Chemical treatments are used to introduce active functional groups and/or to increase the surface roughness of carbon fibres (CF) aiming to improve their interaction with polar polymeric matrices in composites. Considering the new challenges in the field of composite materials, such as the processing of hybrid composites and the growing use of thermoplastic structural composites, the modification of the CF surface has been increasingly studied. In this paper, the effect of various chemical treatments (with HCl, HNO 3 , H 2 SO 4 , CH 3 COOH, NH 4 OH, or H 2 O 2 ) on the thermal stability, chemical composition, and microstructural parameters of a polyacrylonitrile-based carbon fibre was investigated. Raman results indicated greater degree of crystallinity at the surface for the fibres treated (at 80 C for 1 h) with HCl, HNO 3 , H 2 SO 4 , and H 2 O 2 . The treatment with HCl at 80 C for 1 h was effective in reducing disturbance of the carbon structure, as indicated by the higher FWHM G value compared with those of the as-received, acetone pretreated, and the other chemically treated carbon fibres. Fourier transform infrared (FTIR) showed that some treatments promoted an increase in CF polarity (H 2 SO 4 at 80 C/1 h and NH 4 OH at 20 C/1 h), with the incorporation of organic polar groups (i.e., -OH). The apparent roughness of pretreated carbon fibre increased when treated with HNO 3 at 80 C/1 h and H 2 SO 4 at 80 C/1 h, as observed in the AFM analyses. AFM, FTIR, and Raman results suggest that the fibres treated with HNO 3 , H 2 SO 4 , and NH 4 OH were the most promising as reinforcement in high-performance polymer composites.

Este trabalho apresenta o estudo para a estimativa de incerteza nas medidas de temperatura em ensaios de calorimetria diferencial de varredura (DSC), utilizando uma amostra de polipropileno (PP) para determinar as incertezas em relação ao uso de diferentes massas, à repetitividade e à reprodutibilidade e à diferentes taxas de aquecimento. No estudo ainda foram consideradas as fontes de incerteza referentes ao instrumento de DSC, Q20 TA Instruments, e as medidas de verificação de calibração do DSC com padrões de índio e mercúrio com pureza de 99,99 %. Os ensaios foram realizados seguindo a norma ASTM D3418. Mantendo os experimentos apenas para uma taxa de aquecimento de 10 °C/min, usualmente a mais utilizada na rotina do laboratório, a incerteza expandida é de 1,82 °C.