Beneficial effect of new activated carbons in enhancing the performance of particle boards from UF-rice straw
Authors: Basta Altaf Halim , El-Saied Houssni , Baraka Amin Mahmoud , Lotfy Vivian Fayez 
Published: February 2017

PurposeThe purpose of this research paper focused on studying the role of activated carbons (ACs), which were synthesized from long-chain aldehyde-based xerogels (Xs-AC), as benefit additives to enhance the application of a low-cost urea formaldehyde (UF) adhesive for production of rice straw (RS) composites complying with both the standard specifications of particle-board type and the board produced from using conventional adhesive of RS fibers (methylene diphenyl diisocyanate, MDI). The results are supported by differential scanning calorimetry (DSC) analysis, which indicated the curing and interaction of RS fibers with the adhesive systems.Design/methodology/approachRS-based composites of particle-board type were prepared from applying new Xs-AC–UF adhesive systems to RS particles. For comparison, particle boards by using commercial UF and 4 per cent MDI were also prepared. To clear the beneficial effect of X-ACs as new HCHO (formaldehyde)-scavengers, the properties of the resulted boards were compared with those produced from the previous investigated scavenger: amide-containing starch-UF (AM/St–UF), and treated RS. DSC analysis was performed on the RS adhesive system, to follow the curing and the interaction behavior of UF with fibers in the presence of Xs-ACs.FindingsThe promising results obtained of RS particle boards from using the investigated new HCHO-scavenger are modulus of rupture (MOR) = 17.2 MPa, modulus of elasticity (MOE) = 4,689 MPa and internal bond (IB) strength = 0.49 MPa. While, the thickness swelling (TS) and maximum reduction in free-HCHO are 48.5 and 44.6 per cent, respectively; this reduction value specified the particle-board of E1-E2 type.Research limitations/implicationsThe X-AC-UF adhesive systems and treated RS provided particle boards with mechanical properties (MOR, MOE and IB) that met the standard specification values (class M-2 according to ANSI standard and P-2 according to EN standard requirements), together with maximum reduction in toxicity of UF. However, the resistance in water swelling property is weak and needs further study to be solved.Practical implicationsThe incorporation of small percentage of new HCHO-scavenger (X-AC) to UF is an effective way to improve its thermal behavior. Moreover, the mechanical properties of agro-based composites based on the treated RS waste together with the X-AC-UF system exceeded those values of panels produced from (AM/St-UF) and also from (4 per cent MDI).Social implicationsIncorporating the Xs-AC to commercial UF will be of benefit for saving the health of wood co-workers and motivating the wood mill to export its wood products, as well as minimizing the export of MDI.Originality/valueThis paper was based on enhancing the potential utilization of both undesirable RS agro wastes and environmentally unacceptable low-cost UF adhesive in the production of agro-composites that comply with the International Standard Specifications of particle board type. In this respect, a new HCHO-scavenger was synthesized and applied, based on AC from non-conventional xerogels. This study presents a solution to protect the environment from pollution, as a result of burning the undesirable RS, as well as to protect the workers and users of wood panels from exposure to the toxic and carcinogenic gas (formaldehyde). It also benefits in replacing the high cost of the RS adhesive (MDI) by using low-cost modified UF.