Cellulose nanofibers from curaua fibers
Curaua nanofibers extracted under different conditions were investigated. The raw fibers were mercerized with NaOH solutions; they were then submitted to acid hydrolysis using three different types of acids (H2SO4, a mixture of H2SO4/HCl and HCl). The fibers were analyzed by cellulose, lignin and hemicellulose contents; viscometry, X-ray diffraction (XRD) and thermal stability by thermogravimetric analysis (TG). The nanofibers were morphologically characterized by transmission electron microscopy (TEM) and their surface charges in suspensions were estimated by Zeta-potential. Their degree of polymerization (DP) was characterized by viscometry, crystallinity by XRD and thermal stability by TG. Increasing the NaOH solution concentration in the mercerization, there was a decrease of hemicellulose and lignin contents and consequently an increase of cellulose content. XRD patterns presented changes in the crystal structure from cellulose I to cellulose II when the fibers were mercerized with 17.5% NaOH solution. All curaua nanofibers presented a rod-like shape, an average diameter (D) of 6–10 nm and length (L) of 80–170 nm, with an aspect ratio (L/D) of around 13–17. The mercerization of fibers with NaOH solutions influenced the crystallinity index and thermal stability of the resulting nanofibers. The fibers mercerized with NaOH solution 17.5% resulted in more crystalline nanofibers, but thermally less stable and inferior DP. The aggregation state increases with the amount of HCl introduced into the extraction, due to the decrease of surface charges (as verified by Zeta Potential analysis). However, this release presented nanofibers with better thermal stability than those whose acid hydrolysis was carried out using only H2SO4.
KeywordsCuraua fibers Cellulose nanofibers Acid hydrolysis
The authors gratefully acknowledge the financial support provided by CNPq, FAPESP (Process No. 07/50863-4), FINEP and EMBRAPA.
- Borysiak S, Doczekalska B (2005) X-ray diffraction study of pine Wood treated with NaOH. Fibres Text East Eur 13(5):87–89Google Scholar
- Borysiak S, Garbarczyk J (2003) Applying the WAXS method to estimate the supermolecular structure of cellulose fibres after mercerization. Fibres Text East Eur 11(5):104–106Google Scholar
- Chen HZ, Chen JZ, Liu J, Li ZH (1999) Studies on the steam explosion of wheat straw. I-Effects of the processing conditions for steam explosion of wheat straw and analysis of the process. J Cellulose Sci Technol 7(2):60–67Google Scholar
- Dufresne A (2006) Comparing the mechanical properties of high performances polymer nanocomposites from biological sources. J Nanosci Nanotechnol 6:322–330Google Scholar
- Hubbe MA, Rojas OJ, Lucia LA, Sain M (2008) Cellulosic nanocomposites, review. BioResources 3(3):929–980Google Scholar
- Leão AL, Caraschi JC, Tan IH (2000) Curaua fiber—A tropical natural fibers from amazon potencial and applications in composites. In: Frollini E, Leão AL, Mattoso LHC (eds) Natural Polymers and Agrofibers Composites. São Carlos, Brazil, pp 257–272Google Scholar
- Monteiro SN, Aquino RCMP, Lopes FPD, Carvalho EA, D’Almeida JRM (2006) Comportamento Mecânico e Características estruturais de compósitos poliméricos reforçados com fibras contínuas e alinhadas de Curauá. Revista Matéria 11(3):197–203Google Scholar
- Silva R, Haraguchi SK, Muniz EC, Rubira AF (2009) Aplicações de fibras lignocelulósicas na química de polímeros e em compósitos. Quim Nova 32(3):661–671Google Scholar