Investigation of the curing kinetics of alkyd–melamine–epoxy resin system

Properties of coatings based on alkyd resin can be improved via blending with other suitable resins. Recent studies assessed that many properties could be improved by blending with epoxy resins as well as with melamine resins. The aim of this work was to investigate the effect of epoxy resin content on the curing process in alkyd–melamine–epoxy three component blends. The coatings with two mixing ratios of alkyd/melamine (70:30 and 80:20) were formulated. They were made into baking enamels by blending with 3 and 5 wt% of epoxy resin on total resin solid. Curring kinetics was investigated by differential scanning calorimetry (DSC) and application of Ozawa isoconversional method. Fourier transform infrared spectroscopy (FTIR) was used to follow major curing reactions. The absorbance of –OH and –N–CH₂R, showed significant reduction and confirmed that the epoxy resin reacts and inserts in enamel structure. It was found that resin system with alkyd/melamine ratio of 70:30 and 3 wt% of epoxy resin has the lowest apparent activation energy of 141.5 kJ mol⁻¹ and needs the shortest time of 34.2 min to reach final apparent degree of cure. Isothermal DSC experiments have confirmed these findings. The samples with 30 wt% of melamine resin had higher hardness of baked enamels then samples with 20 wt%. They also showed an increase of hardness with the increase of epoxy resin content.     

A Novel Type of Organo Clay Containing Alkyd-Melamine Formaldehyde Resins

In this study, organo clay-modified alkyd resins were synthesized and these modified alkyd resins were cured with different ratios of melamine formaldehyde resin for the first time. Alkyd resins were blended with 30% and 40% of a commercial melamine-formaldehyde resin. Alkyd-melamine formaldehyde resin films were cured at 140°C for 2 h in an oven. The effect of organo clay addition on the physical and chemical film properties was investigated. These surface coating properties of the resins enhanced with amount of organo clay up to 2–3%. These resins are suitable for manufacturing of high-performance industrial baking enamels.     

FTIR studies of the curing reactions of palm oil alkyd–melamine enamels

Three alkyds of high hydroxyl numbers with oil lengths of 21, 30, and 41 were prepared from crude palm oil. The excess hydroxyl groups provided good compatibility with melamine resins, and also served as sites for crosslinking reactions. They were made into baking enamels by blending with 20% of a commercial melamine resin. All of them could be cured at temperatures below 200°C although thermodecomposition might occur above 290°C. The dry‐hard time of these enamels cured at temperatures between 140–180°C ranged from 10 to 180 min. Fourier transform infrared spectroscopy could be used to follow the major curing reactions. The absorbance of ? O? H and ? N? CH₂? OCH₃ groups showed significant reduction. The changes in the absorbance of these peaks with time and temperature were investigated. The predominant reaction was identified as the formation of methylene ether linkages. However, the self‐condensation reactions of the amino resin and ester linkages did not occur to any noticeable extent. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2309–2315, 2001     

Designing of cardanol based polyol and its curing kinetics with melamine formaldehyde resin

Commercially used industrial baking enamels consist of alkyd or polyester resin with melamine formaldehyde. These resins are mainly derived from fossil resources. Considering growing environmental legislation regarding use of petroleum based raw materials, utilization of renewable resources to synthesize various chemistries can be the only obvious option as far as academia and industries are concerns. The present work deals with exploration of one of the natural resources (Cardanol) for polyol synthesis, its characterization (FTIR and NMR) and its curing behavior with melamine formaldehyde resin by differential scanning calorimetry (DSC). The optimized formulations from DSC study were further evaluated for general coating properties to study the suitability of developed polyol for industrial coating application. The experimental studies revealed that melamine content in the curing mixtures and thereby developed crosslinking density played an important role in deciding the coatings properties.     

Preparation and surface characteristics of low-temperature curing fluorinated cathodic electrodeposition coating

Fluorinated cationic cathodic electrodepositing (CED) resins were synthesized by copolymerization of several acrylic monomers including Zonyl. Water dispersible cationic blocked-diisocyanate (denoted as TId) was also synthesized from isophorone diisocyanate (IPDI), cationic triethanolamine (TEOA), and dimethylpyrazole as the cross-linker for the low temperature curing at 90–120 °C. The emulsion stability of the cationic fluorinated CED resin was improved by ionization of the cross-linker TId, showing a mean particle diameter of 140–150 nm and a narrow distribution. 0.5 wt% of curing catalyst dibutyltin dilaurate (DBTL) was enough to accelerate the curing reaction and the gel content of the TId cured fluorinated CED film was higher than 90 wt% after being cured at 130 °C for 40 min. The contact angle and XPS spectrum of the CED film demonstrated that the surface enrichment of C–F₂ and C–F₃ groups effectively reduced the surface tension of the fluorinated CED coating and its surface tension γ_sv is even lower than 15 mN m⁻¹ for PTFE. The preheating of the CED film above T_g but below curing temperature promoted this surface enrichment of the fluorinated groups. Thermal fragmentation of the fluorinated side chains in the CED resins was successfully avoided due to using TId for low temperature curing.     

Mahua‐oil‐based resins for the high‐temperature curing of fly ash coatings

We attempted to prepare medium‐oil‐length glycerol alkyds based on Mahua oil. Fatty acids were isolated from the oil and used in the preparation of alkyds by the fusion method. The resins were characterized by IR spectroscopic analysis. The physicochemical and film properties of these resins were also studied. IR analysis of the resins revealed the formation of phthalate esters showing characteristic peaks at 1720 cm^?1. The resin was modified with melamine formaldehyde, which cured at high temperatures. Alternatively, the resin was made to air dry with ester gum, and the curing behavior was studied. The suitability of these resins for high‐temperature curing fly ash coating applications was established. Coatings were formulated with these resins and with 40% fly ash as an extender. The coatings were characterized by standard techniques, particularly for their anticorrosive and antiabrasive properties. Resistance to corrosion was evaluated in humidity and in salt‐spray conditions. We conducted a high‐stress (two‐body) abrasion test to test the abrasive wear resistance of the coatings. The Mahua‐oil‐resin‐based fly ash coatings were suitable for application in moderately corrosive and abrasive environments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 110–120, 2003     

Effects of urea formaldehyde resin to film properties of alkyd–melamine formaldehyde resins containing organo clay

Organo clay modified alkyd resins were prepared and these modified alkyd resins were cured with different ratios of melamine formaldehyde and urea formaldehyde resins in this work. Alkyds formulated to have oil content 40% were prepared with phthalic anhydride (PA), glycerine (G), coconut oil fatty acid (COFA), dipropylene glycol (DPG) and organo clay. “K alkyd constant system” was used for the formulation calculations of the alkyd resins. Alkyd resins were blended with 40% of a commercial melamine formaldehyde. The films of the alkyd–amino resins were prepared from 60% solid content xylene solutions using 50 μm applicators. After the films were cured at 140 °C for 2 h in an oven, properties of the films were determined. The film properties of the alkyd–amino resins such as drying degree, hardness, adhesion strength, abrasion resistance, water, acid, alkaline, solvent resistance, and resistance to environmental conditions were investigated. The addition of the urea formaldehyde resin and organo clay has positive effect on the physical and chemical resistance of the alkyd–amino resins.     

Synthesis of oil based hyperbranched resins and their modification with melamine-formaldehyde resin

In this research hyperbranched resins containing fatty acid residues were synthesized. Dipentaerythritol which has six hydroxyl groups was used as the core molecule, and it was transesterified with (i) castor oil, and (ii) a mixture of castor oil and linseed oil at 240 °C. The resulting molecule had hydroxyl containing ricinoleic acid residue coming from castor oil. It was then esterified with dimethylol propionic acid at 140 °C in the presence of para-toluene sulfonic acid used as catalyst. The hyperbranched resin thus produced was then mixed with melamine-formaldehyde resin to improve its properties. The resins were characterized by FTIR spectroscopy, and the thermal properties were determined by DSC. The resins were thermally stable up to 316 °C. The viscosity of the resin that was synthesized by using only castor oil was 3.0 Pa s, while the one synthesized by using 50% linseed oil had a viscosity of 1.0 Pa s. When reacted with dimethylol propionic acid the viscosity of the former resin increased to 7.0 Pa s, and that of the second to 3.7 Pa s. The hyperbranched resins showed excellent adhesion, gloss, flexibility, and formability. The mixed resin (i.e. hyperbranched and melamine-formaldehyde) had higher hardness values but lower gloss, adhesion, and bending resistance. Both types of resins also had good impact and abrasion resistances.     

Preparation and properties of acrylic melamine hard coating

Melamine resin polymers exhibit high transmittance, high pencil hardness, and high refractive index. However, high temperatures and long reaction times are required to obtain the desired condensation products. In this study, acrylic‐modified melamine resins were synthesized that were cured by irradiation with ultraviolet (UV) light. The synthesized acrylic‐modified melamine resins could be cured rapidly due to the radical reaction of the acrylic groups and retained high transparency and high refractive index as features of the melamine resin polymers. The polymerized film by UV curing had low shrinkage and high refractive index. Compared with general multifunctional moiety‐type acrylic monomers such as pentaerythritol triacrylate and dipentaerythritol hexaacrylate, the acrylic‐modified melamine resins had the same degree of hardness. In addition, flexibility, a feature of the urethane moiety, was imparted to the polymer by the reaction of residual hydroxyl groups with isocyanate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2010     

Online monitoring of synthesis and curing of phenol-formaldehyde resol resins by Raman spectroscopy

The synthesis and curing of phenol-formaldehyde resol resins were monitored online by Raman spectroscopy. The synthesis of the resins (F/P 2.0, alkalinity 4.5 wt%) was studied at rising temperature (40-90 °C) for 90 min and at constant temperatures (80 °C, 90 °C, 100 °C, and 110 °C) for 120 min. The progress of the curing was investigated isothermally (80 °C, 90 °C, 100 °C, and 110 °C) for 120 min for three resins with different degrees of condensation. The synthesis and curing of the resins were started in the reactor and the advancement of the methylolation and condensation reactions was followed through the window of the reactor in the wave number region of 2000-400 cm⁻¹ with use of a fiber optic probe for the data collection. The Raman spectra of six model compounds (formaldehyde, phenol, 2-hydroxybenzyl alcohol, 4-hydroxybenzyl alcohol, 2-benzylphenol, and 4-benzylphenol) were analyzed to facilitate the interpretation of the spectra of the resins. The consumptions of free phenol and free formaldehyde, as well as the progress of the methylolation and condensation reactions were easily monitored by following the changes in intensity of the characteristic Raman bands. The results for the cured resins obtained by Raman spectroscopy were in good agreement with the structures and residual reactivities studied by CP/MAS ¹³C NMR spectroscopy and differential scanning calorimetry (DSC), respectively. The results of the study show Raman spectroscopy to be a promising tool for the online monitoring and control of phenol-formaldehyde resol resin synthesis and curing; in addition, Raman spectroscopy offers an effective and fast method for structural study of the solid state resins.     

Maleimido-functionalized spirobislactone having enhanced volumetric expansion on polymerization

An approach to enhancing the volumetric expansion on polymerization of spirobislactone is proposed. This approach suggests a molecular modification of spirobislactone through attaching a rigid pendant segment bearing maleimido group to its aromatic ring. An additional volumetric expansion is achieved from loose molecular packing in cured resins due to the steric hindrance effect among rigid pendent segments. Thus a new monomer, maleimido-functionalized spirobislactone (MFS), is prepared. In order to evaluate the volumetric expansion of MFS during curing, tetraglycidyl 4,4′-diamino diphenyl methane (TGDDM) is employed to cure with MFS. The volumetric expansion of MFS on curing is measured to be 12.3%, higher than that of net spirobislactone monomer. The existence of loose molecular packing in MFS/epoxy cured resins is demonstrated by morphology observation of the cured resin stained by the phosphotungstic acid (PTA), and the stained regions are observed to be nanoparticles. Such a cured resin, prepared from 20 mol% of MFS and 80 mol% of TGDDM epoxy resin, shows excellent toughness (Charpy impact strength 13,000 J/m²) and good mechanical strength (flexural strength 120 MPa, storage flexural modulus 4.2 GPa). Its glass transition temperature by dynamic mechanical thermal analysis (DMA) attains 227 °C, much higher than that of the cured resin from net spirobislactone and epoxy resin.     

Impact of curing condition on pH and alkalinity/acidity of structural wood adhesives

Nine formulations were selected for evaluating the effect of different curing methods on pH and alkalinity or acidity of various structural wood adhesives. These included four phenol–formaldehyde (PF) resins with high pH, one phenol–resorcinol–formaldehyde (PRF) resin with intermediate pH, two melamine–urea–formaldehyde (MUF) resins, and two melamine–formaldehyde (MF) resins with low pH. The four curing methods used in the study were: (1) curing at 102–105°C for 1 h (based on CSA O112.6‐1977), (2) four‐hour curing at 66°C followed by 1‐hour curing at 150°C (based on ASTM D1583‐01), (3) curing at room temperature overnight (based on ASTM D 1583‐01), and (4) cured adhesive squeezed out from glue lines of bonded shear block samples. The effect of the different methods on pH and alkalinity/acidity of the cured adhesive depended strongly on the individual adhesives. For the PF, the alkalinity was different for the different formulations in the liquid form, while in the cured form, the difference in the alkalinity depended on the curing method used. The MF and the MUF were the adhesives most affected by the method used. In particular, the MUF showed much higher cured film pH values when cured by method 2 compared to the other three methods, while both the cured MF and MUF exhibited quite variable acidity values when cured with the different methods. The PRF showed reasonably uniform cured film pH but varying acidity values when cured with the different methods. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Curable resins based on recycled poly(ethylene terephthalate) for coating applications

Poly(ethylene terephthalate) waste was depolymerised in the presence of diethylene- or tetraethylene glycol and manganese acetate as a catalyst. An epoxy resin was then prepared by the reaction of these oligomers with epichlorohydrin in presence of NaOH as a catalyst. The produced oligomers were condensed with maleic anhydride and ethylene glycol to produce unsaturated polyester. The chemical structures of the resulting epoxy and unsaturated polyester resins were confirmed by ¹HNMR. The vinyl ester resins were used as cross-linking agents for unsaturated polyester resin diluted with styrene, using free radical initiator and accelerator. The 2-amino ethyl piprazine was used as hardener for epoxy resins. The curing behaviour of the unsaturated polyester resin, vinyl ester resins and styrene was evaluated at different temperatures ranged from 25 to 55 °C to calculate the curing activation energy of the system. The cured epoxy and unsaturated polyester resins were evaluated in coating application of steel.     

双酚A型含氮酚醛树脂的合成及应用研究

以双酚A、甲醛和三聚氰胺等为原料合成了含氮酚醛树脂,并对环氧树脂的阻燃改性,制得了电性能良好且阻燃性优异的阻燃环氧树脂。     

Maleimide-epoxy resins: preparation, thermal properties, and flame retardance

Maleimide modified epoxy compounds were prepared through reacting N-(4-hydroxylphenyl)maleimide (HPM) with diglycidylether of bisphenol-A. Triphenylphosphine and methylethylketone were utilized in the reactions as a catalyst and a solvent, respectively. The resulting compounds possessed both oxirane ring and maleimide group. The kinetics of the curing reactions of the maleimide-epoxy compounds and amine curing agents, 4,4-diaminodipheylmethane (DDM) and dicyandiamide (DICY), were studied. Incorporation of maleimide groups into epoxy resins provided cyclic imide structure and high cross-linking density to the cured resins, to bring high glass transition temperatures (179 °C) and good thermal stability (above 380 °C) to the cured resins. High char yields in the thermogravimetric analysis and high limited oxygen index values (25.5-29.5) were also observed for the cured resins to impy their good flame retardance.     

Synthesis and properties of a series of cyanate resins based on phenolphthalein and its derivatives

Two new cyanate monomers simultaneously containing phthalide group and different alkyl substituents on the phenylene rings (o-PCY and t-PCY) and the Phenolphthalein-based cyanate (p-PCY) were successfully synthesized by the reaction of o-cresolphthalein, thymolphthalein and phenolphthalein with cyanogen bromide in the presence of triethylamine, respectively. Their chemical structures were confirmed by means of FTIR, NMR and elemental analysis methods. All these monomers owned sufficiently wide processing temperature windows and could be readily cured without the addition of catalyst. The dynamic mechanical analysis (DMA) results showed that the introduction of phthalide structure into the polycyanurate network could effectively improve the thermal properties of the cyanate ester (CE) resin. Especially, the T_g values of the fully cured p-PCY, o-PCY and t-PCY resins are 362 °C, 328 °C and 298 °C, respectively, which are apparently higher than that of most bisphenol-based cyanate resins reported in the literatures (190-290 °C). The thermal and thermo-oxidative properties as well as the water absorptions of the cured products were compared with those of the bisphenol A cyanate resin (BACY), and the structure-property relationships were explained according to the chemical structures and crosslinking densities of the formed polymer networks. The high-T_g thermosetting materials thus prepared are expected to expand the usage of CEs to areas where higher temperature requirements are encountered.     

Pore structure control of mesoporous carbon monoliths derived from mixtures of phenolic resin and ethylene glycol

Mesoporous carbon monoliths derived from phenolic resin mixtures have been prepared in the process based on polymerization-induced phase separation. The effect of the composition of resin mixtures and the resin curing temperature on the pore structure of carbon monoliths has been systematically investigated, with emphasis on controlling the apparent porosity and pore size distribution. Fractal dimensions have been introduced to evaluate the morphologies of the carbon monoliths. The results showed that mesoporous carbon monoliths with narrow pore size distribution were obtained. The pore structure of carbon monoliths could be controlled by changing the resin curing temperature and the content of ethylene glycol, curing catalyst and water in the resin mixtures. The apparent porosity of carbon monoliths varied from 54.27% to 26.83%. Carbon monoliths had narrower pore size distribution when more ethylene glycol and higher resin curing temperature were employed. The pore structure of carbon monoliths would be changed radically when the initial resin samples were prepared with excess water (9.8 wt%), i.e. porous carbon foams with sponge structure were obtained. Carbon monoliths inherit their porosity from precursing cured resins where it was formed as a result of phase separation of resin-rich and glycol-rich phases. Volume contraction had certain effect on the pore structure of carbon monoliths.     

MPD在高固体聚酯氨基烘干磁漆中的应用研究

介绍了用MPD(2-甲基-1,3-丙二醇)合成高固体分聚酯的合成工艺、影响条件和高固体分聚酯氨基烘干磁漆的产品性能。     

环氧树脂/三羟甲基三聚氰胺硅化物固化体系阻燃性能与耐热性研究

利用三聚氰胺和甲醛合成了三羟甲基三聚氰胺（TMM）,将其与正硅酸乙酯(TEOS)反应得到三羟甲基化三聚氰胺硅化物（TMMSi）。将TMMSi与环氧树脂复合,采用4,4'-二氨基二苯基甲烷(DDM)作固化剂来制备环氧树脂/TMMSi固化物,并对固化物的热性能和阻燃性能进行了分析。结果表明,与环氧树脂/TMM固化物相比,环氧树脂/TMMSi固化物的玻璃化转变温度变化较小,高温耐热性提高不明显,但是阻燃性能得到了大幅度提高。当TMMSi含量为15份时,环氧树脂/TMMSi固化物的极限氧指数达到29.6 %,比纯环氧树脂固化物提高了40 %。     

Synthesis, preparation and properties of novel high-performance allyl-maleimide resins

Three novel allyl-maleimide monomers (i.e., A₂B, AB and AB₂) were designed, synthesized and thermally cured to yield a series of high-performance allyl-maleimide resins. All the monomers obtained are readily soluble in common organic solvents enabling an easy solution processing. The thermal properties of the three monomers were studied by the differential scanning calorimetry (DSC). A₂B and AB showed fairly low melting temperature (T_m < 90 °C) and wide processing window ranging from 90 °C to 260 °C. The thermal stability of the cured allyl-maleimide resins (i.e., PA₂B, PAB and PAB₂) was studied by the thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical properties of the composites based on the cured allyl-maleimide resins. PA₂B and PAB₂ showed good glass transition temperatures (T_g > 270 °C) and their corresponding composites showed high bending modulus (E′ > 1900 MPa). Allyl-compound-modified BMI resins based on AB monomer were prepared. Rheometer revealed that the processability of the prepolymer (BR-AB-pre) was improved by the addition of AB monomer. The cured BMI resins (BR and BR-AB) showed good thermal stability (T_d > 400 °C, both in nitrogen and in the air), high glass transition temperature (T_g > 320 °C), and good mechanical properties and low water uptake (<2.6%, 120 h).