Synthesis and application of acrylic colloidal unimolecular polymers as a melamine thermoset system

Acrylic polymers were synthesized with a ratio of 1 : 7 or 1 : 8 of acrylic acid to acrylic ester monomers to produce an acid‐rich resin. The polymers were water reduced and solvent was stripped to produce colloidal unimolecular polymers (CUPs). These particles were typically 3–9 nm in diameter depending on the molecular weight. They were then formulated into a clear coating with melamine as the crosslinker with thermal curing. Compared to commercial latex films, these melamine‐cured acrylic CUPs had a distinct advantage of having a near‐zero volatile organic compound, better availability of surface functional groups , and improved water resistance. The coatings were evaluated for their methyl ethyl ketone resistance, adhesion, hardness, gloss, flexibility, abrasion , and impact resistance properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40916.     

Mechanism for environmental etch of acrylic melamine-based automotive clearcoats: Identification of degradation products

This paper focuses on defining the reaction mechanism involved in the environmental etch of acrylic melamine-based automotive clearcoats via an identification of reaction products. This has been accomplished through a comparative study of products formed on acid treatment of neat crosslinkers, and those formed following laboratory acid treatment and field exposure of acrylic melamine clearcoat systems. Bulk elemental, X-ray photoelectron spectroscopy (XPS), and infrared (IR) analyses of sulfuric acid-treated melamine crosslinkers show that acid hydrolysis results primarily in the formation of melamine sulfate. Melamine sulfate formation was also observed following laboratory and field exposure of acrylic melamine clearcoat systems. These results confirm that the primary mode of melamine crosslink decomposition is through hydrolysis of acetal linkages and subsequent formation of melamine sulfates. However, data show that hydrolysis of pendent amino groups on the triazine ring also occurs. Ford Research Laboratory, P.O. Box 2053, MD 3083 SRL, Dearborn MI 48121. E-mail: pschmit1@ford.com     

Acid etch resistance of automotive clearcoats. I: Laboratory test method development

This paper reports on the development of a laboratory test procedure for the evaluation of the environmental etch resistance of clearcoats. The test evaluates the bulk acid hydrolysis resistance of clearcoats by gravimetrically following material weight loss as a function of exposure time to a sulfuric acid solution, under conditions that simulate outdoor exposure. The bulk hydrolysis resistance of five production clearcoat technologies including acrylic melamine, acrylic melamine-silane, carbamate, acrylic urethane, and epoxy acid were evaluated. Results from the weight loss measurements were consistent with those anticipated based on the coating systems bulk chemistry and inherent hydrolysis resistance, for clearcoat systems processed under nominal processing conditions. The relative rankings from the laboratory test were found to correlate with field etch ratings. The test method is inexpensive, quantitative, and generates repeatable results that are not subject to environmental variations associated with current field etch testing. Ford Research Laboratory, Dearborn, MI 48121-2053.     

Degradation of organic coatings. I. Hydrolysis of melamine formaldehyde/acrylic copolymer films

The hydrolysis of melamine formaldehyde crosslinked acrylic copolymer films has been studied using infrared spectroscopy. It has been found that during hydrolysis, crosslinks between the acrylic copolymer and the melamine crosslinker are broken and that crosslinks between melamine molecules are formed. The rate of hydrolysis depends on the following: (1) the type of crosslinker used (partially alkylated melamines hydrolyze faster than fully alkylated melamines); (2) the amount and strength of acid catalyst used and whether or not the catalyst can be extracted from the coating during hydrolysis; (3) the initial crosslink density; (4) the hydrolysis temperature. In some formulations, it can be expected that virtually all of the acrylic–melamine crosslinkes will be hydrolyzed. However, due to the formation of melamine–melamine crosslinks, the overall crosslink density does not necessarily decrease significantly as a result of this hydrolysis.     

Viscoelastic properties and coating performance of water-soluble acrylic copolymers crosslinked with melamine resin

Acrylic copolymers with different amounts of carboxyl and hydroxyl groups for obtaining practical performance of melamine-cured acrylic coatings was investigated. Property testing results indicated that glass transition temperature (T_g) and shear modulus increased, and molecular weight between crosslinks (M_c) decreased with the increase of hydroxyl and carboxyl number in the acrylic copolymers. The degree of crosslinks influenced the resistance to solvent and chemicals at a lower baking temperature. Compared with acrylic acid, itaconic acid as a carboxyl monomer was more effective in inducing a lower baking schedule. The water-soluble acrylic copolymer, which is neutralized with triethylamine, consists of 20 wt % methylmethacrylate, 55 wt % buthylacrylate, 15 wt % hydroxyethyl methacrylate, and 10 wt % itaconic acid. The copolymer showed higher crosslinks when cured with methoxymethyl melamine formaldehyde resin under a relatively lower baking schedule at 135°C for 30 min. It also has excellent solvent and chemical resistance. This coating film has a T_g value of 39°C, modulus of 2 × 10⁸ dyne/cm² in the rubbery state, and M_c value of 464. Also the acrylic copolymer films with M_c < 900 have good properties for solvent, acid, and alkali resistance. © 1995 John Wiley & Sons, Inc.     

Synthesis,characterization, and anticorrosive coating properties of waterborne interpenetrating polymer network based on epoxy‐acrylic‐oleic acid with butylated melamine formaldehyde

The present study reports the synthesis and characterization of waterborne interpenetrating network (IPN) of epoxy‐acrylic‐oleic acid (EpAcO) with butylated melamine formaldehyde (BMF). The effect of BMF on the formation of IPN was investigated in terms of physicochemical, spectral, morphological, and thermal analyses. The coating properties of the IPN were investigated for their physicomechanical, corrosion resistance, and antimicrobial activity. The formation of the IPN was confirmed by FTIR and ¹H NMR analyses as well as physicochemical properties. The EpAcO‐BMF IPN coatings were found to exhibit far superior corrosion resistance performance and good thermal stability when compared with the reported waterborne epoxy acrylic‐melamine formaldehyde systems [EpAc‐MF]. The preliminary antimicrobial investigations of the IPNs were carried out by agar diffusion method against some bacteria and fungi. The results revealed that antimicrobial activities were enhanced upon the formation of IPN. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crosslinker reactivity and the structure of superabsorbent gels

A ¹³C-labeled crosslinker (trimethylolpropane triacrylate, TMPTA) was synthesized and copolymerized with acrylic acid while monitoring the relative rates of reaction of the crosslinker and acrylic acid by ¹³C-NMR. This allowed easy quantification of the concentration of the minor component (crosslinker) in the polymer and monomer mixture to levels as low as 0.02%. Polymerizations were conducted in 5 mm NMR tubes under varied temperature, percent neutralization (pH), and percent solids. Reactivity ratios were determined from the rates of incorporation of the components into the gel by use of the integrated form of the copolymerization equation, and their sensitivity to the above variables was quantified. The relative rate of incorporation of the crosslinker into the gel was exceedingly fast. The reactivity ratio, r₁ for acrylic acid, varied from 0.31 (65% neutralization) to 0.77 (unneutralized). The reactivity ratio was affected by the percent solids (solvent effect), but was insensitive to temperature over the range of 55–80°C. It was observed that all of the double bonds of TMPTA were incorporated into gel network as opposed to prior models predicting only two bonds reacting. The reported inefficiency of TMPTA is postulated to be caused by a solubility problem in the monomer mixture. Very low levels of extractables were found in the products even though the crosslinker was consumed by 70% conversion. Based on these data, we propose that a major component of the gel network is graft polymer that forms late in the polymerization onto the crosslinked gel formed earlier. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 439–451, 1997     

Studying the effects of the chemical structure of an automotive clearcoat on its biological degradation caused by tree gums

The effects of artificial and natural tree gums on the mechanical, chemical, and aesthetic performances of two automotive acrylic/melamine clearcoats were studied. To this end, two clearcoats with different acrylic/melamine ratios were investigated. Biological experiments were performed under post-aging conditions using an accelerated weathering test. Analytical techniques including optical microscopy, scanning electron microscopy (SEM), gloss measurement, FTIR, and DMTA analyses were utilized to reveal the responses of the coating system upon exposure to the aforementioned biological materials. Contact angle measurements were also conducted to estimate the surface energy of the coatings. Greater crosslinking density, together with a higher T _g and damping behavior of the clearcoat, indicative of a greater degree of cure, were obtained as the ratio of melamine crosslinker increased. It was shown that both Arabic and natural tree gums could strongly attach to the clearcoats’ surface, imposing a significant stress during the drying process, thereby leading to a physical failure. In addition, the acidic nature of these biological materials leads to a chemical alteration in the clearcoats’ structure. The greater crosslinking density and lower hydrophilicity of the clearcoats containing higher melamine crosslinker were responsible for the weaker interaction of gums with the surface. This showed a greater capability for stress damping. Small surface cracks with fracture morphology on the coatings exposed to biological materials at higher exposure times (in the xenon test) were also observed. This is discussed based on the adhesion of the coatings to gums at longer exposure times, because of significant stress.     

Synthesis and characterization of a macromonomer crosslinker

A macromonomer crosslinker was synthesized by reacting an hydroxy‐terminated ethylene–butylene diol copolymer with an excess of acrylic acid in toluene. ¹H‐, ¹³C‐, and attached proton test (APT) NMR, Fourier transform IR, and gel permeation chromatography were used to characterize the macromonomer crosslinker. Its dilute solution behavior was also compared with the base diol. The addition of the ester moiety to the copolymer backbone did not involve any other side reactions, as evidenced by the similarities in the structures of the macromonomer crosslinker and the diol. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1362–1368, 2000     

Novel approach for attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels as selective adsorbent for Pb(II) Ion

A novel approach was developed for the preparation of the attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels via the “one-pot” inverse suspension radical polymerization of acrylic acid (AA) with the multi-functionalized attapulgite nanorods (org-ATP) as the sole crosslinker. The parameters of the feeding ratio of the functional attapulgite (org-ATP) nanorods and AA (org-ATP/AA), oil (liquid paraffin)–water ratio, and feeding ratios of dispersing agent (sodium dodecyl benzene sulfonate (SDBS)) and initiator (ammonium persulfate (APS)) were optimized via 4-Variable 3-Level Orthogonal experiments. Under the optimized preparation condition, more than 85% of the monomer AA had been grafted onto the org-ATP nanorods to form the 3-dimensional network of the ATP/PAA nanocomposite microgel. The ATP/PAA nanocomposite microgel exhibited better mechanical stabilities (resistance to pressure and resistance to agitation) and selective adsorption to heavy metal ions, especially to Pb²⁺. The adsorbed Pb²⁺ ion could be completely eluted with HCl solution. The better mechanical stability and regeneration make it potential adsorbent for the heavy metal contaminated water.     

Free-radical synthesis of narrow polydispersed 2-hydroxyethyl methacrylate-based tetrapolymers for dilute aqueous base developable negative photoresists

Novel (meth)acrylate tetrapolymers based on 2-hydroxyethyl methacrylate (HEMA) were synthesized via free-radical polymerization in refluxing xylene under monomer-starved conditions for use in negative photoresist formulations. 2,2′-Azobis(2-methylbutyronitrile) was used as initiator and 2-mercaptoethanol as chain transfer agent. Optimized resist formulations were obtained with a relatively narrow polydispersed (D=1.86) low molecular weight copolymer (M_n=1677) of 2-hydroxyethyl methacrylate (HEMA), isobornyl methacrylate (IBMA), cyclohexyl methacrylate (CHMA) and acrylic acid (AA), in a 40/30/23/7 weight ratio. A novel high-resolution single layer negative tone photoresist suitable for 193 nm and e-beam lithography that meets basic performance requirements (aqueous-base development, enhanced etch resistance, sub-0.2 μm resolution) was developed from the aforementioned (meth)acrylate tetrapolymer, the poly(2-hydroxyethyl methacrylate-co-cyclohexyl methacrylate-co-isobornyl methacrylate-co-acrylic acid) (PHECIMA) and a sulfonium salt photo acid generator. The key-components for the negative image formation (photoacid induced crosslinking) are the hydroxyl groups of the HEMA moieties. The swelling-free negative resist material was developed in diluted aqueous base [tetramethyl ammonium hydroxide, (TMAH) 0.26×10⁻²N] and presented enhanced etch resistance without the use of etch resistance promoters. 0.20-0.14 μm lines were obtained upon 193 nm and/or e-beam lithography.     

A new microemulsion approach for producing molecularly imprinted polymers with selective recognition cavities for gallic acid

Bulk and microemulsion systems were studied in order to obtain molecularly imprinted copolymers selective for gallic acid. Both systems contained acrylic acid as the functional monomer and ethylene glycol dimethacrylate as crosslinker. Microemulsion formation was confirmed by refractive index measurements and by conductivity analyses. Simple uptake tests revealed higher affinities for the microemulsion polymers; a 3.55 imprinting factor and a 0.275 g gallic acid (g polymer)^–1 adsorption capacity were recorded. Competitive uptake tests, from an oak bark extract, were in agreement with the simple uptake results and BET analyses. Microemulsion polymer particles selectively bind 4.58 times more gallic acid molecules relative to other competitor species.     

Synthesis and properties of carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide) as a novel cellulose‐based superabsorbent

A new cellulose‐based superabsorbent polymer, carboxymethyl cellulose‐graft‐poly(acrylic acid‐co‐acrylamide), was prepared by the free‐radical grafting solution polymerization of acrylic acid (AA) and acrylamide (AM) monomers onto carboxymethyl cellulose (CMC) in the presence of N,N′‐methylenebisacrylamide as a crosslinker with a redox couple of potassium persulfate and sodium metabisulfite as an initiator. The influences of reaction variables such as the initiator content, crosslinker content, bath temperature, molar ratio of AA to AM, and weight ratio of the monomers to CMC on the water absorbency of the carboxymethylcellulose‐graft‐poly(acrylic acid‐co‐acrylamide) copolymer were investigated. The copolymer's structures were characterized with Fourier transform infrared spectroscopy. The optimum reaction conditions were obtained as follows: the bath temperature was 50°C; the molar ratio of AA to AM was 3 : 1; the mass ratio of the monomers to CMC was 4 : 1; and the weight percentages of the crosslinker and initiator with respect to the monomers were 0.75 and 1%, respectively. The maximum water absorbency of the optimized product was 920 g/g for distilled water and 85 g/g for a 0.9 wt % aqueous NaCl solution. In addition, the superabsorbent possessed good water retention and salt resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1382–1388, 2007     

Synthesis,characterization, and performance evaluation of hard,anticorrosive coating materials derived from diglycidyl ether of bisphenol A acrylates and methacrylates

Diglycidyl ether of bisphenol A acrylate (DAC) and diglycidyl ether of bisphenol A methacrylate (DMAC) were synthesized by the reaction of an epoxy [diglycidyl ether of bisphenol A (DGEBA)] with acrylic acid and methacrylic acid, respectively. The synthesized resins were characterized by determination of the acid, hydroxyl, and saponification values. Structure elucidation was done by gel permeation chromatography, Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and ¹³C‐NMR spectroscopy. DACs were cured with melamine formaldehyde resin at low pH values. The pH of the resin systems was adjusted with phosphoric acid. The coatings of these systems were formed on mild steel specimens for physicomechanical and chemical/corrosion‐resistance performance. The coatings of DAC and DMAC showed excellent scratch hardness and good impact‐resistance performance. The coatings of DMAC showed better performance than DAC with respect to chemical and corrosion resistance. Thermogravimetric analysis and differential scanning calorimetry were used to investigate the thermal stability and curing behavior of these systems. DAC showed a little higher glass‐transition temperature than DMAC and also showed a higher thermal resistivity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 494–501, 2005     

Preparation and evaluation of acryloyl morpholine modified emulsion fracturing fluid thickener with high temperature resistance and salt resistance

To prepare the thickener of fracturing fluid with temperature resistance, salt resistance and quick dissolution, an emulsion thickener (ASC) was synthesized by acrylamide, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, and acryloyl morpholine. The dissolution, salt resistance and drag reduction of ASC, and the viscoelasticity, temperature resistance and shear resistance and gel breaking properties of fracturing fluid formed by ASC and zirconium crosslinker were investigated. The results showed that the sticky time of ASC was less than 60 s and the drag reduction rate was 72.5% in 100,000 mg/L brine, showing that ASC had thickening ability in high salinity brine and satisfied the requirements of continuous fluid preparation on the fracturing process. The viscosity of ASC fracturing fluid was 98 mPa s after shearing at 200°C and 170 s⁻¹ for 150 min when the salinity was 100,000 mg/L. When the ammonium persulfate concentration was 400 mg/L, the viscosity of the broken fluid was 4.0 mPa s. The temperature resistance, salt resistance and shear resistance of ASC emulsion fracturing fluid could be significantly improved by the introduction of acryloyl morpholine, ASC fracturing fluid had the characteristics of high elasticity and low viscosity, which could meet the application requirements under ultra-high temperature reservoirs.     

Study on superabsorbent composite XXV. Synthesis,characterization, and swelling behaviors of poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composites

In this work, a novel poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composite was prepared by graft copolymerization among acrylic acid, N‐acryloylmorpholine and attapulgite in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The result from FTIR spectra showed that  OH of attapulgite participated in graft copolymerization with acrylic acid and N‐acryloylmorpholine. Proper monomer ratio and atapulgite content could form a loose surface, and improve reswelling ability and initial swelling rate. The buffer action of the  COOH and  COO⁻ groups in the superabsorbent composite keeps the water absorbency a rough constant in the pH range of 4.4–9.6. Both polarity and structure of an organic solvent are responsible for the phase transition point of the superabsorbent composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Polycarbonate-modified acrylic polymers for coating materials

Reactivities of six-membered cyclic carbonates (1) were studied and a carbonate-modified acrylic polymer was synthesized, which was expected to show good water resistance. The carbonates (1) reacted with several alcohols under acidic conditions giving the corresponding alkyl 3-hydroxypropyl carbonates, quantitatively. The reactivities of 1 with alcohol depended on their steric hindrance, on the acidity of the catalyst and on the basicity of the solvents. ¹³C NMR analysis indicated that the reaction proceeded by interaction between the CO group of 1 and the acid catalyst, followed by ring-opening of 1 via the nucleophilic attack by the alcohol on the CO group. This reaction of 5,5-dimethyl-1,3-dioxane-2-one (1a) with n-butanol produced polymers (2) at 50°C in toluene, using methane sulfonic acid as a catalyst. The molecular weights ranged from 2530 to 9310 and ¹H NMR showed that the polymerization was initiated from n-butanol. Also the ring-opening reaction enabled the production of both a carbonate-modified acrylic polymer (4a) containing carbonate units in their side chains by the reaction of 1a with poly(styrene-co-2-hydroxyethyl methacrylate) (3a) and methacrylic monomers (HEMAC) containing 3-hydroxyneopentyl carbonate units by reaction of 1a with 2-hydroxyethyl methacrylate (HEMA). Free radical copolymerization of HEMAC also produced carbonate-modified acrylic polymer (4c). A carbonate-modified acrylic polymer showed excellent hydrolysis resistance when compared with -caprolacton-modified acrylic polymer (5a). Waterborne coatings, consisting of a carbonate-modified acrylic polymer (4c) and a melamine resin, showed excellent storage stability at 40°C when compared with a similar coatings based on an -caprolactone-modified acrylic polymer (5b), and the 4c melamine coating showed nearly the same curability to that of the 5b melamine coating when baked at 140°C for 30 min.     

Synthesis and characterization of chitosan‐graft‐poly(acrylic acid)/nontronite hydrogel composites based on a design of experiments

A 2^4–1 fractional factorial design was used to evaluate the effect of some parameters, such as the acrylic acid (AA)/chitosan (CTS) molar ratio, crosslinker concentration, initiator concentration, and filler concentration, in the swelling capacity of superabsorbent hydrogel composites based on CTS‐graft‐poly(acrylic acid) and nontronite clay. The data from wide‐angle X‐ray scattering and Fourier transform infrared spectroscopy confirmed the syntheses of the hydrogel composites. Main and interaction effects were analyzed by analysis of variance, F tests, and p values. We found that the AA/CTS and crosslinker were the most influential effects in the evaluated response. The proposed statistical model presented a high coefficient of determination (R² = 0.985). In addition to the swelling kinetics, the effects of pH and salt for the both compositions (with and without filler), which presented the best water uptake, were evaluated. Both hydrogels showed responsive behavior in relation to the pH and the salt solution, presenting good potential for application as devices in the controlled release of solutes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and properties of a slow release NP compound fertilizer with superabsorbent and moisture preservation

A slow‐release NP compound fertilizer with superabsorbent and moisture preservation was prepared by carboxyl methyl starch, acrylic acid, ammonia, urea, diammonium phosphate, and so on. The effects of the amount of initiator, crosslinker, and the degree of neutralization of acrylic acid on water absorbency were investigated and optimized. The product was characterized by FTIR, ICP, and element analysis, and the results showed that the product contained 22.6% nitrogen element and 7.2% phosphor (shown by P₂O₅) element. Its water absorbency was about 85 (g · g^?1) times its own weight in tap water. We also investigated the water retention property of the product and the slow release behavior of N and P in the product. The results showed that the product had a good water retention capacity and slow release property. The mechanism of the release of N and P in water was also investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2132–2138, 2005     

The effects of reaction conditions on the electrical conductivity of PAAG hydrogels

The effects of reaction conditions: concentration of crosslinker, monomer, initiator and gelatin and neutralization degree (ND) of acrylic acid (AA), of a graft radical crosslinking polymerization of AA and gelatin, on the specific electrical conductivity and the primary structural parameters of synthesized poly(acrylic acid)-g-gelatin (PAAG) hydrogels were investigated. It was established that: (a) electrical conductivity of all of the investigated hydrogels is higher than of distilled water; (b) the increasing concentration of crosslinker, monomer and initiator leads to the two linear distinct increases of electrical conductivity with different slopes (c) the increasing ND of AA leads to linear decrease in electrical conductivity and (d) gelatin concentration does not significantly influence the electrical conductivity of hydrogel. An analyses of the primary structural parameters of synthesized PAAG xerogels reveals that: (a) values of molar mass between crosslinks and distance between polymer chains are power form function on crosslink density (ρ_c); (b) the critical value of ρ_c corresponds to the percolation threshold of H⁺/K⁺ ions through the hydrogels network and (c) electrical conductivity of PAAG hydrogels is a power form function on ρ_c. Fractal model of conductivity of hydrogel is suggested and explained.