Retention of cellulose, xylan and lignin in kraft pulping of eucalyptus studied by multivariate data analysis: influences on physicochemical and mechanical properties of pulp

Effects of pulping variables on the retention of carbohydrates and lignin in fast kraft pulping of eucalyptus were investigated using a complete factorial design. Influences of pulp chemical composition on physicochemical and mechanical properties were evaluated using Principal Component Analysis. Active alkali (AA) significantly affected the macromolecular degradation of cellulose and retention of xylan and lignin. Cellulose retention was unaffected. The use of low AA in pulping improved all mechanical properties, but increased the kappa number and reduced ISO brightness. The degree of polymerization of cellulose was related to tensile index and elastic modulus while xylan affected the apparent sheet density. Tear index had a positive influence of fiber length and uronic acid groups, which were preserved in xylan by a combination of low AA, thin wood chips and a short pulping cycle. The characteristics, rather than the content of xylan, were suggested to be relevant to tear index.Um planejamento fatorial completo foi empregado na investigação dos efeitos das variáveis de polpação kraft de eucalipto nas retenções de carbohidratos e lignina. As influências da retenção desses componentes nas propriedades físico-químicas e mecânicas da polpa foram avaliadas usando o método de Análise de Componentes Principais. O álcali ativo (AA) foi a variável que mais afetou a degradação macromolecular da celulose e as retenções de xilana e lignina. A retenção da celulose não foi afetada. O uso de baixo nível de AA na polpação favoreceu todas as propriedades mecânicas da polpa, porém apresentou efeito negativo na alvura ISO e número kappa. O grau médio de polimerização da celulose apresentou relação com o módulo elástico e com o índice de tração enquanto que a xilana apresentou relação com densidade aparente das folhas. O índice de rasgo apresentou influência positiva do comprimento médio das fibras e dos ácidos urônicos, que foram preservados na xilana possivelmente devido a combinação de baixo AA, baixa espessura dos cavacos e curto ciclo de polpação. A característica, mais do que o conteúdo de xilana na polpa, foi sugerido como fator relevante ao índice de rasgo.51452

Effects of kraft pulping on the interfacial properties of Eucalyptus pulp fibres

The effects of kraft pulping on the interfacial properties of eucalypt pulp fibres were investigated using polyelectrolyte titration (PT) and contact angle measurements. Changes on surface composition were assessed by FTIR-ATR spectrometry combined with principal component analysis (PCA). Surface lignin was removed by increase in active alkali in pulping as indicated by FTIR-ATR and PCA. In parallel, the surface charge decreased while the surface energy and work of adhesion with water (Wap) increased. The acid-base component (Wap-AB) explained the increase of Wap. Our results suggested that the removal of surface lignin, exposure of carbohydrates and surface mobility of extractives are the main contributors to modifications of interfacial properties by kraft pulping. The role of interfacial properties on development of bleaching sequences and new pulp products was also briefly discussed.Os efeitos da polpação kraft nas propriedades interfaciais da polpa de eucalipto brasileiro foram investigados usando titulação com polieletrólito (PT) e medidas de ângulo de contato. Mudanças na composição química da superfície foram avaliadas por espectrometria de reflexão total atenuada no infravermelho (FTIR-ATR), combinada com análise de componentes principais (PCA). O aumento do álcali ativo na polpação provocou a remoção de lignina da superfície, de acordo com FTIR-ATR e PCA. A carga superficial diminuiu enquanto a energia superficial e trabalho de adesão com a água (Wap) aumentaram. O componente ácido-base (Wap-AB) foi indentificado como o causador do aumento em Wap. Nossos resultados sugeriram que a remoção de lignina superficial combinada com a exposição de carbohidratos e mobilidade superficial de extrativos são as principais causas das modificações nas propriedades interfaciais geradas pela polpação kraft. A contribuição das propriedades superficiais no desenvolvimento de seqüências de branqueamento e novos produtos de polpa também foram discutidos.91592

Influences of surface chemical composition on the mechanical properties of pulp as investigated by SEM, XPS and multivariate data analysis

The effects of bulk and surface chemical composition on the mechanical properties (MP) of eucalyptus kraft pulp were investigated using Liquid Chromatography (HPLC), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS) and Principal Component Analysis (PCA). SEM images of fractured regions during tear (TrID), tensile (TsID) and burst (BuID) tests of refined pulps showed fibre deformation and low proportion of broken fibres, indicating an inter-fibre failure in the sheet network. TrID of unrefined samples was affected by lignin surface coverage (SLig) while TsID and BuID were affected by surface coverage of extractives (SExt) and carbohydrates (SCar). After refining, TrID was affected by uronic acids (UA) in xylan and the influence of bulk composition was more pronounced. Our results also indicated that the fibre-to-fibre bonding rather than the individual fibre strength was the limit factor for MP. A strategy combining surface modification and preservation of polysaccharides in pulping was suggested to improve the MP of this material.Os efeitos da composição química total e da superfície nas propriedades mecânicas (MP) da polpa kraft de eucalipto foram investigados usando cromatografia líquida (HPLC), microscopia eletrônica de varredura (SEM), espectroscopia de fotoelétrons de raio X (XPS) e análise de components principais (PCA). Imagens em SEM das regiões fraturadas durante testes de rasgo (TrID), tração (TsID) e estouro (BuID) em amostras refinadas mostraram deformação das fibras e uma baixa proporção de fibras quebradas, indicando rupturas inter-fibras no arranjo fibroso. TrID de amostras não refinadas foi afetado pela cobertura surperficial de lignina (SLig), enquanto que TSID e BuID foram afetados pela cobertura superficial de extrativos (SExt) e carbohidratos (SCar). Após o refino, TrID foi afetado por ácidos urônicos presentes na xilana e a influência da composição química total foi muito mais pronunciada. Nossos resultados indicaram que as ligações fibra-fibra foram o fator limite para as MP mais do que a resistência das fibras individuais. Uma estratégia combinando modificação da superfície das fibras com a preservação de polisacarídeos durante a polpação foi sugerida para aprimorar as MP desse material.16317

Cellulose Fibre-Reinforced Biofoam for Structural Applications

Traditionally, polymers and macromolecular components used in the foam industry are mostly derived from petroleum. The current transition to a bio-economy creates demand for the use of more renewable feedstocks. Soybean oil is a vegetable oil, composed mainly of triglycerides, that is suitable material for foam production. In this study, acrylated epoxidized soybean oil and variable amounts of cellulose fibres were used in the production of bio-based foam. The developed macroporous bio-based architectures were characterised by several techniques, including porosity measurements, nanoindentation testing, scanning electron microscopy, and thermogravimetric analysis. It was found that the introduction of cellulose fibres during the foaming process was necessary to create the three-dimensional polymer foams. Using cellulose fibres has potential as a foam stabiliser because it obstructs the drainage of liquid from the film region in these gas-oil interfaces while simultaneously acting as a reinforcing agent in the polymer foam. The resulting foams possessed a porosity of approximately 56%, and the incorporation of cellulose fibres did not affect thermal behaviour. Scanning electron micrographs showed randomly oriented pores with irregular shapes and non-uniform pore size throughout the samples.Peer reviewe

Layered Double Hydroxide-Cellulose Hybrid Beads: A Novel Catalyst for Topochemical Grafting of Pulp Fibers

Cellulose-based materials are very attractive for emerging bioeconomy as they are renewable, inexpensive, and environmentally friendly. Cellulose beads are spherical and porous and can be highly engineered to be used as catalyst support material. This type of inorganic catalysts is cost-effective and suitable for multiple re-usage and has been rarely explored in cellulose reaction research. In this work, NiFe-layered double hydroxide (LDH) was tailor-made in situ on anionic cellulose beads to form a hybrid, supported photocatalyst for the first time. The hybrid beads were prepared in a size larger than the pulp fibers in order to make the catalysis reaction heterogeneous in nature. Hydrophilic pulp fibers were converted into hydrophobic pulp by photocatalytic topochemical grafting of ethyl acrylate using the LDH-cellulose bead catalyst. The approach identified for the modification of the pulp fibers is the “hydrogen abstraction–UV photografting” because the low-energy, UV radiation-induced grafting offers advantages, such as a reduced degradation of the backbone polymer and a control over the grafting reaction. After grafting, the pulp fibers showed increased water repellency and unaltered thermal stability, indicating the hydrophobic, plasticizing nature of the pulp, which in turn accounts for its thermoformable behavior. These acrylated pulp fibers can be further designed/customized for waterproof or oil absorption applications.</p

Nanoengineering of Hybrid Lightweight Cellulosic Fibre Foams for better Flame Resistance

We studied the flame propagation and combustion properties of a lightweight fibrous foam produced from a layered double hydroxides (LDH) modified thermomechanical pulp fibres. The in situ synthesis of Mg-Al LDH with pulp fibres was engineered to include both micron and nano-sized particles. The method allowed loading the fibres with LDH up to 34% (w/w). Observed pyrolytic effects included 60% reduction in CO2 production rate, and similar reductions in peak heat release rate (PHRR) and in amount of soot during the oxidative pyrolysis. The in situ synthesised LDH particles shielded the fibres from external heat by reducing the rate of oxidation and liberation of volatile gases. Effective charring was observed at the interphase of LDH nanoparticles and organic material.</p

Uveíte anterior hiperaguda e seu diagnóstico diferencial com endoftalmite endógena em paciente com sopro cardíaco – Um relato de caso / Hyperacute anterior uveitis and its differential diagnosis with endogenous endophthalmitis in a patient with a heart murmur – A case report

As uveítes são caracterizadas por inflamação envolvendo principalmente o trato uveal, embora também possa ocorrer inflamação dos tecidos adjacentes, como retina, nervo óptico e humor vítreo1. O diagnóstico é baseado na anamnese completa do paciente, exame oftalmológico e avaliação sistêmica e laboratorial pertinente. Além dos sinais clássicos, a presença de fibrina e hipópio auxilia no diagnóstico diferencial, pois estão presentes nas endoftalmites , uveítes associadas ao HLA-B27 ou condições neoplásicas. O tratamento, com uso de midriáticos/cicloplégicos e esteróides tópicos, é necessário para redução de sintomas e prevenção de complicações e, portanto, deve ser iniciado precocemente2. 

Exenteração Orbitária por Carcinoma Espinocelular da Conjuntiva – Relato de Caso/Orbital Exenteration Due to Squamous Cell Carcinoma of the Conjunctiva - Case Report

Os tumores conjuntivais representam um amplo espectro de lesões benignas e malignas, algumas capazes de acarretar não somente a perda da visão como, também, da vida. Este trabalho tem como objetivo relatar o caso de paciente com carcinoma espinocelular de conjuntiva com desfecho incomum, revisar o quadro clínico típico e as opções terapêuticas e ressaltar a importância do diagnóstico precoce. A demora em procurar atendimento especializado contribuiu para a progressão da lesão, de modo a inviabilizar o tratamento conservador. O paciente foi submetido a exenteração total com retirada do globo ocular e anexos