scholarly journals Process modification involving strong-acid step in urea-formaldehyde resin preparation

2020 ◽  
Vol 16 (2) ◽  
pp. 212-217
Author(s):  
Dicky Dermawan ◽  
Lucky William Kusnadi ◽  
Jemmy Lesmana
Keyword(s):  
Urea Formaldehyde ◽  
Gelation Time ◽  
Strong Acid ◽  
Raw Material ◽  
Molar Ratio ◽  
Formaldehyde Resin ◽  
Formaldehyde Concentration ◽  
Formaldehyde Content ◽  
Process Modification ◽  
Uf Resin

Urea-formaldehyde (UF) resin adhesive for wood-based panel industries are commonly manufactured using conventional alkaline-acid process. This paper reports a process modification of a conventional UF resin preparation by incorporating a strong-acid step, involving simultaneous methylolation and condensation reactions at very low pH at the beginning of the processing step. The experiment showed that this additional step should be carried out at short duration and at high enough temperature in order to avoid gelation or separation problems. In order to control temperature rise caused by the exothermic nature of the reactions, the modified process requires a higher initial formaldehyde-to-urea (F/U) molar ratio compared to the original. For the same reason, the first urea should be fed incrementally to ensure high F/U ratio at any time during the strong acid step. Using regular formalin concentration as raw material at the same F/U molar ratio, the modified resin showed lower free formaldehyde content thus have lower reactivity in comparison to those of the original. However, when the same procedure was applied using higher formaldehyde concentration at higher solid content, the produced resin showed comparable free formaldehyde content and shorter gelation time. Application test for making plywood showed that the modified process gave a very significant improvement in both the internal bonding strength and formaldehyde emission.

Performances of Modified Urea-Formaldehyde Resins for Bonding Plywood

2011 ◽  
Vol 71-78 ◽  
pp. 3170-3173
Author(s):  
Ji Zhi Zhang ◽  
Xiao Ying Liu ◽  
Ying Ying Qiu ◽  
Xiao Mei Wang ◽  
Jian Zhang Li ◽  
...  
Keyword(s):  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Exothermic Peak ◽  
Urea Formaldehyde Resin ◽  
Molar Ratio ◽  
Formaldehyde Resin ◽  
Formaldehyde Content ◽  
Uf Resin ◽  
Dta Curve ◽  
Modified Urea

Urea-formaldehyde resin was modified by a modifier with different synthetic processes labelled as UFM1, UFM2, and UFM3 respectively. As a comparison, normal UF resin with a F/U molar ratio of 1.1 labelled as UF0 was synthesized. The thermal behavior of modified urea-formaldehyde resins was studied by TG-DTA techniques, and the properties of plywood bonded with the UFM resins were investigated. The conclusions were as follows: (1) the modifier used in this study could significantly reduce the free formaldehyde content of urea-formaldehyde resin and the formaldehyde emission of plywood; (2) The exothermic peak temperatures of DTA curve were 129.37, 125.05, 120.98, and 116.11 °C for UF0, UFM1, UFM2, and UFM3 respectively. (3) The plywood manufactured with UFM2 and UFM3 resins have high bonding strength (1.28MPa and 1.59MPa) and low formaldehyde emission value (E1 grade).

scholarly journals Improving Thermal Conductivity Coefficient in Oriented Strand Lumber (OSL) Using Sepiolite

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 599 ◽  
Author(s):  
Hamid R. Taghiyari ◽  
Abolfazl Soltani ◽  
Ayoub Esmailpour ◽  
Vahid Hassani ◽  
Hamed Gholipour ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Core Temperature ◽  
Thermal Conductivity Coefficient ◽  
Urea Formaldehyde ◽  
Wood Products ◽  
Raw Material ◽  
Formaldehyde Resin ◽  
The Core ◽  
Uf Resin ◽  
Hardness Values

An issue in engineered wood products, like oriented strand lumber (OSL), is the low thermal conductivity coefficient of raw material, preventing the fast transfer of heat into the core of composite mats. The aim of this paper is to investigate the effect of sepiolite at nanoscale with aspect ratio of 1:15, in mixture with urea-formaldehyde resin (UF), and its effect on thermal conductivity coefficient of the final panel. Sepiolite was mixed with UF resin for 20 min prior to being sprayed onto wood strips in a rotary drum. Ten percent of sepiolite was mixed with the resin, based on the dry weight of UF resin. OSL panels with two resin contents, namely 8% and 10%, were manufactured. Temperature was measured at the core section of the mat at 5-second intervals, using a digital thermometer. The thermal conductivity coefficient of OSL specimens was calculated based on Fourier’s Law for heat conduction. With regard to the fact that an improved thermal conductivity would ultimately be translated into a more effective polymerization of the resin, hardness of the panel was measured, at different depths of penetration of the Janka ball, to find out how the improved conductivity affected the hardness of the produced composite panels. The measurement of core temperature in OSL panels revealed that sepiolite-treated panels with 10% resin content had a higher core temperature in comparison to the ones containing 8% resin. Furthermore, it was revealed that the addition of sepiolite increased thermal conductivity in OSL panels made with 8% and 10% resin contents, by 36% and 40%, respectively. The addition of sepiolite significantly increased hardness values in all penetration depths. Hardness increased as sepiolite content increased. Considering the fact that the amount of sepiolite content was very low, and therefore it could not physically impact hardness increase, the significant increase in hardness values was attributed to the improvement in the thermal conductivity of panels and subsequent, more complete, curing of resin.

Study on Urea-Formaldehyde Resin for Glass Wool Products

2013 ◽  
Vol 774-776 ◽  
pp. 1232-1236
Author(s):  
Nan Zhe Zhang
Keyword(s):  
Polyvinyl Alcohol ◽  
Water Resistance ◽  
Urea Formaldehyde ◽  
Glass Wool ◽  
Orthogonal Test ◽  
Urea Formaldehyde Resin ◽  
Molar Ratio ◽  
Formaldehyde Resin ◽  
Resin Adhesive ◽  
Uf Resin

In order to prepare urea-formaldehyde (UF) resin adhesive with good performance for glass wool products, we used polyvinyl alcohol (PVA), p-toluenesulfonamide (PTSA) and methanol to modify UF resin, optimized the molar ratio of formaldehyde (F) / urea (U) and reaction components ratio by orthogonal test, reduced the content of free formaldehyde in UF resin, and enhanced the water resistance, flexibility and stability of UF resin.

Preparation of Water-Resistance Plywood with UF Resin Modified by Emulsifiable Polyisocyanate

2010 ◽  
Vol 26-28 ◽  
pp. 1056-1060
Author(s):  
Li Bin Zhu ◽  
Bo Han ◽  
Ji You Gu ◽  
Yan Hua Zhang ◽  
Hai Yan Tan ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Resistance ◽  
Urea Formaldehyde ◽  
Great Influence ◽  
Physical And Mechanical Properties ◽  
Formaldehyde Emission ◽  
Molar Ratio ◽  
Formaldehyde Resin ◽  
X Ray ◽  
Uf Resin

The purpose of the study was to manufacture water-resistance plywood with using UF resin modified by emulsifiable polyisocyanate. The emulsifiable polyisocyanate which contains plenty of hydrophilic segments and teminal isocyanate groups were synthesized by reaction between various kinds of polyether polyols and polymeric methane dipthenyl diisocyanate (pMDI). A type of composite adhesive was obtained from the mixture of emulsifiable polyisocyanate and urea formaldehyde resin. The process parameters, such as the molar ratio of –NCO and –OH, mass fraction of emulsifiable polyisocyanate in UF resin and accessory ingredient have a great influence on the composite adhesive. X-ray photoelectron spectroscopy (XPS) had been used to analyze the chemical structure of bonding interface. The results showed that the composite adhesive consisting of UF resin and emulsifiable polyisocyanate content of 7.5% and kaolin content of 1.5% was used in plywood with high physical and mechanical properties, water resistance and low formaldehyde emission.

Study on Properties of Modified Low Molar Ratio Urea-Formaldehyde Resins (I)

2010 ◽  
Vol 113-116 ◽  
pp. 2016-2020 ◽  
Author(s):  
Shi Feng Zhang ◽  
Jian Zhang Li ◽  
Ji Zhi Zhang ◽  
Yong Hua Li ◽  
Qiang Gao
Keyword(s):  
Water Resistance ◽  
Ph Value ◽  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
National Standards ◽  
Boiling Water ◽  
Molar Ratio ◽  
Type I ◽  
Formaldehyde Content ◽  
Uf Resin

For improving the performance of urea-formaldehyde (UF) resin, modified low molar ratio UF resins were developed to improve water resistance properties and reduce the formaldehyde emission of its bonded products. The effects of modifier feeding amount on the character of the cured resins were characterized by Fourier transform infrared spectroscopy (FTIR) measurement. The viscosity, pH value, solid content, free formaldehyde content, pot time, and curing time of the UF resins were also tested according to Chinese National Standards methods. The results show that the modified 1.00 molar ratio UF resins show lower free formaldehyde content and higher boiling-water-resistance comparing with unmodified ones. The boiling-water-resistant bonding strength of poplar plywood bonded with modified UF resin at 140 °C hot-press temperature can reach type I grade (100 °C water bath 3h) plywood requirement and the formaldehyde emission can meet the E0 grade plywood need.

scholarly journals Calcium carbonate modified urea–formaldehyde resin adhesive for strength enhanced medium density fiberboard production

RSC Advances ◽  
2021 ◽  
Vol 11 (40) ◽  
pp. 25010-25017
Author(s):  
Li Lu ◽  
Yan Wang ◽  
Tianhua Li ◽  
Supeng Wang ◽  
Shoulu Yang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Urea Formaldehyde ◽  
Medium Density Fiberboard ◽  
Urea Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Medium Density ◽  
Ionic Bond ◽  
Resin Adhesive ◽  
Uf Resin ◽  
Modified Urea

Reactions between CaCO3 and CH2O2 during polycondensation of UF resin produce Ca2+. Ionic bond complexation binds Ca2+ with UF resin. The UF resin crystalline percentage decreases from 26.86% to 22.71%. IB strength of resin bonded fiberboard increases from 0.75 to 0.94 MPa.

scholarly journals Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 220
Author(s):  
Petar Antov ◽  
Viktor Savov ◽  
Ľuboš Krišťák ◽  
Roman Réh ◽  
George I. Mantanis
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Urea Formaldehyde ◽  
Physical And Mechanical Properties ◽  
High Density ◽  
Thickness Swelling ◽  
Formaldehyde Content ◽  
Uf Resin ◽  
Natural Wood ◽  
European Standards

The potential of producing eco-friendly, formaldehyde-free, high-density fiberboard (HDF) panels from hardwood fibers bonded with urea-formaldehyde (UF) resin and a novel ammonium lignosulfonate (ALS) is investigated in this paper. HDF panels were fabricated in the laboratory by applying a very low UF gluing factor (3%) and ALS content varying from 6% to 10% (based on the dry fibers). The physical and mechanical properties of the fiberboards, such as water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), internal bond strength (IB), as well as formaldehyde content, were determined in accordance with the corresponding European standards. Overall, the HDF panels exhibited very satisfactory physical and mechanical properties, fully complying with the standard requirements of HDF for use in load-bearing applications in humid conditions. Markedly, the formaldehyde content of the laboratory fabricated panels was extremely low, ranging between 0.7–1.0 mg/100 g, which is, in fact, equivalent to the formaldehyde release of natural wood.

scholarly journals Repeated thermo-hydrolytic disintegration of medium density fibreboards (MDF) for the production of new MDF

2021 ◽  
Author(s):  
Fahriye Yağmur Bütün Buschalsky ◽  
Carsten Mai
Keyword(s):  
Service Life ◽  
Nitrogen Content ◽  
Manufacturing Process ◽  
Closed Loop ◽  
Reducing Sugars ◽  
Urea Formaldehyde ◽  
Molar Ratio ◽  
Medium Density ◽  
Target Density ◽  
Formaldehyde Content

AbstractMedium density fibreboards (MDF) are currently not recycled after service life, but various publications report on recycling by the disintegration of MDF using various techniques and the properties of obtained recovered fibres (RF). In this study, the main aim was to put back RF into the MDF manufacturing process as closed-loop recycling using repeated thermo-hydrolytic disintegration. Compared to previous studies, the focus was on the recycling of MDF with a relatively low F:U molar ratio (1.11). Urea–formaldehyde-bonded MDF with a target density of 700 kg m−3 was subjected to thermo-hydrolytic disintegration in an autoclave using only water at 95 °C for 20–30 min. Afterwards, the properties of RF and virgin fibres (VF), of MDF produced thereof and the composition of the disintegration water (DW) were determined. The nitrogen content (NC) revealed that RF contained about 30% of the initially applied UF. The pH of the DW hardly changed during recycling and it contained considerable amounts of reducing sugars. Using RF did not result in higher formaldehyde emissions than VF. Compared to earlier studies using a higher formaldehyde content (higher F:U ratio), MDF bonded with modern UF resins can be disintegrated under clearly milder disintegration conditions with respect to temperature and time. The properties of recycled MDF were similar to those of reference MDF; up to 100% RF could be used without severely deteriorating the strength and increasing formaldehyde emissions from these panels.

Effect of wood acidity and catalyst on UF resin gel time

Holzforschung ◽  
2004 ◽  
Vol 58 (4) ◽  
pp. 408-412 ◽  
Author(s):  
C. Xing ◽  
S.Y. Zhang ◽  
J. Deng
Keyword(s):  
Ph Value ◽  
Raw Materials ◽  
Urea Formaldehyde ◽  
Acid Catalyst ◽  
Buffering Capacity ◽  
Raw Material ◽  
Gel Time ◽  
Uf Resin ◽  
Effects Of Ph ◽  
Fiber Materials

Abstract Knowledge of pH and buffering capacity of raw fiber materials is important for understanding the effects of raw material on the curing rate of urea formaldehyde (UF) resin, used for panel manufacturing, especially with some less-desirable wood materials such as bark, top, and commercial thinnings. The effects of pH and buffering capacity as well as catalyst content on the gel time of UF resin were investigated. The results obtained from this study indicate that bark has a lower pH value as well as higher acid and alkaline buffering capacities than wood of the same species due to their extractives. The pH values of the raw fiber materials studied decrease with increased absolute and relative acid buffering capacity due to the increased absolute acidity mass in the solution. At lower levels of added catalyst, the effect of raw material pH on UF resin gel time is significant, while it is insignificant at higher catalyst contents. This may be due to the acidity of wood, which is the main acid catalyst source of the mixture at lower levels of added catalyst, while at higher levels, catalyst is the main source. With higher catalyst contents, all studied raw materials mixed with UF resin result in a longer gel time than does UF resin alone.

The Impact of Different Dosage of Additives on the UF Resin Used in Plywood

2011 ◽  
Vol 197-198 ◽  
pp. 147-150 ◽  
Author(s):  
Wei Wang ◽  
Li Bin Zhu ◽  
Ji You Gu ◽  
Xiang Li Weng ◽  
Hai Yan Tan
Keyword(s):  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Urea Formaldehyde Resin ◽  
Formaldehyde Resin ◽  
Synthetic Process ◽  
Resin Adhesive ◽  
Environmental Friendly ◽  
Uf Resin ◽  
Comprehensive Performance ◽  
The Impact

Through the study of the effects of different dosage of additives on the properties of urea formaldehyde resin adhesive prepared at low mole ratio of formaldehyde/urea, optimize the synthetic process of the UF resin which is used at the E0 grade plywood. The results showed that the product synthesized under the following condition: the mole ratio of formaldehyde/urea is 0.99:1, the dosage of the specific additive is 1.0% and that of melamine is 3-4%, had a good comprehensive performance and the formaldehyde emission of the plywood meets the E0 grade which is environmental-friendly.

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