Study on the Pyrolysis Behaviors of Urea-Formaldehyde Resin and Rice Straw Mixed Pellets

In order to study the effect of biomass on the pyrolysis characteristics of urea-formaldehyde resin, the thermogravimetric experiments were carried out respectively using urea-formaldehyde resin (UF), rice straw (RS), and their mixed pellets with different proportions. The pyrolysis kinetics analysis was conducted. The results showed that the pyrolysis process of UF resin and mixed pellets could be divided into three stages: the drying and dehydration of the material, the rapid decomposition of volatile matter, and residue decomposition. The reaction order of UF resin and mixed pellets was discussed using the Coats–Redfern method, the activation energy of UF resin was 54.27 kJ/mol, and this value decreased with the addition of rice straw. As the mass ratio of UF resin to rice straw was 3:1, the activation energy achieved the lowest value, which means that the addition of rice straw was beneficial to the pyrolysis process of UF. In the process of pellet preparation, the falling strength and compressive strength of UF resin pellets can be improved by adding an appropriate proportion of rice straw. In this test, the yield of pyrolytic carbon reached the highest value of 23.93%, as the mass ratio of UF resin to rice straw was 3:2. When the mass ratio was 4:1, the highest liquid product yield of 43.21% was achieved.

Effect of Copper (II) Sulfate on the Properties of Urea Formaldehyde Adhesive

The purpose of this work is to investigate the effects of copper (II) sulfate on formaldehyde release and the mechanical properties of urea formaldehyde (UF) adhesive. Copper (II) sulfate has been used as a formaldehyde scavenger in UF resin, and its effects on the physical and chemical properties of UF adhesive have been studied. Moreover, the mechanical properties and formaldehyde release of plywood prepared with modified UF resin have been determined. The UF resin has been characterized by Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). FTIR spectra showed that the addition of copper (II) sulfate to the UF resin did not affect the infrared (IR) absorptions of its functional groups, implying that the structure of UF was not modified. Further results showed that: the free formaldehyde content of the UF resin by the incorporation of 3% copper (II) sulfate was 0.13 wt.%, around 71% lower than that of the control UF adhesive. With a copper (II) sulfate content of 3%, the formaldehyde release from treated plywood was 0.74 mg·L−1, around 50% lower than that from the control UF adhesive, and the bonding strength reached 1.73 MPa, around 43% higher than that of the control UF adhesive.

Physico-Mechanical and Thermal Properties of Thermoplastic Poly(Vinyl Alcohol) Modified Thermosetting Urea Formaldehyde Resin

Urea formaldehyde (UF) resins are brittle and to improve their tensile properties poly(vinyl alcohol) (PVA) has been used to modify the UF resin. An easy improved procedure was developed to make PVA modified UF resin on the basis of conventional synthesis of UF resin. Prepolymer of UF was mixed with different weight percentages of PVA (1-5%) to synthesize modified UF resin which can be used to make adhesive for forest products. Both UF and modified UF resins were characterized by FTIR, physico-mechanical and thermal properties analyses. Modified UF resin containing 2 wt. % PVA exhibited better results than the UF.

Particleboards from Recycled Pallets

Worldwide production of wooden pallets continually increases, and therefore in future higher number of damaged pallets need to be recycled. One way to conveniently recycle pallets is their use for the production of particleboards (PBs). The 3-layer PBs, bonded with urea-formaldehyde (UF) resin, were prepared in laboratory conditions using particles from fresh spruce logs (FSL) and recycled spruce pallets (RSP) in mutual weight ratios of 100:0, 80:20, 50:50 and 0:100. Particles from RSP did not affect the moisture properties of PBs, i.e., the thickness swelling (TS) and water absorption (WA). The mechanical properties of PBs based on particles from RSP significantly worsened: the modulus of rupture (MOR) in bending from 14.6 MPa up to 10 MPa, the modulus of elasticity (MOE) in bending from 2616 MPa up to 2012 MPa, and the internal bond (IB) from 0.79 MPa up to 0.61 MPa. Particles from RSP had only a slight negative effect on the decay resistance of PBs to the brown-rot fungus Serpula lacrymans, while their presence in surfaces of PBs did not affect the growth activity of moulds at all.

Surfactant-Induced Reconfiguration of Urea-Formaldehyde Resins Enables Improved Surface Properties and Gluability of Bamboo

The high-efficiency development and utilization of bamboo resources can greatly alleviate the current shortage of wood and promote the neutralization of CO2. However, the wide application of bamboo-derived products is largely limited by their unideal surface properties with adhesive as well as poor gluability. Herein, a facile strategy using the surfactant-induced reconfiguration of urea-formaldehyde (UF) resins was proposed to enhance the interface with bamboo and significantly improve its gluability. Specifically, through the coupling of a variety of surfactants, the viscosity and surface tension of the UF resins were properly regulated. Therefore, the resultant surfactant reconfigured UF resin showed much-improved wettability and spreading performance to the surface of both bamboo green and bamboo yellow. Specifically, the contact angle (CA) values of the bamboo green and bamboo yellow decreased from 79.6° to 30.5° and from 57.5° to 28.2°, respectively, with the corresponding resin spreading area increasing from 0.2 mm2 to 7.6 mm2 and from 0.1 mm2 to 5.6 mm2. Moreover, our reconfigured UF resin can reduce the amount of glue spread applied to bond the laminated commercial bamboo veneer products to 60 g m−2, while the products prepared by the initial UF resin are unable to meet the requirements of the test standard, suggesting that this facile method is an effective way to decrease the application of petroleum-based resins and production costs. More broadly, this surfactant reconfigured strategy can also be performed to regulate the wettability between UF resin and other materials (such as polypropylene board and tinplate), expanding the application fields of UF resin.

Structural Application of Lightweight Panels Made of Waste Cardboard and Beech Veneer

In recent years, the furniture design trends include ensuring ergonomic standards, development of new environmentally friendly materials, optimised use of natural resources, and sustainably increased conversion of waste into value-added products. The circular economy principles require the reuse, recycling or upcycling of materials. The potential of reusing waste corrugated cardboard to produce new lightweight boards suitable for furniture and interior applications was investigated in this work. Two types of multi-layered panels were manufactured in the laboratory from corrugated cardboard and beech veneer, bonded with urea-formaldehyde (UF) resin. Seven types of end corner joints of the created lightweight furniture panels and three conventional honeycomb panels were tested. Bending moments and stiffness coefficients in the compression test were evaluated. The bending strength values of the joints made of waste cardboard and beech veneer exhibited the required strength for application in furniture constructions or as interior elements. The joints made of multi-layer panels with a thickness of 51 mm, joined by dowels, demonstrated the highest bending strength and stiffness values (33.22 N∙m). The joints made of 21 mm thick multi-layer panels and connected with Confirmat had satisfactory bending strength values (10.53 N∙m) and Minifix had the lowest strength values (6.15 N∙m). The highest stiffness values (327 N∙m/rad) were determined for the 50 mm thick cardboard honeycomb panels connected by plastic corner connector and special screw Varianta, and the lowest values for the joints made of 21 mm thick multi-layer panels connected by Confirmat (40 N∙m/rad) and Minifix (43 N∙m/rad), respectively. The application of waste corrugated cardboard as a structural material for furniture and interiors can be improved by further investigations.

Effect of urea–formaldehyde nanoparticles on the barrier property and delamination resistance for epoxy coating

Purpose The purpose of this paper is to investigate the effect of urea–formaldehyde (UF) nanoparticles on the barrier property and delamination resistance for epoxy coating in a 3.5% NaCl aqueous solution. Design/methodology/approach The UF resin was synthesized via sol–gel method, and UF/epoxy composite coating was prepared through ball-milling process; the microstructure and chemical composition of UF resin were observed using the Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy; the bonding strength of coating/metal interface was investigated through adhesion test; the mechanical properties of the coatings were studied by tensile tests; and the barrier and corrosion resistance properties were verified using salt spray test, cathodic delamination test and electrochemical impedance spectroscopy measurements. Findings The experimental results indicated that the UF resin presented uniformly dispersed nanoparticles in the epoxy matrix and enhanced the bonding strength of coating/metal interface and then improved the delamination resistance for composite coating, which resulted in the enhancement of the barrier property and corrosion resistance for UF/epoxy composite coating. Originality/value In this paper, an easily prepared blending compounding coating with excellent corrosion resistance property was synthesized via sol–gel method and ball-milling process. The effects of UF nanoparticles on the barrier property and delamination resistance were investigated in detail.

Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker

The purpose of this study was to evaluate the feasibility of using magnesium and sodium lignosulfonates (LS) in the production of particleboards, used pure and in mixtures with urea-formaldehyde (UF) resin. Polymeric 4,4′-diphenylmethane diisocyanate (pMDI) was used as a crosslinker. In order to evaluate the effect of gradual replacement of UF by magnesium lignosulfonate (MgLS) or sodium lignosulfonate (NaLS) on the physical and mechanical properties, boards were manufactured in the laboratory with LS content varying from 0% to 100%. The effect of LS on the pH of lignosulfonate-urea-formaldehyde (LS-UF) adhesive compositions was also investigated. It was found that LS can be effectively used to adjust the pH of uncured and cured LS-UF formulations. Particleboards bonded with LS-UF adhesive formulations, comprising up to 30% LS, exhibited similar properties when compared to boards bonded with UF adhesive. The replacement of UF by both LS types substantially deteriorated the water absorption and thickness swelling of boards. In general, NaLS-UF-bonded boards had a lower formaldehyde content (FC) than MgLS-UF and UF-bonded boards as control. It was observed that in the process of manufacturing boards using LS adhesives, increasing the proportion of pMDI in the adhesive composition can significantly improve the mechanical properties of the boards. Overall, the boards fabricated using pure UF adhesives exhibited much better mechanical properties than boards bonded with LS adhesives. Markedly, the boards based on LS adhesives were characterised by a much lower FC than the UF-bonded boards. In the LS-bonded boards, the FC is lower by 91.1% and 56.9%, respectively, compared to the UF-bonded boards. The boards bonded with LS and pMDI had a close-to-zero FC and reached the super E0 emission class (≤1.5 mg/100 g) that allows for defining the laboratory-manufactured particleboards as eco-friendly composites.

Properties of High-Density Fiberboard Bonded with Urea–Formaldehyde Resin and Ammonium Lignosulfonate as a Bio-Based Additive

The potential of ammonium lignosulfonate (ALS) as an eco-friendly additive to urea–formaldehyde (UF) resin for manufacturing high-density fiberboard (HDF) panels with acceptable properties and low free formaldehyde emission was investigated in this work. The HDF panels were manufactured in the laboratory with very low UF resin content (4%) and ALS addition levels varying from 4% to 8% based on the mass of the dry wood fibers. The press factor applied was 15 s·mm−1. The physical properties (water absorption and thickness swelling), mechanical properties (bending strength, modulus of elasticity, and internal bond strength), and free formaldehyde emission were evaluated in accordance with the European standards. In general, the developed HDF panels exhibited acceptable physical and mechanical properties, fulfilling the standard requirements for HDF panels for use in load-bearing applications. Markedly, the laboratory-produced panels had low free formaldehyde emission ranging from 2.0 to 1.4 mg/100 g, thus fulfilling the requirements of the E0 and super E0 emission grades and confirming the positive effect of ALS as a formaldehyde scavenger. The thermal analyses performed, i.e., differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and derivative thermogravimetry (DTG), also confirmed the main findings of the research. It was concluded that ALS as a bio-based, formaldehyde-free adhesive can be efficiently utilized as an eco-friendly additive to UF adhesive formulations for manufacturing wood-based panels under industrial conditions.

Potential of Seaweed (Kappaphycus alvarezii) as a Particleboard

Recently, the utilization of lignocellulosic materials to produce eco-friendly products is very promising as biodegradable reinforcing elements for composite materials like particleboards and medium density fiberboards. The growing shortage of wood supply has also led to the development of suitable alternative materials for construction. For this reason, the industry is working to develop high-efficiency green materials including the use of seaweed. This research is aims to study the potential of seaweed from Kappaphycus species as a particleboard. Several different target densities were produced according to following proportions: seaweed particles from 150 to 200 grams and UF resin from 15% to 20%. Mechanical properties including internal bonding and bending testing were tested in this study. Samples were also investigated by utilizing microscopy for surface characterization. The outcome showed that seaweed particleboard with highest amount of seaweed particle and UF resin resulted in highest MOE, MOR and internal bonding strength values with results 457.47, 1.5, and 4.73 MPa, respectively. According to Japanese Standard, Internal bonding (IB) strength values for all the samples met the IB requirements of the standards for general uses. Thus, seaweed particle has potential to be an alternative raw material in the manufacture of particleboards.