Particleboard is a wood-based composite panel products produced from lignocellulosic materials and combined with adhesive as a binder then through a hot press process into sheets [1, 2]. Particleboard products are widely used for furniture, partitions, insulation and other non-structural components of buildings. Partition is a non-structural component of a building with the main function as a room divider or insulator that is flexible, lightweight, movable, and related to the life cycle of a building. The partition thickness ranging from 6 to 150 mm with a density varying from 0.2 to 1.2 g/cm3 depending on the partition material and other functions of the partition installation [3–5].
Generally, partitions are consisting of frames and materials. Partition materials (PM) is able to resist sound between rooms that are insulated so that they do not interfere with the adjoined room. The PM is also related to its ability to resist noise, preventing sound from entering or leaving a room or building. The soundproofing level of a partition wall is measured by the sound transmission class (STC) and absorption coefficient (AC) values. On the other hand, research results conducted by Addis et al. [6]mentioned that the impact on the environment related to the use of materials from non-structural components of buildings i.e. partitions (41%), floors (18%), roofs (14%), windows and doors (12%), kitchen furniture (6%) and others (9%). The research shows that partitions have a more negative impact on the environment than other building components.
The PM on the market based on two main types of raw materials i.e. inorganic and organic. The products of PM made from inorganic materials such as asbestos, gypsum, cement, glass fiber, glass wool and rockwool are not environmentally friendly, non-renewable and have a negative impact on health. The sulfate components of gypsum board are degraded by sulfate-reducing bacteria to produce hydrogen sulfide which is toxic, flammable and hazardous to health [7]. Partition materials for polymer-based sound insulation panels such as polystyrene (PS), polyvinylchloride (PVC) and polyethylene (PE) are also less environmentally friendly and take longer in the natural recycling process [8]. On the other hand, organic-based PM i.e. wood, multiplex, fiberboard and particleboard as an alternative to substituted inorganic materials such as gypsum and cement also have several disadvantages such as limited sources of wood raw materials, relatively low dimensional stability and the presence of formaldehyde emissions.
Lignocellulosic materials for the manufacture of particleboards is still dominated by wood particles. On the other hand, the shortage of wood in the panel industry, increased of environmental concerns and interest in sustainable manufacturing based on renewable resources other than wood are encourage some studies to find alternative resources that could be used as materials in the production of particleboard, like agricultural by-products [9, 10]. In this context, several studies have succeeded in developing substitutes for wood particles using non-wood and agricultural by-products such as rice husk [11], sugarcane bagasse-corn cob [12], oil palm trunk [13], coconut husk [14] for particleboard manufacturing. Karlinasari et al. [15]stated that the medium density particleboard made of Betung bamboo particles (density of 0.8 g/cm3) was effective as a sound insulation board compared to particleboard with density of 0.5 g/cm3. According to Kang et al. [16] particleboard composed rice husk and wood sawdust is a potential sound absorbing material because it has a high sound absorption coefficient value. The research results by Wong et al. [17] showed that the Betung bamboo and kenaf particles for particleboard with density of 0.4 g/cm3 had a higher NRC value which the higher percentage of Betung bamboo particles resulted in a particleboard with a better sound-absorbing value.
One of agricultural by-products that potential and suitable to develop as raw material for particleboard production is corn husk. As an information, corn yields produce corn husk with weights ranging from 10 to 38.38% [18]. It is calculated from the worldwide corn production in 2020/2021 is around 1129.29 million metric tons, so that around 112.92 to 433.42 million metric tons of corn husk can be obtained [19]. A study conducted by De Carvalho Mendes et al. [20] reported that corn husk biomass has holocellulose (73.1%), α-cellulose (35.3%), hemicellulose (37.5%), extractive and water soluble components (13.9%), lignin (7.9%) and ash content (5%). Meanwhile, Ibrahim et al. [21] mentioned that corn husk contained cellulose at 45.7%, hemicellulose at 35.8%, lignin at 4.03% and ash at 0.38%. Mohammed et al. [22] stated that corn husk and cob have the highest percentage of cellulose compared with other natural fibers, such as wheat husk, rice husk, wheat straw, wheat bran and rice straw [23–27].
Among the above identified agricultural by-products of corn plant, corn husk has an additional advantage in terms of suitable application for alternative processed products because it does not collide with the worldwide food stock and it is generally considered as agricultural by-products. Several studies on the use of corn husks have been carried out by Yu et al. [28] for fiberboard bonded PLA, Theng et al. [29] for fiberboard, Sari et al. [30] for sound absorber composite bonded with polyester, Lihua et al [31] for flame retardant composite reinforced PLA.
Currently, particleboard is produced using with formaldehyde-based adhesives such as urea formaldehyde (UF) and phenol formaldehyde (PF) as main binder. Formaldehyde-based adhesives can cause health and environmental problems [32, 33]. To overcome the problem of using formaldehyde-based adhesives and synthetic polymers in the manufacture of particleboard such as release of formaldehyde emission and toxic substance, need to use an alternative natural resources and non-formaldehyde-based adhesives for particleboard manufacture, like polysaccharide polymers i.e. water soluble chitosan (WSC) is used as substitute adhesive. The WSC is a chitosan derivative which is substituted by a carboxymethyl group in the hydroxyl group (-OH) and an amine group (-NH2) [34]. WSC is also an amphoteric derivative of chitosan due to its -COOH and -NH2 groups, so that its application becomes wider, such as antimicrobial, adsorbent, membrane and can be used to increase the mechanical and electrical strength of paper [35–37].
The manufacture of WSC can be prepared by hydrolyzing method, which is a chemical decomposition process using an aqueous solvent with the aim of breaking the chemical bonds of the substance i.e. chitosan [38, 39]. The functional group of WSC can be seen from the FTIR test results that showed a specific functional group similarity with acid soluble chitosan (ASC) i.e. -OH, -NH and -CH groups. The WSC has a molecular weight range from low to moderate and a high degree of deacetylation compared to ASC which generally have only a high molecular weight. This makes WSC have a high solubility level.
Generally, WSC is soluble in water and it become more compatible in many sectors such as pharmaceutical, medicine, and food industries. Several studies have been done to investigate the suitability of WSC at composite film [40], sustainable materials [41], phytoremediation [42], coating material [43], hydrogel [44]. Yu et al. [45] stated that WSC also potential to developed as active packaging film incorporated with cellulose. The properties of WSC which are soluble at neutral pH or in water can increase the solubility and lead to a decrease in acidity, which affects the wider use of WSC as a derivative of chitosan.
Chitosan and its derivatives such as WSC show great potential to be developed as binders or adhesives in the gluing process, with or without additives or cross-linkers [46]. So far, the type of chitosan that has been developed as an adhesive is ASC. Ibrahim et al. [47] developed a cheap and safe adhesive formulation based on mixture of modified lignin and ASC which was tested for its adhesion to wood joints. Meanwhile, Ji et al. [48, 49] has been used ASC as an adhesive that combined with glutaraldehyde for medium density fiberboard (MDF) and with lignin made of sawdust. The study conducted by Ningsi et al. [50] showed that particleboard bonded with ASC as an adhesive still has limited at dimensional stability, screw holding power and internal bonding properties.
The existence of several limitations from ASC as an adhesive for wood panel and composite products has encouraged the development of a chitosan derivative i.e. WSC as an adhesive for wood panel products like particleboard. Meanwhile, the study on the use of WSC as a particleboard adhesive to replace formaldehyde-based adhesives has not yet been carried out. This has become an interesting research object by looking at the specific and unique characteristics of WSC that described previously. Therefore, in order to substitute un-renewable partition materials made of particleboard bonded with synthetic adhesives, two materials were studied: corn husk and water soluble chitosan (WSC) which are abundant, renewable and sustainable. This study will show and evaluate the feasibility of using corn husk and WSC as an new alternative raw materials in particleboard production and aimed to investigate the influence of WSC content and pressure temperature variations on particleboard properties as partition material.