Formaldehyde-based resins are conventionally used as a binder in formulation of particleboard. Epidemiologic studies have shown that formaldehyde is carcinogenic. Efforts to reduce the health hazard effects of the fomaldehyde-based resin in the particleboard formulation have included use of scavengers for formaldehydes and use of an alternative binder. Use of scavengers for the formaldehyde increases the cost and maintenance of particleboard formulation. There is no proof that scavengers eliminate the emission of formaldehyde from particleboard. Use of biobased binders in particleboard formulation provides an alternative for eliminating use of the formaldehyde-based resin. However, the alternative is hindered by challenges, which include limitations of physical and mechanical properties. The challenge has continuously been acted upon through research. The paper presents an overview of the use of starch as an alternative binder. Improvement over time of the starch and limitations thereof requires to be addressed. Use of the modified starch has shown increased particleboard performance. Mechanical strength, such as modulus of rupture, modulus of elasticity, and internal bonding in particleboards, however, remains to be a challenge.

Efforts to reduce pressure on use of wood in particleboard formulation have included the use of non-wood materials such as crop residues. Physical and mechanical properties are determined by the number of the hydroxyl (-OH) groups. Hydroxyl (-OH) groups attracts water molecules through hydrogen bonding affecting water absorption (WA) and thickness swelling (TS). WA and TS affect curing process of adhesive. Curing process of adhesives affects the mechanical characteristics of formulated particleboards. These challenges have been acted upon continuously through research. This review paper presents crop residues used as alternative lignocellulose material source in particleboard formulation and the various advances that have been made to improve on the properties of the resultant particleboards. Improvement over time of the non-wood material in composite materials focusses on increasing water resistance and compatibility between lignocellulose and binder. Crop residues-based are used in making medium and low density particleboards. These boards have shown good mechanical characteristics which include modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB). MOR, MOE and IB have over time been improved by enhancing chemical compatibility of lignocellulose material and the binders. Water absorption and thickness swelling remain challenge. This review paper further explored various methods of improving water absorption and thickness swelling of crop-residue based particleboards.

Conventional binders in the particleboards formulation involve use of formaldehyde resins. Epidemiologic studies show that formaldehyde is carcinogenic. Efforts to reduce formaldehyde emissions by use of scavengers has not been proven to reduce the emission. Molecular bonding of biobased adhesive molecules with lignocellulose materials provides an alternative way of producing composite material. In this study, maize stalk (MS), rice husks (RH) and sugarcane bagasse (SB) were used as sources of lignocellulose materials for particleboard formulation. SB, MS and RH were collected from their respective sites, sorted and dried. MS and RH were ground. Lignin content determination was done by drying lignocellulose material at 105 °C. Lignocellulose materials were prepared by hydrolysis of dried lignocellulose material with sodium hydroxide. Oxidized starch was prepared by oxidation of cassava peel starch using alkaline hydrogen peroxide. Particleboards were formulated through starch-lignocellulose polymerization at 60 °C compressed with 6.5 Nmm −2 pressure. Characterization of raw materials and formulated particleboards was done using XRD for mineralogical analysis, FTIR and NMR for elucidation of functional groups transformation. The results showed that esterification is the main process of chemical bonding in the particleboard formulation due to reaction between –COOH from starch and and OH- from lignocellulose. Etherification between hydroxyl groups from starch with hydroxyl groups from lignocellulose material. RH combined more through silication process with cassava peels starch than RH and SB showing materials containing high cellulose and hemicellulose content are more compatible. Composite materials formulated were used to produce medium density particleboards that can be used for making furniture and room partitioning.

Conventional methods of making particleboards utilize wood chips. This has resulted in a decrease in the tree cover due to the increase in wood demand. The effect has been climatic change. Wood is bound using phenol formaldehyde resin. Because of the decrease in the forest cover, alternative lignocellulose materials are required. In this study, lignocellulose materials used include sugarcane bagasse, maize stock, and rice husks. The cassava-starch mix with borax was used as a binder in particleboard formulation. The lignin content was determined, and its effect on properties of boards was investigated. The resultant composite material was molded at a pressure of 6.5 N/mm2 and at 30°C. The resultant particleboards had mean densities ranging from 0.604 to 0.611 g/cm3. The modulus of elasticity ranged from 2364.2 N/mm2 to 3329.93 N/mm2, modulus of rupture ranged from 13.55 N/mm2 to 14.83 N/mm2, and internal bonding ranged from 1.613 N/mm2 to 2.370 N/mm2. The performance of the board was dependent on the lignocellulose material used. Fourier transform infrared spectroscopy analysis showed that main chemical bonding in the particleboard resulted from esterification of –COOH from lignocellulose and OH- from starch. The particleboards formulated were found to be of low-density-fibre standard used in a similar manner to the conventional low-density particleboards.