Some aspects of acetylation of untreated and mercerized sisal cellulose

Ciacco, Gabriela T.; Morgado, Daniella Lury; Frollini, Elisabete; Possidonio, Shirley; Seoud, Omar A. El

doi:10.1590/s0103-50532010000100012

Cited by 28 publications

(27 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Expansão das cadeias ou de estruturas associadas, devido à repulsão estérica entre os grupos acetatos, o que, em princípio aumentaria as interações polímero/solvente (LiCl/DMAc); 2. Diminuição das interações polímero/solvente, uma vez que a substituição de H pelos grupos acetatos diminuiria as interações cel-OH---Cl -, as quais são importantes no processo de solubilização da celulose em LiCl/DMAc, e provavelmente no de seus derivados [6][7][8]11] . Para os acetatos com diferentes GS, alguns valores da constante de Huggins, indicaram que cadeias agregadas, ou associadas estavam presentes.…”

Section: Resultsunclassified

“…A celulose utilizada foi a de linter de algodão, de baixa massa molar média (usada para fins têxteis), gentilmente cedida pela Indústria Fibra S.A. (Americana, São Paulo), tendo sido submetida a um pré-tratamento com solução alcalina, denominado mercerização, necessário para solubilizar a mesma em LiCl/DMAc, seguindo o procedimento descrito em trabalho anterior [6] . Os acetatos de celulose foram sintetizados em LiCl/DMAc e caracterizados seguindo o procedimento descrito previamente [7] , o mesmo ocorrendo com o Grau de Substituição (GS) dos acetatos de celulose, determinado por 1 H NMR [7] .…”

Section: Methodsunclassified

See 1 more Smart Citation

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Morgado¹,

Martins²,

Plepis³

et al. 2011

Polímeros

Self Cite

View full text Add to dashboard Cite

Resumo: Celulose de linter foi acetilada, visando obter acetatos de celulose com diferentes Graus de Substituição (GS) em meio homogêneo, usando cloreto de lítio/N,N-dimetilacetamida (LiCl/DMAc) como sistema de solvente, e anidrido acético como reagente acetilante. A agregação entre cadeias de celulose ou acetatos de celulose (GS 0,8, 1,5 e 2,0) em solução foi avaliada através de medidas viscosimétricas. Os resultados mostraram que a formação de agregados no sistema de solvente utilizado (LiCl/DMAc) é diferente para celulose e acetatos, e dependente da temperatura e do GS, no caso dos acetatos. Este trabalho corresponde à primeira etapa de um estudo em que se pretende preparar filmes de acetatos, assim como de acetatos reforçados com celulose, diretamente a partir de soluções destes em LiCl/DMAc. Os resultados apresentados permitem uma escolha melhor embasada do intervalo de concentração mais adequado para preparação de filmes, a partir de soluções de acetatos e celulose nesse sistema de solvente. Palavras-chave: Celulose de linter, acetato de celulose, sistema de solvente LiCl/ DMAc, agregação. Aggregation of Chains of Cellulose Acetates in LiCl/DMAc: Evaluation Via ViscometryAbstract: Linters cellulose was acetylated to obtain cellulose acetates with different degrees of substitution (DS) in homogeneous medium, using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) as solvent system, and acetic anhydride as acetylating agent. The aggregation among chains of cellulose or cellulose acetates (DS 0.8, 1.5 and 2.0) in solution was studied through viscometric measurements. The results showed that aggregation in LiCl/DMAc is different for cellulose and acetates, and depends on the temperature and DS in the case of acetates. This study corresponds to the first step of a project, which aims at to prepare cellulose acetates films, as well as acetates films reinforced with cellulose, by casting directly from these solutions in LiCl/DMAc. The results presented here allow for an optimized choice of concentration range for preparing films from LiCl/DMAc solutions of acetates and cellulose.

show abstract

Section: Resultsunclassified

Section: Methodsunclassified

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Morgado¹,

Martins²,

Plepis³

et al. 2011

Polímeros

Self Cite

View full text Add to dashboard Cite

show abstract

“…Ia has a triclinic unit cell containing one chain (Nishiyama et al 2003), whereas Ib is represented by a monoclinic unit cell containing two parallel chains (Nishiyama et al 2008). The crystal structure of native cellulose, mostly cellulose Ib, from higher plants can be converted to cellulose II with NaOH, a treatment known as mercerization (Ciacco et al 2010;Dinand et al 2002;Revol and Goring 1981). During mercerization, entire fibers are converted into a swollen state, a process that involves formation of one or more sodacellulose complexes.…”

Section: Introductionmentioning

confidence: 99%

Comparative properties of cellulose nano-crystals from native and mercerized cotton fibers

et al. 2012

View full text Add to dashboard Cite

Stable aqueous suspensions of cellulose nano-crystals (CNCs) were fabricated from both native and mercerized cotton fibers by sulfuric acid hydrolysis, followed by high-pressure homogenization. Fourier transform infrared spectrometry and wide-angle X-ray diffraction data showed that the fibers had been transformed from cellulose I (native) to cellulose II (mercerized) crystal structure, and these polymorphs were retained in the nanocrystals, giving CNC-I and CNC-II. Transmission electron microscopy showed rod-like crystal morphology for both types of crystals under the given processing conditions with CNC-II having similar width but reduced length. Freeze-dried agglomerates of CNC-II had a much higher bulk density than that of CNC-I. Thermogravimetric analysis showed that CNC-II had better thermal stability. The storage moduli of CNC-II suspensions at all temperatures were substantially larger than those of CNC-I suspensions at the same concentration level. CNC-II suspensions and gels were more stable in response to temperature increases. Films of CNC and Poly(ethylene oxide) were tested. Both CNC-I/PEO and CNC-II/PEO composites showed increased tensile strength and elongation at break compared to pure PEO. However, composites with CNC-II had higher strength and elongation than composites with CNC-I.

show abstract

“…When hemicellulose is present, as in sisal pulp, it can be degraded during alkali treatment, facilitating subsequent hydrolysis. Hemicelluloses are found in non-crystalline regions, and they have lower average molar masses than those of cellulose, which facilitates their degradation (Mosier et al 2005;Ramos et al 2005a, b;Ass et al 2006;Paiva and Frollini 2006;El Seoud et al 2008;Ciacco et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Saccharification of Brazilian sisal pulp: evaluating the impact of mercerization on non-hydrolyzed pulp and hydrolysis products

et al. 2012

Self Cite

View full text Add to dashboard Cite

Cultivation of sisal, a plant with a short growth cycle, is highly productive in Brazil. This work is part of extensive research in which sisal is valued. In these studies, sisal fibers are used in the preparation of bio-based composites and in the derivatization of the pulp, including posterior preparation of films. This study aimed to examine the use of sisal pulp in the production of bioethanol, which can potentially be a high efficiency process because of the cellulose content of this fiber. A previous paper addressed the hydrolysis of sisal pulp using sulfuric acid as a catalyst. In the present study, the influence of the mercerization process on the acid hydrolysis of sisal pulp was evaluated. Mercerization was achieved in a 20% wt NaOH solution, and the cellulosic pulp was suspended and vigorously mixed for 1, 2 and 3 h, at 50°C. The previously characterized mercerized pulps were hydrolyzed (100°C, 30% H 2 SO 4 , v/v), and the results are compared with those obtained for unmercerized pulp (described in a companion paper). The starting sample was characterized by viscometry, a-cellulose content, crystallinity index and scanning electron microscopy. During the reactions, aliquots were withdrawn, and the liquor was analyzed by HPLC. The residual pulps (non-hydrolyzed) were also characterized by the techniques described for the initial sample. The results revealed that pretreatment decreases the polyoses content as well as causes a decrease of up to 23% in the crystallinity and up to 21% in the average molar mass of cellulose after 3 h of mercerization. The mercerization process proved to be very important to achieve the final target. Under the same reaction conditions (30% and 100°C, 6 h), the hydrolysis of mercerized pulp generated yields of up to 50% more glucose. The results of this paper will be compared with the results of subsequent studies obtained using other acids, and enzymes, as catalysts.

show abstract

Some aspects of acetylation of untreated and mercerized sisal cellulose

Cited by 28 publications

References 27 publications

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria

Comparative properties of cellulose nano-crystals from native and mercerized cotton fibers

Saccharification of Brazilian sisal pulp: evaluating the impact of mercerization on non-hydrolyzed pulp and hydrolysis products

Contact Info

Product

Resources

About