Methylated Melamine Formaldehyde Research Articles

Thermal energy regulated and thermochromic composite film with temperature-sensitive “breathable” stomata

Intelligent breathable membranes with multiple functions attach wide attentions of people which provide protection and comfort to meet the pressing demand for future protective clothing. We proposed a novel thermal energy regulated and thermochromic composite film with temperature-sensitive “breathable” stomata consisted of thermochromic nanofibrous membrane (TC-NFM) and thermo-sensitive polyurethane (PU) film. Thermochromic nanoencapsulated phase change materials (TC-NPCMs) were introduced as functional fillers into polyvinyl alcohol/water-soluble polyurethane (PVA/WPU) solution for electrospinning process. And methylated melamine–formaldehyde (MMF) was innovatively used to modify the water resistance of TC-NFM. By adjusting the molecular weight of the soft segment, the thermo-sensitive PU film was successfully prepared. Consequently, the prepared TC-NFM exhibited high enthalpy of 44.3 J g−1 and kept superior energy storage and release property even after 100th cyclic experiments. The water vapor permeability of thermo-sensitive PU film was triggered near the comfortable temperature of the human body. The results presented here might facilitate improvements in the field of thermal regulation clothing, intelligent clothing, wearable temperature sensor and reversible thermochromic coating materials.

The effect of melamine formaldehyde impregnation and hot-pressing parameters on the density profile of densified poplar wood

The vertical density profile (VDP) of thermo-hydro-mechanically (THM) densified wood is a result of the combined effect of process parameters and properties of unmodified wood. The effect of thermosetting resins on VDP of THM densified wood has not been extensively studied. The aim of this study was to determine the combined effect of methylated melamine–formaldehyde (MF) resin impregnation along with thermal compression at 150 °C on the VDP of poplar wood acquired by X-ray densitometry. Four different stress levels were applied: 0, 10, 20 and 30 kg/cm2. Control specimens (without MF) were also impregnated and densified under the same conditions. The results showed that the use of MF increased the density compared to control specimens for the respective CR level. The increase in CR resulted in a linear decrease in WPG values as a result of the MF loss during pressing. Due to the bulking effect of cell walls, thermal compression resulted in higher CR for control than for MF-treated specimens. In the case of uncompressed specimens, MF-treated specimens showed slight density peaks near the surfaces probably due to migration of MF solution from the core to the heated surfaces of the specimens. MF-impregnated specimens generally showed a more uniform density profile since the differences between maximum density and minimum density were smaller than the control ones. Peak width did not seem to be affected by CR for MF-treated specimens. Maximum density was not formed in the outer surface of the specimens but was measured in deeper regions as CR increased. This trend was clearer for control specimens than for MF-impregnated ones.

The influence of curing conditions on properties of melamine modified wood

The curing conditions influence the material properties of wood modified with methylated melamine formaldehyde resin. To identify the most influential parameters, the process conditions were varied separately. The degree of conversion (differential scanning calorimetry; DSC), work in bending, nitrogen fixation, formaldehyde emission, formaldehyde content and content of free formaldehyde were measured to verify the influence of the curing conditions on the material properties. The temperature and duration positively influenced the curing of melamine resin as the DSC results and the nitrogen fixation indicate. However, the relative humidity (RH) had the greatest influence on the material properties: the formaldehyde properties and the work in bending differed most between dry and high RH processes with the latter producing material being less brittle and having lower formaldehyde emissions. It can be derived that DSC measurements, formaldehyde emission and -content are valuable methods to characterize the influence of curing conditions on the material properties. The formaldehyde content in combination with the emission revealed a different formaldehyde release factor for dry and high RH processes. In the future, the curing process conditions can be designed depending on the desired material properties: dry, high temperature processes will lead to more complete curing, whereas hot steam processes can be used for material with low formaldehyde emissions.

Hardness and indentation modulus of resin-treated wood

This study assesses the potential of instrumented macrohardness testing for the fast and convenient characterisation of resin-treated wood. The effect of WPG (weight per cent gain; percentage mass of resin based on dry wood; high, low) and curing conditions (dry, wet) on hardness and indentation modulus of Scots pine (Pinus sylvestris L.) sapwood was investigated for two thermosetting resins, phenol formaldehyde and methylated melamine formaldehyde. Thickness of the treated specimens broadly confirmed the findings of earlier studies that dry curing conditions increase degree of cell wall penetration. Dry curing resulted in equal or lower hardness, but it mostly increased indentation modulus. Hardness improvement seems to depend on the overall reduction of the void volume fraction in the wood, while indentation modulus depends on cell wall modification. Therefore, indentation modulus is expected to show a much better correlation with dimensional stability and durability of resin-treated wood than hardness.

Impact of the Mixture of Hexa(N-hydroxymethyl)amidocyclotriphosphazene and Partially Methylated Melamine Formaldehyde Resin on the Flame Retardancy of Paper

Impact of the Mixture of Hexa(N-hydroxymethyl)amidocyclotriphosphazene and Partially Methylated Melamine Formaldehyde Resin on the Flame Retardancy of Paper

Resistance of modified wood to marine borers

The resistance of differently modified wood to the common shipworm, Teredo navalis, and the wood boring crustacean, Limnoria quadripunctata, was assessed in a field trial and by means of a short term laboratory assay, respectively. Scots pine (Pinus sylvestris) sapwood was treated with TEOS (tetra-ethoxy-ortho-silane) and different thermosetting resins, namely phenol formaldehyde (PF) and methylated melamine formaldehyde (MMF). Additionally, acetylated and untreated Radiata pine (Pinus radiata) was included. In the field trial according to EN 275 in the Baltic Sea over a period of six years the specimens were exclusively attacked by T. navalis. For the laboratory assay, matchstick-sized samples cut from spare panels prepared for the field trial were subjected to individuals of L. quadripunctata; faecal pellet production served as a measure of feeding rate. Treatments that prevented shipworm attack in the field also reduced feeding of L. quadripunctata in the laboratory assay: efficacy of resin treatments was enhanced by parameters that increase the amount of resin in the cell wall (i.e. high WPG and dry curing conditions); acetylation resulted in high resistance; and TEOS treatment was not effective. The results suggest that modification on cell wall level is required to impart marine borer resistance.

Interface-driven phase-separated coatings

A homogeneous mixture of two polymers dissolved in a common solvent or a mixture of solvents was applied as a thin film. The first component was a bisphenol-A based epoxide derivative modified with tetraethoxysilane (TEOS) oligomer and the second component was a high-solids fluorinated acrylic copolymer. The thin films were coated on steel substrates and were thermally crosslinked using a methylated melamine formaldehyde and/or a polyamide-amine curing agent. The films were evaluated via x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) with integrated energy dispersive spectroscopy (EDS). It was found that the molecular weight of the resins, fluorine content, epoxide inorganic modification, and curing agent affected the degree of stratification.

The influence of curing conditions on the chemical distribution in wood modified with thermosetting resins

Scots pine (Pinus sylvestris L.) sapwood was impregnated with aqueous solutions of phenol formaldehyde and methylated melamine formaldehyde resins and subsequently cured in an oven. One set of specimens was cured in plastic bags to avoid drying (wet curing) while another set of samples was heated and water was allowed to freely evaporate (dry curing). Macroscopic resin distribution was investigated using X-ray densitometry and infrared spectroscopy (FTIR-ATR). During dry curing, the resins migrated to the wood surface resulting in a gradient. Wet curing resulted in even distribution of the resins because it was immobilized due to condensation and precipitation in the wood. Neither densitometry nor FTIR-ATR was found to be generally applicable for investigating resin distribution in modified wood. Wet curing resulted in low cell wall bulking as compared to dry curing, probably because resin precipitated before drying. Storing impregnated wood prior to curing under non-drying conditions (“diffusion phase”) also reduced cell wall penetration and bulking.

Acrylate-based fluorinated copolymers for high-solids coatings

A series of low, medium, and high molecular weight copolymers containing methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl methacrylate, and 2,2,2-trifluoroethyl methacrylate were synthesized by solution polymerization under monomer-starved conditions. The acrylate-based copolymers were characterized by FTIR; 1H, 13C, and 19F NMR, and MALDI-TOF mass spectrometry. The molecular weights and the glass transition temperatures of the copolymers were determined using Gel Permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). The copolymers were crosslinked with a methylated melamine formaldehyde resin in order to obtain thermosetting acrylics. Surface, optical, barrier, mechanical, and viscoelastic properties of the acrylic coatings were investigated. An enrichment of fluorinated units at the acrylic surface was directly verified measuring dynamic contact angles. Lower wettability, higher oxygen permeability, and lower refractive index were observed for higher concentrations of fluorinated monomer in the copolymer composition. High number-average hydroxyl functionality of high molecular weight copolymers increased the crosslink density of the acrylic films, resulting in improved tensile strength and tensile modulus.

Curing behavior of anionic poly(urethane urea) dispersions crosslinked with partially methylated melamine formaldehyde

AbstractA rigid‐body pendulum rheometer was used to observe the isothermal cure behavior of an anionic poly(urethane urea) dispersion crosslinked with different amounts of partially methylated melamine formaldehyde (PMMF). In this experiment, the anionic poly(urethane urea) dispersion had a large number of >NH crosslinking or branching sites in urethane and urea groups per molecule, which allowed a large amount of PMMF to couple with the elastic polyurethane (PU) backbone. The test results showed that the cure response of the PU dispersion crosslinked with PMMF was a function of the concentration of PMMF and indicated that 30 phr PMMF could be the optimum amount of the crosslinking agent and that 120°C was the optimum temperature for the curing process. In addition, PMMF self‐condensation could take place during the curing process. The self‐condensation of PMMF also was monitored by a thermogravimetric method. Moreover, the dynamic mechanical properties of PMMF‐crosslinked PU films were affected by the concentration of PMMF. From the curing behavior and dynamic mechanical analysis test results, it was reasonable to assume that highly PMMF branched PUs with partial crosslinking structures could be formed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Structure–property relationships of anionic poly(urethane–urea) dispersion cross-linked with partially methylated melamine formaldehyde

An anionic poly(urethane–urea) dispersion (PUD) was cross-linked with different amount of partially methylated melamine formaldehyde (PMMF). The isothermal curing behavior was observed by a rigid-body pendulum rheometer. The test results showed that cure response of PUD cross-linked with PMMF was a function of the concentration of PMMF. Also, PMMF self-condensation could take place during the curing process. In this experiment, the anionic poly(urethane–urea) dispersion has a large number of >N–H cross-linking or branching sites in urethane and urea groups per molecule that allow a large number of PMMF to couple into elastic PUD backbone to form branched structure with partial cross-linking. The dynamic mechanical properties of PUD cross-linked with PMMF were affected by the concentration of PMMF. It was further shown that the tensile properties were strongly influenced by the concentration of PMMF and curing temperature.

Material properties and their interrelation in chemically modified clear wood of Scots pine

Abstract The mechanical and physical properties of modified wood were assessed experimentally. Timber studs with a cross-section of 45 mm×70 mm were modified on a semi-industrial scale by four different methods: 1) acetylation (AC) with acetic anhydride; 2) modification with methylated melamine formaldehyde resin (MMF); 3) heat treatment in vegetable oil (HT); and 4) furfurylation (FA). Sapwood of Scots pine (Pinus sylvestris) with test specimen dimensions of 10×10×200 mm3 was investigated. A total of 2449 specimens were included in the study. The following properties and their correlations were studied: density, modulus of elasticity (MOEdyn) measured dynamically, equilibrium moisture content (EMC), and swelling behaviour. The properties were measured at humidity levels of 30%, 65%, and 90% RH, while the temperature was kept constant at 23°C. Significant changes in material properties took place. AC increased the density and reduced MOEdyn, EMC and swelling strain. FA increased the density and the swelling coefficient and reduced EMC and swelling strain. HT reduced the EMC, while MMF modification increased it.

Experimental study of material properties of modified Scots pine

The mechanical and physical properties of modified timber were assessed by experimental work. The timber was modified using three different methods: acetylation with acetic anhydride, modification with methylated melamine formaldehyde resin and heat treatment in an oil bath. The wood material was sapwood of Scots pine (Pinus sylvestris) with dimensions of 45×70×1100 mm. A total of 99 specimens were included in this study. The following properties and their inter-relations were studied: density, modulus of elasticity (MOE), bending creep deflection and relative creep. It was found that all the modifications successfully reduced the relative creep. However, the performance properties of modified timber ought not to be calculated on the basis of density, as is the case for untreated wood. On the other hand, the long-term performance of modified timber can be assessed by its initial MOE and the difference in equilibrium moisture content (EMC) between two climates.

Differently modified wood: comparison of some selected properties

To turn wood into a material with enhanced and less varied properties, many methods of chemical modification have been developed in the past few decades. In this work, the mechanical and physical properties of wood modified using nine methods were studied. The modification methods were acetylation, maleoylation, succinylation, furfurylation, modification with N-methylol acryl amide, modification with reactive linseed oil derivative, modification with methylated melamine resin, thermal modification in vegetable oil, and a combination of acetylation and modification with methylated melamine resin. The wood species used were Scots pine (Pinus sylvestris L.), beech (Fagus sylvatica L.) and birch (Betula pubescens Ehrh.). Both pure sapwood and heartwood specimens of pine were used. The following properties were studied: equilibrium moisture content, strength and stiffness in different climates, stiffness stabilization efficiency, antiswelling efficiency, impact bending strength and hardness. Acetylation and furfurylation were the most effective modification methods for achieving high dimensional stability, high stiffness stability and low equilibrium moisture content. The impact strength was reduced by all the methods, but to a varying extent. Acetylation, furfurylation and modification with methylated melamine formaldehyde resin led to a slight increase in bending strength. Furfurylation at high degrees of modification resulted in a substantial increase in hardness.

Influence of the formaldehyde content of waterbased melamine formaldehyde resins on physical properties of Scots pine impregnated therewith

This paper presents a systematical approach to the properties of wood impregnated with different waterbased melamine resins, to provide a basis for further research. Therefore, ten commercially available methylated melamine formaldehyde resins with increasing ratios of melamine to formaldehyde have been compared in respect of their influence in dimension stabilisation, sorption behaviour, formaldehyde emissions, and water repellency of the treated wood. The dimension stabilisation caused by resin molecules that penetrated the wooden cell wall correlated with the molar mass of the resins used for impregnation. The changes in the sorption isotherms were attributed to a bulking effect. Formaldehyde emissions during and after curing increased with an increasing ratio of formaldehyde to melamine in the resins.

Effects of composition variations and curing conditions on the gloss of water reducible clear coatings prepared from palm stearin alkyds

Water-based clear stoving coating materials could be prepared by mixing the water-reducible palm stearin alkyds with a commercial methylated melamine formaldehyde in ratios ranging from 1 to 9. TGA analysis could be used to estimate the solid content of each of the coatings, as well as the curing temperature that could be used to prevent thermal degradation. Gloss of the coating after cure is affected by the oil length, alkyd/melamine ratio and curing temperature, for the same curing duration. For each alkyd, monitoring the changes in gloss due to variation of alkyd/melamine ratio and curing temperature could be useful for designing the formulation to give the desired gloss.

Convenient determination of methoxy groups of methylated melamine-formaldehyde resins by IR spectroscopy

The content of methoxy groups of methylated melamine-formaldehyde resins was determined by infrared spectroscopy. The correlation between the area ratio (S) of 815 cm−1 band to 913 cm−1 band, which are the characteristic absorption bands of triazine and methoxy residue, respectively, and methoxy groups values (OMe) determined by gas liquid chromatography analysis was expressed as S = 1.08 × OMe + 0.24. The correlation coefficient was found to be 0.997.

Melamine–formaldehyde resins: Constitutional characterization by fourier transform 13C‐NMR spectroscopy

AbstractThe random chemical structures of melamine–formaldehyde resins, including methylated melamine–formaldehyde resins and urea–melamine formaldehyde resins, were investigated by 13C‐NMR spectroscopy (Fourier transform). All the combined formaldehydes, methylol and methyl ether groups, methylene structures, and dimethylene ether structures were assigned. A 13C chemical shift of methylene carbon occurred by substitution of other constituents of the methylene group for a proton of the adjacent monosubstituted nitrogen atom, as shown in a 13C‐NMR spectrum of urea–formaldehyde resins. It was found that the chemical shift of each corresponding carbon of both melamine resins and urea–melamine resins was almost superimposed with that of urea resins.