h i g h l i g h t s Effects of oil heat treatment on wood are reviewed. Advantages and disadvantages of using vegetables are discussed. Different types of treatment procedures are compared. Factors governing the treatment effectiveness are listed. Potential applications of oil heat treated wood are discussed.

Lignin is a natural and renewable organic compound that can be easily obtained from spent pulping liquors. It can be used as feedstock for making wood adhesives. Nonetheless, lignins need to be modified to enhance reactivity prior to being used as feedstock for making wood adhesives. Appropriate crosslinkers are also needed to ensure the bonding quality of the ligninbased wood adhesives. In the present review, the drawbacks of using lignins alone as wood adhesives, modifications to enhance the reactivity of lignins and production of lignin-based copolymer adhesives for composite wood panels are reviewed and discussed. The objective of this review is to provide background information about the recent status on the development of lignin-based copolymer adhesives for the production of composite wood panels as well as the future prospects of these adhesives in industry. Several modifications such as demethylation, oxidation, methylolation, phenolation, reduction and hydrolysis have shown promising results for enhancing the reactivity of lignins. Several crosslinkers such as phenolic resin, tannin, polymethylene polyphenyl isocyanate (pMDI), furfural and ethylenimine are capable of copolymerizing with lignins to produce lignin-based wood adhesives. The performance of composite wood panels bonded with modified lignin-based copolymer adhesives have been shown to meet the requirements of relevant standards. The main obstacles for the composite wood panels industry to widely adopt to lignin-based copolymer adhesives are the economic and technical issues. Nevertheless, lignin modification methods are proving to enhance the reactivity of lignins and the optimization in such modification methods would justify the economic issue. Together with the public awareness on the safety, health and environment concerns, the utilization of lignin-based adhesives in the composite wood panels industry is feasible.

Cellulose whiskers were isolated from kenaf (Hibiscus cannabinus L.) bast fibers via sulfuric acid and hydrochloric acid hydrolysis. Raw kenaf bast, NaOH treated, bleached fibers, sulfuric acid whiskers (SAW) and hydrochloric acid whiskers (HClW) morphology, functional groups, crystallinity, and thermal stability were characterized. The TEM images showed that the sulfuric acid and HCl whiskers have average diameters and length range of 3 nm and 100 -500 nm, respectively. The FTIR study indicated that during the conversion process, most of the hemicellulose and almost all the lignin were removed by the NaOH and subsequent bleaching treatments. The crystallinity of HCl whiskers was found to be higher (84%) than that of sulfuric acid whiskers (72%). Thermogravimetric analysis indicated that HCl whiskers had better thermal stability than the sulfuric acid ones. In addition, a two-stage decomposition behavior was revealed by TGA in the sulfuric acid whiskers because of incorporation of the sulfate group with the cellulose crystals.

Owing to the recent trend and increasing awareness toward sustainable product design, natural fiber-based materials are gaining a revival popularity to replace synthetic fiber in the composites industries, especially for automotive structural and semi-structural applications. In this work, natural fibers bilayer hybrid composites were fabricated by hand-lay-up technique by reinforcing oil palm empty fruit bunch (EFB) and kenaf fiber mats with epoxy matrix. Experiments were carried out to study the effect of hybridizing of oil palm EFB-reinforced kenaf fiber on mechanical properties. Bilayer hybrid composites were prepared by hybridizing oil palm EFB and kenaf fiber by maintaining different weight ratios of oil palm EFB and kenaf fiber at 4:1, 1:1, and 1:4, with total fiber loading at 50% by weight. Results showed that the tensile and flexural properties improved substantially on increasing the content of kenaf fiber to oil palm EFB composites, whereas the impact properties of pure EFB composite was much higher than those of hybrid composites. The fracture surface morphology of tensile samples of the composites was determined using scanning electron microscopy (SEM).

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Crystalline nanocellulose was prepared from Semantan bamboo (Gigantochloa scortechinii) via acid hydrolysis and was used to synthesize a nanocomposite of polyaniline/crystalline nanocellulose (PANi/CNC) via in situ oxidative polymerization of aniline in the presence of crystalline nanocellulose. The electrochemical properties of the nanocomposite were studied using a modified PANi/CNC electrode via cyclic voltammetry, and higher current response was observed for the PANi/CNC-modified electrode compared to that for the modified electrode with PANi. The results obtained from EIS displayed lower value of R ct for the PANi/CNCmodified electrode, indicating that the incorporation of CNC into the PANi structure could enhance the electron transfer rate. The characteristic peaks of PANi and CNC were observed in the FTIR spectra of the nanocomposite, indicating the incorporation of CNC inside the nanocomposite structure. Moreover, in the XRD diffractogram, lower crystallinity was observed at the 2 theta values of 22.6 and 16.1 for PANi/CNC compared to that for pure CNC. The FESEM images showed high porosity of the nanostructure with no phase separation, revealing the homogenous polymerization of the monomer on the surface of the crystalline cellulose. Aggregation of PANi particles was observed with the increasing aniline concentration.

The improving effect of an increase in the thermal conductivity caused by nano-wollastonite (NW) on the physical and mechanical properties of medium-density fiberboard (MDF) was studied. Nanowollastonite was applied at 2, 4, 6, and 8 g/kg, based on the dry weight of wood-chips, and compared with control specimens. The size range of wollastonite nanofibers was 30 to 110 nm. The results show that NW significantly (p < 0.05) increased thermal conductivity. The increased thermal conductivity resulted in a better curing of the resin; consequently, mechanical properties were improved significantly. Furthermore, the formation of bonds between wood fibers and wollastonite contributed to fortifying the MDF. It was concluded that a NW content of 2 g/kg did not significantly improve the overall properties and therefore cannot be recommended to industry. Because the properties of NW-6 and NW-8 were significantly similar, a NW-content of 6 g/kg can be recommended to industry to significantly (p < 0.05) improve the properties of MDF panels.

Sequential optimization strategy was used to enhance the production of extracellular polygalacturonase by a newly isolated Aspergillus fumigatus R6 using rice bran as a substrate in solid state conditions. Three significant variables influencing the polygalacturonase production were identified as initial moisture level, temperature and incubation time (P < 0.0001). The model established by face-centered central composite design was significant (P < 0.05) with high R2 (0.98). The model validity was verified and the optimum conditions were at an initial moisture level of 49.6%, 33 °C and 129 h of incubation time with the maximum polygalacturonase activity of 565 U/g, resulted in 2.65 fold increase in polygalacturonase activity compare to the unoptimized conditions. Kenaf stem treated with A. fumigatus R6 polygalacturonase enzyme at 72 h produced high strength of kenaf bast fibers (287 MPa) with high Young's modulus (10404 MPa) and the color is in satisfactory.