Fibrillation of Aspen by Alkaline Cold Pre-treatment and Vibration Milling

In this article an attempt to fibrillate aspen bleached chemi-thermo mechanical pulp (BCTMP) fibre in an environmentally friendly way is reported. The effects of various NaOH, KOH, urea and ethanol aqueous solutions at lowered temperature were tested for pre-treatment. The pre-treatment was followed by vibration milling aiming to peel off outer cell wall layers and to fibrillate S2 layer of the aspen wood fibre. The effects of the treatments were evaluated by scanning electron microscopy (SEM). The results show that it is possible to fibrillate BCTMP aspen fibres by using alkaline aqueous solutions at low temperatures followed by a mechanical treatment. A strong dependence on fibrillation of cellulose on temperature, time and alkali concentration was established

Analysis of causes of the end of service life of a spray polyurethane foam and polyurea roof

Spray polyurethane foam (SPF) roofs are widely used in North America. Much fewer usage examples and experience can be found in Northern European cold climatic conditions. This study analyses hygrothermal performance and the reasons for the roof’s degradation and end of service life of an SPF and polyurea roof. The service life of the roof is over and major reconstruction is needed eight year after construction. The current study uses field measurements included onsite temperature and humidity measurements and extensive surveying, the roof was opened from several locations and test samples were taken for laboratory tests. The influence of UV radiation on the loss of adhesion was tested. Solar radiation quickly degraded the top surface of the in-situ sprayed polyurethane foam insulation causing a weak connection between the foam layers. Due to mechanically damaged and UV degraded polyurea roofing, water has leaked into the SPF. The water inside or below the foam evaporated during sunny days and broke the adhesion of different foam layers. Larger foam blisters were observed on the upper part of the insulation caused by high water vapour pressure. This is considered the most realistic cause of separation of the SPF layers. The analyse of hygrothermal performance, service life, and durability prediction should be included into the design process, especially for structures with small or without long term performance experience

DataSheet1_Preparation and characterization of lignin-derived carbon aerogels.pdf

Lignin is considered a valuable renewable resource for building new chemicals and materials, particularly resins and polymers. The aromatic nature of lignin suggests a synthetic route for synthesizing organic aerogels (AGs) similar to the aqueous polycondensation of resorcinol with formaldehyde (FA). The structure and reactivity of lignin largely depend on the severity of the isolation method used, which challenges the development of new organic and carbon materials. Resorcinol aerogels are considered a source of porous carbon material, while lignin-based aerogels also possess great potential for the development of carbon materials, having a high carbon yield with a high specific surface area and microporosity. In the present study, the birch hydrolysis lignin and organosolv lignin extracted from pine were used to prepare AGs with formaldehyde, with the addition of 5-methylresorcinol in the range of 75%–25%, yielding monolithic mesoporous aerogels with a relatively high specific surface area of up to 343.4 m2/g. The obtained lignin-based AGs were further used as raw materials for the preparation of porous carbon aerogels (CAs) under well-controlled pyrolysis conditions with the morphology, especially porosity and the specific surface area, being dependent on the origin of lignin and its content in the starting material.</p

Morphology and ultrastructure of steam-exploded wood

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