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The açaí fruit depulping produces large amounts of long lignocellulosic fiber bundles that are disposed in the environment. Chemical pretreatments may improve açaí fibers favoring their usage in advanced materials. This work aimed to define optimal alkali reaction parameters to improve the properties of açaí fibers. Two NaOH concentrations (5 % and 10 %) and two reaction temperatures (80 °C and 100 °C) were tested. The raw and treated fibers were analyzed by scanning electron microscopy, Fourier transformed infrared spectroscopy, X‐ray diffraction, and thermal analyses. All the alkali pretreatments separated fibers from the bundles, unblocked pit channels by removing silicon structures, exposed the inner lignin, partially removed non‐cellulosic compounds, and raised the cellulose crystalline index. The highest temperature and NaOH content resulted in better cleaning and isolation of the fibers, while milder conditions better preserved the cellulose crystalline structure and thermal stability.

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Abstrad: Transformer condition monitoring is carried out regularly to establish state of the health of transformer. Based on results corrective actions are taken to preserve and prolong the lifetime ofthe unit. All insulation materials used in construction of transformer are, made from organic compounds and therefore, decomposes and deteriorates at high temperature. Insulating oil in service will oxidise and eventually reach to a step, which is not kit for the purpose. In such case maintenance guide recoinmend to change the oil. Insulating paper in service is similarly subjected to heat and also damaged by the oil oxidation products. The same maintenance regime is not applicable to the paper and reaction of paper degradation is not reversible, therefore life of transformer is life ofthe paper. In practice, it is impossible to have an accurate condition asessment without opening the transformer and have paper sample. In the other hand this is impossible practice and condition of the paper is assessed indirectly. It is established earlier that furfurals are by-products of paper ageing and can be used as indication of paper ageing. However, to relate furfuraldehyde, also named furfural (ZFAL), content of a unit to age and extend of paper deterioration more research and laboratory studies are required. This paper describes laboratory studies of paper ageing and relating by-product of paper ageing to state of the insulating paper. Oil and paper are aged at different temperature, ZFAL, gases and moisture of aged samples are measured. A model for paper ageing is established.

Cover Picture. The wine fruit of açaí (Euterpe oleraceae, Mart.) has been widely consumed in the north Brazilian region providing food security for urban and forestry communities. The major drawback of the açaí production chain lays on the large amounts of fibrous wastes from the fruit depulping that are disposed in the environment. In an attempt to improve the properties of açaí fibers favoring their usage in advanced materials, alkali pretreatments were carried out. Enhancements achieved were separation of fibers into bundles, unblocking of pit channels by removing silicon structures, exposure of the inner lignin, partial removal of non‐cellulosic compounds, and increase of the cellulose crystalline index. This study reveals that the unique structure of açaí fibers has strong potential for purposes related to silicon‐containing structures extraction and filters due to their large pits and highly porous structure, as reported by de Oliveira et al. in their full paper at 10.1002/cbdv.201900275.