Melamine Modified Urea Formaldehyde Resin Research Articles

Synthesis and Properties of Melamine Modified Urea Formaldehyde Resin for Impregnation Under New Process

In this paper, the basic properties of UF and UMF resins for impregnation under conventional and new processes were compared, and their chemical structures were characterized by ¹³C NMR. The effects of synthetic process and melamine addition on the bonding strength and formaldehyde emission of UF and UMF resins were studied. The resin synthesized by the new process has higher linear and methylene ether bond content, relatively lower methylene content, longer curing time and storage life and lower free formaldehyde content than the conventional resin; When melamine was added at the initial stage of UF resin synthesis reaction, it did not significantly change the total amount of methylene ether and hydroxymethyl in the resin system, but the content of class I hydroxymethyl increased and the content of class II hydroxymethyl decreased. The reason may be that the added melamine and urea react not only with the remaining formaldehyde in the system, but also with the formaldehyde removed from hydroxymethyl due to dehydroxylation reaction, Hydroxymethylmelamine and monobasic substituted urea are produced. At this time, about 50% of melamine still exists in UMF resin in the form of free or low hydroxymethylate, and does not participate in the formation of the main structure of the resin. Melamine was added in the early stage of the reaction. The modified resin bonded plywood has high bonding strength and low formaldehyde emission.

Preparation and thermal degradation property analysis of the tea-based melamine-modified urea–formaldehyde (TMUF) resin

In this work, tea powder was used as a filler to produce low-formaldehyde-emission tea-based melamine-modified urea–formaldehyde resin (TMUF). The thermal stabilities of TMUF and the resin without tea powder (MUF0) were characterized using thermogravimetry. The optimal amount of tea powder m(tea)/m(tea + urea) was equal to 0.15. The formaldehyde emission of the three-layer plywood produced by TMUF was reduced by 75.43%, and the wet bonding strength of the plate was increased by 26.67% as compared with the plywood prepared by MUF0. Compared with MUF0, the thermal degradation peak temperature of TMUF resin was shifted to higher temperature, while the carbon residue was increased. The thermal degradation activation energies of TMUF and MUF0 were similar, while TMUF had a lower pre-exponential A. The Flynn–Wall–Ozawa model-free method is used to estimate various activation energy values at different conversion rates and to predict possible reaction mechanisms. Judging the reaction mechanism according to the slope of the straight line fitted by different models, the best model was based on random nucleation.

Thermal Behavior Analysis of Melamine Modified Urea-Formaldehyde Resin with Different Molar Ratios

In this study, Thermogravimetry (TG) were used to analyze thermal degradation properties of two kinds of low-molar ratio of the melamine-modified urea-formaldehyde resin (MUF). The MUF was calculated using Kissinger equation and Flynn-Wall-Ozawa equation Resin pyrolysis activation energy. The results showed that the curing time of low mole was longer than that of MUF resin (muf-b), the content of free formaldehyde was lower, and the formaldehyde emission and wet bonding strength of plywood were reduced by 65.79% and 21.90%, respectively. TG test showed that the pyrolysis process of MUF resins with different molar ratios can be divided into three stages: dehydration, rapid pyrolysis and carbonization. At the same heating rate, the weight loss rate, peak conversion rate and carbon residue of the high molar ratio MUF resin (MUF-a) in the fast pyrolysis stage are larger than those of the MUF-b resin. The MUF-a resin pyrolysis activation energy is 166.76 kJ/mol, and the MUF-b resin pyrolysis activation energy is 95.30 kJ/mol. High molar ratio resin has higher pyrolysis activation energy and better thermal stability.

Effect of various compounding methods on acid red 18050- melamine modified urea formaldehyde resin compound as wood modifier

In order to simultaneously improve the strength and decoration properties of plantation wood, a multi-effect modifier was prepared by compounding acid red 18050(G) with melamine-modified urea formaldehyde resin (MUF). Various compounding methods for MUF synthesis such as adding dye with the first part urea (U1G) or with the second part urea (U2G), or direct blending with MUF resin (BG) were tested. Chinese fir plantation wood was impregnated with these modifiers separately, and its color, color fastness, and dyeing mechanism were studied. The results showed that G had good compatibility with MUF and could prolong its storage time, and all compound modifiers exhibited permeability and coloring effect on Chinese fir wood. Compared with G-dyed wood under the same conditions, all the compound dyed wood had better color fastness to water, and the U2G-dyed was the best, the color fastness to xenon light of U2G dyed wood was greatly improved.. Fourier transform infra-red (FTIR) analysis showed that compared with MUF-modified wood, the dye affected MUF hydroxyl-methylation reaction in U1G, lowered the polycondensation degree, and extended its storage time. The dye might have promoted the ionic reaction between resin amino and dye sulfonic groups in U2G, thus displaying better color fastness.

The flammability of expandable polystyrene foams coated with melamine modified urea formaldehyde resin

ABSTRACTUrea formaldehyde resin (UF) was modified by introducing melamine during the condensation in order to reduce the amount of free formaldehyde and increase the solid content. The melamine modified UF (MUF) was firstly mixed with intumescent flame retardant (IFR) and then coated on the surface of pre‐expanded polystyrene (PS) particles to prepare flame retardant expandable PS (EPS) foams. The flammability of EPS foam samples was characterized by limiting oxygen index (LOI), UL‐94 vertical burning and cone calorimeter tests, and the results indicated that the peak heat release rate was significantly reduced from 406 to 49 kW/m2 and LOI value could reach 36.3 with V‐0 rating in UL‐94 test after coated with IFR. The smoke density test indicated that the maximum smoke density was decreased by the addition of IFR. Thermal analysis suggested that the thermal stability and char formation were significantly improved by the presence of coated flame retardants. The residual char observation revealed that MUF and IFR were beneficial to form integrated char layers with hollow stents, which could be the main reason for the improvement of flame retardant properties. The mechanical properties of flame retardant EPS foams can still meet the standard requirements for industrial applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44423.

Dual Protection of Wood Surface Treated with Melamine-Modified Urea-Formaldehyde Resin Mixed with Ammonium Polyphosphate against Both Fire and Decay

Abstract Surface coatings of melamine-modified urea-formaldehyde resins (MUFs) containing ammonium polyphosphate (APP) have been shown to significantly improve the fire retardancy of wood by prolon...

Assessment of lowering formaldehyde release of particleboards using urea as a scavenger by chamber, perforator and flask method

Addition of urea to a melamine modified urea formaldehyde resin in the surface and core layer reduces significantly the formaldehyde release of the particleboards bonded therewith. Under the used boundary conditions (long press time) urea addition seems to have no noticeable negative impact on the physical–mechanical properties of the boards. The reduction of formaldehyde release due to urea addition as a scavenger can be followed by measuring the emission in the chamber according to EN 717-1, the perforator method according to EN 120 and the flask method as described in EN 717-3. The results reveal that under the used conditions a good correlation exists between the emission in the chamber and the corrected perforator values (R2 = 0·865), as well as between the chamber value and the formaldehyde emission measured by the 3h-flask method (R2 = 0·792) according to EN 717-3, a slightly better correlation was found between the measured flask values after 24 h and the emission in the chamber (R2 = 0·869). The correlations seem to hold in the emission range between 0·06 and 0·016 ppm.

The fire-retardant properties of the melamine-modified urea–formaldehyde resins mixed with ammonium polyphosphate

Fire retardancy of melamine-modified urea–formaldehyde resin (MUF) containing intumescent fire-retardant ammonium polyphosphate (APP) (MUF/APP) was conducted by cone calorimeter with surface treatment of medium density fiberboard (MDF). The results showed that the six MUF resins synthesized with different F/(M + U) and M/U molar ratios containing APP significantly improved the fire retardancy of the MDF by prolonging ignition time, reducing heat release rate and total heat release, and decreasing mass loss rate. The fire-retardant properties of the six synthesized MUF/APP acted differently even though each MUF resin containing the same mass ratio of APP. The melamine content in the MUF should not be too high, otherwise it would decrease the fire-retardant properties of MUF/APP. Based on this study, the higher the APP amounts, the better the fire-retardant performance of the resin was. The fire retardancy of MUF/APP increased with the increase in the amount of glue that spread on the material surface. However, only the amount of glue spread exceeded 250 g/m2, whereas the ability of MUF/APP in inhibiting heat release did not increase significantly any longer.

Preparation and Characterization of Melamine Modified Urea-Formaldehyde Foam

Abstract Melamine-urea-formaldehyde (MUF) foam was prepared using melamine modified urea formaldehyde resin. The effects of blowing agent, curing agent and surfactant on the properties of MUF foam such as apparent densities, compression strength, microstructure, fragility, limited oxygen index, thermal conductivity and formaldehyde emission were investigated. The best performance of MUF was obtained as the composition of blowing agent, curing agent and surfactant were 2.5%, 18% and 12% respectively. The water resistance of MUF foam, contents of foam's burning gas, curing mechanism and physical properties were also studied by Contact angle analyzer, TGA-FT-IR, FT-IR and 13C NMR.

Effect of Melamine Content in MUF Resin on the Durable Properties of Plywood

The effect of melamine content in melamine modified urea formaldehyde (MUF) resin on durable properties of plywood was investigated using ammonium chloride (NH4Cl) with different melamine/urea (M/U) ratios. The plywood specimens were exposed to laboratory accelerated aging and/or cyclic soak-dry (SD). The experiment results indicated that the melamine contents in MUF resin showed an unobservable effect on the durable properties of MUF resin bonded plywood. The mechanical properties of plywood decreased more severely after accelerated aging test in acidic condition. However, the influence of different curing catalyst contents on mechanical properties and formaldehyde emission of UF resin can be minimized by adding melamine to the resin.

Catalytic influence of wood on the hardening behavior of formaldehyde-based resin adhesives used for wood-based panels

The aim of this work was to monitor the hardening behavior of two different ureaformaldehyde (UF) resins and to investigate the possible catalytic effect of cold water extractives of different wood species on the hardening characteristic. A pure UF resin and a melamine-modified UF resin were used for this investigation. For the experiments, ammonium chloride, ammonium sulphate, acetic acid and oxalic acid at different addition levels were used as hardeners. The gel times determined at three temperatures, the pH drop of the resins after the hardener addition, the buffering behavior and changes in the complex viscosity η * with time, as well as the development of the bond strength were chosen as parameters for characterizing the systems both with and without wood extractives. As expected, the buffering capacity of the melamine fortified resin was found to be much greater than for the pure UF resin. The gel times of the investigated resins were strongly dependent on the applied temperature, decreasing steeply at higher temperatures. Based on these data the apparent activation energies for various hardener additions have been calculated. The complex viscosity and the development of the internal bond strength indicated that cold water wood extractives had little or no effect on the curing progress of the resins.

Thermal analysis study of viscoelastic properties and activation energy of melamine-modified urea-formaldehyde resins

The objective of this research was to investigate the activation energy and viscoelastic properties of urea-formaldehyde (UF) resin, melamine-formaldehyde (MF) resin and UF-MF resin mixtures by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The purpose of adding MF resin to the UF resin was to reduce the formaldehyde emission. As the MF resin content was increased in the UF-MF resin mixture, the formaldehyde emission decreased. The storage modulus (E′), loss modulus (E″) and loss factor (tan δ) of each resin were measured by DMTA. With increasing temperature, as the resin cured, the storage modulus (E′) increased in all resin systems. The storage modulus (E′) increased both as a function of increasing temperature and with increasing MF content. The activation energies (E a) of the curing reactions of the UF and MF resins alone, as well as the mixed resins, on different substrates, were calculated on the basis of the variation of the temperature of the maximum of each DSC scan exotherm using the Kissinger equation. The E a value of the UF resin decreased as the MF resin content ratio increased, and because of this lower activation energy the UF-MF resins cured faster than the UF resin. Formaldehyde is incorporated more easily and completely into melamine than into urea. The results showed that MF resin reacts with formaldehyde faster than UF resin because of its high −NH content.