Experimental validation of a mathematical model for the evolution of the particle morphology of waterborne polymer-polymer hybrids: paving the way to the design and implementation of optimal polymerization strategies

Polymer-polymer composite nanoparticles allow both the improvement of the performance in stablished applications of waterborne polymer dispersions and targeting new applications that are out of reach of currently available products. The performance of these materials is determined by the particle morphology. To open the way to process optimization and on-line control of the particle morphology, the capability of the recently developed model to predict the evolution of the particle morphology during seeded semibatch emulsion polymerization process was evaluated. Structured polymer particles were synthesized by copolymerization of styrene and butyl acrylate (St-BA) on methyl methacrylate and butyl acrylate (MMA–BA) copolymer seeds of different Tgs. The model captured well the effect of process variables on the evolution of the particle morphology, opening the way to the design and implementation of optimal strategies.The financial support of the RECOBA project (funding from European Framework Horizon 2020, No. 636820) is gratefully acknowledged

Forces Driving the Development of Particle Morphology of Waterborne Polymer Dispersions

[EN] Particle morphology is a key characteristic of the waterborne polymer dispersions and plenty of effort has been dedicated to understand the mechanisms controlling the development of the morphology during polymerization. The availability of new characterization techniques that provide unprecedented quantitative details of the particle morphology have questioned the ideas about the driving forces ruling the development of the morphology. In this article, the case is considered of a seeded emulsion polymerization in which the second stage polymer (Polymer 2) is more hydrophobic than the seed polymer and a water-soluble initiator is used. Simulations of the effect of the different forces involved in the formation of the particle morphology carried by integrating the Navier-Stokes are compared with available experimental results. If is found that the interfacial tensions are responsible for the penetration of clusters of polymer 2 within the seed polymer and the spread of these clusters over the surface of the particle. On the other hand, van der Waals forces control coalescence of the clusters both at the surface and in the interior of the particle.The support of the partners of the Industrial Liaison Program on Polymerization in Disperse Media (Allnex, Akzo-Nobel, Arkema, Asian Paints, BASF, DSM, Elix Polymers, Inovyn, 3M, Stahl, Synthomer, Vinavil, Wacker) is acknowledged

Flexible aromatic disulfide monomers for high-performance self-healable linear and cross-linked poly(urethane-urea) coatings

Implementation of the self-healing concept in coatings is challenging because they have to combine mechanical strength and chain mobility. This challenge is addressed in this work by studying the effect of the polymer microstructure on the mechanical properties and self-healing ability of waterborne poly(urethane-urea) coatings containing aromatic disulfide dynamic bonds. The structural modifications studied are the concentration and flexibility of the aromatic disulfide units and the effect of cross-linking. The effects and limits of these structural changes on the mechanical properties of the polymers and their healability were determined via a combination of DMA measurements, tensile tests, and rheological and scratch closure experiments. It was found that the flexibility of the disulfide unit was key to develop more efficient self-healing materials which offer the necessary molecular mobility for self-healing while simultaneously maintaining a level of mechanical strength that are essential for coating applications.The European Union’s Horizon 2020 research and innovation programme is accredited for the financial support through Project TRACKWAY-ITN 642514 under the Marie Sklodowska-Curie grant agreement. N.B. acknowledges the financial support obtained through the Post-Doctoral fellowship Juan de la Cierva - Incorporación (IJCI-2016-28442), from the Ministry of Economy and Competitiveness of Spai

Modeling the shear-dependent viscosity of nonionically stabilized waterborne dispersions

[EN] The performance of a rheological model that accounts for the effect of the volume fraction, the particle size distribution, and shear rate on the viscosity of water-borne dispersions stabilized with conventional nonionic surfactants and polymeric stabilizers is assessed. The model that contains three parameters fitted well the experimental data. The parameters were independent of the volume fraction, the particle size distribution, and the shear rate. Furthermore, two of them were not affected by the surfactant type and concentration, and temperature. The other parameter increased with the surfactant molecular weight and surface covering, but decreased with increasing temperature.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This study was supported by Ministerio de Ciencia e Innovacion (PID2019-107889GA-I00)

Truth, Justice, and Reparation. Human Rights Violations and their Impact on the Police Forces and their Families in the Context of ETA Terrorism

ETA violence had an impact not only on Basque and Spanish society as a whole, but especially on certain groups who suffered the effects of being direct targets of ETA attacks. One of the most directly affected groups were the police forces (members of the Ertzaintza and of the Spanish security forces), as well as their families. This article uses a qualitative methodology (based on semi-structured in-depth interviews) to reflect and analyse the threat that ETA posed for these police forces and their families in the Basque Country, with special emphasis on the way in which their fundamental rights were affected by ETA actions

Synthesis of mechanically strong waterborne poly(urethane-urea)s capable of self-healing at elevated temperatures

Although various chemistries have been introduced into polyurethanes in order to obtain self-healing abilities, implementing these materials in applications requiring high strength is challenging as strong materials imply a limited molecular motion, but without movement of polymer chains self-healing is not possible. Here, waterborne poly(urethane-urea)s (PU(U)s) based on aromatic disulfide compounds are developed which balance these contradictory requirements by presenting good mechanical properties at room temperature, while showing the mobility necessary for healing when moderately heated. The influence of hard monomers on the stability and mobility of the materials is investigated by scratch closure, cut healing and rheological measurements, so that the limits of the readily available aromatic disulfide compounds, bis(4-aminophenyl)- and bis(4-hydroxyphenyl)disulfide, can be determined. Subsequently, a modified aromatic disulfide compound, bis[4-(3'-hydroxypropoxy)phenyl]disulfide, with increased reactivity, solubility and flexibility is synthesized and incorporated into the PU backbone, so that materials with more attractive mechanical properties, reaching ultimate tensile strengths up to 23 MPa, and self-healing abilities at elevated temperatures could be obtained.The European Union’s Horizon 2020 research and innovation programme is accredited for the financial support through Project TRACKWAY-ITN 642514 under the Marie Sklodowska-Curie grant agreement. N.B. acknowledges the financial support obtained through the Post-Doctoral fellowship Juan de la Cierva - Incorporación (IJCI-2016-28442), from the Ministry of Economy and Competitiveness of Spai

Phase Separation Driven On-Demand Debondable Waterborne Pressure-Sensitive Adhesives

A waterborne pressure-sensitive adhesive (PSA) that shows high adhesive performance and easy debondability on demand without leaving residues on the substrate (adhesive failure) has been developed. A key component of the PSA is a semicrystalline phase that is beneficial for the adhesive properties and that becomes fluid when heated above the melting temperature. Migration of this liquid-like polymer to the substrate-adhesive interface and hardening upon cooling results in a hard non-tacky interface that facilitates debonding. The effect of the particle morphology on the debonding ability is discussed.This research was funded by AkzoNobe

Waterborne Acrylate-Based Hybrid Coatings with Enhanced Resistance Properties on Stone Surfaces

The application of coating polymers to building materials is a simple and cheap way to preserve and protect surfaces from weathering phenomena. Due to its environmentally friendly character, waterborne coating is the most popular type of coating, and improving its performance is an important key of research. The study presents the results regarding the mechanical and photo-oxidation resistance of some water-based acrylic coatings containing SiO2 nanoparticles obtained by batch miniemulsion polymerization. Coating materials have been characterized in terms of hydrophobic/hydrophilic behavior, mechanical resistance and surface morphology by means of water-contact angle, and scrub resistance and atomic force microscopy (AFM) measurements depending on silica-nanoparticle content. Moreover, accelerated weathering tests were performed to estimate the photo-oxidation resistance of the coatings. The chemical and color changes were assessed by Fourier-transform infrared spectroscopy (FTIR) and colorimetric measurements. Furthermore, the nanofilled coatings were applied on two different calcareous lithotypes (Lecce stone and Carrara Marble). Its properties, such as capillary water absorption and color modification, before and after accelerated aging tests, were assessed. The properties acquired by the addition of silica nanoparticles in the acrylic matrix can ensure good protection against weathering of stone-based materials

Surfactant-free latexes as binders in paint applications

[EN] The leakage of surfactant from waterborne coatings is a matter of concern. Therefore, there is a strong interest in developing surfactant-free polymer dispersion as binders for waterborne coatings. This will accelerate the sub-stitution of solventborne binders by the more environmentally friendly waterborne latexes. However, as the performance of the coating depends on the interaction of the latex with pigments and fillers and this interaction is controlled by the composition of the surface of the polymer particles, it is an open question if the surfactant-free latexes are adequate for coating applications. In this work, surfactant-free latexes synthesized under industrial-like conditions using sodium styrene sulfonate (NaSS) to provide stability to the latex were used to formulate exterior paints and their performance compared with that of a commercial latex binder. It was found that for most of the application properties, the paints based on the NaSS binders present improvements with respect to the surfactant stabilized commercial binder

Modeling and characterization of the morphology of multiphase polymeric nanoparticles

Multiphase polymeric nanoparticles that synergistically combine the properties of their constituents present enhanced properties and display new functionalities. Therefore, they are used in a wide range of applications including anticorrosive, superhydrophobic and anti-molding coatings; switchable adhesives; photoswitchable fluorescent particles; energy storage; gene and drug delivery; anticounterfeiting and LEDs. Although it is recognized that application properties strongly depend on the morphology of the nanoparticles, there is a surprising lack of progress towards the knowledge-based synthesis of these materials with well controlled morphologies. There are two main reasons for this. Firstly, the difficulties associated to the accurate characterization of the morphology of the polymeric nanoparticles, and secondly, the lack of quantitative understanding of the processes controlling the morphology. Please click Additional Files below to see the full abstrac