An analytical approach to relating powder characteristics and rheological properties of powder injection molding feedstocks

This study quantitatively analyzes the relationship between the material structure (powder characteristics) and flow properties of highly filled compounds. The model parameters are the powder particle-size distribution and its volume fraction in a compound. The simulated material structure is developed using the Hard Spheres Model, from which the structural functions in terms of the statistical distribution of inter-particle distances and the histograms of effective volumes of groups of close particles are calculated. A close similarity between simulated and real functions was obtained. The results obtained imply that numerical modeling might serve as a reliable and sensitive approach for analyzing the influence of powder particle-size distribution on the ability to process highly filled compounds.     

A novel approach to prepare large-scale and narrow-dispersed latex particles by emulsion polymerization based on particle coagulation mechanism

In order to understand the mechanism of narrow particle size distribution of the final latex during particle coagulation, a series of experiments were performed to investigate the effect of polymer nature on particle coagulation capability. In particular, thermodynamics and kinetics in aqueous phase were considered to illustrate the detail process of particle coagulation. The final particle size decreased with the increasing side chain length of alkyl methacrylate from 181.5 nm in MMA to 131.6 nm in EMA, 119.3 nm in PMA, and 115.1 nm in BMA, indicating that the particle coagulation capability was proportional to the hydrophilicity of polymer. With increasing polymer hydrophilicity, the affinity between surfactant molecules and particle surface decreased, thus enhancing the particle coagulation capability. Moreover, the critical length of oligomer radical also increased with increasing hydrophilicity and the efficiency of radical capture decreased, thus increasing the saturation of monomer concentration in the inner part of particle, promoting particle coagulation. Combining these results and the La Mer Diagram, a novel approach was developed to prepare large-scale, narrow-dispersed, and high solid content polymer latex based on particle coagulation mechanism. Three criteria, namely, rapid nucleation, fast coagulation, and a long growth period, should be met to produce latex with a narrow particle size distribution.     

The strength of multi-scale modeling to unveil the complexity of radical polymerization

The strength of multi-scale modeling to support the fundamental understanding and design of radical polymerization processes is illustrated, considering both controlled and free radical polymerization (CRP/FRP) in non-dispersed (bulk/solution) and dispersed (suspension/emulsion) media. At the molecular scale, the importance of joint experimental and theoretical studies is highlighted. At the micro-scale, the concept of apparent rate coefficients is elaborated to account for the possible influence of diffusional limitations on the local reaction rates. At the meso-scale, the key characteristics to fundamentally describe the evolution of the particle size distribution are covered and the possible interaction with the micro- and macro-scale is discussed. At the macro-scale, the main mathematical tools to assess the relevance of mixing and temperature gradients are provided. Several examples on CRP and FRP processes are included to showcase the modeling capabilities for each scale, focusing both on laboratory and industrial reactors.     

Facile preparation of poly(3,4‐ethylenedioxythiophene) nanoparticles via a miniemulsion polymerization process

Poly(3,4‐ethylenedioxythiophene) (PEDOT) nanoparticles were prepared via a miniemulsion polymerization process. The chemical oxidative polymerization of 3,4‐ethylenedioxythiophene (EDOT) occurred in the presence of β‐1,3‐glucan with the injection of an aqueous oxidant solution, and the nanodroplets of EDOT were transformed to PEDOT nanoparticles dispersed in the aqueous medium. The aqueous emulsion of PEDOT nanoparticles showed relatively long emulsion stability (> 8 weeks), and the recovered solid nanoparticles were also redispersible in deionized water without deposition. The size and size distribution of PEDOT nanoparticles could be controlled by adjusting the operating conditions of the ultrasonifier before the polymerization process. The building‐up of a shearing force decreases the size of the PEDOT nanoparticles and also causes the occurrence of a multimodal size distribution for the PEDOT nanoparticles. The electrical conductivity of the PEDOT nanoparticles was 0.28–1.20 S cm⁻¹. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel approach to graft silicones onto waterborne polyacrylate for synthesizing anti-graffiti coatings by polydimethylsiloxane-functionalized RAFT agent

Linear organoalkoxysilane-based RAFT agent functionalized polydimethylsiloxane (RAFT-PDMS) has been prepared for the first time via co-condensation of a new organoalkoxysilane based RAFT agent (RAFT-Agent), 2-((methyldimethoxysilyl)propyl)carbontrithio-2-methyl-propanoicacidmethylester, with diethoxydimethylsilane (DDS) in an aqueous acidic solution. The RAFT-Agent and RAFT-PDMS was confirmed by FT-IR and ¹H NMR spectroscopy techniques. The obtained RAFT-PDMS was used to prepare the silicone-modified polyacrylate anti-graffiti emulsions via RAFT polymerization with functional monomers. The living character of RAFT polymerization of RAFT-PDMS and the narrow molecular weight distribution of the polymerization product were confirmed by GPC. The transformation of the particle state from a small micelle structure to a spherical core-shell micelle structure during polymerization was verified by TEM and dynamic light scattering analysis. Moreover, DSC and TGA analysis disclosed that increasing the content of RAFT-PDMS can reduce the glass transition temperature and improve the thermal stability of the resin. Finally, the effect of RAFT-PDMS on the surface morphology and properties of coatings were examined by SEM and contact angle. These experimental results suggest that increasing the content of RAFT-PDMS increases the surface porosity of the coating film and thus enhances its hydrophobic properties.     

A new approach to continuous emulsion polymerization

The application of a continuous Couette-Taylor vortex reactor to continuous emulsion polymerization was studied. First, the mixing characteristics of the reactor were examined by the stimulus-response method. It was found that the reactor performance was similar to that of a continuous flow reactor consisting of more than 60 well-stirred tanks in series if the reactor was properly designed and operated near the critical Taylor number. It was also demonstrated by a comparison of the particle size distributions of the latexes produced in a batch reactor and in the continuous Couette-Taylor vortex reactor that the continuous reactor could produce latex particles with fairly narrow size distribution. Furthermore, since no stirrer is involved, this continuous reactor is suited for the purpose of avoiding coagulation of latex particles that are very sensitive to mechanical shear.     

A novel approach to color matching of automotive coatings

The coatings industry requires a fast and accurate color formulating process. Today the manual/visual color matching procedures are time consuming and require high skills, in particular when metallic and pearlescent colors are involved. For that reason, a new approach to the colorimetry of paints was followed. This resulted in the development of a system employing an easy to use instrument and powerful software allowing instant formulation of almost any desired color. The system comprises a portable multi-angle spectrophotometer in combination with a personal computer and dedicated color matching software. Development of both the instrument and the software resulted from research on optics, vision science, color mixing properties and computational procedures. In the software new algorithms describing the light-paint interactions (absorption and scattering) and the procedures applied at on site color matching are imbedded. The system retrieves the optimum paint formula through fully automated multi-angle spectral measurements followed by an analysis of the spectra and subsequent data bank search. When desired, correction procedures allow adjustment of the formula through additional measurements on a spray out sample.     

Influence of the geometric factors of the experimental device used in suspension polymerization on the properties of poly(styrene‐co‐divinylbenzene) microparticles

The prediction of the final particle size for reactive systems such as the reactions of suspension polymerization is a complex matter. Thus, the preparation of very small microparticles is specially challenging, probably because of the coalescence of the polymeric beads taking place during the later stages of the polymerization. In this work, very small gel‐type styrene‐co‐divinylbenzene beads were synthesized by using a previously determined set of experimental synthesis conditions in which the stabilization of the dispersion of the monomeric droplets was ensured, and, under these conditions, the factors related to the geometry of the experimental device were modified to determine their actual effect on the final size of the microparticles. From the experimental results, a very simple and useful model was obtained that was able to predict the final size of the microparticles as a function of the values of the geometric factors of the reactor. This model indicates that the most influential factors in the final size of the microparticles are the liquid depth inside the reactor and the stirrer diameter; thus, an increase in the liquid depth produces larger particles, and, conversely, the particle size decreases when using larger stirrer diameters. Additionally, the model permits the design of polymerization experiments aimed at obtaining microparticles with a diameter smaller than 50 μm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A facile one‐step synthesis of flame‐retardant coatings on cotton fabric via ultrasound irradiation

This article reports a facile one‐step methodology to increase fire resistance properties of cotton fabric. The flame‐retardant coating for cotton fabric was synthesized with methyltriethoxysilane and organophosphates (M102B) through an ultrasound irradiation process. The coating structure and surface morphology of uncoated and coated fabrics were investigated by Fourier transform infrared spectroscopy and scanning electron microscope, respectively. The flame‐retardant properties, bending modulus, air permeability and thermal stability were studied by vertical burning test, cantilever method, air permeability test and thermogravimetric analysis (TGA). As a result, the cotton fabric coated with 29.2% (mass increased) of flame‐retardant coating was able to balance the flame retardant property and wearing comfort of the fabrics. The TGA results showed that the residue char of cotton was greatly enhanced after treatment with the coating, which has a high char forming effect on cellulose during testing. Furthermore, flame‐retardant property of coated fabrics did not change significantly after 10 washing cycles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45114.     

A model of the infrared cure of powder coatings based on surface absorptivities in-situ measurements

The efficiency of radiative powder coatings curing depends both on the coating radiative properties and the spectral emissivities of the infrared emitters. This investigation is structured to develop a mathematical model using the radiative properties of the coating to describe precisely the coating temperature and deduce the degree of polymerization conversion during the cure. The reflectance measurements results obtained with a FTIR equipped with an integrating sphere are analyzed and implemented in a thermal model. These results show that reflectance values vary with the chemical composition, the pigment nature, and are influenced by the powder coatings cure. The thermal model, solved with the finite volume method, permits to compute the varying temperature within the thickness of the powder-coated metal sample and provides a good prediction of the temperature within the “coating + substrate” system. The experimental cure of powder coatings supporting this study was performed in a small test oven equipped with electrical infrared emitters. Presented at 2006 FutureCoat! Conference, sponsored by Federation of Societies for Coatings Technology, November 1–3, 2006, in New Orleans, LA.     

A novel approach for synthesis of poly(norbornene)‐co‐poly(styrene) block copolymers via metathesis polymerization and free‐radical polymerization

It is successfully realized that block copolymers are synthesized via metathesis polymerization followed by free‐radical polymerization. This method is performed using styrene (St) and norbornene, one block is synthesized using the Grubbs second generation catalyst in the presence of chain transfer agents, and the subsequent polymerization of St is initiated by azo compounds to complete the additional blocks in the copolymers. The use of free‐radical polymerization instead of controlled radical polymerization or ionic polymerization can be potentially superior for industrialization. As a result, the molecular weights of the block copolymers ranging from 10.4 to 54.3 kDa and polydispersity indices ranging from 1.30 to 1.91 are obtained. In principle, this new method can be potentially useful to prepare a broad range of block copolymers with cyclic olefin groups in the main chains, which may be used in some particular applications.     

Computationally efficient solution of population balance models incorporating nucleation, growth and coagulation: application to emulsion polymerization

A computationally efficient solution technique is presented for population balance models accounting for nucleation, growth and coagulation (aggregation) (with extensions for breakage). In contrast to earlier techniques, this technique is not based on approximating the population balance equation, but is based on employing individual rates of nucleation, growth and coagulation to update the PSD in a hierarchical framework. The method is comprised of two steps. The first step is the calculation of the rates of nucleation, growth and coagulation by solving an appropriate system of equations. This information is then used in the second step to update the PSD. The method effectively decomposes the fast and the slow kinetics, thereby eliminating the stiffness in the solution. In solving the coagulation kernel, a semi-analytical solution strategy is adapted, which substantially reduces the computational requirement, but also ensures the consistency of properties such as the number and mass of particles.     

In‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to miniemulsion polymerization

We present in‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to prepare hybrid latex particles by miniemulsion polymerization. On the surface of a silver nanoparticle/silica nanoparticle/acrylic polymer hybrid layer formed in‐situ on a polyethylene terephthalate (PET) substrate, a copper film is deposited using electroless copper deposition. Silver nanoparticles, which are formed in‐situ via the reduction of silver ion by radical species and subsequent annealing, work as a catalyst for the electroless deposition. Miniemulsion polymerization via the in‐situ formation of nanoparticles affords nanoparticle/acrylic polymer hybrid latex particles and polymer particles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42675.     

Water‐based crosslinkable coatings via miniemulsion polymerization of acrylic monomers in the presence of unsaturated polyester resin

Hybrid miniemulsion polymerization was performed with a three‐component acrylic system of methyl methacrylate, butyl acrylate, and acrylic acid in the presence of a Bayer® Roskydal TPLS2190 unsaturated polyester resin. Latexes were obtained in which the polyester resin was grafted to the acrylic polymer, forming a water‐based crosslinkable coating. Grafting between the resinous component and the acrylic polymer is a feature different from the work of others who have attempted to combine the properties of both systems in water‐based blends. Both emulsions and latexes were shelf‐stable for over 6 months, shear‐stable, and resistant to at least one freeze/thaw cycle. Resin‐to‐monomer ratios were studied as high as 1 : 1 (wt : wt), and total emulsion solids, as high as 45%. Monomer droplet and latex particle sizes were similar, suggesting evidence of the preponderance of droplet nucleation. A high level of crosslinking (>70%) during polymerization was observed in this particular hybrid system in contrast to those involving alkyd or polyurethane resins (<5%). Films, both homogeneous and hard, were achieved with exceptional adhesion. Electron microscopy showed the hybrid particle morphology to have internal domains of polyester resin in an acrylic matrix. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 916–927, 2000     

Role of acrylic acid in the synthesis of core‐shell fluorine‐containing polyacrylate latex with spherical and plum blossom‐like morphology

The core‐shell fluorine‐containing polyacrylate latex was successfully synthesized by two‐stage semicontinuous emulsion copolymerization of methyl methacrylate (MMA), butylacrylate (BA), acrylic acid (AA), and dodecafluoroheptyl methacrylate (DFMA). The fluorine‐containing polyacrylate latex was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC). The effects of AA content on monomer conversion, polymerization stability, particle size, corsslinking degree, carboxyl groups distributions (latex surface, aqueous phase or buried in latex), as well as mechanical properties and water absorption rate of latex film were investigated. The obtained fluorine‐containing polyacrylate latex exhibited core‐shell structure with a particle size of 120–150 nm. The introduction of AA was beneficial for the increase of monomer conversion and the polymerization stability, and had little effects on the mechanical property of latex film. However, the hydrophilicity of AA made the water resistance of latex film get bad. With the increase of AA content, the carboxyl groups preferred to distribute on aqueous phase, and the possibility of homogeneous nucleation increased and more oligomers particles were formed. Moreover, the oligomers would distribute to the latex and continued to grow up, making the latex morphology changed from spherical to plum blossom‐like. The core‐shell latex had two T_g corresponding to the rubber polyacrylate core and hard fluorine‐containing polyacrylate shell, and the latex film possessed excellent thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42527.     

A novel approach to the preparation of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring‐opening polymerization of ε‐caprolactam

Blends of thermoplastic polyether‐based urethane elastomer (TPEU) and monomer casting polyamide 6 (MCPA6) were prepared using ε‐caprolactam as reactive solvent, with caprolactam sodium as a catalyst in the presence of TPEU, with TPEU content varying from 2.5% to 10% by weight. In situ anionic ring‐opening polymerization and in situ compatibilization to prepare TPEU/MCPA6 blends were carried out in one step. The TPEU chains, which underwent thermal dissociation in amine solvents to bear isocyanate groups, acted as macroactivator to initiate MCPA6 chain growth from the TPEU chains and form graft copolymers of TPEU‐co‐MCPA6 to improve compatibility between TPEU and MCPA6. The structure and thermal properties were characterized by means of Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, differential scanning calorimetry and scanning electron microscopy. Copyright © 2006 Society of Chemical Industry     

Preparation of novel MgCl2‐adduct supported spherical Ziegler–Natta catalyst for α‐olefin polymerization

In this article, preparation of novel MgCl₂‐adduct supported spherical Ziegler–Natta catalyst for α‐olefin polymerization is reported. The factors affecting the particle size (PS) and particle size distribution (PSD) of the prepared support were investigated. In this method, the internal donor added while preparing MgCl₂‐adduct support was supposed to act as a crosslinking agent. Therefore it provided a reasonable way to enhance the morphology and control the PS of the resultant polymer particles. The possible mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 945–948, 2006     

A renewable approach toward the development of mahua oil‐based wood protective polyurethane coatings: Synthesis and performance evaluation

In the current scenario, the demand for renewable resources is increasing day by day due to numerous factors. In view of this, current work represents the preparation of wood protective polyurethane (PU) coatings from mahua oil. Mahua oil was used as a starting material for the synthesis of fatty amide by base catalyzed aminolysis reaction. The synthesized fatty amide was converted into the polyetheramide polyols by a condensation reaction with bisphenol C. The structure of the synthesized products was confirmed by the attenuated total reflection‐Fourier transform infrared and ¹H‐NMR spectroscopy. The synthesized polyetheramide polyols were used as precursors for the preparation of PUs and the prepared PUs were applied on the wood surface as a protective coating. The coating performance of the PUs was evaluated by the measurement of mechanical, thermal, and microbial properties as well as water, solvent, and chemical resistance. The coating performance revealed that mahua oil can be used as a renewable resource for the preparation of wood protective PUs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46722.     

Synthesis and characterization of a novel silicone containing vinylic macromonomer and its uses in the preparation of poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite nanocomposite emulsion

A new silicone containing macromonomer, 4‐(methacrylamido) phenoxy polymethylhydrosiloxane (4‐MPMHS) with a vinyl group, was successfully synthesized. Then poly (silicone‐co‐styrene‐co‐butylacrylate) with montmorillonite, P (Si‐co‐St‐co‐BA) with MMT nanocomposite emulsion was prepared by in situ intercalative emulsion polymerization of styrene (St), butyl acrylate (BA), and 4‐MPMHS, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1.0, 1.5, and 2 wt %). Potassium persulphate (KPS) was used as an initiator and sodium lauryl sulfoacetate (SLSA) and nonyl phenol ethylene oxide—40 U (NP‐40) were used as anionic and nonionic emulsifiers, respectively. The resulting macromonomer was characterized by elemental analysis, Fourier transformer infrared (FT‐IR), proton (¹H NMR), and carbon (¹³C NMR) nuclear magnetic resonance spectroscopes. The OMMT was characterized by FT‐IR and X‐ray diffraction (XRD). The nanocomposite emulsions were characterized by using Fourier Transform infrared spectroscopy (FT‐IR), laser light scattering, and surface tension method. Thermal properties of the copolymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) and then the effects of OMMT percent on the water absorption ratio and drying speed were examined. Results showed that OMMT could improve the properties of emulsion. In other words, the properties of nanocomposite emulsions were better when compared with those of the silicone‐acrylate emulsion. The property of nanocomposite emulsion containing 1 wt % OMMT was the best one, and the following advantages were obtained: smaller particle size, faster drying speed, smaller surface tension, and improved water resistance by the incorporation of OMMT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011