RESUMO
The effect of the crystallization of polypropylene (PP) forming an immiscible polymer blend with polystyrene (PS) containing conductive multi-wall carbon nanotubes (MWCNTs) on its electrical conductivity and electrical percolation threshold (PT) was investigated in this work. PP/PS/MWCNTs composites with a co-continuous morphology and a concentration of MWCNTs ranging from 0 to 2 wt.% were obtained. The PT was greatly reduced by a two-step approach. First, a 50% reduction in the PT was achieved by using the effect of double percolation in the blend system compared to PP/MWCNTs. Second, with the additional thermal treatments, referred to as slow-cooling treatment (with the cooling rate 0.5 °C/min), and isothermal treatment (at 135 °C for 15 min), ultra-low PT values were achieved for the PP/PS/MWCNTs system. A 0.06 wt.% of MWCNTs was attained upon the use of the slow-cooling treatment and 0.08 wt.% of MWCNTs upon the isothermal treatment. This reduction is attributed to PP crystals' volume exclusion, with no alteration in the blend morphology.
RESUMO
A aceitaçäo e uso correto das placas interoclusais pelos pacientes dependem de sua qualidade estética. Neste trabalho, avaliamos quatro diferentes técnicas de confecçäo da placa interoclusal, onde foram observados a translucidez e o desenho. Quanto à translucidez, as placas de resina termopolimerizável, com polimento em politriz, apresentaram melhores resultados estéticos e a placa em resina termopolimerizável com fios ortodônticos em forma de gota ou auxiliar, o melhor desenho estético, favorecendo uma maior aceitaçäo por parte dos pacientes
