Film Formation Temperature Research Articles

Incorporation of an acrylic fatty acid derivative as comonomer for oxidative cure in acrylic latex

An acrylic fatty acid derivative (AcFAD) was evaluated as comonomer for promotion of oxidative cure in waterborne latexes. AcFAD was polymerized by solvent homopolymerization and copolymerization and by emulsion copolymerization, and the final products characterized. In the two polymerization processes, NMR analyses confirmed that the reaction occurred involving both the terminal acrylic double bond and the conjugated double bonds of the aliphatic chain. Compared with a reference acrylic latex, the results obtained after AcFAD incorporation showed a time-dependent increase in gel content and in solvent resistance of dry films. These were ascribed to oxidative cure and consequent self-crosslinking of the acrylic polymer, involving the conjugated double bonds in AcFAD side chains. Oxidative cure was also confirmed by FTIR analyses. In addition, reduction in minimum film-forming temperature evidenced that AcFAD has an internal plasticization effect during film formation. Incorporation of this comonomer in acrylic paint binder formulations constitutes a promising alternative to the use of volatile coalescing agents.

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.

Low VOC self-crosslinking waterborne acrylic coatings incorporating fatty acid derivatives

Acrylic waterborne coatings free of volatile coalescing agents were produced and characterized. The film-formers used in the coatings were resins incorporating an allylic fatty acid derivative (AFAD) and an acrylic fatty acid derivative (AcFAD), either as reactive (non-volatile) coalescing agents or as co-monomers. The minimum film-forming temperatures of the new coatings were lower than the reference, confirming that AFAD and AcFAD act as coalescing agents. On the other hand, the observed reductions in through drying-time and increase in scrub resistance, more evident for AcFAD, indicating that reaction between the conjugated double bonds in the fatty acid derivatives and atmospheric oxygen–oxidative cure–took place and provided an effective self-crosslinking drying mechanism.

Correlation between water permeability of latex-modified concrete (LMC) and water diffusion coefficient of latex film

Cement-based materials are generally known as weak materials in flexure and tension in comparison with compression. Polymers are used in cement-based materials to improve their flexural and tensile behaviors. The composite is called as polymer-modified concrete/mortar. Furthermore, polymers decrease permeability of water into cementitious matrices. Polymers are usually used as admixtures in concretes in form of latexes. Latexes are water-based polymers, which are consistent with water-based concrete matrices. On this basis, these kinds of products are called latex-modified concretes (LMCs). However, it has been found that chemical composition, particle size distribution, molecular weight, physical/mechanical properties of latexes affect performance of modified concretes. In this investigation, six latexes in three categories (acrylic, SBR and polyvinyl acetate) were used as concrete admixtures. They were characterized for chemical composition (by FTIR analysis), minimum film formation temperature, pH, glass transition temperature (T g), particle size and particle size distribution to evaluate the effect of each property on LMC performance. Due to the formation of latex film in the microcracks and pores of concrete microstructure, it was suggested that diffusion of water into films controls permeability of whole concrete structures. On this basis, the diffusion coefficient of the latex films subjected to water was measured using a new method (continuous FTIR analysis). Capillary water absorption test was performed on concrete specimens to verify validity of the suggestion. It was found that there is a correlation between capillary water absorption of LMCs and water diffusion coefficient of latex films.

Adhesion properties of eco-friendly PVAc emulsion adhesive using nonphthalate plasticizer

An eco-friendly poly (vinyl acetate) emulsion adhesive was synthesized without phthalate. Four types of eco-friendly plasticizers for use in these adhesives were selected to confirm their primary properties by injecting the eco-friendly plasticizer without any prior change to its processing or cost. The four types of eco-friendly plasticizers used were dibutyl phthalate DBP-based product, dialkyl ester, acetyl tributyl citrate, and pentandiol-di-isobutyrate. Their properties were determined by comparison with the existing (DBP)-based product. As a result, an emulsion adhesive was produced without addition of phthalate or need for additional additives, resulting in a significant decrease in cost. However, the low temperature characteristics of the eco-friendly plasticizers were slightly inferior to those of DBP. These adhesives containing eco-friendly plasticizer were studied and their characteristics for adhesion strength, water resistance, ability for low temperature film formation, excellent storage stability, and lack of volatile organic compounds productions (including phthalate) were confirmed.

Emulsion Copolymerization of Vegetable Oil Macromonomers Possessing both Acrylic and Allylic Functionalities

AbstractSummary: A soybean oil‐based vegetable oil macromonomer (VOMM) was incorporated as a comonomer into an all‐acrylic copolymer via semi‐continuous emulsion polymerization. Structurally, VOMMs are comprised of long hydrocarbon fatty acid moieties with allylic double bonds which enable auto‐oxidative crosslinking at ambient temperature. VOMMs facilitate low temperature film formation and the fatty acid chains tethered to the polymer backbone auto‐oxidize upon film formation to yield crosslinked films. Latexes with varying VOMM levels were synthesized to elucidate the effect of VOMMs on the pre‐cure and post‐cure glass transition temperature (Tg) and minimum film formation temperature (MFT). Thermoplastic control latexes (without VOMM) were also synthesized via copolymerization of butyl acrylate and methyl methacrylate. This paper details the characterization performed to validate and quantify the VOMM allylic unsaturation retention before, during, and after polymerization, and to quantify and confirm the increase in Tg resulting from auto‐oxidative crosslinking via solid state 13C nuclear magnetic resonance spectroscopy and differential scanning calorimetry.

Physicochemical properties of dirt-resistant cool white coatings for building energy efficiency

The physicochemical properties of two newly developed dirt-resistant cool white coatings were systematically measured in light of the relevant standard testing methods, and the influences of dirt accumulation and washing on the long-term cooling performance of cool coatings were investigated and discussed. Both cool white coatings owe their outstanding physicochemical properties to the optimized formulations, high glass transition temperature and minimum film formation temperature of selected aqueous self-curing acrylic emulsions. The high solid content was also influential. Dirt accumulation leads to a decline in the cooling performance of coatings, which may be almost fully restored by simply washing the coatings with a mild soap solution.

Phosphate film free of chromate, fluoride and nitrite on AZ31 magnesium alloy and its corrosion resistance

A phosphate solution free of chromate, fluoride and nitrite was prepared and an environment-friendly film was obtained on AZ31 magnesium alloy surface via the chemical deposition method. The morphology, composition, phase structure and its corrosion resistance were studied. The effects of film-forming temperature and free acid on corrosion resistance, microstructure and electrochemical behavior of the film were discussed. The results indicate that the corrosion resistance of AZ31 with the phosphate film was better than blank AZ31 substrate, which was most attributed to the great inhibitive action on the anodic dissolution and cathodic hydrogen evolution of the film.

Delayed Ignition of Autocatalytic Combustion Precursors: Low-Temperature Nanomaterial Binder Approach to Electronically Functional Oxide Films

Delayed ignition of combustion synthesis precursors can significantly lower metal oxide film formation temperatures. From bulk In(2)O(3) precursor analysis, it is shown here that ignition temperatures can be lowered by as much as 150 °C. Thus, heat generation from ~60 nm thick In(2)O(3) films is sufficient to form crystalline In(2)O(3) films at 150 °C. Furthermore, we show that the low processing temperatures of sufficiently thick combustion precursor films can be applied to the synthesis of metal oxide nanocomposite films from nanomaterials overcoated/impregnated with the appropriate combustion precursor. The resulting, electrically well-connected nanocomposites exhibit significant enhancements in charge-transport properties vs conventionally processed oxide films while maintaining desirable intrinsic electronic properties. For example, while ZnO nanorod-based thin-film transistors exhibit an electron mobility of 10(-3)-10(-2) cm(2) V(-1) s(-1), encasing these nanorods within a ZnO combustion precursor-derived matrix enhances the electron mobility to 0.2 cm(2) V(-1) s(-1). Using commercially available ITO nanoparticles, the intrinsically high carrier concentration is preserved during nanocomposite film synthesis, and an ITO nanocomposite film processed at 150 °C exhibits a conductivity of ~10 S cm(-1) without post-reductive processing.

Drying and cracking of soft latex coatings

The minimum film formation temperature (MFFT) is the minimum drying temperature needed for a latex coating to coalesce into an optically clear, dense crack-free film. To better understand the interplay of forces near this critical temperature, cryogenic scanning electron microscopy (cryoSEM) was used to track the latex particle deformation and water migration in coatings dried at temperatures just above and below the MFFT. Although the latex particles completely coalesced at both temperatures by the end of the drying process, it was discovered that particle deformation during the early drying stages was drastically different. Below the MFFT, cracks initiated just as menisci began to recede into the packing of consolidated particles, whereas above the MFFT, partial particle deformation occurred before menisci entered the coating and cracks were not observed. The spacing between cracks measured in coatings dried at varying temperatures decreased with decreasing drying temperature near the MFFT, whereas it was independent of temperature below a critical temperature. Finally, the addition of small amounts of silica aggregates was found to lessen the cracking of latex coatings near the MFFT without adversely affecting their optical clarity.

Multiphase coatings from complex radiation curable polyurethane dispersions

The waterborne nature of radiation curable polyurethane dispersions largely respond to the current environmental concerns and do not require any additional coalescent since the film formation (drying) and hardening (photo-curing) take place in distinct steps. It is possible to design aqueous dispersions with distinct polymer particle populations resulting in micro-structured coatings with optimized properties over a wide range of curing conditions. Mixed dispersions based on hard and soft acrylated polyurethane particles were used as model systems for the present study. The minimum film formation temperature has been investigated as a function of the hard:soft polymer ratio. The elastic modulus of the dry coatings shows a reinforcing effect consistent with the inclusion of hard domains in a soft continuous matrix. However, the level of reinforcement is not properly predicted by the usual mechanical models and it is qualitatively accounted for by assuming a composition gradient (interphase) between the hard domains and the matrix. The multiple-phase structure was clearly established by Atomic Force Microscopy in agreement with thermal analysis data. Furthermore the local nanoscale mechanical properties were mapped using a new imaging mode based on real-time force–distance curve analysis. Finally, the coatings prepared using this multiple-phase pattern present a clear benefit over conventional homogeneous coatings by offering an improved balance of chemical and mechanical resistance in pigmented systems applied on melamine-coated MDF panels.

Preparation and Properties of Sensing Membrane for Fiber Optic DNA Sensor

To detect DNA concentration, a novel fiber optic biosensor based on fluorescence quenching was designed and constructed by using lock-in amplifier for signal measurement. The sensor head was fixed on a sensing membrane prepared by the mixture of ethyl silicate, formamide, HCl and fluorescence indicator [Ru(phen)3]2+. The optimal film-forming conditions were that the contents of [Ru(phen)3]Cl2, HCl and formamide were 2.1 mg/ml, 12 % and 16 % respectively, the aging temperature and time of sol-gel solution were 4 oC and 5 d, and the film-forming temperature and time were 4 oC and 48 h, respectively. A linear relationship between the relative phase delay Δφ of sensing membrane and ctDNA concentration was observed in range from 2.0×10-9 to 4.0×10-7 M in Tris buffer, and the detection limit is 8.0×10-10 M. The biosensor had a response time of 65 s and showed good stability and repeatability.

Preparation and characterization of high-refractive-index polymer/inorganic hybrid films containing TiO2 nanoparticles prepared by 4-aminobenzoic acid

In this study we used 4-aminobenzoic acid (4ABA) as the chelating ligand to synthesize anatase TiO2 nanoparticles (NPs) in an aqueous solution. The chelating behaviors of 4ABA with respect to TiO2 NPs were evaluated by infrared spectroscopy, zeta potential analysis, x-ray photoelectron survey spectra, and differential scanning calorimetry. The pre-made TiO2 NPs were incorporated into epoxy resin with various NP contents to fabricate high-refractive-index hybrid films at a low film-forming temperature. We found that the hybrid films featuring TiO2 NPs prepared by 4ABA had higher refractive indices than those by acetic acid—a traditional chelating ligand. The difference can reach to 0.044 at 80% NP content. We suspect that the increase in refractive indices may arise from the fact that 4ABA features a higher refractive index and less demand due to the higher coordinating stability.

Preferred partitioning: the influence of coalescents on the build-up of mechanical properties in acrylic core–shell particles (I)

The partitioning of three coalescents of different polarity in different phases of multiphase acrylic particles was studied to provide a rationale for obtaining the desired performance of binders for wood coatings in terms of the ideal balance between hardness development, blocking resistance, and blushing resistance. Minimum film formation temperature- and aqueous differential scanning calorimetry-measurements on the hard phase polymer by itself showed the different extents to which both hydroplasticization and plasticization by the coalescent occur. Dynamic mechanical thermal analysis was subsequently used to visualize wet-T g effects of three different coalescents in the hard and soft polymer phase of these multiphase acrylic particles. The results have important consequences for the formulation of such binders in applications for exterior wood coatings and coatings in general.

Preparation and Characterization of Phosphate Film for Magnesium Alloy AZ31

Abstract An anticorrosion phosphate film with free of chromate, fluorides and nitrite, was successfully prepared on the surface of the magnesium alloy AZ31 via chemical deposition method. The effects of film-forming temperature and free acid on the corrosion resistance of the film were investigated through SEM. The analysis results indicate that the compactness of the film increased with the increase of film-forming temperature, but more residues is brought. While increasing FA in the proper range can decrease the residues. The EDS characterizations of the film confirm that the phosphate film contains only three elements of Mn, P and O. The analysis of the polarization curves further prove that the film has great inhibitive action on anodic dissolution and cathodic hydrogen evolution, and the corrosion resistance is improved with the increase of temperature

Temperature and Relative Humidity Dependency of Film Formation of Polymeric Latex Dispersions

Thermogravimetric analysis and a synchrotron small-angle X-ray scattering technique were employed to characterize the structural evolution of a polymeric latex dispersion during the first three stages of film formation at different temperatures and relative humidities. Three intermediate stages were identified: (1) stage I*, (2) stage I**, and (3) stage II*. Stage I* is intermediate to the conventionally defined stages I and II, where latex particles began to crystallization. The change of drying temperature affects the location of the onset of ordering, whereas relative humidity does not. Stage I** is where the latex particles with their diffuse shell of counterions in the fcc structure are in contact with each other. The overlapping of these layers results in an acceleration of the lattice shrinkage due to a decrease of effective charges. Stage II* is where the latex particles, dried well above their T(g), are deformed and packed only partially during film formation due to incomplete evaporation of water in the latex film. This is because of a rapid deformation of the soft latex particles at the liquid/air interface so that a certain amount of water is unable to evaporate from the latex film effectively. For a latex dispersion dried at a temperature close to its minimum film formation temperature, the transition between stages II and III can be continuous because the latex particles deform at a much slower rate, providing sufficient surface area for water evaporation.

Structural Reorganization of a Polymeric Latex Film During Dry Sintering at Elevated Temperatures

Structural rearrangement in a latex powder during dry sintering at temperatures higher than the minimum film formation temperature was investigated by means of synchrotron small-angle X-ray scattering. Two major effects were identified: (1) Deformation of latex particles leads to a closure of voids between them and an extensive perfectioning of the face centered cubic colloidal crystalline ordering. Such an improvement of the colloidal crystalline structure involves preferential crystal growth along certain crystallographic directions as was evidenced by the measured unmatched relative diffraction intensity distribution of the crystallographic (111) and (220) planes. (2) Interdiffusion of polymeric chains between adjacent particles promotes a nanometer sized aggregation of nonpolymeric materials previously located in the interstices between particles. Size and size distribution of the aggregates at different dry sintering conditions were evaluated by using a model considering spheres dispersed in the system.

Self-Stratification Silicon Gradient Film Prepared by Emulsion Blend Technique

We investigated the effect of film-formation temperature andTg’s difference on the self-stratification gradient silicone film prepared by emulsion blend (poly(3-[tris(trimethyl silyloxy)silyl] propyl methacrylate-co-methyl methacrylate) /poly(butyl acrylate-co-methyl methacrylate) 50/50 by wt) (PTRIS-co-MMA/PBA-co-MMA) technique. The self-stratification film with gradient distribution of silicon was relatively easily obtained when both blend components could fully fuse to form a continuous film. Moreover, proper nonparallelTgs facilitated migration of the silicon component to the film-air interface during the film-formation and hence the gradient distribution was obtained. WhenTgof silicon-free component was 40°C, self-stratification gradient film with concentration of silicon components varying in a gradient-like manner along the overall transaction of the film was fabricated.

New additives to offer freeze–thaw stability and increase open time of low/zero VOC latex paints

With increasing pressure from regulations to reduce VOC in waterborne coatings and the push toward low odor coatings, coalescing aids are being taken out of the formulations. As film forming properties need to remain identical, binder polymers that exhibit low minimum film formation temperatures (MFFT) are being developed and utilized for formulating coating with the expectation that the resulting products exhibit the same if not better performance as the traditional ones containing significant amounts of solvents. However, this change of binder, has a negative impact on a number of properties including freeze–thaw stability – due to destabilization of the latex during transport, storage and application through cold climate – and open time. New additives, Additive FT-100 and Additive OTE-500 were designed as novel solutions to these issues. These additives are added either to the resin or to the paint formulation to provide a finished coating formulation that exhibits five cycles of freeze–thaw stability as well as significant extension in open time. Other paint properties, such as gloss, scrub resistance, stain resistance, etc., were also improved when Additive FT-100 or Additive OTE-500 products were incorporated. An extensive comparison between formulations with and without these additives will be discussed.

High-refractive-index polymer/inorganic hybrid films containing high TiO 2 contents

In this study we used a low film-forming temperature to fabricate high-refractive-index polymer/TiO 2 hybrid films featuring high TiO 2 contents. We incorporated pre-made TiO 2 nanoparticles (NPs) into titanium alkoxide and/or epoxy resin at various NP contents and then investigated the effects of the relative proportions of TiO 2 NPs, titanium alkoxide, and epoxy resin on the refractive indices. The variation of the refractive index was examined in terms of the morphologies and compositions of the hybrid films. The maximum values of the refractive indices of the hybrid films occurred at high TiO 2 NP contents, but not at pure TiO 2 NP contents. Microstructural images suggested that this phenomenon occurred because of the presence of spaces existing between the NPs as a result of our use of an ex situ synthesis method. The maximum values of the refractive indices of the hybrid films featuring a matrix comprising both titanium alkoxide and epoxy resins were larger than those obtained when the matrix was either titanium alkoxide or epoxy resin alone; indeed, the refractive index of a titanium alkoxide/epoxy/TiO 2 hybrid film reached as high as 1.972—close to that of a pure anatase titania thin film fabricated at high temperature.