w. Estas fueron envejecidas en un horno a 60°C por 100 dias. Las modificaciones fisico-quimicas fueron evaluadas por: espectroscopia infrarroja de transformada de Fourier, Calorimetria Diferencial de Barrido y ensayos de traccion. Los valores de temperatura de cristalizacion (Tc), temperatura de fusion (Tm) y transicion vitrea (Tg) resultaron ser los parametros mas sensibles para deteccion temprana de cambios estructurales. Todos los materiales aditivados con oxo exhibieron una reduccion significativa en la elongacion a la ruptura y se hicieron fragiles a tiempos variables. Se aprecio mediante FTIR la aparicion de senales atribuidas a grupos carbonilo e hidroxilo. El material mas sensible fue el PSAI con 3% de aditivo oxo. This article investigates the influence of pro-oxidant additives on the accelerated degradation of samples of polypropylene homopolymer (PPh), polypropylene copolymer (PPc) and high impact polystyrene (HIPS). Extruded films were prepared with two amounts of a pro-oxidant (0% and 3% w/w). The films were subjected to air oven aging (60 °C) tests for 100 days. The chemical and physical changes induced by aging were monitored by: Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and tensile tests. For accelerated degradation, a complete loss of mechanical properties (i.e., strain at break) was obtained although at different exposure times. DSC values of Tc , Tm and Tg were shown to be the most sensitive parameters since they evidenced early structural changes during degradation. HIPS samples with 3% prooxidant exhibited increased susceptibility to oxidative degradation .For all materials with prodegradant additive signals characteristics of carbonyls and hydroxyl functional groups were observed by FTIR analysis.