4634
journal of materials research and technology 2022;20:4630 e 4658
Fig. 6 e Particleboard export volumes in 2020 by region [2].
solids worldwide, are the most widely used adhesive system in particleboard production, accounting for about 85% of the total volume due to their chemical versatility, high reactivity, water-solubility, low curing temperatures, short press times, colourless glue line, and relatively low cost [29]. In recent years, some experiments were made to improve physical, mechanical, and biological properties, reduce hot- press time, and reduce formaldehyde emission of UF resin by addition of different nano-fillers (such as nano silver, nano copper, and nano-minerals like wollastonite) to produce wood-based composite panels [30 e 35]. Though the initial re- sults were promising both at laboratory scale and pilot batch at factories, the experiments have not yet been used at full industrial scales. PF resins are the second most important type of wood adhesives, with an estimated annual con- sumption of approx. three million tons worldwide are used to produce water- and weather-resistant particleboard. Mean- while, polymeric 4,4-diphenyl methane diisocyanate (pMDI) is mainly used for manufacturing exterior-grade particleboard [27], or in applications where concerns about the harmful free- formaldehyde emission associated with UF adhesives, are present. pMDI has excellent adhesion properties and can be used in significantly lower proportions than UF, PF, and MUF
2.
Adhesives used in particleboard
manufacturing
Adhesive and wood particles/chips are the two major com- ponents of particleboard. Approximately 95% of the total ad- hesives used for manufacturing wood-based panels are based on formaldehyde. These resins are made by reacting formal- dehyde with other chemicals such as urea, melamine, phenol, resorcinol, or combinations [27]. Urea-formaldehyde (UF), melamine fortified UF (MUF), melamine e urea e phenol-form- aldehyde resin (MUPF), melamine-formaldehyde (MF), phenol-formaldehyde (PF), phenol e urea-formaldehyde (PUF), polymeric methylene diisocyanate (pMDI), as well as natural, bio-based adhesives such as tannins, lignins, carbohydrates, and natural rubber latex are among the commonly used ad- hesives in particleboard manufacturing [27]. Among these, aminoplastic resins derived from non-renewable petrochem- ical materials such as MF and UF are the most prevalently used adhesives in particleboard manufacturing. These resins are normally characterized by a molar ratio of formaldehyde to urea (F/U) between 1.00 and 1.10 [28]. UF resins, with an estimated annual consumption of about 11 million tons of
Table 1 e Particleboard made of less known or underutilized wood species. Raw material
Adhesive
Source
Polymeric 4,4 0 -diphenylmethane diisocyanate (pMDI) and urea-formaldehyde (UF) resin
Athel ( Tamarix aphylla )
[12]
Eastern redcedar ( Juniperus virginiana )
UF UF UF UF UF UF
[13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [11]
Peterebi ( Cordia trichotoma )
Willow ( Salix spp.)
Kiri ( Paulownia tomentosa )
Kadam( Anthocephalus chinensis )
Peach, apple, pear, cherry and apricot tree branches
Mangrove tree ( Rhizophora spp.) Date palm( Phoenix dactylifera ) Mangrove tree ( Rhizophora spp.) Mangrove tree ( Rhizophora spp.) Sengon ( Paraserianthes falcataria )
Binderless
UF
gumArabic
Tannin
Natural rubber latex
Made with FlippingBook - Online magazine maker