Lignocellulose composition

Most research on chemical modification of lignocellulosic materials has focused on improving either the dimensional stability or the biological resistance of wood. This paper reviews the research on these properties for wood and other lignocellulosic composites and describes opportunities to improve fire retardancy and resistance to ultraviolet degradation. 

All laboratory tests for biological resistance conducted to this point show that acetylation is an effective means of reducing or eliminating attack by soft-, white-, and brown-rot fungi, tunneling bacteria, and subterranean termites. Tests are presently underway on several lignocellulosic composites in outdoor environments. 

Other properties of lignocellulosic composites can be improved by changing the basic chemistry of the furnish (fQ). Acetylation has been shown to improve ultraviolet resistance of flakeboards. 

Kamel, S. Nanotechnology and its applications in lignocellulosic composites, a mini review eXPRESS. Polym. Lett. 1, 546-575 (2007)... 

Both concentrated and dilute acids such as H2SO4 and HCl have heen used for hiomass separation. Acid treatment solubilizes the cellulose and hemi-celluloses and thereby disrupts the lignocellulosic composite material linked by covalent bonds, hydrogen bonds, and van der Waals forces. However, acids are toxic, corrosive, hazardous, and thus require reactors that are resistant to corrosion, which makes the separation process veiy expensive. In addition, the acid must be recovered after hydrolysis to make the process economically feasible. ... 

The most common resin for lignocellulosic composites is urea formaldehyde. About 90% of all lignocellulosic composite panel products are bonded with UF [12]. UF is inexpensive, reacts quickly when the composite is hot-pressed, and is easy to use. UF is water-resistant, but not waterproof. As such, its use is limited to interior applications unless special treatments or coatings are applied. UF resins are typically used in the manufacture of products where dimensional uniformity and surface smoothness are of primary concern, for example, particleboard and medium density fibreboard (MDF). Products manufactured with UF resins are designed for interior applications. They can be formulated to cure anywhere from room temperature to 150 °C press times and temperatures can be moderated accordingly. UF resins (often referred to as urea resins) are more economical than PF resins and are the most widely used adhesive for composite wood products. The inherently light colour of UF resins make them quite suitable for the manufacture of decorative products. 

Except for two major uncertainties, expectations are that UF and PE systems will continue to be the dominant wood adhesives for lignocellulosic composites. The two uncertainties [4] are the possibility of much more stringent regulation of formaldehyde-containing products and the possibility of limitations or interruptions in the supply of petrochemicals. One result of these uncertainties is that considerable research has been carried out in developing new adhesive systems from renewable resources. 

The most common additive to lignocellulosic composite panels other than resin is wax. Even small amounts 0.5-1%, act to retard the rate of liquid water pick up. This is important when the composite is exposed to wet environments for short periods of time. However, wax addition has little effect on long-term equilibrium moisture content. Flame retardants, biocides, and dimensional stabilisers are also added to panel products [4]. 

Leao A L (1997), Fire retardants in lignocellulosic composites , in Leao A L, Carvalho F X and Frollini E, Lignocellulosic-plastics Composites, Sao Paulo, Brazil, USP and UNESP, 111-161. 

Table 5.1 Lignocellulosic composition of palm-based biomass and price for Cases 1 and 2...

Once the optimal product is designed, the optimal conversion pathways that convert biomass into the bio-based fuel are identified in the second stage of the methodology. In this case study, palm-based biomass known as empty fruit bunches (EFB) is chosen as feedstock of the integrated biorefinery. The lignocellulosic composition of the EFB is shown in Table 11.9. 

This chapter is organized into three sections, apart from this introduction. The first section surveys in detail various feedstock that can be obtained from the forests and their lignocellulosic composition. Various classifications of forest-based feedstocks and their useful fermentation products are also discussed here. The second section presents the application of forest-based feedstocks in light of biorefinery and platform chemical production. To better understand the relationship between feedstock requirements and decreases in forest cover, a detailed analysis of land occupied by each forest-based feedstock will also be presented. The final section provides conclusions and suitable remedial measures to minimize deforestation due to biorefinery. 

Lignocellulosic composites using polyolefins (including polyethylene) have gained increasing interest over the past two decades, both in the scientific community and industry [55]. The main drawback with the use of natural based components such as natural fibres in polyolefin composites is their hydrophilicity due to the high surface hydroxyl groups concentration which leads to poor interface and moisture resistance in composite materials [7]. The fibre-matrix interaction can be improved either via the fibre. 

Table 5.3 Reported work on polyethylene/lignocellulosic composites and manufacturing process.

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