PP Particles Research Articles

Preparation of functionalizable poly(propylene–styrene)/polyacrylonitrile millimeter‐scale particles with core‐shell morphology

AbstractCore‐Shell (CS) polymeric particles have attracted great interest due to their high mechanical, thermal, and chemical stability and their surface properties. In this study, functionalizable CS poly(propylene/styrene)/poly(acrylonitrile) (PP/PS/PAN) particles were prepared through heterogeneous polymerizations in a batch reactor. Commercial PP particles and PP/PS particles (prepared by seeded suspension polymerization of styrene (Sty) on PP spheres) were applied as core components of the final structure, while the shell was prepared through acrylonitrile dispersion polymerization. The degree of swelling of the core particles by Sty played an important role for the adhesion of the PAN shell, which for PP particles was 24 wt%, whereas for PP/PS hybrid particles it was 57 wt%. The particles (PP/PS and CS) were characterized through image analysis, revealing a uniform and smooth surface for PP/PS spheres and a uniform porous shell for CS particles. Particle size distributions, thermal degradation, chemical structures, degrees of crystallinity, and textural properties were also evaluated. The PAN shell adhered to the PP/PS particles without forming a copolymer, and the CS particles formed by a PP/PS core and PAN shell had sizes of 4.54 ± 1.24 mm, specific area of 2.70 m2g−1 and PAN content of 15.98 ± 0.82% (m/m) of total particles.

Recycled Household Plastic and Oil Palm Filler Reinforced Epoxy Composite for Lightweight Construction Applications

Polypropylene is extensively used in aerospace, automotive and construction applications due to its versatile properties. This project aims to reduce plastic and oil palm waste and promote the development of strong, sustainable and eco-friendly construction materials. The objective of this project is to develop a sustainable yet high-performance construction material by incorporating polypropylene particles, oil palm empty fruit bunch (OPEFB) fibres and oil palm shell (OPS) particles into epoxy composites through the hand lay-up method. The composite specimens undergo ASTM D638 tensile test to determine the tensile properties. The addition of PP particles in varying weights shows decrease in tensile strength, likely due to poor dispersion and compatibility with the epoxy matrix. Incorporating 3 wt% OPEFB fibres with fibre length from 2mm to 4mm improves tensile strength by 2.32% and 23.36% respectively at higher PP particle loadings which are 15 wt% and 25 wt%. Adding 1 wt% and 3 wt% OPS particles improves the tensile strength by 2.96% and 4.68% respectively, in composites with 10 wt% PP particles and 3 wt% OPEFB fibres. The tensile performance may be improved by treating PP particles with compatibilizers such as silane or maleic anhydride grafted polypropylene.

Assessment of inhalation exposure to microplastic particles when disposable masks are repeatedly used

Wearing masks to prevent infectious diseases, especially during the COVID-19 pandemic, is common. However, concerns arise about inhalation exposure to microplastics (MPs) when disposable masks are improperly reused. In this study, we assessed whether disposable masks release inhalable MPs when reused in simulated wearing conditions. All experiments were conducted using a controlled test chamber setup with a constant inspiratory flow. Commercially available medical masks with a three-layer material, composition comprising polypropylene (PP in the outer and middle layers) and polyethylene (PE in the inner layer), were used as the test material. Brand-new masks with and without hand rubbing, as well as reused medical masks, were tested. Physical properties (number, size, and shape) and chemical composition (polymers) were identified using various analytical techniques such as fluorescence staining, fluorescence microscopy, and micro-Fourier Transform Infrared Spectroscopy (μFTIR). Scanning Electron Microscopy (SEM) was used to scrutinize the surface structure of reused masks across different layers, elucidating the mechanism behind the MP generation. The findings revealed that brand-new masks subjected to hand rubbing exhibited a higher cumulative count of MPs, averaging approximately 1.5 times more than those without hand rubbing. Fragments remained the predominant shape across all selected size classes among the released MPs from reused masks, primarily through a physical abrasion mechanism, accounting for >90 % of the total MPs. The numbers of PE particles were higher than PP particles, indicating that the inner layer of the mask contributed more inhalable MPs than the middle and outer layers combined. The released MPs from reused masks reached their peak after 8 h of wearing. This implies that regularly replacing masks serves as a preventive measure and mitigates associated health risks of inhalation exposure to MPs.

Influence of synthetic and natural microfibers on the growth, substance exchange, energy accumulation, and oxidative stress of field-collected microalgae compared with microplastic fragment

Synthetic microfibers (MFs), which are Microplastics (MPs), have not received attention commensurate with their abundance in the environment. Currently, limited studies on MFs have focused on their effects on marine organisms. It is therefore necessary to conduct exposure experiments of MFs on freshwater organisms to provide reference data for the ecological risk assessment of MFs. As a primary producer in freshwater ecosystems, microalgae have an ecological niche that is highly overlapping with that of MFs. In this study, we examined the effects of MFs on the growth of Chlorella and indicators of oxidative stress to examine their potential risk on the microalgae population. The results showed that inhibition rate of microalgae increased with MF concentration in the range of 0.01–100 mg/L. Compared with natural fibers such as cotton and wool, PET and PP fibers showed significant growth inhibition, but less so when in fragment form with the same material and concentration. PP and PET particles, whether fibers or fragments, increased the total antioxidant capacity of microalgal cells and caused oxidative damage. To determine the influence of MFs on the interaction of cells in the environment, the exchanged substances and accumulated energy of microalgae cells were also detected. The results indicated that PP and PET fibers, as well as fragments, increased the diameter and membrane permeability of microalgae cell, thus interfering with the cell division and substance exchange processes. PET fibers and fragments showed different interactions at the level of individual cells and populations. This suggests that the evaluation of MPs should consider examinations from cells to population and even community levels in the future.

Rapid shipboard measurement of net-collected marine microplastic polymer types using near-infrared hyperspectral imaging

Isolation and detection of microplastics (MP) in marine samples is extremely cost- and labor-intensive, limiting the speed and amount of data that can be collected. In the current work, we describe rapid measurement of net-collected MPs (net mesh size 300 µm) using a benchtop near-infrared hyperspectral imaging system during a research expedition to the subtropical North Atlantic gyre. Suspected plastic particles were identified microscopically and mounted on a black adhesive background. Particles were imaged with a Specim FX17 near-infrared linescan camera and a motorized stage. A particle mapping procedure was built on existing edge-finding algorithms and a polymer identification method developed using spectra from virgin polymer reference materials. This preliminary work focused on polyethylene, polypropylene, and polystyrene as they are less dense than seawater and therefore likely to be found floating in the open ocean. A total of 27 net tows sampled 2534 suspected MP particles that were imaged and analyzed at sea. Approximately 77.1% of particles were identified as polyethylene, followed by polypropylene (9.2%). A small fraction of polystyrene was detected only at one station. Approximately 13.6% of particles were either other plastic polymers or were natural materials visually misidentified as plastics. Particle size distributions for PE and PP particles with a length greater than 1 mm followed an approximate power law relationship with abundance. This method allowed at-sea, near real-time identification of MP polymer types and particle dimensions, and shows great promise for rapid field measurements of microplastics in net-collected samples.

Exposure to Polypropylene Microplastics via Oral Ingestion Induces Colonic Apoptosis and Intestinal Barrier Damage through Oxidative Stress and Inflammation in Mice.

Extensive environmental pollution by microplastics has increased the risk of human exposure to plastics. However, the biosafety of polypropylene microplastics (PP-MPs), especially of PP particles < 10 μm, in mammals has not been studied. Thus, here, we explored the mechanism of action and effect of exposure to small and large PP-MPs, via oral ingestion, on the mouse intestinal tract. Male C57BL/6 mice were administered PP suspensions (8 and 70 μm; 0.1, 1.0, and 10 mg/mL) for 28 days. PP-MP treatment resulted in inflammatory pathological damage, ultrastructural changes in intestinal epithelial cells, imbalance of the redox system, and inflammatory reactions in the colon. Additionally, we observed damage to the tight junctions of the colon and decreased intestinal mucus secretion and ion transporter expression. Further, the apoptotic rate of colonic cells significantly increased after PP-MP treatment. The expression of pro-inflammatory and pro-apoptosis proteins significantly increased in colon tissue, while the expression of anti-inflammatory and anti-apoptosis proteins significantly decreased. In summary, this study demonstrates that PP-MPs induce colonic apoptosis and intestinal barrier damage through oxidative stress and activation of the TLR4/NF-κB inflammatory signal pathway in mice, which provides new insights into the toxicity of MPs in mammals.

Microplastic and heavy metal interactions (adsorption and desorption) at different salinities

Heavy metals and microplastics (MPs) are two pollutants that are currently gaining a lot of attention, and it has been observed that they can interact. The objective of this research was to observe the adsorption and desorption of heavy metals concerning various types of MP particles, different heavy metals and concentrations, and salinity. The findings demonstrate that among all particle types, PP particles absorb heavy metals at the highest rate. Contrarily, PP particles release lower heavy metals and more slowly than other particles. Pb consistently absorbed more metal by MPs than Cu, Zn, or Cd. Cd had the highest rate of heavy metal desorption, followed by Pb, Cu, and Zn. The adsorption capacity of MPs particles increases together with the concentration of heavy metals, whereas the adsorption rate decreases. Salinity has an enormous impact on how MPs and heavy metals interact. The adsorption and desorption of heavy metal in MPs particles decreases and takes longer to reach equilibrium at increased salinities. Between the three different salinities, even the adsorption and desorption results demonstrate a significant difference (p&lt;0.05). Finally, our results indicate that MPs particles have the potency as a vector for heavy metal in freshwater, brackish water, and ocean.

Microplastics identification in landfill leachates by different spectroscopic techniques

Discovered more than 40 years ago, microplastics have become a major environmental issue. With increasing global plastic production, microplastics are of growing concern. Landfills have been pinpointed as primary sources of microplastics to surface waters and they have, in fact, been identified and quantified as such. Due to their small size, different polymers and interfering non-plastic materials, microplastics are difficult to analyse in a complex matrix such as leachate. To elucidate the impact of pre-treatment on the performance of the most common microspectroscopical analytical methods employed, i.e., FT-IR and Raman, we re-examined previously pre-treated and analysed leachate samples. Additionally, we subjected duplicates of previously analysed samples to different concentrations of H2O2 with varied reaction times to digest and remove non-plastic organic matter. The pre-treated samples were subjected density separation and (re-)analysed by means of FT-IR and Raman microspectroscopy. Larger particles were also analysed by near-infrared (NIR) hyperspectral imaging. We found the concentration of H2O2 to impact the possibility of identifying and quantifying PET particles, with Raman scattering microspectroscopy enabling more particles to be counted than with FT-IR. This is likely due to the increased detectable particle size range, from around 50 μm for FT-IR to 1 μm for Raman scattering microspectroscopy. Optimized H2O2 concentration with subsequent density separation enabled to clearly identify numerous PE particles, but also PP, PS, and PET particles and carbon compounds with Raman scattering microspectroscopy. Hyperspectral imaging performed well for particles larger than 30 μm.

Kinetics and Size Effects on Adsorption of Cu(II), Cr(III), and Pb(II) Onto Polyethylene, Polypropylene, and Polyethylene Terephthalate Microplastic Particles

Due to its small size, large specific surface area and hydrophobicity, microplastics, and the adsorbed contaminants may together cause potential negative effects on ecosystems and human beings. In this study, kinetics and size effects on adsorption of Cu(II), Cr(III), and Pb(II) onto PE, PP and PET microplastic particles were explored. Results indicated that the PE and PET microplastics have the higher adsorption capacity for Cu(II), Cr(III), and Pb(II) than that for PP microplastic. The adsorption capacity was affected by microplastic types and metal species. Among the three metals, Pb(II) had the largest adsorption amount on microplastic particles, especially on PET particles. Moreover, the adsorption capacities of microplastics increase with the decrease of particle size. The metal adsorption capacity of &amp;lt;0.9 mm microplastics is greater than that of 0.9–2 mm and 2–5 mm microplastics. The size effect on metal adsorption was largest for PE microplastic. More attention should be paid in case of the coexistence of heavy metals and tiny PE and PET microplastics in the environment.

Numerical Study of Microplastic Dispersal in Simulated Coastal Waters Using CFD Approach

Microplastics are accumulated in coastal regions due to human activity. Although limited data from beach surveys show an increase in microplastics in marine habitats, continuous monitoring is required on microplastics loading and distribution in the marine environment. In this study, CFD numerical simulations using VOF and Airy wave models coupled with DPM were carried out to investigate the effects of various variables on microplastics motion and distribution in a simulated coastal marine environment. PET, PU, and PP microplastic particles were released from the oceanside to investigate the effects of microplastic type, size, and shape with two different ocean–water flow velocities and temperature conditions. Particle position data from their tracking were used to determine the effect of each variable on the spatial distribution of particles. The quantitative analysis of vertical and horizontal distribution of microplastics particles revealed that, with low water velocity, most of the large denser spherical PET and PU microplastics would sink towards the bottom and settle at the ocean floor, while most of the small non-spherical particles would float near the surface and travel towards the shoreline. For lighter PP microplastics, larger spherical particles would float more readily than denser spherical ones. Large spherical and smaller non-spherical PP particles travel farthest reporting to the shoreline. Increasing the oceanwater velocity altered the distribution patterns in which lighter PP particles, almost independent of shape and size, travel swiftly to the shoreline together with smaller non-spherical denser microplastics. Lastly, the simulation results revealed that the oceanwater temperature did not play any significant role in the spatial distribution of microplastic particles.

Particle trajectory model for tribo-electrostatic separating mixed granular plastics

Tribo-Electrostatic Separation (TES) is suitable for recycling plastic from waste to avoid losing its virgin value. The separation model, which comprised of computing the electric field and the analysis of forces on the particles, was utilized to write a program by MATLAB language. The particle trajectory model based on TES is established. The model includes electric field computation and part of an analysis of forces on the particles. The electrode parameters and material parameters can be changed in the model. A photographic system including a high-speed camera (1000fps) was used to capture the plastic particle trajectories and to verify the model. Both waste PVC and waste PP particles were captured. The results computed by the model have a good agreement with the experimental results. The model can find suitable parameters for separating different waste plastics and help explore TES applications. • Establish a model to simulate the trajectory of plastic granules in TES. • Design the photographic system to capture the practical trajectories. • The model has a good agreement with the experimental results.

Evaluation and Optimization of Bioethanol Production from Pomegranate Peel by Zymomonas mobilis

Introduction: The large amount of production and use of pomegranate in Iran has made the waste of this important product a suitable source for the production of bioethanol. This research examined the ability of Zymomonas mobilis for producing bioethanol from Pomegranate peel.Materials and Methods: The hydrothermal treatment method and enzymatic hydrolysis were used to release the fermentable sugars from PP particles. Cellulase loading of 30 U/g solid was used for enzymatic hydrolysis. Zymomonas mobilis PTCC 1718 was used as the ethanol-producing strain. The Response Surface Methodology experimental design was performed to optimize the fermentation process conditions for maximum ethanol production and minimum fermentation time.Results: The amount of sugar released after hydrolysis was about 18.37% of the fresh PP weight. The amount of meat peptone and yeast extract (as nitrogen sources added to the medium), bacterial dry weight (as inoculum) and fermentation time were considered as the effective factors in the RSM experimental design. The maximum amount of 0.218 g ethanol was produced at 0.37 g meat peptone, 0.28 g yeast extract, 0.021 g bacterial dry weight and 30 h fermentation time (in 50 ml of culture medium). The maximum ethanol production yield of 45.5% (which is 89.2% of the theoretical yield) was achieved in this process.Conclusions: Z. mobilis has good ability for producing bioethanol from PP. However, more research should be conducted in order to industrialize the process.

Polypropylene Composites Reinforced by Nonmetallic from Waste Printed Circuit Boards Using Spout-Fluid Bed Coating with PP Particles Enhance Fluidization

Nonmetallic materials recycled from waste printed circuit boards (N-WPCBs) were modified by coating KH-550 in a spout-fluid bed. To improve the effect of the modification, PP particles were used to enhance the fluidization quality of the N-WPCB particles in the coating modification. Then, the modified N-WPCBs were used as fillers to fabricate PP/N-WPCB composites. The method of coating in a spout-fluid bed with PP particles enhanced fluidization and showed the best modification effect compared to other coating methods. The FT-IR and SEM results demonstrated that interfacial bonding between N-WPCBs and PP could be enhanced by modified N-WPCBs, which improved the mechanical properties of the composites. When the mass ratio of PP to N-WPCBs is 100:75 and the dose of KH-550 is 4 phr, the flexural strength, tensile strength, and impact strength of the composites increase by 16.60%, 23.22%, and 23.64%, respectively. This would realize the high-value utilization of N-WPCBs with coating modification in the spout-fluid bed.

Water model study of the removal effect of soluble gas floatation technology (SGFT) on inclusions with different characteristics

In this study, the removal effects of soluble gas floatation technology (SGFT) on inclusions with different characteristics were studied by using a self-made water model experimental device and Coulter counter. The water/CO2 system was used to simulate the molten steel/(H2, N2) system, and PP, PE and ABS particles were used to simulate the inclusions in molten steel. The experimental results show that this technology has good removal effects on particles with different characteristics. A large amount of fine bubbles can be formed when adding particles via heterogeneous nucleation, while no bubbles were formed without adding particles due to lack of nucleation cores. The removal rate of the particles increases with the increase of particle number. The size of the particles has a significant impact on its removal effect that the removal rate increases with the increase of particle size. The Ostwald ripening may appear on the bubble nucleation process on the surface of large particles, which can promote floating behavior and removal effect of the particles. The particles with different contact angles can be removed effectively by soluble gas floatation technology (SGFT), while the removal effect of particles with large contact angles is better.

Microplastics identification by infrared spectroscopy – Evaluation of identification criteria and uncertainty by the Bootstrap method

The assessment of microplastic contamination in an environmental compartment involves identifying and counting microplastics in a representative fraction of the compartment. Microplastics can be identified by μFTIR spectroscopy where spectra are manually examined for characteristic polymer bands or by an automatic comparison of particle spectrum with reference spectra of polymers. The automatic spectra comparison can involve calculating a correlation coefficient, CC, between particle and reference spectra where a minimum correlation above which identification is adequately reliable should be defined. Correlation can be calculated from original or transformed signals, such as taking the first derivative, and by using unweighted or weighted CC. Weighted CC can highlight the spectral features more relevant to distinguish polymers. This work describes a methodology for setting the minimum CC, P5»P, associated with a true positive result rate, TP, of 95% and for checking if this threshold allows identifications with a false positive result rate, FP, not greater than 5%. This methodology was successfully applied to the use of various CC determined from original or transformed spectra for the identification of polyethylene, PE, and polypropylene, PP, microplastics in river sediments by μFTIR. The analytical portions of sediments were digested with H2O2 and microplastics separated from the remaining particles by density using a saturated NaCl solution. Pearson’s, Spearman’s and Alternative unweighted and weighted correlation coefficients were studied. The P5»P was estimated by the Bootstrap method that resamples spectra CC between a reference material and microparticle of the same polymer collected from the environment. This resampling allows simulating CC distribution required to estimate its 5th percentile (i.e. P5»P). The FP was estimated from the probability of a particle not from the same polymer type of the reference material producing a CC greater than P5»P. Some unweighted and weighted CC determined from original or transformed spectra were successfully used to identify PE or PP particles in river sediments. More particle spectra need to be collected to ensure performance is assessed from a representative diversity of aged polymers with different additives. The spreadsheets used for CC calculations and Bootstrap simulations are made available and can be used for the validation of the identification of other polymer types by μFTIR or ATR-FTIR spectroscopy.

Rheological behavior and fresh properties of self-compacting high strength concrete containing recycled PP particles with fly ash and silica fume blended

Solid waste management can be regarded as one of the major environmental concerns across the globe. Annually, substantial quantities of plastics are produced. The utilization of this waste can result in a variety of huge problems such as health hazards, disposal, and environmental pollution. In this paper, the workability and rheological characteristics of self-compacting high strength concrete (SCHSC) made with recycled polypropylene plastic particles (RPPP) with fly ash (FA) and silica fume (SF) are investigated. The SCHSC was employed by replacing the medium-coarse aggregate (MCA) with five percentages of RPPP contents at 0%, 10%, 20%, 30%, and 40% by volume. The first group of mixtures contained 20% FA and 80% Portland cement (PC). On the other hand, the second group of the mixes made with 20% FA, 10% SF, and 70% PC. To investigate such workability-related properties as slump flow diameter (SFD), T50 slump flow time (SFT), V-funnel flow time (VFT), L-box height ratio (LHR), and L-box T200 and T400 flow times, 10 concrete mixtures were produced and tested. ICAR rheometer in the rheological testing of fresh SCHSCs was used to determine the rheological parameters. For all mixtures, the compressive strength was measured at 28 days. With respect to the experimental results of the current study, the Herschel-Bulkley and modified Bingham models can provide well defined rheological representations for SCHSC with RPPP. The mixtures containing a combination of FA, SF, and RPPP can have better fresh characteristics compared to those without SF. Moreover, all produced SCHSC mixtures can be at a satisfactory level with the limitations required for the fresh properties of SCC.

Analysis of a novel insulating conveyor-belt tribo-electrostatic separator for highly humid granular products

The objective of this work is to describe a new configuration of tribo-electrostatic separator equipped with an insulating rubber belt conveyor, to facilitate the processing particles saturated with moisture. The insulating belt is continually charged by corona discharge produced by a fine-wire electrode, placed at a distance of 5 mm above it. The experiments were carried out under conditions of high humidity using samples of HDPE and PP particles. Separation experiments have shown that when the belt is charged by corona, more than 50% of the particles were separated with purity higher than 95%.

An assessment of the toxicity of polypropylene microplastics in human derived cells

Environmental pollution caused by plastic waste is a growing global problem. Discarded plastic products and debris (microplastic particles) in the oceans detrimentally affect marine ecosystems and may impact human. Humans are exposed to plastic debris via the consumption of seafood and drinking water, contact with food packaging, or inhalation of particles. The accumulation of microplastic particles in humans has potential health risks such as cytotoxicity, hypersensitivity, unwanted immune response, and acute response like hemolysis. We investigated the cellular responses of secondary polypropylene microplastics (PP particles) of approximately ~20 μm and 25–200 μm in different condition and size to normal cells, immune cells, blood cells, and murine immune cells by cytokine analysis, ROS assay, polarization assay and proliferation assay. We found that PP particles showed low cytotoxicity effect in size and concentration manner, however, a high concentration, small sized, DMSO method of PP particles stimulated the immune system and enhanced potential hypersensitivity to PP particles via an increase in the levels of cytokines and histamines in PBMCs, Raw 264.7 and HMC-1 cells.

Study on the capability and characteristics of heavy metals enriched on microplastics in marine environment

In this study we examined the adsorption characteristics of heavy metals on microplastic through laboratory test and field test. We demonstrated that polyvinyl chloride, polypropylene, polyethylene, polyamides and polyformaldehyde could adsorb lead, copper and cadmium in the simulating solution, and the heavy metals showed higher adsorbance on PVC and PP particles compared with PA, PE and POM. In the field experiment, the adsorption rate and concentration of heavy metals varied significantly among different plastic types and locations. The adsorbability of PP and PVC toward Pb and Mn was strongly correlated with the metal concentration in seawater. We also compared the adsorption quantity of PP to heavy metals and polycyclic aromatic hydrocarbons which resulted in an order of magnitude within one month. During the adsorption, the surface morphology of the microplastics which were washed and corroded by seawater underwent a rough-smooth-rough changing process, and different materials had great differences.

Effect of localization of carbon nanotubes on fracture behavior of un-vulcanized and dynamically vulcanized PP/EPDM/MWCNT blend-nanocomposites

Effect of localization of multiwall carbon nanotube (MWCNT) on the fracture toughness and deformation mechanisms of un-vulcanized and dynamically vulcanized polypropylene/ethylene-propylene terpolymer/multiwall carbon nanotube (PP/EPDM/MWCNT) blend-nanocomposites were investigated under both the Izod impact loading and the essential work of fracture (EWF) test as quasi-static loading conditions. The localization of MWCNT in the PP matrix led to increased impact fracture toughness via multiple crazing and crack deviation induced by MWCNT aggregates in the PP matrix, while it had negative effect on the fracture toughness under EWF test condition through hindrance effect on the yielding and necking processes. This contradiction was attributed to the different dominant deformation mechanisms in the PP matrix under high speed multiaxial Izod impact and low speed plane biaxial EWF fracture tests (crazing and shear yielding, respectively). Although the various toughening mechanisms such as nano-bridge mechanism were activated during the fracture processes, vulcanization induced interfacial adhesion improvement between the PP and EPDM particles played the main role in determining of the fracture toughness of the vulcanized blend-nanocomposites.