Tracking Hydroplasticization by DSC: Movement of Water Domains Bound to Poly(Meth)Acrylates during Latex Film Formation

The film formation step of latexes constitutes one of the challenges of these environmentally friendly waterborne polymers, as the high glass transition (TG) polymers needed to produce hard films to be used as coatings will not produce coherent films at low temperature. This issue has been dealt by the use of temporary plasticizers added with the objective to reduce the TG of the polymers during film formation, while being released to the atmosphere afterwards. The main problem of these temporary plasticizers is their volatile organic nature, which is not recommended for the environment. Therefore, different strategies have been proposed to overcome their massive use. One of them is the use of hydroplasticization, as water, abundant in latexes, can effectively act as plasticizer for certain types of polymers. In this work, the effect of three different grafted hydroplasticizers has been checked in a (meth)acrylate copolymer, concluding that itaconic acid showed the best performance as seen by its low minimum film-formation temperature, just slightly modified water resistance and better mechanical properties of the films containing itaconic acid. Furthermore, film formation monitoring has been carried out by Differential Scanning Calorimety (DSC), showing that itaconic acid is able to retain more strongly the water molecules during the water losing process, improving its hydroplasticization capacity.This research was funded by the Industrial Liaison Program of POLYMAT and by the Basque Government “Grupos Consolidados del Sistema Universitario Vasco”, grant number IT999-16

Waterborne Acrylic/CeO2 Nanocomposites for UV Blocking Clear Coats

The encapsulation of inorganic nanoparticles into polymer particles opens the door to countless applications taking advantage of the properties of both phases. In this chapter the UV absorbing capacity of CeO2 nanoparticles and the film forming capacity of acrylic polymers are combined. A synthetic route to produce waterborne acrylic/CeO2 hybrid nanocomposites for UV absorbing coatings applications is presented. This strategy leads to encapsulated morphology of the CeO2 nanoparticles into the polymer particles and therefore to the lack of agglomeration during film formation. A mathematical model developed for inorganic/organic hybrid systems is able to explain the morphology evolution from the initial monomer droplet to the polymer particles. The films cast from these latexes are transparent and show excellent UV absorption that increases with the amount of cerium oxide nanoparticles in the hybrid latex. Finally, the photoactivity behavior that the CeO2 nanoparticles may have on the polymeric matrix is studied, discarding additional effects on the acrylic polymer matrix

Emulsion polymerization of very hydrophobic bio-based monomers: Challenges and limitations

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Development of waterborne anticorrosive coatings by the incorporation of coumarate based corrosion inhibitors and phosphate functionalization

Waterborne coatings are more industrially appealing for corrosion protection due to their low toxicity when compared to traditional solvent based coatings. In waterborne latex systems, the presence of surfactants is crucial, which can nevertheless contribute later to a poor performance of the final films in terms of barrier protection. This can be avoided by the use of polymerizable surfactants covalently bonded to the polymeric chains. In this work, particles of a latex loaded with an organic corrosion inhibitor, methoxy p-coumaric acid (H1), are further functionalized by the incorporation of a polymerizable surfactant, Sipomer® PAM-200 (SIP), by semibatch emulsion polymerization. The proposed system was hypothesized to ideally have higher barrier and corrosion protection properties due to the combination of H1 and SIP. However, the Electrochemical Impedance Spectroscopy results of the latexes cast on metal substrates indicate an antagonistic effect on the corrosion inhibition process rather than synergistic, as both species compete for the same moieties of the metallic surface. Thus, while the control coating with SIP (13.3 mg of SIP/g of polymer) showed impedances of 107.1–106.4 Ω and phase angles of 84–88 degrees over 24 h, the coating with H1 (3.3 mg of H1/g polymer) and SIP (13.3 mg of SIP/g of polymer) showed a less stable behavior with changes in impedances with time from 107.1 to 105.5 Ω and in phase angle from 86 to 72 degrees. The production of a bi-layer system avoids this antagonistic effect.Financial support from Eusko Jaurlaritza (GV-IT1525-22), MICINN (PDC2021-121416-I00) and MINECO (PID2021-123146OB-I00) is gratefully acknowledged

Crosslinking versus interdiffusion in two pot one pack acetoacetoxy-amine based binder system

A two-pot-one-pack waterborne crosslinking system is studied by following the crosslinking and interdiffusion between the polymer particles functionalized with acetoacetoxy on one hand and with polyethyleneimine on the other. FTIR spectroscopy and rheological measurements are used to follow the evolution of crosslinking, while pyrene excimer fluorescence is used to analyse the interdiffusion of polymer chains between neighbouring particles during film formation. Both crosslinking and interdiffusion proceed slowly at room temperature. However, crosslinking is complete after 24 h at 60 °C, while interdiffusion does not proceed further at this temperature. TEM images confirm the presence of a honeycomb structure in the final film, produced by the crosslinked moieties between polymer particles that can act as a barrier for interdiffusion of polymer chains between particles. Nevertheless, strong films are produced even in the absence of significant interdiffusion, due to the crosslinks between particles.We acknowledge the financial support provided by the Industrial Liaison Program of POLYMAT

Producción de látex híbridos acrílicos/alquídicos

In this work, the production of high solids content hybrid acrylic/alkyd latexes by miniemulsion polymerization is discussed. First, the miniemulsification procedure to achieve colloidally stable hybrid nanodroplets is presented. Next, the efficient nucleation of most nanodroplets during the polymerization, avoiding other nucleation mechanisms is presented. Finally, the key aspects to control the polymer architecture as well as the particle morphology are analyzed.Fil: Goikoetxea, Monika. Universidad del País Vasco; EspañaFil: Minari, Roque Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Beristain, Itxaso. Universidad del País Vasco; EspañaFil: Paulis, María. Universidad del País Vasco; EspañaFil: Asua, José M.. Universidad del País Vasco; EspañaFil: Barandiaran, María J.. Universidad del País Vasco; Españ

Green Electrospinning of Polymer Latexes: A Systematic Study of the Effect of Latex Properties on Fiber Morphology

Green electrospinning is a relatively new promising technology in which a polymer (latex) can be spun from an aqueous dispersion with the help of a template polymer. This method is a green, clean and safe technology that is able to spin hydrophobic polymers using water as an electrospinning medium. In this article, a systematic study that investigates the influence of the template polymer molar mass, the total solids content of the initial dispersion and the particle/template ratio is presented. Furthermore, the influence of the surfactant used to stabilize the polymer particles, the surface functionality of the polymer particles and the use of a bimodal particle size distribution on the final fiber morphology is studied for the first time. In green electrospinning, the viscosity of the initial complex blend depends on the amount and molar mass of the template polymer but also on the total solids content of the dispersion to be spun. Thus, both parameters must be carefully taken into account in order to fine-tune the final fiber morphology. Additionally, the particle packing and the surface chemistry of the polymer particles also play an important role in the obtained nanofibers quality.This research was funded by the MINECO of the Spanish Government, grant number CTQ-2017-87841-R and by the Basque Government “Grupos Consolidados del Sistema Universitario Vasco”, grant number IT999-16

Comparison of the Corrosion Inhibition Ability of Different Coumarate-Based Compounds Incorporated into Waterborne Binders

One of the most widely applied methods for the mitigation of corrosion is to cover metallic surfaces with polymeric coatings; however, the barrier properties provided by the polymer may not be enough to prevent corrosion. To improve the performance of the coatings, the incorporation of corrosion inhibitors in their formulation can be done to provide active protection to the system. Among the organic corrosion inhibitors, p-coumaric acid (p-CA) is promising for corrosion protection. Therefore, in this work, the corrosion protection efficiency of four p-coumaric-based inhibitors, methyl (H1), butyl (H4), trifluoromethoxy (HCF3), and p-4-ethyloxymethacrylate p-coumaric acid (HMA), is investigated. The inhibitors are incorporated into environmentally friendly waterborne polymeric binders by batch miniemulsion polymerization. The barrier corrosion protection of the coatings produced from these hybrid latexes is analyzed by electrochemical impedance spectroscopy (EIS) of the intact and scratched coated steel substrates. Of the intact coatings, the one with H1 showed the best response, with impedances of 10(6.3)-10(6.7) Omega and phase angles of 82-84 degrees, considerably higher than the control without inhibitor (10(5)-10(5.2) Omega and 60-66 degrees, respectively). The better performance of H1 has been attributed to its higher solubility in the media. However, the best impedance results for the scratched films have been obtained for the coating with HMA, as the impedance was maintained at similar to 10(4.3) Omega for 24 h, while the impedance drops from similar to 10(4.6) to 10(4.1) Omega for the control scratched sample. As HMA is attached to the polymeric chains, it is likely able to protect the exposed metallic area without completely leaching from the coating, thus explaining why it is able to maintain its performance. The EIS analysis also strongly suggests that the inhibitors have an additional protective effect through increasing pore resistance and decreasing metal corrosion as indicated from the higher R-pore and lower C-dl data extracted from the fits.We are thankful for the financial support received from the Basque Government (IT-1525-22), from the Spanish Government (MINECO PID2021-123146OB-I00 and MICINN PDC2021-121416-I00), and from Deakin University

Strategies to incorporate a fluorinated acrylate monomer into polymer particles: from particle morphology to film morphology and anticorrosion properties

[EN] Four strategies to incorporate a fluorinated monomer (perfluoro octyl acrylate, POA) into a waterborne polymeric dispersion are investigated. Due to the very low water solubility of the POA monomer, three of the strategies use miniemulsion droplets containing the whole POA monomer in the initial charge. The rest of the comonomers of the formulation (methyl methacrylate, MMA, and n-butyl acrylate, BA) are partially incorporated in the initial miniemulsion or fed to the reactor as a preemulsion. In the fourth strategy, a conventional seeded semibatch emulsion polymerization is carried out using cyclodextrin in the seed and feeding the POA/MMA/BA preemulsion to the reactor. Each process strategy led to a distinct particle morphology and hence a particular film morphology. We found that the strategy that produced core-shell particles with the core composed by pure polyPOA yielded the films that showed the best corrosion protection as measured in salt-spray test (1200 h standing without damage).Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

Challenges to incorporate high contents of bio-based isobornyl methacrylate (IBOMA) into waterborne coatings

Emulsion polymerization of (meth)acrylic bio-based monomers is a promising method to obtain waterborne coatings with reduced carbon footprint. However, the high hydrophobicity of some bio-based monomers can hinder the straightforward incorporation of such monomers in waterborne dispersions. In this work, we explore the copolymerization of bio-based isobornyl methacrylate (IBOMA) with 2-octyl acrylate (2-OA) to produce latexes with >70 % bio-content suitable for coating applications. First, the homopolymerization of IBOMA is studied to gather more information on the emulsion polymerization of the monomer producing high Tg polymer with different surfactants. It is found that the batch emulsion homopolymerization of IBOMA is challenging due to coagulation during the polymerization, likely as a result of mass transport limitations due to the high hy-drophobicity of IBOMA. Interestingly, stable dispersions are achieved when 5 % of the IBOMA is substituted by methyl methacrylate. The stability of the IBOMA/2-OA copolymer system is found to be dependent on both the IBOMA concentration in the copolymer and the solids content of the latex. Thus, we provide a stability map for IBOMA/2-OA copolymers with different compositions and solids contents showing the areas where stable and not-stable dispersions are obtained.Financial support from Eusko Jaurlaritza (GV-IT-999-16), MICINN (PDC2021-121416-I00) and MINECO (CTQ2017-87841-R) is gratefully acknowledged