Development of waterborne UV-A curable clear coat for car refinishes

The development of a waterborne UV-A curable clear coat for car refinish application is described. The clear coat formulations are based on specially developed acryloyl or maleimide functional polyurethane dispersions. The functional PUR dispersions are characterized by a relatively low molecular weight, a high CC functionality and an optimized amount of poly(ethylene oxide). These characteristics are necessary for obtaining optimal film formation which results in good appearance and other film properties. It was found that poly(ethylene oxide) had a positive effect on surface cure when irradiated with UV-A light (less influence of oxygen inhibition). The synthesis of PUR dispersions and their performance in clear coats are described, including several aspects on film formation (conversion of CC, AFM measurements) and film properties (durability, physical and chemical properties).     

Waterborne two-pack isocyanate-free systems for industrial coatings

Two-pack paint systems are used in various segments of the industrial coatings market. Stringent legislation concerning the emissions of organic solvents has led to an increasing demand for green alternatives, for the current solventborne products. Water, in this respect, is one of the most interesting technologies for ambient curing systems. A novel waterborne isocyanate-free two-pack system for high gloss topcoats is herewith described. The system is based on two waterborne acrylics with different functional groups. Properties of the system were compared with the performance of waterborne two-pack polyurethanes based on polyisocyanates and waterborne acrylic polyols. Solventborne versions of both two-pack systems were also used as references.     

New resin systems for high performance waterborne coatings

Restrictions on the emission of solvents have led to the search for environment-friendly coatings. Waterborne systems are an alternative to high solids and powder coatings. New single-component polyurethane dispersions are suitable for replacing many standard systems. A new generation of waterborne two-component polyurethane systems may be used for applications where high performance is expected.     

Novel synthesis of low VOC polymeric dispersions and their application in waterborne coatings

A new approach for the synthesis of reactive solvent-free polyurethane dispersions is discussed in detail. A powerful tool is introduced by incorporating β-ketoester groups in the polymer chain. β-Ketoesters have two different reaction sites. On the one hand the keto groups can react with nucleophiles like polyamines. On the other hand the carbon atoms of the activated CH₂ groups are centers for the attack of electrophiles like aldehydes and isoyanates. Polymers functionalized in this way are interesting new intermediates in chain extension reactions for aqueous polyurethane dispersions. Another advantage of the functionalized polyurethane dispersions is the possibility of additional crosslinking with melamine resins or blocked isocyanates.     

Chemical resistance of waterborne epoxy/amine coatings

Waterborne epoxy/amine coatings, compared to solvent-based, show considerably lower chemical resistance. This fact is often blamed on hydrophilic emulsifiers or crosslinking agents remaining inside the coating after curing. To judge this assertion, the influence of surfactants and hardeners, as well as various other parameters were investigated. Surfactants appear just to influence the solvent resistance slightly. The main responsibility for the poor resistance to other chemicals – especially acids – lies with unreacted amine curing agents and/or water trapped inside the coating, and, most important, an inhomogeneous film structure due to insufficient coalescence during the curing process. Incremental improvements are possible by using excess epoxy, increasing the film thickness, or curing at elevated temperatures. The latter forces water out of the coating, drives the epoxy/amine reaction to completion, and also somewhat improves the coalescence. However, the resistance can still not be enhanced to the level of a solvent-based system. But although there seem to be inherent limitations to the chemical resistance of waterborne epoxy systems, for many practical applications it is adequate.     

Electrochemical impedance spectroscopy study of waterborne coatings film formation

In order to establish electrochemical impedance spectroscopy (EIS) as a viable quantitative method for characterization of latex film formation, three waterborne acrylate and styrene–acrylate polymer dispersions were periodically analyzed during a course of 2 weeks. Impedance spectra were fitted on the base of equivalent circuit consisting of a capacitor in parallel with a Warburg element representing film capacitance and the extent of ion diffusion through the film. Calculated EIS parameter values showed a decrease in Warburg diffusion over time, which is a result of particle coalescence and in agreement with the established theory of latex film formation. Atomic force microscopy (AFM) of the samples showed a smoothing of the surface and blurring of interparticle boundaries which confirmed that EIS can be used to study film formation of latex.     

Efficient strategy for hard nano-sphere usage: Boosting the performance of waterborne coatings

This work describes a study on the efficient use of waterborne hard-polymeric nanoparticles to improve properties of waterborne coatings such as: early hardness, blocking and resistance to fat. The waterborne nano-hard-spheres were synthesized by a special emulsion polymerization process enabling the use of low-surfactant concentration and high solid levels, and then blended with different commercial decorative binders. The colloidal stability of these bimodal systems was carefully analyzed, through rheology and dynamic light scattering analysis. Afterwards, different clear coatings were formulated, prepared, and applied onto different substrates to evaluate their properties. Results showed that the implementation of this waterborne technology enhanced the performance of the systems evaluated for decorative and industrial purposes.     

Synthesis of bio-based unsaturated polyester resins and their application in waterborne UV-curable coatings

In this paper, three bio-based unsaturated polyesters were synthesized from itaconic acid and different diols which could be derived from renewable resources. Their chemical structures were confirmed by FT-IR, ¹H NMR and acid value as well as hydroxyl value. Waterborne UV curable networks based on these polyesters were manufactured and their mechanical properties, thermal stability and coating properties including pencil hardness, flexibility, adhesion, water resistance and solvent resistance were investigated. Results showed that the UV-cured polyester coatings exhibited high hardness, good water resistance and solvent resistance. The coatings reported in this paper combined the merits of bio-based materials, UV-curing process and water distribution.     

Evolution of the film properties of 3-methacryloxypropyl trimethoxysilane containing waterborne acrylic coatings during storage

The use of alkoxysilane monomers is one of the most attractive methods to obtain one-pot self-crosslinkable latexes for coating applications. The copolymerization kinetics shows that the alkoxysilane monomer is effectively incorporated into the copolymer. However, the hydrolysis and condensation reactions that give the latex the self-crosslinking ability can also prematurely happen. As a result, the microstructure of the latex, and consequently of the dried polymer film, will change during the storage. Herein, the evolution of key film properties, such as, water uptake and tensile strength as a function of the storage time of latexes with different alkoxysilane monomer loadings is presented. As storage time increases, there is an improvement on the mechanical properties, obtaining a harder polymer as the result of the development of the hydrolysis and condensation reactions during the first 4 weeks. However, for more extended storage periods (17 weeks) there is a significant decrease in the mechanical performance, because the crosslinking in the latex has developed enough to hinder the film formation.     

A complete new design for waterborne 2-pack PUR coatings with robust application properties

In this paper, a new approach to the paint composition design of WB 2-pack PUR coatings for car refinish application is presented. New hydroxy-functional binder emulsions are described that offer a better basis for the mixing process and the pot-life/reactivity balance with polyisocyanate hardeners. In addition, it will be shown that with these binder systems the overall balance of appearance, pot-life and curing speed can be enhanced to a very attractive level by the use of a well tuned catalyst package, allowing sufficient time for application, flow and de-aeration while offering the required fast curing characteristics as well. Thirdly, it will be shown how the aspects relating to undesired foam formation can be managed. Finally, the performance of low VOC paint compositions for car refinish application based on this new generation of WB 2-pack PUR system will be discussed.     

Synthesis and characterization of low crystalline waterborne polyurethane for potential application in water-based ink binder

Waterborne polyurethane dispersions (PUDs) with low crystallization and narrow nanoparticles distribution were synthesized from poly(propylene glycol) (PPG), isophorone diisocyanate (IPDI), dimethylolpropionic acid (DMPA) via a environmental and simple process combined prepolymer isocyanate process with acetone process. For used as ink binder, the acid numbers of PUDs were analyzed. It was found that the acid number changed with the solid content and mainly increased with increasing hard-/soft-segment molar ratio. Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance spectroscopy (¹H NMR), transmission electron microscope (TEM), differential scanning calorimetry (DSC), thermogravimetric (TG), X-ray diffractometer (XRD) and polarizing optical microscopy (POM) measurements were utilized to characterize the bulk structures and thermal properties of PUDs. The results show that nanoscale waterborne polyurethane dispersions synthesized through the combined process have good thermal stability and weakly crystallinity, which is suitable for the use of water-based ink binder. The performance of PUDs can be optimized for the application as ink binder when the hard-/soft-segment molar ratio is 4 or 5.     

纳米TiO2的表面改性及其在水性涂料中的应用

介绍了水性苯丙乳液涂料的配方以及改性纳米TiO2水性涂料的配制方法。通过正交实验和单因素实验确定了分散剂、偶联剂、纳米TiO2和pH的最佳用量为:m(六偏磷酸钠)=0.5 g,v(偶联剂)=1.5 mL,w(TiO2)=0.5%,pH7.8。与普通水性涂料相比,新合成的纳米涂料具有优异的物理性能,附着力达到1级,耐水性超过120 h,耐碱性超过96 h,耐擦洗性超过5 000次。     

Recent advances in aqueous two-component systems for heavy-duty metal protection

Although waterborne coatings have successfully replaced their solventborne counterparts in a variety of areas, their use generally has been limited to applications with relatively modest performance requirements. Recently, advances in technology have allowed for the design of waterborne coatings with performance suitable for more demanding applications. The emergence of two-component waterborne polyurethane coatings exemplifies this trend. These coatings can provide performance similar to that of solventborne 2-pack urethanes, but with much lower VOC. The chemistry of these coatings is discussed, in light of its relevance to some of the technical challenges, e.g., pot life and CO₂-gassing in thick films, unique to these systems. The use of 2-pack waterborne urethane topcoats in combination with low VOC waterborne acrylic/epoxy primers and intermediate coats is also described. Such multiple coat systems offer the promise of long term corrosion protection in severe industrial and marine environments, coupled with very low VOC.     

水性涂料的涂装和储运环境

叙述了水性涂料在涂装和储运环境的重要性。     

Fluorinated waterborne shape memory polyurethane urea for potential medical implant application

A series of crosslinked fluorinated waterborne shape memory polyurethane urea (PUU) ionomers were synthesized from polycaprolactone diol, perfluoropolyether (PFPE) diol, dimethylolproionic acid, isophorone diisocyanate, ethylenediamine (EDA), and diethylenetriamine (DETA). The effect of PFPE content in the soft segment and the degree of crosslinking on the molecular structure and the properties of these PUU films was examined and studied. Differential scanning calorimetry showed that the transition temperature for these T_m type shape memory PUU could be fine tuned by PFPE weight percentage and EDA/DETA ratio in the range between 33 and 44°C, covering the range of body temperature. Although incorporating amorphous fluorinated units into semicrystalline soft segment compromised the shape memory performance of PUU with linear structure as expected, the introduction of crosslinking structure using DETA as a trifunctional chain extender could still retain quite high strain recovery rate (above 90%) at 100% stretching deformation. Furthermore, the relationship of these properties as well as thermal stability with hydrogen bonding was also discussed by evaluation of the carbonyl stretching region in Fourier transform infrared spectra. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Two advanced styrene‐butadiene/polybutadiene rubber blends filled with a silanized silica nanofiller for potential use in passenger car tire tread compound

Styrene‐butadiene rubber (SBR) and polybutadiene rubber (BR) were mixed together (75:25 by mass) to produce two SBR/BR blends. The blends were reinforced with a precipitated amorphous white silica nanofiller the surfaces of which were pretreated with bis(3‐triethoxysilylpropyl)‐tetrasulfide (TESPT). TESPT is a sulfur‐bearing bifunctional organosilane that chemically bonds silica to rubber. The rubbers were primarily cured by using sulfur in TESPT and the cure was optimized by adding non‐sulfur donor and sulfur donor accelerators and zinc oxide. The hardness, Young's modulus, modulus at different strain amplitudes, tensile strength, elongation at break, stored energy density at break, tear strength, cyclic fatigue life, heat build‐up, abrasion resistance, glass transition temperature, bound rubber and tan δ of the cured blends were measured. The blend which was cured with the non‐sulfur donor accelerator and zinc oxide had superior tensile strength, elongation at break, stored energy density at break and modulus at different strain amplitudes. It also possessed a lower heat build‐up, a higher abrasion resistance and a higher tan δ at low temperatures to obtain high‐skid resistance and ice and wet‐grip. Optimizing the chemical bonding between the rubber and filler reduced the amount of the chemical curatives by approximately 58% by weight for passenger car tire tread. This helped to improve health and safety at work and reduce damage to the environment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Adjustable amine–epoxy composition in a stratified thin film with a spin‐coating process: A useful tool for establishing relationships between the local glass‐transition temperature at the interface and the network structure

An easy method for preparing supported homogeneous epoxy–amine thin films on a silica surface consisting of two distinct layers was developed via spin coating from epoxy–amine solutions. Because of these two layers had the controlled properties of the upper layer, we showed that it was possible to precisely control the epoxy–amine stoichiometry in the sublayer through the initial epoxy–amine ratio, the spin‐cast process, and the overall film thickness. First, in the thin films, the primary amine–epoxy conversion was constant, whatever the thickness and initial epoxy–amine stoichiometry for a given curing schedule. As the primary amine conversion can be independently tuned in thin films, it thus provided a rather unique and easy method for better understanding the relationship between the network structure curing at the interface and the resulting properties, such as the glass‐transition temperature (T_g) and elastic modulus. Here, we also showed that we could access the local T_g; this implied a potential application of these experimental data in predictive composite material properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42078.     

Chemorheological study of DGEBA/IPD system for reactive rotational molding (RRM)

The identification of kinetic parameters controlling the crosslinking of Diglycidyl ether of bisphenol/isophorone diamine reactive system was achieved via optimization program (Inverse method) based on Fourier transform near infrared spectroscopy results. The reactivity ratio (k₂/k₁) was determined using a new method based on the variation of amine conversion ratio versus epoxy conversion ratio. Gelation and vitrification of the reactive system were also analyzed. Time, temperature, transformation diagram was established to assess the rotational molding of this reactive system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel Method for Coating Magnetic Iron Oxide Particles with Carbon Black

Magnetic particles with finer size, higher coercive force, higher blackness, and lower electrical resistance are required to produce better magnetic tape materials. A new method to coat iron oxide particles with carbon black using an adhesive agent is reported in this paper. Magnetic tapes prepared using the coated particles in the recording layer exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of ∼20% and a reduction in electrical resistance of ∼1 order of magnitude relative to conventionally prepared tapes are achieved when ∼5% of the particle weight is carbon black. Surface smoothness and the orientation ratio are also improved because the dispersibility of these particles in magnetic lacquer is better than that of uncoated magnetic iron oxide particles. Higher electromagnetic performance relative to the conventionally prepared layers is also obtained. TEM photographs indicate that all the carbon black is firmly bound to the surface of the magnetic iron oxide particles in a distinct layer.     

A model for modulus development of dual-cure resin systems

A phenomenological model for cure-dependent modulus is described for materials undergoing a two-stage curing reaction. These dual-cure resin systems commonly use a thermally activated reaction in the second stage with temperatures exceeding the glass transition temperature of the intermediate product. This leads to a non-linear development of the elastic modulus, with an observable softening effect and the potential for large structural deformations. In this study, the elastic modulus was measured at discrete levels of thermal conversion and processing temperatures. The results are used to determine the cure and temperature dependent-modulus and create a model capable of following the modulus development throughout the entire thermal processing stage. Applications and a processing guideline are discussed.