Dispersions Of Polystyrene Particles Research Articles

Raman spectra characterization of size-dependent aggregation and dispersion of polystyrene particles in aquatic environments

Aqueous environments are generally thought to be a source of pooling and re-distribution for both micro-plastics (MPs) and nano-plastics (NPs); however, significantly less data on NPs than MPs have been reported. The occurrence of salts, proteins, and other organic matter may promote or inhibit the aggregation of NPs to form agglomeration particles, making their detection more difficult. In this study, 80 and 500 nm polystyrene nano-plastics (PS-NPs) modified by four different functional groups (PS-Bare, PS-COOH, PS-NH2, and PS–CHO–500 nm) were selected to mimic the flocculation and/or sedimentation of NPs in salts (NaCl, CaCl2, and Na2SO4) and protein solutions. The results showed that the 80 nm PS-NPs are only colloidal in pure water. All four strong electrolyte solutions that were tested significantly promoted the aggregation of PS-NPs, including those that were protein-coated. In addition, 500 nm PS-CHO did not flocculate but gradually settled into sedimentation. Therefore, Raman spectrometry can be used to analyze assembled PS-NPs, but is not suitable for analyzing normal PS-NPs. By combining fractal morphology, this study provides insight into the comprehensive analysis of PS-NPs in water solutions, including the digestion of biological samples.

Study of Mechanical Properties of Micron Polystyrene-Toughened Epoxy Resin

Epoxy resin has a tight three-dimensional mesh structure after curing; due to this reason, the epoxy resin is brittle and not tough enough, which becomes the main reason for the destruction of the epoxy adhesive-steel/CFRP interface under fatigue loading of CFRP-reinforced steel structures. To prepare epoxy adhesives with good performance and suitable for CFRP-reinforced steel structures, the mechanical properties of epoxy adhesives are improved by adding polystyrene (PS) microspheres. In this work, five modified adhesives with PS weight fractions of 0 wt%, 1.25 wt%, 2.50 wt%, 3.75 wt% and 5 wt% are prepared by dispersion of PS particles through an ultrasonic cell crusher using a room-temperature curing process, and the tensile, flexural and impact properties of PS adhesives with different doping are investigated. Then, the microscopic morphology of the tensile section of the colloids is observed by scanning electron microscopy (SEM). The results show that the optimum dosing of PS is 2.5 wt%, and the tensile strength, tensile modulus of elasticity, flexural strength, flexural modulus and impact strength of the adhesive are increased by 77%, 147.7%, 71%, 35% and 22%, respectively, with this dosing. SEM analysis shows that PS particles produce large deformation to absorb energy when the matrix is fractured, and crack expansion needs to bypass or shear the PS particles, thus inhibiting crack expansion and achieving the purpose of toughening. Adhesion agglomeration of PS particles in the resin is the main reason for the decrease in the mechanical properties of adhesives.

The challenge in preparing particle suspensions for aquatic microplastic research

The occurrence of small particles consisting of organic polymers, so-called microplastic (MP), in aquatic environments attracts increasing interest in both public and science. Recent sampling campaigns in surface waters revealed substantial numbers of particles in the size range from a few micrometers to a few millimeters. In order to validate sample preparation, identification and quantification and to investigate the behavior of MP particles and potential toxic effects on organisms, defined MP model particles are needed. Many studies use spherical compounds that probably behave differently compared to irregularly shaped MP found in environmental samples. However, preparation and handling of MP particles are challenging tasks and have been systematically investigated in the present study. Polystyrene (PS) as a commonly found polymer with a density slightly above that of water was selected as polymer type for milling and fractionation studies. A cryogenic ball mill proved to be practical and effective to produce particles in the size range from 1 to 200 µm. The yield of small particles increased with increasing pre-cooling and milling durations. Depending on the concentration and the size, PS particles do not completely disperse in water and particles partly creep vertically up along glass walls. Stabilized MP suspensions without use of surfactants that might harm organisms are needed for toxicological studies. The stabilization of PS particle suspensions with ozone treatment reduced the wall effect and increased the number of dispersed PS particles but increased the dissolved organic carbon concentration and changed the size distribution of the particles.

Dimensional impact of nanofillers on the micromorphology and rheology of PP/PS composites under continuous elongation flow

Three kinds of nanoscaled fillers, namely, zero‐dimensional nanosphere titanium dioxide (TiO2), one‐dimensional multi‐walled carbon nanotubes (MWCNTs), and two‐dimensional nanoplate montmorillonite (MMT), were added to the representative polypropylene (PP)/polystyrene (PS) blends by eccentric rotor extruder based on elongation flow. Confirmed from images of transmission electron microscopy and scanning electron microscopy, three kinds of nanofillers were uniformly dispersed in the blends under continuous elongation flow and the presence of nanofillers led to a marked decrease of dispersed phase size of PS. The dispersed PS particles were turned into spherical status in matrix with the addition of TiO2 and MWCNTs and showed irregular shapes in the composites with MMT. The PS particle size of PP/PS/MMT was decreased most obviously, dropping from 4.44 to 1.42 μm, which resulted in obvious improvements in storage modulus and complex viscosity of the composites. The results of wide‐angle X‐ray diffraction and dynamic mechanical analysis indicated that MMT nanoparticles were highly intercalated in PP/PS blends, which obviously improved compatibility of PP and PS. Our work certified that the two‐dimensional nanoplate MMT are better compatibilizers compared with the zero‐dimensional nanosphere TiO2 and one‐dimensional MWCNTs for PP/PS composites.

Polymerization kinetics of styrene in isotactic polypropylene pellets and evolution of phase morphology during polymerization

ABSTRACTPolymerization kinetics of styrene (St) in commercially available isotactic polypropylene (iPP) pellets and the phase morphology evolution during polymerization are investigated. The polymerization rate of St in iPP pellets is slightly faster than in the corresponding bulk and suspension polymerizations carried out under similar reaction conditions due to the existence of two reaction sites: amorphous PP and polystyrene (PS), which are formed by polymerization‐induced phase separation. Two mechanisms are proposed for the phase morphology evolution: nucleation and growth, and St‐assisted coarsening of phase structure. During polymerization, the size of the dispersed PS particles increases with polymerization time no matter at which position of the pellet, but the increasing amplitude is much bigger at 200 μm distance to the edge than at the center due to much more significant occurrence of St‐assisted coarsening of phase structure which is attributed to both high values of PS/PP and St/PP resulted from polymerization‐induced diffusion of St. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43934.

RAFT Polymerization in a Miniemulsion System Using a Novel Type of Amphiphilic RAFT Agent with Poly(ethylene glycol) Bound to a Dithiobenzoate Group

In this study, reversible addition–fragmentation chain transfer (RAFT) miniemulsion polymerization using a novel type of amphiphilic RAFT agent was investigated. The novel amphiphilic RAFT agent has a specific chemical structure in which a hydrophilic poly(ethylene glycol) chain is directly bonded to the “Z-group” position, and not the leaving group (R group), of the thiocarbonylthio group (RAFT group). As a result, the RAFT groups are localized at the interface of the water/monomer droplets (polymer particles) throughout the polymerization, unlike with a conventional amphiphilic RAFT agent. Polystyrene (PS) particles with a broad molecular weight distribution and 69% degree of livingness were successfully prepared using the novel RAFT agent in a manner similar to that for a conventional RAFT system. Notably, after the completion of polymerization, the RAFT groups could be easily removed from the dispersed PS particles via treatment with an excess of potassium persulfate, because the RAFT groups only exis...

Analysis of fluid flow and particle transport in evaporating droplets exposed to infrared heating

Analysis of fluid flow and particle transport inside evaporating droplets exposed to external radiation was carried out by experiments and numerical simulations. In this study, we have shown that by altering the free surface temperature we can modify the fluid flow profile inside the droplet and hence the deposition pattern of solute particles on the substrate. The fluid velocity and particle concentration profiles inside the evaporating droplet were measured by Particle Image Velocimetry (PIV) technique. Experiments were carried out on a small sessile water droplet containing dispersed polystyrene particles. To avoid problem of image correction encountered in PIV measurements with 3D droplets, our experiments were performed on an equivalent disc shaped 2D drop sandwiched between two non-wetting surfaces, while the base of the droplet was pinned to a wetting surface. The top surface of the droplet was heated by Infrared (IR) light. The temperature of droplet surface was measured by thermocouples. The velocity field, particle concentration profile and particle deposition patterns were studied during evaporation process. We have also performed numerical simulations by solving continuity, momentum and energy transport equations. The computed velocity profiles resulting from buoyancy and Marangoni convection are in qualitative agreement with the experiments.

Blood-Mimicking Fluid for Testing Ultrasonic Diagnostic Instrument

We present a blood-mimicking fluid (BMF) for the Doppler test object of medical diagnostic instruments. Accurate measurement in a flow Doppler test requires a BMF that has the acoustic velocity and density defined in the International Electrotechnical Commission (IEC) standard, and furthermore, they must be stable over time. To formulate a fluid with the desired density and acoustic velocity, we have developed a new fluid made of glycerine and water-soluble silicone oil. The new BMF includes dispersed polystyrene particles as scatterers. The density of the liquid can be adjusted to maintain it at the same value as that of the polystyrene particles, thus ensuring neutral buoyancy of the particles. The MBF was stable over a period of 2 weeks, during which the density and acoustic velocity did not change.

A Study on Compatibility and Properties of POE/PS/SEBS Ternary Blends

Ethylene‐α‐olefin copolymer (POE)/polystyrene (PS)/poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) blends were prepared via melt blending in a co‐rotating twin‐screw extruder. The effects of SEBS copolymer on the morphology and rheological and mechanical properties of the blends were studied. Scanning electron microscopy (SEM) photos showed that the addition of SEBS copolymer resulted in finer dispersion of PS particles in the POE matrix and better interfacial adhesion between POE and PS compared with POE/PS blends, which exhibited a very coarse morphology due to the immiscibility between them. Interestingly, the tensile strength increased from 12.5 MPa for neat POE to 23.5 MPa for the POE/PS/SEBS (60/10/30) blend, whereas the tensile strengths of POE/PS (85.7/14.3) blend and POE/SEBS (66.7/33.3) blend were only 10.5 and 16.5 MPa, respectively. This indicates that both SEBS copolymer and PS have a synergistic reinforcing effect on POE. Dynamic mechanical thermal analysis (DMTA) and dynamic rheological property measurement also revealed that there existed some interactions between POE and SEBS as well as between SEBS and PS. DMTA results also showed that the storage modulus of POE increased when PS and SEBS were incorporated, especially at high temperature, which means that the service temperature of POE was improved.

Temperature‐Triggered Modification of Polymer‐ Solvent Interactions: From Fluid‐to‐Gel Transitions to Particle Capture

AbstractTemperature‐responsive polymers are of considerable interest in the literature. In this work the ability to combine temperature‐responsive polymer‐solvent interactions with architectural control to achieve a range of macroscopic effects is considered. The first part of the work considers poly(DEA) (N,N‐dieth ylacrylamide) microgel particles. The particles exhibit temperature‐triggered particle collapse at temperatures more than ca. 27 °C. As a consequence concentrated temperature‐responsive microgel dispersions change from gels to fluids when heated. The opposite effect is observed when dispersions or emulsions are stabilised by temperature‐responsive polymer surfactants. Recent results involving a gel‐forming castor oil‐in‐water emulsion are considered. The gelled emulsion releases a model drug (lidocaine) according to first‐order kinetics. We extend the principle of temperature‐triggered control of particle‐surface interactions to test a new approach for immobilising particles on surfaces. The method consists of electrodepositing Laponite particles onto a carbon surface, grafting of poly(NIPAM) (N‐isopropylacrylamide) onto the deposited particles and then increasing the temperature of the modified surface to trigger capture of dispersed polystyrene particles. This new approach uses chemistry that is potentially applicable to any conductive surface.

Temperature‐Triggered Capture of Dispersed Particles Using a Laponite‐Poly(NIPAM) Temperature‐Responsive Surface

In this study a new method is investigated that enables a conductive surface to be modified so as to capture dispersed particles when the temperature is increased. Poly(NIPAM) (NIPAM is N‐isopropylacrylamide) was grafted from electrodeposited Laponite RD particles using surface‐initiated atom transfer radical polymerization (ATRP) to give a temperature‐responsive surface. This was used to capture dispersed polystyrene particles. In the first part of the study the conditions used to electrodeposit Laponite onto a carbon foam electrode were determined. The ability of the temperature‐responsive surface to capture dispersed polystyrene particles was investigated between 20 and 50°C. Temperature‐triggered particle capture was reversible or irreversible depending on the conditions used during ATRP. A high surface concentration of poly(NIPAM) on the particle electrodes is believed to increase the extent of polystyrene particle capture and also reversibility. A theoretical analysis in terms of interaction energy–distance curves is presented for the capture behavior. It is concluded that the temperature‐responsive surface has both electrostatic and steric contributions to the total interaction energy. The steric component (which originates from poly(NIPAM)) is temperature‐dependent and provides the basis for temperature‐triggered particle capture.

Flow of Dilute Colloidal Dispersions in Water through a Small Orifice

Fluctuation of flows through a small orifice has been measured for water and two kinds of colloidal dispersions including fine particles about 100 nm in diameter with 1 % volume fraction in water. In this volume fraction, a surface potential of the particles is composed of an electrostatic repulsion and a van der Waals attraction and it affects flow properties. Experiments clarify that a specific flow instability occurs for water at the Reynolds number about 60, and the dispersion of polystyrene particles having strong repulsion increases the specific flow instability in low salt concentrations(LSC) but makes it disappear in high salt concentrations(HSC). Meanwhile, it is found that the dispersion of silica particles having strong attraction is stable in flows except the specific flow instability in LSC but it suppresses the specific flow instability in HSC as in the case of polystyrene particles. Criterion whether the orifice flow is stable or not is predicted by comparison of the second minimum location of the surface potential and the mean surfaces distance of the particles.

Temperature-triggered capture of dispersed particles using deposited Laponite with grafted poly(N-isopropylacrylamide) chains

A method has been developed that enables a conductive surface to be modified so as to capture dispersed particles when the temperature is increased; poly(N-isopropylacrylamide) was grafted from electrodeposited Laponite particles using surface-initiated atom transfer radical polymerisation and used to capture dispersed polystyrene particles.

Electrically Controlled Two-Dimensional Cluster Formation of Polystyrene Particles and Cluster Fixation with Adsorbed Polyelectrolyte

An attempt was made to orderly arrange a large number of polystyrene particles dispersed in aqueous medium on the electrode surface and fix the formed particle arrangement. The measuring cell used consisted of two transparent indium tin electrodes 500 μm apart from each other in the vertical direction. The gap between the electrodes was filled with a dispersion of polystyrene particles (5 μm size) and the behavior of the particles in electric fields applied between the electrodes was on-site observed with an optical microscope. Simultaneous application of DC and AC fields caused polystyrene particles to form single-layered clusters each consisting of several tens particles on the lower electrode. Densely arranged clusters were formed for the particles with polyallylamine hydrochloride (PAH), a cationic polyelectrolyte, adsorbed on their surface upon application of DC and AC fields and the clusters formed remained unbroken after removal of the fields. No cluster formation was observed, however, for the particles after adsorbing the cationic polyelectrolyte and then poly (sodium styrenesulfonate) (PSS), an anionic polyelectrolyte. These findings suggested that particle arrangement and its fixation of polystyrene particles are appreciably affected by polyelectrolyte adsorption.