Latex Particle Size Distribution Research Articles

Effects of dispersion techniques on the emulsion polymerization of methyl methacrylate

Poly(methyl methacrylate) (PMMA) latices for organic coating systems were prepared via emulsion polymerization using various emulsifying techniques. The dispersion modes have an important effect on the particle size and particle size distribution (PSD) of polymeric latices during the emulsion polymerization process. The different dispersion modes, such as magnetic stirring, ultrasound, and the combination of magnetic stirring and ultrasound, were examined to prepare particle size small and narrow PSD polymer latex. PMMA latex of size less than 20 nm in diameter and narrow PSD was successfully produced using the probe ultrasound method. By modifying the amplitude, temperature, and duration of the ultrasound probe and surfactant/water ratio, the optimal ultrasound conditions for the microemulsion polymerization were determined. This research provides new insights into the relationship between the dispersion modes and the colloidal properties of latex, which may offer more effective and simpler routes to prepare latices with fast polymerization rate and high conversion.

Preparation of monodisperse polystyrene nanoparticles with tunable sizes based on soap-free emulsion polymerization technology

Herein, a one-step procedure for the preparation of monodispersed nanoparticles was achieved, with tunable size in range of around 30~300 nm based on soap-free emulsion polymerization using sodium p-styrene sulfonate as ionic comonomer. The polymerization reaction kinetics (i.e., monomer conversion, particle number, and particle size distribution) were investigated in detail. The experimental results indicated that the particle number increased in low ionic comonomer NaSS concentrations (< 10 wt%). The particle number reached maximum value at 10 wt% NaSS concentration, and minimum particle size nanoparticles (22.3 nm) were obtained. The particle size increased when NaSS concentration exceeded 10 wt%. The particle size distribution of latex gradually narrowed as the polymerization reaction was carried out due to the eversible particle coagulation process and competitive growth kinetics of a particle growth period. This method is conventional and practical for the production of nanoparticles.

On Particle Size Distributions in Catalytic Chain Transfer Emulsion Polymerization: Chain-Extension and the Use of Derived Macromonomers as Reactive Surfactants in Emulsion Polymerization.

Catalytic chain transfer emulsion polymerization (CCTP) and subsequent chain extension via reversible addition-fragmentation chain transfer (RAFT) were used to synthesize amphiphilic macromonomers (MM), in the form of polymer latexes. The macromonomers consisted of two blocks whose first was a random copolymer of methacrylic acid and methyl methacrylate, at 35:65 mol:mol, while the second block was n-butyl methacrylate P[(MAA-co-MMA)-block-PBMA]. The block copolymer colloids were disintegrated and micellized upon addition of ammonia. The resulting nanosized polymer dispersions were used as reactive surfactants in the emulsion polymerization of n-butyl methacrylate. For this, a dual stage slow-fast monomer feed profile was used. The final polymer latexes were in the sub-100 nm range for the particle diameter at 30% w/w total polymer content. The emphasis of the work is to discuss and find an explanation for the observed particle size distributions in the three consecutive emulsion polymerization steps. The particle size distribution of the ω-unsaturated macromonomer latex synthesized by CCTP emulsion polymerization was found to be much broader than expected. This discrepancy is attributed to an extended particle nucleation period. The chain extension step in the macromonomer latex preparation showed considerable secondary nucleation. The presence of water-soluble macromonomer species from the CCTP emulsion polymerization step assured that control of chain growth persisted. The use of the amphiphilic macromonomers as reactive surfactants in the form of a nanosized aggregate seed dispersion showed that the average particle diameter could be tuned and that the molecular weight distributions could be regulated, when monomer starved conditions were used in the emulsion polymerizations.

Emulsifier-free emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers: a kinetic study based on polymerization pressure profile

Emulsion polymerization of acrylonitrile-butadiene-carboxylic acid monomers (XNBR latexes) in the absence of emulsifier is associated with thermodynamic and kinetic complexities and is very sensitive to colloidal stability. In this paper, polymerization pressure profiles were utilized for kinetic studies of emulsifier-free emulsion terpolymerization of acrylonitrile, butadiene and two carboxylic acid monomers (i.e., acrylic acid and methacrylic acid). It was found that the type and amount of acidic monomer have a great impact on the nucleation rate as well as particle size distribution and carboxyl group distribution of XNBR latexes. Also, the type of the acidic monomer affects the rates of entry and exit of radicals to and from particles and consequently the average number of radicals per particle, where a higher rate of polymerization was observed for methacrylic acid latexes. The reaction temperature has profound effects on polymerization rate, particle size distribution and colloidal stability of the latex. Partitioning of pressure profiles into four distinct regions in accordance with well-established intervals of Harkins model and analyzing particle size distribution and carboxyl group distribution, established a conceptual framework for kinetic studies in emulsion polymerization of XNBR latexes.

Binary mixtures of anionic double-chain sulfonate emulsifiers in VCM emulsion polymerization with high solid content: effect of emulsifier’s combination ratio and concentration

Binary mixtures of anionic double-chain sulfonate emulsifiers, sodium di-isodecyl sulfosuccinate and sodium pentadecan-sulfonate (SPS) were employed in batch reactor at different combination ratios and concentration for vinyl chloride emulsion polymerization. Reaction performances were evaluated by monitoring conversion rate and molecular weight by K-value parameter. Particle size and its distribution were investigated as a criterion for particle nucleation and the growing process by calculating the number of latex particles and the average number of growing chains per particle, respectively. The final latexes were evaluated by means of the coarse matter content as a qualitative character of the latex. The results showed that the overall reaction rate increases by high amount of SPS. Also, by increasing SPS content in binary mixture, coarse particle formation decreased and latex stability and particle size distribution increased. Furthermore, it has been found that the particle size was nonlinearly dependent on the combined ratio and amount of emulsifier and has shown a minimum within the scope of the study.

Влияние размерного распределения наномодифицированных частиц латекса на структуру гипсовых материалов

Влияние размерного распределения наномодифицированных частиц латекса на структуру гипсовых материалов

On the mechanism of particle formation above the CMC in emulsion polymerization

The mechanism of particle nucleation has great influence on the kinetics and the particle size distribution of polymer latexes produced in emulsion polymerization. These are key aspects for the application of these products and for the development of emerging processes, such as living/controlled free-radical polymerizations. One very popular theory publish in the 80s establishes that the new-born (primary) particles undergo limited coagulation even when the concentration of surfactant is above its critical micellar concentration. In this communication, the experiment that was the base for the formulation of such theory is reexamined and discussed to determine whether it can be considered as “typical condition”, such that the general character of their conclusions can be justified. In this context, the positive skewness of the PSD observed in that time and taken as an evidence of the coagulative nucleation is discussed as well.

Coupling of CFD Simulations and Population Balance Modeling to Predict Brownian Coagulation in an Emulsion Polymerization Reactor

AbstractIn this study a framework consisting of a computational fluid dynamics simulation coupled to a population balance model for the modeling of emulsion polymerizations is proposed. The combined approach is used to understand the impact of changing length and time scales, as well as mixing conditions on the particle size distribution (PSD) of a polymer latex under different conditions. It is shown that the effect of agitation rate can have a profound impact on the distribution of ionic species in the reactor, and thus on the evolution of the PSD. image

Synthesis of large-scale, narrowly dispersed, highly cross-linked, and spherical latex particles via one-step emulsion polymerization through particle coagulation

ABSTRACTParticle coagulation technology is a facile approach to prepare large-scale and narrowly dispersed polymer particles. However, diverse shapes such as ellipsolid, snowman, dumbbell, and trimer among others were obtained if the cross-linker was directly added into the initial reaction mixtures due to the restriction of the highly cross-linking particle fusion process. In this study, we prepared sub-200 nm, narrowly dispersed, highly cross-linked, and spherical latex particles using particle coagulation technology by controlling the relation between the cross-linking net formation and particle coagulation. Depending on the addition time or feeding rate of the cross-linker (divinylbenzene, DVB), the particles with different sizes or shapes were obtained. The later the addition start time of DVB, the narrower the particle size distribution of the latex particles. Alternatively, the increase of the continuing feeding time could also be used to decrease the width of particle size distribution of the ultimate latex. In addition, narrowly dispersed and spherical latex particles also could be directly obtained by advancing the particle coagulation time using 2, 2′-Azobis (2-methylpropionamidine) dihydrochloride as a cationic initiator. Our study presents a new method that will further widen the fields of application of particle coagulation technology.

In situ charge neutralization-controlled particle coagulation and its effects on the particle size distribution in the one-step emulsion polymerization

A novel approach to prepare sub-200nm, narrowly dispersed polystyrene latex particles is proposed for the emulsion polymerization of a ca. 40wt% solid-content solution. The presented method exploits the cationic comonomer methacryloxyethyltrimethyl ammonium chloride (MATMAC) or the initiator 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AIBA) to generate cationic oligomeric radicals shielded the negatively charged surfactant molecules adsorbed on the particles surface, further induced particle coagulation by in situ charge neutralization. By adjusting the types and amounts of the comonomer, the extent of the in situ charge neutralization is controlled. In consequence, the extent of the particle coagulation is controlled, resulting in the production of large-size latex particles. The particle coagulation induced by in situ charge neutralization occurs at the particle nucleation stage, which extends the times of particle completive growth and reversible coagulation, and therefore, narrowed the width of the particle size distribution of the ultimate latex particles. The resulting colloidal latexes containing 40wt% solid content are very stable by presenting the absolute value of zeta potentials larger than 40mV. This approach is likely to be used for large-scale industrial productions of narrowly dispersed polymer particles.

The influence of aggregation of latex particles on membrane fouling attachments & ultrafiltration performance in ultrafiltration of latex contaminated water and wastewater

The goal of the present study was to investigate the influence of latex particle aggregation on membrane fouling attachments and the ultrafiltration performance of simulated latex effluent using Cetyltrimethyl Ammonium Bromide (CTAB) as a cationic surfactant. Hydrophilic polysulfone and ultrafilic flat heterogeneous membranes, with molecular weight cut off (MWCO) of 60,000 and 100,000, respectively, as well as hydrophobic polyvinylidene difluoride with MWCO of 100,000, were used under a constant flow rate and cross-flow mode in ultrafiltration of latex solution. In addition, a polycarbonate flat membrane with uniform pore size of 0.05μm was likewise used during the experiment. The effects of CTAB on the latex particle size distribution were investigated at various concentrations, different treatment times, and diverse agitation duration times. The effects of CTAB on the zeta potential of membrane surfaces and latex particles were also investigated. The data obtained indicate that the particle size distribution of treated latex effluent experienced significant shifts in the peaks toward a larger size range caused by the aggregation of particles. As a result, the mass of fouling contributing to pore blocking and the irreversible fouling were noticeably reduced. The optimum results occurred in the instance when CTAB was added at the critical micelle concentration of 0.36g/L, for the duration of 10min and with minimal agitation. Notably, a higher stirring rate had an overall negative effect on the membrane fouling minimization.

Synthesis of narrowly distributed polystyrene-encapsulated silica nanoparticles via emulsion polymerization

ABSTRACTPolystyrene (PS)-encapsulated silica nanoparticles were successfully synthesized by conventional emulsion polymerization for solving the aggregation matter of nanoscaled silica. The grafting coupling agents and PS on the silica surface were detected by Fourier Transform Infrared (FTIR) spectroscopy. The influence of silica and monomer to water ratios and initiator concentration on particle size distribution of the nanocomposite latex was investigated. The particle size distribution firstly narrowed and then broadened with the increase of silica and monomer to water ratios and initiator concentration. The narrow distribution could be controlled in an appropriate silica and monomer to water ratio and an initiator concentration of 1/15 and 2 wt%, respectively. From the evaluation of transmission electron microscopy (TEM) micrographs and dynamic light scattering (DLS) measurement, it was proved that the nanocomposite latex did not have all sphere-like shape, but contained tiny amounts of irregular bodies. The formation mechanism of PS-encapsulated silica nanoparticles was also discussed.

New insights on estimating pore size distribution of latex particles: Statistical mechanics approach and modeling

New statistical mechanics approach for pore size distribution applied in wide the relative pressure range is proposed. The new proposed model was applied to nitrogen adsorption-desorption isotherms at 77 K onto five functionalized polystyrene latices. Results showed that the proposed model can reproduce all results found by traditional methods such as NLDFT, BJH and VBS where some of them can be applied only for a specific range of pore size. A segmentation procedure is adopted and it is shown that the corresponding algorithm can be successfully applied for determining pore size distributions over a wide range of pore size. When this method is applied an isotherms Type II and III (materials with larger mesopores and/or macropores) gives additional information that is not obtained with the other methods. The obtained results showed that the copolymerization plays an important role in the porosity and the specific surface area, whereas, the high polydispersity index, PDI, can reduce the porosity. The samples studied within the present work present small and large mesopores and even macropores as it is suggested by the new proposed model, and part of this porosity could be related to the interparticle and also to the intraparticle porosity.

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.

Synthesis and characterization of poly(styrene-block-n-butyl acrylate) pentablock copolymer via RAFT emulsion polymerization mediated by amphiphilic macroRAFT agent combined with pre-emulsion technology

Well-defined poly(styrene-block-n-butyl acrylate) pentablock copolymers were synthesized via RAFT (reversible addition-fragmentation chain transfer) emulsion polymerization with the combination of using a carefully designed amphiphilic macroRAFT at the nucleation stage and the pre-emulsion technology at the growth stage. The multiblock copolymers were produced within seven hours with narrow latex particle size distribution, high solid content and good latex stability. The thermal stability, thermal processability, microphase separation and mechanical properties of multiblock copolymers as well as corresponding random and blending (co)polymers were also investigated by thermogravimetric analysis (TG) instrument, Haake torque rheometer, differential scanning calorimetry (DSC) and scanning electron microscope (SEM), tensile and impact tests, respectively. The TG results revealed the multiblock copolymer has a good thermal stability with the initial decomposition temperature higher than 350 °C. Rheological results demonstrated that the multiblock copolymers have higher torque values than corresponding random and blending (co)polymers. DSC and SEM analysis denoted that there exists phase separation of multiblock and blending (co)polymers. For multiblock copolymer, the impact strength increased by 27.39 % to 7. 44 kJ m−2 with the composition of 60 wt% of styrene units and 40 wt% of n-butyl acrylate units. The tensile strength of multiblock copolymer increased with the increase of styrene composition.

Facile synthesis of large scale and narrow particle size distribution polymer particles via control particle coagulation during one-step emulsion polymerization

This study is an extension of the previous research results reported by our group (Colloid and Surf. A: Physicochem. Eng. Aspects 452 (2014) 159–164), where a novel approach to prepare large-scale polymer particles with a narrow distribution was reported. However, many important problems such as the visual evidence of particle coagulation, the relationship between particle distribution and particle coagulation, and the reasons of particle coagulation were not addressed in this article. In this manuscript, the polyisoprene latex particles were added to the polymerization systems as the indicator to follow the process of particle coagulation, and the reasons of particle coagulation are also discussed. The experimental results show that the final latex particles possessed a special structure similar to multicores and single-shell structure for the system containing polyisoprene particles and could be considered as a direct evidence of the particle coagulation. In addition, the competitive growth kinetics and reversible particle coagulation were used to analyze the reasons of a narrow particle size distribution of the final latex particles. In the combination with the Derjaguin–Landau–Verwey–Overbeek theory, the effect of the aqueous phase composition and initiator types on the particle coagulation were explained in the view of interaction energy.

New thermal deblocking characterisation method of aqueous blocked polyurethane

Purpose – The mechanisms of the deblocking reaction of the polyurethane with blocking agent were investigated in detail relatively using thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FTIR) and X-ray photoelectron spectroscopy (XPS). This kind of method for polyurethane as the application of wood adhesives can provide the conditions of application and the main theoretical basis. Design/methodology/approach – The blocking rate and latex particle size distribution were determined using the titrimetric analysis and the laser particle analysis, respectively. TGA, FTIR, XPS and differential scanning calorimetry were used to investigate the deblocking temperature and time of the blocked isocyanate in detail. Findings – The results indicated that the blocking rate was approximately 97 per cent and the average particle size was 360 nm. The results of laser particle analysis have confirmed that the dispersivity of the blocked polyurethane emulsion was good. XPS results showed that the amount of –O = C-N-benzyl groups increased with an increasing deblocking temperature and subsequently reached equilibrium. In summary, the blocked isocyanate was deblocked at temperatures ranging from 50 to 90°C. Research limitations/implications – An important approach in future wood adhesive work would be to gain access to man-made board application data. Practical implications – The paper provided some useful information about deblocking mechanisms of blocked polyurethane that would be helpful to guide applied practical applications as wood adhesive. Social implications – To promote China’s wood processing technology progress and solve the problem of shortage of the natural quality of wood is of important practical significance. Originality/value – The paper is the first to use the XPS characterisation method to characterise deblocking polyurethane solution.

A Novel Route to Prepare Cationic Polystyrene Latex Particles with Monodispersity

Relatively clean cation-charged polystyrene (PS) latex particles were prepared via a novel and simple route in the absence of steric stabilizers. The reaction system only included medium, styrene, and initiator with quaternary ammonium moiety. The influences of initiator concentration, and medium composition on the diameter and size distribution of PS latex particles were systematically investigated. The particle morphology and size, the surface N content, and the particle size distribution were respectively determined by SEM, XPS, and laser particle size analyzer. The results indicated that monodisperse and cation-charged PS latex particles with diameter of 0.45–0.95 μm could be successfully produced via the simple reaction system, and cationic initiator concentration played a key role in the preparation of uniform PS latex particles. Finally, a plausible mechanism was proposed for explaining nucleation, growth, and stabilization of PS latex particles.

Preparation and characterization of latex particles as potential physical shale stabilizer in water-based drilling fluids.

The poly(styrene-methyl methacrylate) latex particles as potential physical shale stabilizer were successfully synthesized with potassium persulfate as an initiator in isopropanol-water medium. The synthesized latex particles were characterized by Fourier transform infrared spectroscopy (FT-IR), particle size distribution measurement (PSD), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA). FT-IR and TGA analysis confirmed that the latex particles were prepared by polymerization of styrene and methyl methacrylate and maintained good thermal stability. TEM and PSD analysis indicated that the spherical latex particles possessed unimodal distribution from 80 nm to 345 nm with the D90 value of 276 nm. The factors influencing particle size distribution (PSD) of latex particles were also discussed in detail. The interaction between latex particles and natural shale cores was investigated quantitatively via pore pressure transmission tests. The results indicated that the latex particles as potential physical shale stabilizer could be deformable to bridge and seal the nanopores and microfractures of shale to reduce the shale permeability and prevent pore pressure transmission. What is more, the latex particles as potential physical shale stabilizer work synergistically with chemical shale stabilizer to impart superior shale stability.

Synthesis and characterization of acrylic latex: Effects of fluorine and silicon components on properties of the latex copolymers

A series of silicon-containing acrylic copolymers, fluorine-containing acrylic copolymers with two kinds of fluorinated acrylic monomers, as well as fluorosilicone acrylic copolymers were synthesized via seeded emulsion polymerization. Effects of fluorine and silicon components on properties of the copolymers were studied. Chemical structure of the copolymers was characterized by Fourier transform infrared spectrum (FT-IR) and 19F NMR. Glass transition temperature (Tg) of the copolymers was tested via differential scanning calorimetry (DSC). Molecular weight distribution of the copolymers was investigated by gel permeation chromatography (GPC). Morphology and particle size distribution of the copolymer latexes were investigated by transmission electron microscope (TEM) and particle size distribution analysis, respectively. Thermostability of the copolymers was explored by thermo gravimetric analysis (TGA). Hydrophobicity of the copolymer films was studied by the water contact angle data measured via sessile-drop method. Surface feature was investigated by atomic force microscope (AFM). The results showed that fluorine and/or silicon components which were incorporated chemically within the copolymers had little influence on the particle size and morphology of the latexes. The silicon component contributed better heat resistance, while the fluorine component contributed better hydrophobicity to the copolymers. The synergic effect of the two components resulted in a rough surface. The existence of both fluorine and silicon components, as well as the surface roughness, gave rise to a more hydrophobic film.