Polymer Particle Size Distribution Research Articles

E7 nematic liquid crystal encapsulated in a polymeric photonic crystal

This study presents the synthesis and characterization of nano encapsulated liquid crystals in the polymer (nano-ELCP) obtained by the soap-free emulsion polymerization of the system styrene (ST) and acrylic acid (AA) in the presence of the liquid crystal E7 (LC). The obtained emulsion and the photonic crystal film (PC) were characterized by optical microscopy, SEM, DLS, UV–Vis, DSC, TEM, GPC, TGA, and fluorescence spectroscopy to highlight the encapsulation of E7 in the polymer particles and their properties. The DLS and SEM analyses confirmed a narrow polymer particle size distribution and the possibility to form highly arranged PCs, which contain the dispersed LC. The DSC, TEM, and TGA analyses sustain the encapsulation of E7 with an LC content of 11.87 % and 25.19 % (weight %) for ST-AA-E7-1 and ST-AA-E7-2, respectively. An increase in the fluorescence response was demonstrated for the polymer encapsulated LC which can be attributed to PCs that augments the intensity of the nematic crystal fluorescence response, in the absence of external stimuli.

Real-time release testing of dissolution based on surrogate models developed by machine learning algorithms using NIR spectra, compression force and particle size distribution as input data

In this work spectroscopic measurements, process data and Critical Material Attributes (CMAs) are used to predict the in vitro dissolution profile of sustained-release tablets with three machine learning methods, Artificial Neural Networks (ANN), Support Vector Machines (SVM) and Ensemble of Regression Trees (ERT). Beside the effect of matrix polymer content and compression force, the influence of active pharmaceutical ingredient (API) and matrix polymer particle size distribution (PSD) on the drug release rate of sustained tablets is studied. The matrix polymer PSD was found to be a significant factor, thus this factor was included in the dissolution prediction experiments. In order to evaluate the importance of the inclusion of PSD data, models without PSD data were also prepared and the results were compared. In the developed models, the API and hydroxypropyl-methylcellulose (HPMC) content is predicted from near-infrared (NIR) spectra, the compression force is measured by the tablet press and HPMC particle size is measured off-line. The predictions of ANN, SVM and ERT were compared to the measured dissolution profiles of the validation tablets, ANN yielded the most accurate results. In the presented work, data provided by Process Analytical Technology (PAT) sensors is combined with CMAs for the first time to realize the Real-Time Release Testing (RTRT) of tablet dissolution.

Fabrication of methyl methacrylate-based polymer particles by miniemulsion and combined miniemulsion/emulsion polymerization using an atomization apparatus

The present study evaluated the fabrication of methyl methacrylate-based polymer nanoparticles by miniemulsion and combined miniemulsion/emulsion polymerization using an atomization apparatus with two-fluid nozzle. In both reactions, the effects of the operational conditions were investigated on the morphology and particle size distribution of polymer particles. After multivariate analysis, it was observed that the size of the poly(methyl methacrylate) particles is a function of gas pressure in the experiments stabillized by sodium lauryl sulfate (SLS), but this did not occur in reactions stabillized by inorganic and polymeric stabilizers. The use of inorganic stabilizer made possible the fabrication of polymer particles smaller than 300 nm. In combined miniemulsion/emulsion polymerization with SLS, high concentrations of surfactant (> 0.4% w/w) and intermittent monomer feeding enabled not only an increase of the solid concentrations, but also a reduction of particle size. In addition, styrene-methyl methacrylate nanoparticles were successfully obtained (< 30 nm), according to dynamic light scattering and transmission electron microscopic analyses.

Dual function of Eosin Y in miniemulsion polymerization: Stabilizer and FRET acceptor

Recent studies have shown that water-soluble fluorescent dyes can be used as miniemulsion stabilizers to avoid a series of deficiencies in traditional stabilizers. However, visual means to demonstrate the stabilizing performance of water-soluble dyes are still scarce. In this study, the principle of fluorescence resonance energy transfer (FRET) is combined with dual emission of fluorescent polystyrene nanoparticles prepared by miniemulsion polymerization. For this purpose, 4-(1,2,2-triphenylethyl) phenylundecene-10-enoate (TPE-Aly) was employed as aggregation induced emission (AIE) dye and donor and Eosin Y as acceptor and stabilizer. The polymer molecular weight, particle size and size distribution of the nanoparticles were optimized by regulating the amount of Eosin Y and ultrasonication time, respectively. The average number of Eosin Y molecules per nanoparticle was firstly estimated by combining dialysis and Lambert-Beer law. FRET between TPE-Aly and Eosin Y indicates the presence of Eosin Y on the surface of the polymer nanoparticles. With increasing concentration of Eosin Y, the as-prepared dual-emission nanoparticles display a decreasing particle size along with an enhancing FRET efficiency. Moreover, various stability tests show that Eosin Y can be used as an excellent stabilizer for miniemulsion polymerization and has broad application prospects in the field of functional materials research.

Preparation of monodisperse polymer particle via an in situ charge neutralization-controlled particle coagulation mechanism in macroemulsion polymerization

Styrene emulsion polymerizations using sodium dodecyl sulfate as an anionic surfactant and in the presence of cationic initiators 2, 2′- Azobis (2-methylpropionamidine) dihydrochloride (AIBA) and 2,2′-azobis(N,N′-dimethyleneisobutyramidine) dihydrochloride (ADIBA) were studied. In this work, an explanation for in situ charge neutralization is proposed, and the effect of in situ charge neutralization on the particle size distribution of the ultimate polymer particles is discussed. Charges of cationic radicals from initiator decomposition shield the anionic charges of surfactant molecules adsorbed on the particle surface and induce particle coagulation during the early particle formation period. As the occurrence of in situ charge neutralization, the particle number decreases and the rate of micelle capture for the initiator radical is enhanced. Thus, the particle nucleation period is shortened, and monodisperse polymer particles with a diameter of ～200−300 nm are prepared using this simple emulsion polymerization process. In addition, hydrolysis of the initiator AIBA at different pH conditions is used to control particle size and stability. Compared to conventional emulsion polymerization theories, the emulsion polymerization in the presence of in situ charge neutralization presents unique kinetics.

Ziegler–Natta catalyst sonofragmentation for controlling size and size distribution of the produced polymer particles

AbstractThe size of the Ziegler–Natta catalyst (ZNC) particles can have a strong impact on their activity and the size and size distribution (SD) of the final polymer particles. In this work, we apply sonofragmentation to break the ZNC particles dispersed in hexane. Our main goals are first to monitor the breakage induced by the ultrasonic power to understand the kinetics and the effect of sonofragmentation on the colloidal stability of the ZNC particles. Second, we explore the effect of sonofragmentation on the polymerization performance of the ZNC particles. It is found that sonofragmentation can not only reduce the size but also narrow the SD of the ZNC particles. From the tests of ethylene polymerization, we observed that the catalyst yield of the sonofragmentation‐treated ZNC is substantially higher than that of the untreated one and that the obtained polymer particles exhibit a smaller average size and a narrower SD.

Synthesis of monodisperse, re-dispersable polymer particles by one-step high solid emulsion polymerization in the presence of reactive surfactant

In this study, monodispersed and re-dispersed poly (methyl methacrylate) (PMMA) particles were prepared by high solid content (50 wt%) macroemulsion polymerization using commercial macromonomer (Emulsogen APS 100) as a reactive surfactant (surfmer). Highly monodispersed, re-dispersed PMMA particles with sizes around 300 nm were obtained using this process. The effect of recipe composition including surfmer content, monomer/water ratio and electrolyte concentration on particle formation and growth were also investigated. Compared to classical macroemulsion polymerization theory, the formation of particles was found different. The number of formed particles firstly increased to a maximum value, then rapidly decreased to reach a constant value stabilized at around 1/5 of the maximum particle number. The particle coagulation theory was used to explain the process of particle formation and growth. The relationship between polymer particle size distribution and particle coagulation was also examined and the results were discussed. The proposed method would probably find applications in industrial production of monodisperse particles.

Insight into the Synthesis Process of an Industrial Ziegler–Natta Catalyst

In Ziegler–Natta catalysis, the catalyst particle size has a strong influence not only on catalyst performance but also on the morphology and particle size distribution of the final polymer particles. Fundamental insight into the catalyst particle formation process is therefore of industrial importance when addressing specific requirements in the final products. In the present work, we fully characterize a single-step catalyst preparation process, which comprises a reactive precipitation of a MgCl2-supported Ziegler–Natta catalyst, through decomposition of the hetero-bimetallic complex, Mg(OR)2·Ti(OR)4, by addition of ethyl aluminum dichloride (EADC). We track the evolution of both of the concentrations of the metals (Mg, Ti, Al) as well as Cl in the liquid phase and the size of the formed catalyst particles. It is observed that the liquid-phase composition is governed by the EADC feed rate under fully Cl-starved conditions. The process can be divided into two stages: The first stage is dominated by the p...

A Monte Carlo Method to Quantify the Effect of Reactor Residence Time Distribution on Polyolefins Made with Heterogeneous Catalysts: Part IV—Intraparticle Transfer Resistance Effects

AbstractAn integrated Monte Carlo/polymeric multilayer model (MC/PMLM) is developed to predict the polymer particle size distribution (PSD) and microstructures of polyolefins made with heterogeneous catalysts under intraparticle mass transfer limitations. The Monte Carlo model is used to randomly sample particle sizes and residence times from the catalyst PSD and reactor residence time distribution (RTD), respectively, while the polymeric multilayer model is used to describe single‐particle growth considering intraparticle mass transfer resistances. The effect of reactor RTD, catalyst PSD, and polymerization kinetics on polymer PSD and polymer properties is systematically investigated with the MC/PMLM for the first time. The results show that intraparticle mass transfer limitations under various operating conditions may affect polymer PSD and polymer properties. In addition, due to the versatility of the Monte Carlo approach, the proposed MC/PMLM is adequate to describe complex cases, such as reactor systems with arbitrary RTD and catalyst particles having any PSD.

Computational Fluid Dynamics Modeling of Temperature Distribution in Fluidized Bed Polymerization Reactor for Polypropylene Production

Propylene polymerization process is one of the chemical processes that take place in the fluidized bed reactor. The gas monomer is fed through the distributor to react with the solid catalyst particles inside the reactor. The polymer particles are produced from the heterogeneous exothermic polymerization reaction. Although the fluidized bed polymerization reactor has high heat and mass transfer rate, the thermal efficiency is usually limited due to the formation of hot spots and improper mixing. In this research, a computational fluid dynamics (CFD) model of the fluidized bed polymerization reactor for polypropylene production is developed in order to study the temperature distribution within the reactor. The polymer growth rate and particle size distribution are included in the CFD model development. The heat is generated from highly exothermic polymerization reaction and removed in the heat exchanger. By proper adjusting the monomer feed velocity, the uniform temperature distribution inside the reactor is obtained in axial and radial directions. Additionally, the temperature of the outlet gas stream can be reduced, thus reducing the external cooling duty.

Role of added amphiphilic cationic polymer in the stabilization of inverse emulsions

The amphiphilic cationic polymer, poly(acryloyloxyethyl dimethylbenzyl ammonium chloride) (PAODBAC), has been studied as an additive for the stabilization of water-in-oil inverse emulsions prepared from mixed surfactants. The interaction behavior of PAODBAC with the surfactants, the effect of the PAODBAC concentration on the stability of the inverse emulsion obtained after polymerization, the characteristics of the polymer particle after polymerization, and the rheological properties with different concentrations of PAODBAC have been systematically investigated. A mechanism is proposed to account for the stabilizing effect of PAODBAC on the inverse emulsion system. The PAODBAC chains can interact with the surfactant molecules. When the concentration of PAODBAC was 0.067% (w/w), the interactions between the polymer chains and surfactant molecules were optimized, resulting in the best stability of the inverse emulsion. The presence of PAODBAC in the inverse emulsion system aided the establishment of a small mean polymer particle size distribution.

The effect of aluminum alkyls and BHT‐H on reaction kinetics of silica supported metallocenes and polymer properties in slurry phase ethylene polymerization

ABSTRACTIn slurry and gas phase catalytic ethylene polymerization processes, aluminum alkyl (AlR3) compounds are usually present inside the reactor and their role either as co‐catalyst or scavenger is of considerable importance. Silica supported metallocene/methyl aluminoxane (MAO) catalysts show specific interactions with AlR3 compounds. Therefore, this study shows an attempt to analyze and compare the effect of concentration as well as type of commonly used AlR3 on slurry phase ethylene homopolymerization kinetics of silica supported (n‐BuCp)2ZrCl2/MAO catalyst. The obtained results indicate that the lower the concentration of smaller AlR3 compounds, the higher the instantaneous catalytic activity. Concerning the polymer particle size distributions, a rise in fines generation has been observed with increasing AlR3 content inside the reactor. Finally, it has been shown that the addition of 2,6‐di‐tert‐butyl‐4‐methylphenol (a substituted phenol) into the reactor containing AlR3 reduces the influence of AlR3 compounds on the reaction kinetics of silica supported metallocene/MAO catalysts. Polyethylene properties remain similar in all the studied scenarios. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45670.

Role of emulsifier on the particle size and polymer particle size distribution using multiwavelength spectroscopy measurements

ABSTRACTLatex emulsions depend strongly on the polymer composition, and particle size distribution, which in turn, is a function of the preparation of the latex and on the formulation and composition variables. This study reports measurements of particle size and particle size distribution of latex emulsions as function of the reaction time and the type and concentration of emulsifier by using the multiwavelength spectroscopy technique. Results show changes in the particle size of latex emulsions with the reaction time, obtaining larger particles and broader distributions with increasing of Tween 80 ratio. The steric stabilization provides the sole nonionic emulsifier is not enough to protect the polymer particle, causing the flocculation among the interactive particles, resulting in unstable latex. However, latex emulsions prepared with Tween 80 ratio <70 wt.% can stabilize efficiently the nucleated particles, probably due to the effects provided by both, the electrostatic and steric stabilization mechanisms. The same effect is shown in the curves of conversion (%) as a function of reaction time, resulting in slower polymerization rate for Tween 80 ratio >70 wt.%. On the other hand, smaller polymer particles, in all range of emulsifier mixture, have been obtained to higher emulsifier concentration.

Design of spray dried ternary solid dispersions comprising itraconazole, soluplus and HPMCP: Effect of constituent compositions

A range of 17 ternary formulations of itraconazole (ITZ), HPMCP and Soluplus have been manufactured using spray drying. These amorphous solid dispersions (ASDs) were very stable against crystallisation and ITZ was found to be amorphous in all formulations after one year at 40°C/75% RH. A number of solid state analytical techniques including PXRD, DSC, small angle X-ray scattering, FTIR and solid state NMR were used to characterise the physicochemical properties of the ASDs following processing and storage and to assess any interactions between components. Microtrac laser scattering analysis revealed a relationship between polymer levels and particle size distribution (PSD). Dissolution studies indicated that higher Soluplus content in the formulation resulted in higher concentrations of ITZ in acidic media.

Design and preparation of porous polymer particles with polydopamine coating and selective enrichment for biomolecules

Pore size distribution of novel gigaporous polymer particles were visualized characterization by laser scanning confocal microscopy, and this gigaporous materials had preferable selective enrichment performance for biomolecules.

An innovative microwave cavity sensor for non-destructive characterisation of polymers

This paper investigates the feasibility of using an innovative microwave sensing technology to characterise and study various properties of polymer material such as difference between various polymer types, particle size and particle size distribution, contamination and pigmentation. A microwave sensor designed previously has been utilised to carry out this initial study to analyse the capability of microwave techniques to carry out the analysis. The curves obtained from material response to microwaves are distinguishable showing the shift to the lower frequency end with the insertion of polymer material. S11 measurements have shown distinctive peaks for each size and type of the sample tested. The results are quantifiable in terms of various polymer properties under consideration. In terms of S21 measurements, microwave sensor clearly distinguishes between coarse and fine polymer samples in terms of particle size. The effect of air voids in the sample and the particle size distribution has also been studied. The results are promising and justifies a thorough design and development of a dedicated microwave sensor unit for the characterisation of polymers. The sensor will have a significant industrial benefit in terms of costs associated with the industrial analysis, increase in the efficiency of manufacturing and production operation as well as material quality, control and validation.

A CFD-PBM model considering ethylene polymerization for the flow behaviors and particle size distribution of polyethylene in a pilot-plant fluidized bed reactor

In large-scale industrial fluidized bed reactors (FBRs) for polyethylene (PE) production, the prediction of the interactions between polymerization, gas–solid two phase flow and particle kinetics is very challenging. This paper aims at providing a new insight into the effects of ethylene polymerization on the particle flow behaviors and particle size distributions (PSDs) of PE in a pilot-plant FBR via a CFD-PBM modeling approach. An Eulerian–Eulerian two-fluid model involving ethylene polymerization kinetics is coupled with a population balance model (PBM) to track the polymer PSDs. The particle growth, aggregation and breakage are taken into account in the PBM. The predicted pressure drop and temperature agree well with the available experimental data. Compared with the cold-model, the flow characteristics of polymer particles and the PSDs show noticeable differences in the case of considering polymerization. A slightly higher bed expansion height and lower axial particle velocity are also presented in this case. The core-regions of the core–annulus flow structures in terms of the solid concentration and particle velocity are obviously broader than that of the cold-model. Moreover, due to the polymerization reaction and mass/heat transfer effects, more PE particles are concentrated on the middle–upper areas of the FBR. As expected, particle breakage leads to a decrease in the average PE particle diameter and an increase in the bed expansion height.

Quantitative understanding of the self-sharpening of growing polymer particle size distributions in soap-free emulsion polymerization

Soap-free emulsion polymerization is an environmentally desirable process that can produce highly monodisperse polymer particles with high purity. In the polymerization, knowledge on the mechanism of particle growth is important for size control of the polymer particles. Experimental and theoretical study is performed on the self-sharpening of particle size distributions appearing with particle growth in soap-free emulsion polymerization. The dependence of particle growth rate on particle size was determined with two experimental methods of the seeded growth and non-seeded polymerizations of styrene. In the seeded growth polymerization, polymer particles with two different sizes were used to measure relative growth rate of the particles in the same reaction field. In the non-seeded polymerization, the relative growth rates were measured from time-variation of a particle size distribution during the particle growth. Two initiators, potassium persulfate and 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate at various pH, were employed to conduct the experiments in a wide range of particle sizes 0.1–2 μm. Both the experiments showed the same tendency of the size-dependence, which indicated that the self-sharpening becomes weak with an increase in particle size. This tendency is quantitatively explained by the particle growth mechanism that considers the gel effect of radical polymerization and the interfacial energy of monomer-swollen polymer particles.

Modeling and simulation of polypropylene particle size distribution in industrial horizontal stirred bed reactors

AbstractThis work aims at developing a steady‐state particle size distribution (PSD) model for predicting the size distribution of polypropylene particles in the outflow streams of propylene gas‐phase horizontal stirred bed reactors (HSBR), on the one hand and investigating the effect of the catalyst residence time distribution (RTD) on the polymer PSD, on the other hand. The polymer multilayer model (PMLM) is used to describe the growth of a single particle. Knowing the PSD and RTD of a Ziegler–Natta type of catalyst and polymerization kinetics, this model allows calculating the polymer PSD of propylene polymerization in the HSBRs. The calculated polypropylene PSDs agree well with those obtained from the industrial reactors. The results reveal that both the PSD and the RTD of the catalyst affect the polymer PSD but in different manners. The effect of RTD on the PSD is less significant in the case of a nonuniform size catalyst feed. This model also allows investigating the effects of other process parameters on the polymer PSD under steady‐state conditions, including intraparticle mass‐ and heat‐transfer limitations, initial catalyst size, and polymer crystallinity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Dispersion copolymerization of methyl methacrylate and styrene in supercritical carbon dioxide

A method for producing finely dispersed powders of methyl methacrylate (MMA)-styrene copolymer by radical polymerization in a supercritical carbon dioxide medium (SC-CO2) was proposed, studied, and experimentally implemented. The dispersing agent (surfactant), which made it possible to obtain nearly monodisperse size distribution of polymer particles, was poly(dimethylsiloxane methacrylate), a SC-CO2-soluble substance. The copolymer, synthesized with a molecular mass of Mw ∼ 36000 in the form of spherical particles with a characteristic size of ∼1 μm, exhibited a higher thermal stability as compared to poly(methyl methacrylate) with a similar molecular mass. Varying the percentage ratio between MMA and styrene monomers, it was possible effectively control the integral hydrophobicity and physicomechanical characteristics of the methacrylate-styrene copolymer.