New melamine–formaldehyde–ketone polymers. III. Coatings from melamine and reactive solvents based on cyclohexanone

The conditions and methods of preparing novel melamine–formaldehyde–cyclohexanone coatings are presented. The coatings were prepared by dissolving melamine in reactive solvents based on formaldehyde and cyclohexanone. The latter were prepared at different molar ratios of the components. The water resistance of the resulting coatings was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1083–1092, 2006     

New melamine–formaldehyde–ketone polymers. II. Dissolution of melamine in reactive solvents prepared from cyclohexanone

Reactive solvents of melamine were prepared from cyclohexanone and excess of formaldehyde in the presence of triethylamine catalyst. The solubility of melamine in the solvents was evaluated and the mechanism of dissolution explained on the basis of ¹H‐NMR and IR spectroscopy. Attempts to cure the melamine solutions resulted in melamine–formaldehyde–cyclohexanone polymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 77–85, 2005     

Colloidal aggregation of aminoplastic polycondensation resins: Urea–formaldehyde versus melamine–formaldehyde and melamine–urea–formaldehyde resins

Colloidal particles formation followed by their clustering have been shown to be the normal way of ageing of aminoplastic resins, namely urea–formaldehyde (UF) resins, melamine–formaldehyde (MF) resins, and melamine–urea–formaldehyde (MUF) resins. Ageing or further advancement of the resin by other means such as longer condensation times causes whitening of the resin. This is a macroscopic indication of both the formation of colloidal particles and of their clustering. It eventually progresses to resins, which are mostly in colloidal, clustered state, followed much later on by a supercluster formation starting to involve the whole resin. The initial, filament‐like colloidal aggregates formed by UF resins have different appearance than the globular ones formed by MF resins. MUF resins present a short rod‐like appearance hybrid between the two. GPC has been shown to detect the existence of colloidal superaggregates in a UF resin, while smaller aggregates might not be detected at all. The star‐like structures visible in the colloidal globules of MF resins are likely to be light interference patterns of the early colloidal structures in the resins. These star‐like interference patterns become more complex with resin ageing or advancement due to the advancement of the resin to more complex aggregates, to eventually reach the stage in which filament‐like and rod‐like structures start to appear. The next step is formation of globular masses that are representative of the true start of physical gelation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1406–1412, 2006     

New melamine–formaldehyde–ketone polymers. IV. Dissolution of melamine in reactive solvents prepared from methyl ethyl ketone

Reactive solvents of melamine were prepared from methyl ethyl ketone and formaldehyde in the presence of the catalyst triethylamine. The solubility of melamine in the resulting solvents was determined, and the mechanism of dissolution was explained with ¹H‐NMR and IR spectroscopy. Preliminary experiments aimed at curing the melamine solutions in reactive solvents into melamine–formaldehyde–butanone resins are reported. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1496–1505, 2006     

Separation and recovery of gold(III) from base metal ions using melamine–formaldehyde–thiourea chelating resin

Melamine–formaldehyde–thiourea (MFT) chelating resin has been prepared. Au³⁺ ions uptake behavior and selectivity of the chelating resin were investigated by both batch and column methods. MFT resin showed higher affinity toward Au³⁺ compared with base metal ions, Cu²⁺ and Zn²⁺. The highest Au³⁺ uptake values were obtained at pH 2 and Au³⁺ adsorption capacity of the resin was calculated as 48 mg Au³⁺/g resin (0.246 mmol Au³⁺/g resin) by batch method. It was concluded that Au³⁺ ions could be selectively concentrated from the solution including Cu²⁺ and Zn²⁺ base metal ions by column method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New melamine–formaldehyde–ketone resins. VI. Preparation of filled molding compositions and compression‐molding materials from reactive solvents based on cyclohexanone

The conditions and a method of preparing new molding compositions and filled compression‐molding materials from melamine–formaldehyde–cyclohexanone resins are described. The resins were obtained from melamine solutions in a reactive solvent prepared by the reaction of 1 mol of cyclohexanone with 7 mol of formaldehyde. The fillers were wood powder and sulfite cellulose. The thermal properties of the samples prepared from the compositions were studied with dynamic thermal analysis, thermogravimetry, and differential scanning calorimetry analysis. Selected mechanical properties [Brinell hardness, unnotched impact strength (Charpy method), and bending strength] of the cured resins were also measured. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Syntheses and properties of low‐level melamine‐modified urea–melamine–formaldehyde resins

Syntheses of urea–melamine–formaldehyde (UMF) resins were studied using 2–12% melamine levels and UF base resins that were preadvanced to various different extents. The melamine reaction was carried out at pH 6.3 with F/(U + M) mole ratio of 2.1 until a target viscosity of V was reached (Gardener–Holdt) and then the second urea added at pH 8.0 to give a final F/(U + M) mole ratio of 1.15. Analyses with ¹³C‐NMR and viscosity measurements showed that MF components react fast and the UF components very slowly in the melamine reaction. Therefore, as the extent of preadvancement of UF base resin was decreased, the reaction time to reach the target viscosity became longer and the MF resin components showed high degrees of polymerization. The overpolymerization of MF components resulted in increasingly more opaque resins, with viscosity remaining stable for more than a month. As the preadvancement of UF base resin was increased, the extent of advancement of MF components decreased, to give clearer resins, with viscosity slowly increasing at room temperature. Overall, preadvancing the UF base resin components to an appropriate extent was found to be a key to synthesizing various low‐level melamine‐modified UMF resins. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2559–2569, 2004     

Polypropylene–phenol formaldehyde‐based compatibilizers. I. Preparation and characterization

This work deals with the synthesis of a new type of compatibilizer suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complimentary to hydroxyl. Polypropylene–phenol formaldehyde graft copolymers from thermoplastic phenol formaldehyde (PF) resins and functionalized polypropylene (f‐PP) were synthesized by reactive extrusion. The content of PF in the graft copolymer was determined by reaction variables like type and density of functionality on PP, molecular weight of PF, and viscosity ratio of f‐PP and PF. The results showed that the viscosity ratio is of primary importance for such reactive processing. Also, type and concentration of the functional groups were important variables. The glycidyl methacrylate functionality resulted in higher conversions than did PP‐g‐maleic anhydride within the available reaction times. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 347–354, 2000     

Physicochemical and thermal properties of phenol–formaldehyde‐modified polyphenol impregnate

Tannin, a natural polymer belonging to the polyphenolic group of compounds, is widely used in the leather industry, specifically as a tanning agent for the conversion of putrescible collagen fibers into leather matrix during the leather‐manufacturing process. Unspent tannin poses a serious environmental threat to the public because it has a very high half‐life, leading to groundwater pollution when discharged into soil. Attempts have been made to separate tannins through chemical means and recovered tannin needs to be encapsulated for its safe disposal. In the present study the recovered tannin was impregnated in phenol–formaldehyde (PF) resin. Spectroscopic and thermogravimetric (IR, NMR, TGA and DSC) studies revealed that the modified polyphenol was held physically in the impregnate. The impregnated matrix showed resistance to mineral acids, strong alkalis and organic solvents and was tested for its adhesive property on leather sheets. The leather that bonded with PF‐modified polyphenol impregnate (PFT) had a 27% increase in peel strength and a 40% increase in lap shear strength as compared to the sample bonded with PF resin. The corrosive resistance result of the PFT resin shows it has potential application as an anticorrosive paint in the paint industry. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1567–1571, 2001     

Preparation,characterization, and composites from low formaldehyde emission urea–formaldehyde–casein copolymer

A modified urea–formaldehyde resin was synthesized by the condensation of urea and formaldehyde in the presence of varying proportions of casein up to 25% (w/w) of urea under alkaline conditions. All the prepared resins were characterized by free‐formaldehyde content, viscosity measurements, and number‐average molecular weight determination by vapor pressure osmometry and IR spectroscopy. Their curing kinetics were studied isothermally and by differential scanning calorimetry on dynamic runs. The resin samples were cured isothermally at 60, 80, and 100°C using ammonium chloride and hydroxylamine hydrochloride as curing agents. The isothermal curing study was also performed with hexamine at 120°C. Cured resins were characterized by IR and thermogravimetric analysis. The resin samples were employed for the fabrication of glass fiber and jute fiber reinforced composites by maintaining 2 : 3 and 3 : 2 proportions of resin/reinforcement, respectively. The prepared composites were tested for their mechanical properties and resistance toward various chemicals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 531–537, 2005     

Synthesis and molecular weight characterization of rubber seed oil‐modified alkyd resins

Alkyd resins of 40% (I), 50% (II), and 60% (III) oil length (OL) were prepared with rubber seed oil (RSO), phthalic anhydride (PA), and glycerol (GLY), employing the two‐stage alcoholysis method. Changes in the physical characteristics of the reaction medium were monitored by determination of the acid value and the number‐average molecular weight, M_n , of in‐process samples withdrawn at different stages of the reaction. The mode of variation of these properties denotes that the preparation of RSO alkyds is complex. Molecular weight averages and the molecular weight distribution (MWD) of the finished alkyds were determined by GPC, cryoscopy, and end‐group analysis. Molecular weight averages and the MWD vary with differences in the formulation, with sample II exhibiting the narrowest size distribution. Values of M_n with the corresponding polydispersities in brackets are 3234 (1.91), 1379 (1.56), and 3304 (2.56) for samples I, II, and III respectively. M_n values obtained by cryoscopy are comparable to those obtained by gel permeation chromatography (GPC), while end‐group analysis seems to grossly overestimate their molecular weights. Correlation of M_n and the MWD with the quality of the finished alkyds shows that the narrower the size distribution the better the quality of the alkyd. Properties such as the rate of drying and resistance of the alkyds are optimum at 50% OL. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2431–2438, 2001     

Intrinsic viscosity–molecular weight relationship and hydrodynamic volume for pullulan

A numerical method for determination of Mark–Houwink–Sakurada (MHS) equation constants, a and K, was tested with success for two series of pullulan standard samples having narrow and broad molecular weight distributions (MWD) and taken into account their polydispersity. Different solvents, which were used to determine the intrinsic viscosities and the viscometric constants, a and K (published in the literature for pullulan), were compared. The various parameters affecting the constants are discussed. The procedure to determine the correct value of the hydrodynamic volume for pullulan was also described. This study resulted in the following MHS equations for narrow and broad MWD series of pullulan samples with M_w in the range of 5–1000 kDa: where q_MHS is the polydispersity correction factor and [η] is the intrinsic viscosity in dL g^?1. The plot of log K versus exponent a was linear and inversely related. This curve was used to estimate the constant K for pullulan with a known exponent a. Among various reported solvents, the diluted aqueous salt solutions have more advantages than other solvents. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4325–4332, 2006     

Preparation and characterization of poly(methyl methacrylate) grafted sago starch using potassium persulfate as redox initiator

In this article, the graft copolymerization of methyl methacrylate (MMA) onto sago starch (AGU) was carried out in aqueous medium using potassium persulfate (PPS) under nitrogen gas atmosphere. The maximum percentage of grafting achieved was 90% under optimized conditions of reaction temperature, monomer, PPS, AGU, and reaction period corresponding to 50°C, 47 mmol, 1.82 mmol, 6.17 × 10^?3 mol L^?1, and 1.5 h, respectively. The grafting of MMA onto sago starch was confirmed by the differences in infrared spectroscopy. The viscosity measurement and the average molecular weight determination were estimated using Huggin's and Mark Houwink's equations, respectively. This material may have application as a biodegradable plastic. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1891–1897, 2004     

Stability and spinnability of modified melamine–formaldehyde resin solution for centrifugal spinning

Melamine microfibers were first prepared by centrifugal spinning. The stability and spinnability of a melamine–formaldehyde (MF) resin solution were improved as expected by adding various modifier combinations. Considering the storage stability of solutions characterized by visual inspection, turbidity tests, and viscosity measurements and combined with the fiber morphology, the optimal modifier combination was obtained. The spun fibers manifested a good morphology and thermal stability as measured by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Moreover, microfibers prepared by three spinning methods (centrifugal spinning, electrospinning, and centrifugal electrostatic spinning) were compared to choose the suitable spinning method for different fields in the future. This work provides systematic and scientific guidance on the synthesis of MF resin solutions and rapid mass production of melamine microfibers and also demonstrates that centrifugal spinning of melamine microfiber is a promising candidate for flame retardance and CO₂ adsorption at elevated temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46072.     

Tannins/melamine–urea–formaldehyde (MUF) resins substitution of chrome in leather and its characterization by thermomechanical analysis

A new sulfonated melamine–urea–formaldehyde (MUF) resin of relatively low melamine content, prepared according to a sequential formulation, has been shown to be highly effective when coupled with different natural vegetable tannins to produce leather with the same good characteristics of leather prepared with chrome salts. In particular, the antishrinkage effectiveness of the leather prepared according to the new approach is comparable to that obtained with chrome tanned leathers. The comparison of the traditional leather shrinkage temperatures test method with a new thermomechanical analysis (TMA) test method in tension yields thermograms presenting three major modulus of elasticity (MOE) peaks. These are closely connected to molecular level phenomena determining the shrinkage temperature of leather. The three determining parameters appear to be as follows: (1) The average value of the temperatures at which the three MOE peaks occur: the higher the value of this average, the lower is the shrinkage of leather. (2) The average of maximum MOE values of the TMA peaks: the higher this average is, the better is the leather in regard to antishrinkage effectiveness. This means the leather maximum MOE at each peak is a measure of the resistance to the contraction force induced by heat. (3) The relative intensity of the first TMA peak in relation to the second: the higher the value of the MOE for the first TMA peak is in relation to the second peak, the lower the leather shrinkage appears to be. However, it has not been possible to better define or quantify this latter effect. This new TMA test method in tension has also yielded a mathematical relationship correlating the thermogram peak temperatures and MOE averages with the traditional shrinkage temperature to a high degree of confidence. A previous TMA test method, in compression, has proven to yield more problematic and finally not very reliable results when one needs to apply it to a wide variety of different cases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1889–1903, 2003     

Examination of selected synthesis parameters for typical wood adhesive‐type urea–formaldehyde resins by 13C‐NMR spectroscopy. II

A particleboard adhesive‐type urea–formaldehyde (UF) resin was made at a formaldehyde ratio of 2.10 and added with a second urea at low temperature to the typical final formaldehyde/urea ratio of 1.15. Time samples taken during heat treatments of the resin sample up to 70°C over a period of 250 min showed decreases in Type II/IIi hydroxymethyl group content, accompanied with decreases in resin sample viscosity and increases in formaldehyde emission of bonded particleboards. The results indicate that various hydroxymethyl groups of polymeric UF resin components migrate to the second urea to form Type I hydroxymethyl groups. Time samples taken during the room‐temperature storage of the resin sample over a period of 1 month behaved similarly initially, but in the later stage, some polymerization progressed, shown by increases in viscosity and methylene and methylene–ether group contents. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1243–1254, 2000     

Sorption and diffusion of water into melamine–formaldehyde‐incorporated poly(vinyl acetate)–polyester nonwoven fabric composites

A series of composites were fabricated by impregnating a polyester nonwoven fabric with melamine–formol (MF)‐incorporated poly(vinyl acetate) (PVAc) latex. The effect of different weight ratios of MF/PVAc, i.e. 0/100, 5/100, 10, 100, 15/100 and 20/100 (dry, wt/wt), on the water sorption and diffusion into the composites was evaluated. Water sorption studies were carried out at different temperatures, i.e. 30, 50 and 70 °C, based on the immersion weight gain method. From the sorption results, the diffusion (D) and permeation (P) coefficients of water penetrant were calculated. A significant increase in the diffusion and permeation coefficients was observed with an increase in the temperature of sorption. Drastic reductions in diffusion and permeation coefficients were noticed with increasing MF content in the composites. Attempts were made to estimate the empirical parameters like n, which suggests the mode of transport, and K, a constant which depends on the structural characteristics of the composite in addition to its interaction with water. The temperature dependence of the transport coefficients was used to estimate the activation energy parameters for diffusion (E_D) and permeation (E_p) processes from Arrhenius plots. Copyright © 2006 Society of Chemical Industry     

Viscosity–molecular weight relationship for aminopropyl‐terminated poly(dimethylsiloxane)

Aminopropyl‐terminated poly(dimethylsiloxane) (ATPS) with different molecular weights was prepared by base‐catalyzed equilibration of octamethylcyclotetrasiloxane and 1,3‐bis(3‐aminopropyl)‐1,1,3,3‐tetramethyldisiloxane with different ratios. Their number‐average molecular weights (M_n) were determined by end–group analysis, and intrinsic viscosity ([η]) in toluene was measured with a Ubbelohde viscometer. A relationship between M_n and [η] was obtained for ATPS. For 1.0 × 10⁴ < M_n < 6.0 × 10⁴, it was in accord with [η]_{toluene,25°C} = 5.26 × 10^?2 M_n^0.587. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 975–978, 2001     

Preparation and characterization of spinnable pitch for general-purpose carbon fiber from refined pitch

Four types of spinnable pitches (MP-N-A, MP-A, MP-A-H, and MP-A-N) for general-purpose carbon fiber have been prepared under certain conditions with the refined pitch as the raw materials. Fourier transform infrared spectrum and solid-state nuclear magnetic resonance spectra combined with curve-fitting analysis have been used to characterize the average molecular structure (I_ar, CH₃/CH₂, S_AR, and S_HFG) of spinnable pitches. Thermogravimetric analyses and polarizing microscope have been used to observe the thermal stability and the microstructure of spinnable pitches, respectively. The X-ray diffraction combined with curve-fitting analysis have showed that, the stacking heights (L_c) of these four kinds of spinnable pitches were 2.21, 1.78, 1.79, and 1.76 nm, respectively. The parallel layers (N) of each spinnable pitch were 7.30, 6.02, 6.06, and 5.97. What is more, the numbers of aromatic ring in each layer (n) were 17.03, 11.61, 11.75, and 11.41. Finally, the scanning electron microscopy has been used to characterize the surface morphology of carbon fibers which obtained by each spinnable pitches. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47880.