Hybridization of MMT/Lignocellulosic Fiber Reinforced Polymer Nanocomposites for Structural Applications: A Review

In the recent past, significant research effort has been dedicated to examining the usage of nanomaterials hybridized with lignocellulosic fibers as reinforcement in the fabrication of polymer nanocomposites. The introduction of nanoparticles like montmorillonite (MMT) nanoclay was found to increase the strength, modulus of elasticity and stiffness of composites and provide thermal stability. The resulting composite materials has figured prominently in research and development efforts devoted to nanocomposites and are often used as strengthening agents, especially for structural applications. The distinct properties of MMT, namely its hydrophilicity, as well as high strength, high aspect ratio and high modulus, aids in the dispersion of this inorganic crystalline layer in water-soluble polymers. The ability of MMT nanoclay to intercalate into the interlayer space of monomers and polymers is used, followed by the exfoliation of filler particles into monolayers of nanoscale particles. The present review article intends to provide a general overview of the features of the structure, chemical composition, and properties of MMT nanoclay and lignocellulosic fibers. Some of the techniques used for obtaining polymer nanocomposites based on lignocellulosic fibers and MMT nanoclay are described: (i) conventional, (ii) intercalation, (iii) melt intercalation, and (iv) in situ polymerization methods. This review also comprehensively discusses the mechanical, thermal, and flame retardancy properties of MMT-based polymer nanocomposites. The valuable properties of MMT nanoclay and lignocellulose fibers allow us to expand the possibilities of using polymer nanocomposites in various advanced industrial applications.

Recent Progress and Trends in the Development of Microbial Biofuels from Solid Waste—A Review

This review covers the recent progress in the design and application of microbial biofuels, assessing the advancement of genetic engineering undertakings and their marketability, and lignocellulosic biomass pretreatment issues. Municipal solid waste (MSW) is a promising sustainable biofuel feedstock due to its high content of lignocellulosic fiber. In this review, we compared the production of fatty alcohols, alkanes, and n-butanol from residual biogenic waste and the environmental/economic parameters to that of conventional biofuels. New synthetic biology tools can be used to engineer fermentation pathways within micro-organisms to produce long-chain alcohols, isoprenoids, long-chain fatty acids, and esters, along with alkanes, as substitutes to petroleum-derived fuels. Biotechnological advances have struggled to address problems with bioethanol, such as lower energy density compared to gasoline and high corrosive and hygroscopic qualities that restrict its application in present infrastructure. Biofuels derived from the organic fraction of municipal solid waste (OFMSW) may have less environmental impacts compared to traditional fuel production, with the added benefit of lower production costs. Unfortunately, current advanced biofuel production suffers low production rates, which hinders commercial scaling-up efforts. Microbial-produced biofuels can address low productivity while increasing the spectrum of produced bioenergy molecules.

Cornhusk retting by pectinase enzyme combined with NaOH and effects on fiber properties

Cornhusk fiber is a kind of biodegradable lignocellulosic fiber. The conditions of enzyme and NaOH retting were optimized on the basis of weight loss rate and the Fried test score to extract the cornhusks fiber. Taking raw cornhusk fiber as a contrast, physicochemical properties of the fiber extracted from cornhusk was researched in detail by chemical analysis (GB5889-86), X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR). The optimal retting condition of cornhusk fiber is the following: Pectinase 9032 0.5% concentration, at 40–55°C, pH 4.2–5.8, and then 5% NaOH treatment for 15 min. The crystallinity index of raw cornhusk fiber, enzyme-treated cornhusk fiber and enzyme-alkali-treated cornhusk fiber are 20.30%, 35.05% and 51.00%, respectively, and the structure of these fibres all correspond to cellulose I. The FTIR spectra showed that higher amounts of lignin and hemicellulose were removed by NaOH treatment compared with enzyme treatment.

Isolation and characterization of lignocellulosic fiber from jute bast by the organic solvent degumming system: an alkali-free method

Degumming is the dominant method for insolating lignocellulosic fibers in textile applications. Traditional alkaline degumming (TAL), as a common method, requires a high-concentration alkali and has been a severe challenge to the environment. In the research reported here, the possibility of innovative jute degumming by organic solvents 1-2 propylene glycol and a combination of additive green oxygen (GO-OS) was studied. The results revealed that fibers could be extracted by this system (under condition of 0.9% GO-OS, 180°C, 120 min), and obtained fibers with higher breaking tenacity (7.1 cN/dtex), yield (65.7%), breaking elongation (2.87%) and residual gum (11.7%), which all meet the requirement of the relevant Chinese Textile National Standards. Notably, the required reaction time (120 min) of the GO-OS system was 180 min shorter than that of the TAL method. Furthermore, the modifications introduced by the degumming effect on physicochemical aspects were characterized and confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. This study provides a promising degumming method for separating jute lignocellulose without acid and alkali consumption.

Thermal and flammability properties of polyethylene composites with fibers to replace natural wood

Composites of high-density polyethylene and lignocellulosic fiber residues from banana, papaya, and peach palm trees, in addition to sponge gourd and coconut fiber, were investigated to identify the least flammable composite as a potential substitute for natural pine wood. The high-density polyethylene/lignocellulosic fiber composites were prepared in a twin-screw extruder, injection molded to obtain specimens, and characterized in terms of thermogravimetry, flammability using the UL-94 burning test and limiting oxygen index, impact resistance and heat deflection temperature. The high-density polyethylene/sponge gourd fiber composite showed the best impact resistance and was selected for further tests, with the addition of 10wt% magnesium hydroxide and (or) rice husk ash as flame retardants. The use of both retardants provided greater thermal stability to the composite. The addition of magnesium hydroxide to the high-density polyethylene/sponge gourd fiber composite improved the flammability properties of horizontal burning and thermal stability and is a potential candidate to replace natural wood.

Development of lignocellulosic fiber reinforced cement composite panels using semi-dry technology

There is a growing interest in developing cement bonded lignocellulosic fiber (LF) composites with enhanced mechanical performances. This study assessed the possibility of developing composite panels with 12 mm thickness and around 1200 kg/m3 nominal densities from ordinary Portland cements (OPC) and mixed LFs from seven different woody plants found in Hungary. Once the mixed LFs were sieved and found fine (0–0.6 mm) and medium (0.6–0.8 mm) length fibers. The optimum ratio for LF, OPC, water glass (Na2SiO3), and cement stone was found to be 1:3.5:0.7:0.07. The semi-dry process, which is a comparatively cheaper and less labor intensive technology, was used for producing the composites. After 28 days of curing, the composite panels were characterized for mechanical, physical, thermal, and morphological properties. A scanning electron microscopy (SEM) test was conducted to observe the fiber orientation in the matrix before and after the bending test, which showed the clear presence of the fibers in the composites. The FTIR (Fourier transform infrared spectroscopy) was conducted to investigate the presence of chemical compounds of LF in the composite panels. Different physical (water absorption and thickness swelling) characteristics of the composite panels were investigated. Furthermore, mechanical properties (flexural properties and internal bonding strength) of the composite panels were also found to be satisfactory. The flexural modulus and internal bonding strengths of composite panel 2 is higher than other three boards, although the flexural strength is a little lower than composite panel 1. The thermogravimetric analysis and differential thermogravimetry also indicated better thermal stability of composite panels which could be used as potential insulation panel for buildings. Graphic abstract