38 documents found, page 1 of 4
Impact of bacterial cellulose on the physical properties and printing quality o...
Lourenço, Ana F.; Martins, Daniela; Dourado, Fernando; Sarmento, Pedro; Ferreira, Paulo J.; Gamelas, José A. F.Bacterial nanocellulose (BNC), due to its inherent nanometric scale and strength properties, can be considered as a good candidate to be used in papermaking. This work explored the possibility of using it in the production of fine paper as a wet-end component and for the paper coating. Filler-containing handsheet production was performed with and without the presence of common additives typically used in the fu...
Eco-friendly Methods for Extraction and Modification of Cellulose: An Overview
Magalhães, Solange; Fernandes, Catarina; Pedrosa, Jorge F. S.; Alves, Luís; Medronho, Bruno; Ferreira, Paulo J.; Rasteiro, Maria da GraçaCellulose is the most abundant renewable polymer on Earth and can be obtained from several different sources, such as trees, grass, or biomass residues. However, one of the issues is that not all the fractionation processes are eco-friendly and are essentially based on cooking the lignocellulose feedstock in a harsh chemical mixture, such as NaOH + Na2S, and water, to break loose fibers. In the last few years, ...
Synergetic effect of cationic starch (ether/ester) and Pluronics for improving ...
Sharma, Mohit; Aguado, Roberto; Murtinho, Dina; Valente, Artur J. M.; Ferreira, Paulo J.Improving the printability of paper is still a relevant challenge, despite the fast development of digital communications. While it is well-known that cationic starches enhance ink density, their commercial paper-grade forms are limited to ethers with low degree of substitution. This work addresses the underexplored potential of highly substituted cationic starch for paper coating and its combination with tribl...
Novel approach on the synthesis of starch betainate by transesterification
Sharma, Mohit; Aguado, Roberto; Murtinho, Dina; Valente, Artur J. M.; Ferreira, Paulo J.Transesterification of starch with methyl betainate was studied for the first time, both in aprotic media and in solid state, and both under alkaline and acidic conditions. Betaine hydrochloride was first esterified in methanol, attaining a conversion of 86%. Starch was then converted into starch betainate in either N,N-dimethylformamide or dimethyl sulfoxide, and using sulfuric acid as catalyst or pre-activati...
Seedless Cu electroplating on Co-W thin films in low pH electrolyte: early stag...
Santos, Rúben F.; Oliveira, Bruno M. C.; Chícharo, Alexandre; Alpuim, P.; Ferreira, Paulo J.; Simões, Sónia; Viana, Filomena; Vieira, Manuel F.The use of Ta/TaN barrier bilayer systems in electronic applications has been ubiquitous over the last decade. Alternative materials such as Co-W or Ru-W alloys have gathered interest as possible replacements due to their conjugation of favourable electrical properties and barrier layer efficiency at reduced thicknesses while enabling seedless Cu electroplating. The microstructure, morphology, and electrical pr...
Atomic electrostatic maps of point defects in MoS2
Velasco, Sebastian Calderon; Ferreira, Rafael V.; Taneja, Deepyanti; Jayanth, Raghavendrarao T.; Zhou, Langyan; Ribeiro, R. M.; Akinwande, DejiIn this study, we use differential phase contrast images obtained by scanning transmission electron microscopy combined with computer simulations to map the atomic electrostatic fields of MoS2 monolayers and investigate the effect of sulphur monovacancies and divancancies on the atomic electric field and total charge distribution. A significant redistribution of the electric field in the regions containing defe...
Cationic cellulosic derivatives as flocculants in papermaking
Aguado, Roberto; Lourenço, Ana F.; Ferreira, Paulo J.; Moral, Ana; Tijero, AntonioWater-soluble cationic cellulose derivatives were synthesized by three different procedures, cationizing bleached hardwood kraft pulp with (3- chloro-2-hydroxypropyl) trimethylammonium chloride. The first procedure involved a previous depolymerization step with orthophosphoric acid. The second one consisted on dissolving cellulose in NaOH/urea before cationization. For the third procedure, the reaction medium w...
Towards a new generation of functional fiber-based packaging: cellulose nanofib...
Tarrés, Quim; Oliver-Ortega, Helena; Ferreira, Paulo J.; Àngels Pèlach, M.; Mutjé, Pere; Delgado-Aguilar, MarcThe present work shows the suitability of using industrial fluting papers as raw material for the development of four different substrates, enzymatically refined and/or containing cellulose nanofibers (CNF) in bulk. These four substrates were deeply studied and treated with different coating formulations, containing cellulose nanofibers, polyvinyl alcohol, native starch and alkyl ketene dimer, with the purpose ...
Influence of TEMPO-oxidised cellulose nanofibrils on the properties of filler-c...
Lourenço, Ana F.; Gamelas, José A. F.; Nunes, Tiago; Amaral, José; Mutjé, Pere; Ferreira, Paulo J.In this work, cellulose nanofibrils (CNF) were produced from a Eucalyptus globulus bleached kraft pulp by TEMPO-mediated oxidation and mechanical homogenisation, and their effects in papermaking, namely filler flocculation and retention, dry and wet-web strength and structural properties, were studied in detail. Cellulose nanofibrils possessing 0.6 mmol/g carboxyl groups and a degree of polymerisation (DP) of c...
Surface properties of xylan and xylan derivatives measured by inverse gas chrom...
Sousa, Sónia; Pedrosa, Jorge; Ramos, Ana; Ferreira, Paulo J.; Gamelas, José A. F.Xylan (the most common hemicellulose in wood and annual plants) and xylan derivatives have a very wide field of uses for which physico-chemical surface properties play an important role (e.g. in composites or barrier materials). In the present work, for the first time, inverse gas chromatography (at infinite dilution conditions) was used to assess the surface properties of xylan and xylan derivatives. Firstly, ...