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.

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).

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.

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.

scholarly journals Synthesis of Lignin-Based Polyacid Catalyst and Its Utilization to Improve Water Resistance of Urea–formaldehyde Resins

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 175 ◽  
Author(s):  
Shishuai Gao ◽  
Yupeng Liu ◽  
Chunpeng Wang ◽  
Fuxiang Chu ◽  
Feng Xu ◽  
...  
Keyword(s):  
Maleic Anhydride ◽  
13C Nmr ◽  
Water Resistance ◽  
Urea Formaldehyde ◽  
Medium Density Fiberboard ◽  
Formaldehyde Emission ◽  
Medium Density ◽  
1H And 13C Nmr ◽  
Uf Resin ◽  
Improve Water Resistance

In this study, a lignin-based polyacid catalyst was synthesized via two steps to enhance water resistance of urea–formaldehyde (UF) resins. The first steps involved a hydroxymethylation reaction to increase the hydroxyl content in lignin. Then, hydroxymethylated lignins were reacted with maleic anhydride to form maleated lignin-based polyacids. The acid groups were expected to function as acid catalysts to catalyze the curing process of UF resin. In order to elucidate the structural variation, 3-methoxy-4-hydroxyphenylpropane as a typical guaiacol lignin structural unit was used as a model compound to observe the hydroxymethylation and the reaction with maleic anhydride analyzed by 1H and 13C NMR. After the structural analysis of synthesized lignin-based polyacid by FTIR and 13C NMR, it was used to produce UF resin as an adhesive in plywood and medium density fiberboard (MDF) production, respectively. The results showed that when the addition of lignin-based polyacid was 5% in plywood, it could effectively improve the water resistance of UF resins as compared to commercial additive NH4Cl. It also exhibited a lower formaldehyde emission. Like plywood, lignin-based catalysts used in medium density fiberboard production could not only maintain the mechanical properties, but also inhibit the water adsorption of fiberboards.

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.

Study on Curing Behavior of Low Molar Ratio Urea-Formaldehyde Resins with Different Curing Agents

2010 ◽  
Vol 150-151 ◽  
pp. 965-968
Author(s):  
Yao Hui Dong ◽  
Qiang Gao ◽  
Yue Zhang ◽  
Jian Zhang Li
Keyword(s):  
Thermal Analysis ◽  
Bonding Strength ◽  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Molar Ratio ◽  
Curing Agent ◽  
Curing Time ◽  
Curing Behavior ◽  
Uf Resin ◽  
Curing Agents

In order to characterize the curing behavior of low molar ratio urea-formaldehyde (UF) resin, the curing time and thermal analysis in curing reaction of the UF resins and the bonding strength and formaldehyde emission of plywood bonded by five kinds of low molar ratio UF resins with six different curing agents were studied. The results indicated that the UF resins with the molar ratio of formaldehyde to urea more than 1.0 could get reasonable curing time. The heat enthalpy of UF resins significantly increased with the enhancing the acidity of curing agent. The plywood manufactured by the UF resins with 1.1 molar ratio showed much higher bonding strength and lower formaldehyde emission.

Melamine-urea-formaldehyde resins with low formaldehyde emission and resistance to boiling water

2019 ◽  
Vol 48 (3) ◽  
pp. 229-236 ◽  
Author(s):  
Bo Wang ◽  
Yanhua Zhang ◽  
Haiyan Tan ◽  
Jiyou Gu
Keyword(s):  
High Temperature ◽  
Heat Resistance ◽  
Bonding Strength ◽  
Water Resistance ◽  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Boiling Water ◽  
Curing Agent ◽  
Content Type ◽  
Application Range

Purpose The purpose of the study was to prepare melamine-urea-formaldehyde (MUF) resin that would be resistant to boiling water and high temperature and exhibit low formaldehyde emission. Design/methodology/approach The authors prepared MUF resin with different F/(M + U) and changed the amount of melamine added, through the analysis of MUF resin properties to get the best reaction parameters, and used different amino acid cure systems including NH4Cl cured the resin. Findings Resin’s heat resistance and water resistance are mainly determined by the amount of melamine added, and formaldehyde emission of the plywood can be changed by adjusting F/(M + U). The peak temperature of the curing agent-cured resin increases as compared with the self-curing resin. Stronger the acidity of curing agent, faster the viscosity increased in probation period and lower the bonding strength and heat resistance of the resin. Research limitations/implications Melamine improves the heat resistance and water resistance of the resin. When the amount of melamine is more than a certain value, water resistance of the resin decreased. Practical implications MUF resin that is resistant to boiling water and exhibits low formaldehyde emission can be used in high temperature, high humidity and strict formaldehyde emission environment and can also be combined with other materials. Social implications It was helpful to reduce the effect of formaldehyde emission on people’s health and environmental pollution and is also beneficial for the expansion of the application range of aldehyde resin. Originality/value The originality is twofold: the influence of the acid strength of curing agent on the bonding strength of the resin adhesive and the method for preparing high performance MUF resin by following the traditional process.

Modified Nanocrystalline Cellulose Used for Improving Formaldehyde Emission and Bonding Strength of Urea Formaldehyde Resin Adhesive

2013 ◽  
Vol 562-565 ◽  
pp. 846-851
Author(s):  
Hao Zhang ◽  
Ying She ◽  
Shu Ping Song ◽  
Jun Wen Pu
Keyword(s):  
Bonding Strength ◽  
Urea Formaldehyde ◽  
Formaldehyde Emission ◽  
Nanocrystalline Cellulose ◽  
National Standards ◽  
Control Group ◽  
Formaldehyde Resin ◽  
Hydroxyl Groups ◽  
Resin Adhesive ◽  
Uf Resin

Nanocrystalline cellulose (NCC) was used for improving the formaldehyde (HCHO) emission and bonding strength of urea formaldehyde (UF) resin adhesive in fiberboard and plywood. The original NCC was modified by 3-aminopropyltriethoxysilane (APTES) and the wetting property with UF resin adhesive was improved by 26.4%. The UF resin adhesive with modified NCC was characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TG) and Fourier transform infrared (FT-IR). The crystal region of UF resin adhesive was influenced by NCC and the diffraction intensity of the peak at 2θ = 22.82° was enhanced significantly. The thermal stability of UF resin adhesive with 1.0% modified NCC increased by 4.9%. And modified NCC led hydroxyl groups into the UF resin adhesive. HCHO emission and bonding strength of the UF resin adhesive with modified NCC were tested according to Chinese National Standards GB/T 17657-1999 and GB/T 9846-2004. The HCHO emission of fiberboard and plywood with 1.5% modified NCC decreased by 13.0% and 53.2%, respectively. The bonding strength of fiberboard increased by 158.3% (from 0.12 MPa of control group to 0.31 MPa of fiberboard with 1.5% modified NCC), while 1.5% modified NCC led to a 23.6% increase in the plywood.

Preparation and Properties of Low Formaldehyde Emission Plywood with Flame Resistance

2010 ◽  
Vol 139-141 ◽  
pp. 649-652
Author(s):  
Shi Feng Zhang ◽  
Fei Song ◽  
Qiang Gao ◽  
Jian Zhang Li
Keyword(s):  
Bonding Strength ◽  
Urea Formaldehyde ◽  
Weight Percent Gain ◽  
Formaldehyde Emission ◽  
Weight Percent ◽  
Molar Ratio ◽  
Flame Resistance ◽  
Uf Resin ◽  
High Molar Ratio ◽  
Grade Requirement

In order to improve the flame resistance and reduce the formaldehyde emission of plywood, a multifunctional formaldehyde scavenger with flame resistance (FSFR) was prepared and used to treat plywoods bonded with high molar ratio urea-formaldehyde (UF) resin. The weight percent gain (WPG), formaldehyde emission, oxygen index (OI), and bonding strength of plywoods after FSFR treated were measured to evaluated properties of FSFR. The results showed that the formaldehyde emission of the treated plywood was 0.1-0.32 mg/L, which could meet the E0 grade requirement (<0.5 mg/L ). The flame resistance of treated plywood increased significantly and the bonding strength changed little. The formaldehyde emission decreased 96.8 % and OI increased 47.2 % and the bonding strength kept unchanged when FSFR reached 8.87 % compared with that of untreated plywood.

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.

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