Untreated and alkali treated fibers from Alfa stem: effect of alkali treatment on structural, morphological and thermal features

Abstract

International audienceAlfa stems are rich in cellulose and they are an inexpensive, easily renewable source of natural fibers with the potential for polymer reinforcement. However, large amounts of non-cellulosic materials, surface impurities and low degradation temperature make natural fibers less attractive for reinforcement of polymeric materials, unless they can be modified in a proper way. In this paper, Alfa stems were treated with NaOH solution with two different concentrations (1 and 5 wt%). Raw and treated stems were crushed to obtain fibers. Stems and fibers were characterized by scanning electron microscopy (SEM) and optical microscopy, respectively. Their crystallinity index was determined by X-ray diffraction, thermal stability by thermogravimetry and structural change by FT-IR and C-13 NMR spectroscopy. Comparison and analysis of results confirmed some thermal, structural and morphological changes of the fibers after treatment due to removal of some non-crystalline constituents from the plant. SEM showed rougher surfaces after alkalization. FT-IR and 13C NMR showed a gradual improvement in cellulose level by alkali treatment with increasing NaOH concentration. The crystallinity index and thermal stability of treated Alfa fibers were also found to be improved

Alkali and Peroxide Bleach Treatments on Spring Harvested Switchgrass for Potential Composite Application

“…The bleach treatment clearly indicated a decrease in hemicellulose and lignin content. Similar results have been observed for alkali treated alfa stem fibers subjected to a bleach treatment using sodium hypochlorite (Borchani et al 2015). Extreme reductions in hemicellulose and lignin contents have been observed by previous researchers.…”

“…for the -C=O groups corresponding to non-cellulosic components, 1510 cm -1 for the C=C of aromatic groups found in lignin, 1460 cm -1 for the CH deformation found in lignin, 1424 cm -1 for the CH deformation of lignin, 1238 cm -1 for the C-O-C groups found in hemicellulose, and at 1032 cm -1 for the C-O-C groups of cellulose (Pasangulapati et al 2012;Borchani et al 2015). The alkali and bleach treatments of switchgrass affected the characteristic peaks of non-cellulosic components through partial or complete removal.…”

“…Extreme reductions in hemicellulose and lignin contents have been observed by previous researchers. The contents were reduced from 30.2 to 3.7% hemicellulose content and from 19.9 to 0.8% lignin content in a 5% alkali solution (Borchani et al 2015). It is usually not possible to completely remove the hemicellulose and lignin contents from lignocellulosic fibers through these types of treatments due to the hydrogen bonding that occurs between the remaining hemicellulose and cellulose fibrils and the chemically resistant bonds found in lignin (Saha et al 2010).…”

“…In addition, the number of hydroxyl groups on the surface are increased, which can result in advantageous chemical interactions between the fiber and polymer (Ridzuan et al 2016). A number of natural fibers such as agave (El Oudiani et al 2012), alfa (Borchani et al 2015), bamboo (Das and Chakraborty 2006;Liu and Hu 2008;Das and Chakraborty 2008;Zhang et al 2015), century fiber (Obi , hemp (Mwaikambo and Ansell 2002;Liu et al 2013), jute (Mwaikambo and Ansell 2002;Saha et al 2010), Prosopis jujiflora (Saravanakumar et al 2014), reed (Barman et al 2014), sisal (Mwaikambo and Ansell 2002;Khan et al 2012), kapok (Mwaikambo and Ansell 2002), and Indian grass (Liu et al 2004) have been subjected to an alkali pretreatment before combining with polymer matrix. It was observed by several researchers (Mwaikambo and Ansell 2002;Das and Chakraborty 2006;Liu and Hu 2008;Das and Chakraborty 2008;Saha et al 2010;El Oudiani et al 2012), that the sodium hydroxide concentration greatly affects the properties of the fibers.…”

Effect of Alkaline Peroxide Pre-treatment on Microfibrillated Cellulose from Oil Palm Fronds Rachis Amenable for Pulp and Paper and Bio-composite Production

“…Different kinds of procedures have been reported on cellulose production. All these methods are characterised by various advantages and disadvantages related to the quantity and quality of cellulose (Kwon et al 2014;Borchani et al 2015). Factors that influence the cellulosic fibres properties include physicochemical composition, mechanical character, which is a measure of the cellulose crystallinity (Ju et al 2015), and fibre morphology, which differs with different plants, cellulose type, and different plant parts (Fahma et al 2011;Khalil et al 2015).…”