Polyethylene Content Research Articles

Use of Domestic Waste Polyethylene as a Bitumen Modifier in Bituminous Pavement Applications

The present study evaluated the use of domestic waste polyethylene (PE) in the applications of bituminous pavement. This study investigates the performance of the mixes using different waste PE percentages, i.e., 1%, 2%, 3%, 4% and 5%. It is observed that the softening point and elastic recovery value increase with PE content increases. The penetration index (PI) and temperature susceptibility of binders were evaluated. Adding PE to bitumen shows an improvement in the temperature susceptibility of the modified binders. The Marshall Stability value of bitumen containing 3% PE is higher at 69.65% than virgin binder stability. When 3% PE modified bitumen to the mixes, its indirect tensile strength (ITS) is 70.44 % higher than the conventional mix. The tensile strength ratio (TSR) value improved from 62% (unmodified binder) to 91.18% (modified binder) at 3% PE content, which is 47% higher than the conventional mixture. It indicates that the moisture susceptibility of mixes using PE is higher than conventional mix. Additionally, the mix deformation resistance with 3% PE was found to be 68.75% higher than the mix made with the unmodified binder. The study found that the bituminous mixes using PE have shown higher effectiveness in the properties such as stability, indirect tensile strength, rutting resistance, etc. of the mixes. It indicates that bituminous mixes with modified binders with PE provide higher resistance to permanent deformation.

Characteristics and Mechanism of Cd Release and Transport in Soil Contaminated with PE-Cd

Microplastics （MPs） are a type of emerging contaminants that pose a potential threat to global terrestrial ecosystems. The accumulation of MPs in soil inevitably affects soil physical and chemical properties， both directly and indirectly. Additionally， owing to their small size and surface features， MPs have excellent sorption capacity for both organic and inorganic materials， thus affecting their fate in the environment. However， the influence of MPs on heavy metal sorption and transport in soil is still not fully understood. In this study， polyethylene （PE） and Cd were selected as research objects， and on the basis of clarifying the adsorption mechanism of Cd on PE MPs， the effects of PE concentration and particle size on Cd release and transport behavior in soil under different ionic strengths and types （Ca2+ and Na+） were studied using column leaching experiments. The results of the batch experiments showed that the adsorption capacity of PE MPs for Cd2+ decreased with the increase in particle size. Scanning electron microscopy （SEM）， Fourier transform infrared spectroscopy （FTIR）， and Zeta potential were used to analyze the properties of PE MPs and adsorption behavior of Cd2+ onto MPs. The adsorption was mainly a physical process and was controlled by intra-particle diffusion. The adsorption kinetics could be described well by the quasi-second-order kinetics and Webber-Morris model. The adsorption isotherm conformed to the Langmuir model， indicating monolayer adsorption. The results of leaching experiments showed that the effect of PE MPs on Cd release and transport in soil was related to the CaCl2 concentration. At high ionic strength （0.05 mol·L-1 and 0.1 mol·L-1）， PE promoted the transport of Cd. The effluent concentration of Cd2+ increased from 6.48 mg·L-1 and 16.79 mg·L-1 to 7.12 mg·L-1 and 23.45 mg·L-1， whereas at low ionic strength （0.01 mol·L-1）， Cd transport was inhibited by PE MPs， and the effluent concentration of Cd2+ decreased from 0.66 mg·L-1 to 0.57 mg·L-1. The larger the amount of PE added， the more significant the promoting or inhibiting effect. Additionally， the release and transport of Cd in soil were also affected by the MPs particle size and concentration. When the addition amount was small （1%， 4%）， the large-sized MPs were more conducive to the transport of Cd in soil. When the addition amount was large （7%， 20%）， MPs with small particle sizes promoted Cd2+ transport more significantly. When the leaching solution used was NaCl， soil permeability decreased significantly. PE MPs had no significant effect on Cd release and transport but changed the stability of soil aggregates. In conclusion， PE MPs could change the release and transport behavior of Cd in soil， and the impact results were not only related to the particle size and content of MPs but were also influenced by the chemical properties of the soil solution.

Comparison of principal component regression (PCR) and partial least square regression (PLSR) modeling methods for quantifying polyethylene (PE) in recycled polypropylene (rPP) with near-infrared spectrometry (NIR)

Recycled polypropylene (rPP) often contains a small amount of polyethylene (PE). Since polypropylene (PP) and PE are incompatible, the presence of PE compromises the performance of rPP materials and needs to be closely monitored. In our previous work, Raman and near-infrared (NIR) spectrometries were evaluated to monitor PE content in rPP with partial least square regression (PLSR) modeling. The NIR spectrometry exhibited a wider application range, but the accuracy of the prediction models might be further improved. In the current work, a different modeling method, principal component regression (PCR) was employed to analyze PE content in rPP with NIR spectrometry. Spectrum pretreatment methods, including multivariate scatter correction (MSC), standard normal variate transformation (SNV), smoothing, and first derivative, were investigated to improve the NIR spectrum quality. Forward and backward interval methods were used to optimize spectral range selection. The outcomes were compared with our previous PLSR modeling results. The highest accuracy in independent validation was achieved by a PCR model with an R 2 of 0.9991 and a root-mean-square error of prediction (RMSEP) of 0.1596 PE%. On the other hand, a PLSR model achieved the lowest RMSEP of 0.9712 PE% for a non-colored post-consumer rPP sample. The PCR models might be sensitive to interference and more suitable for post-industrial materials, which have a simpler chemical composition. The PLSR models might have better stability and be more suitable for complicated post-consumer samples. Both the PCR and PLSR models were successfully applied to a gray commercial rPP sample.

Synergistic effect study of Chlorella vulgaris and polyethylene in co-pyrolysis process based on kinetic and thermodynamic analysis

The co-pyrolysis of algae and plastics shows great potential for bio-oil production. In this study, thermogravimetric analyzer was used to investigate the pyrolysis behavior of Chlorella vulgaris (CV) and polyethylene (PE) at different mixed ratios and heating rates. Their synergistic effects were discussed through kinetic and thermodynamic analyses. According to the thermogravimetric (TG) and Derivative thermogravimetric (DTG) curves, the co-pyrolysis process can be divided into five stages, corresponding to the decomposition of moisture, carbohydrates, proteins, lipids, and biochar, respectively. In the fifth stage, a clear synergistic effect is observed, with the highest ∆TG reaching about 4%. During the co-pyrolysis process, the average activation energy of the mixtures is much lower than expected, indicating the presence of a synergistic effect in co-pyrolysis. Among them, 3CV1PE is the optimal mixing ratio, with the average activation energy of 3CV1PE being 6% lower than that of CV pyrolysis alone. The master plots revealed that the power law reaction models (P3 and P4) are suitable for describing the experimental behavior of mixtures with higher CV content, while the third-order (F3) and eighth-order model (F8) are more appropriate for the decomposition reaction with higher PE content. The calculation of thermodynamic parameters further show that the co-pyrolysis of CV and PE is beneficial to the decomposition process, and the mixed ratio of 3:1 is the most favorable for the reaction. Results obtained in this work are valuable for guiding research on the co-pyrolysis of biomass and plastics.

H2-rich gas production from co-gasification of biomass/plastics blends: A modeling approach

East Asia experiencing massive population growth, which will certainly challenge traditional waste management systems. In recent years, gasification has attracted much attention since it converts carbon-based residues into valuable gas and requires cheaper gas cleaning equipment compared to available technologies. This study presents an ASPEN plus model for simulation of steam co-gasification of polyethylene (PE) and pine (PI) using various temperatures (740–830 °C), steam/waste ratio, S/W (0.5–0.8) and PE content in the feedstock mixture (0–60 %). The predicted results were compared with the experimental data available in the literature, and a good agreement was achieved. In general, an increase in gasifier temperature and S/W led to higher H2 production and lower tar content in the syngas resulting from co-gasification process. Regarding tar conversion, increasing the gasifier temperature played a more important role compared to adding steam to the gasifier. H2 content and H2 yield gradually increased from 33.01 to 47.81 % and 48.09–57.76 g/kg, respectively, when PE increased from 0 to 60 %, which may be due to a greater amount of hydrogen present in PE. Over a PE content range from 0 to 60 %, tar concentration had a nearly linear increase, which can be attributed to lower oxygen content available in the mixture.

Utilizing Chlorella vulgaris algae as an eco-friendly coagulant for efficient removal of polyethylene microplastics from aquatic environments

Polyethylene (PE) microplastics (MPs) are small particles of plastic made from polyethylene, which is a commonly used type of plastic. These microplastics can be found in water sources, such as rivers, lakes, and oceans. They are typically less than 5 mm in size. Chlorella vulgaris (C. vulgaris) is an excellent, simple and inexpensive biocoagulant that can effectively remove a wide range of pollutants through the coagulation and flocculation mechanism. In this study, C. vulgaris algae were used to remove PE MPs. The experiments were designed using the Behnken Box model. The evaluated parameters were the initial PE concentration (100–400 mg/L), the C. vulgaris dose (50–200), and the pH (4–10). The findings showed that increasing the concentration of polyethylene had a positive effect on the efficiency of removal. In addition, the dose of C. vulgaris and pH parameters were inversely and directly related to removal efficiency, respectively. The highest removal efficiency was observed under alkaline conditions. Overall, the maximum PE removal efficiency was 84 % when the concentration of PE was 250 mg/L, the dose of C. vulgaris was 50 mg/L, and the pH was 10. It can be concluded that algae can be used as an environmentally friendly coagulant for effectively removing MPs from aquatic environments.

Influence of polyethylene content on preparation and properties of lead zirconate titanate piezoelectric ceramics via vat photopolymerization

Vat photopolymerization has garnered significant research interest due to its capabilities in achieving complicated designed structures and high resolution. However, there are still significant technical difficulties in manufacturing some piezoceramic parts because of the high refractive index and ultraviolet light absorptivity of these ceramic powders. Herein, we overcome this challenge for lead zirconate titanate (PZT) ceramics by introducing polyethylene (PE) additions with ultralow refractive index and UV light absorptivity into PZT slurries. As the PE content increases, the curing depth shows a clear upward trend. When the PE content is 30 vol%, the curing depth of PZT slurry could ensure the adequate interlayer combination. Besides, PZT ceramics with different volumes of porosity could be obtained by modulating PE content. The relative density of sintered PZT ceramics decreased from 83.12 % to 68.06 %. Furthermore, the samples with 30 vol% PE exhibited satisfactory dielectric and piezoelectric properties (ϵr =1911, tanδ=0.027, d33 = 308 pC/N, g33 = 1.82 × 10−2 Vm/N and d33g33= 5.61 × 10−12 m2/N). These results indicate that the addition of PE additives is an effective and universal approach to improve the curing depth of ceramic slurries and expand the range of processable materials for vat photopolymerization technologies.

Effects of hexabromocyclododecane and polyethylene microplastics on soil bacterial communities

Hexabromocyclododecane (HBCD) and polyethylene (PE) microplastic are ubiquitous pollutants, and knowledge about the effects of HBCD and PE pollution on soil bacterial communities remains obscure. In this study, the effects of different HBCD and PE concentrations and combined HBCD and PE exposure on the diversity, composition, and function of agricultural soil bacterial communities over 4 months were systematically examined for the first time. Generally, soil bacterial communities were influenced in both the 1-month and 4-month scenarios through HBCD and PE separately as well as combined exposure. After 4 months of exposure, PE and combined exposure significantly affected soil bacterial alpha diversity, however, low concentration of HBCD showed no apparent influence. 1-month and 4-month HBCD, PE, and combined exposure significantly influenced bacterial beta diversity. Compared with 1 month of exposure, HBCD, PE, and combined exposure demonstrated remarkable influences on soil bacteria after 4 months of exposure, especially on Nitrospirae, Elusimicrobia, Rokubacteria at the phylum level, and on MND1, Ruminiclostridium, Lysobacter, Anaeromyxobacter, Alistipes, WCHB1 at the genus level. The bacterial function analysis indicated that amino acid metabolism, carbohydrate metabolism, and membrane transport were the three predominant enriched bacterial functions after 1-month and 4-month HBCD and PE exposure. This research provides a comprehensive grasp of the effects of HBCD and PE pollution on soil microbial communities, which could have a beneficial impact on future soil pollution control.

Distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress

Microplastics (MPs) and antibiotic resistance genes (ARGs) are both enriched in soil-vegetable systems as a consequence of the prolonged use of agricultural mulches. MPs can form unique bacterial communities and provide potential hosts for ARGs. Therefore, MPs stress may promote the spread of ARGs from soil to crops. Increasing ARGs pollution in soil-vegetable system. In our research, we investigated the distribution and major driving elements of antibiotic resistance genes in the soil-vegetable system under microplastic stress. The results showed that MPs treatment decreased the relative abundance of ARGs in non-rhizosphere soil. High concentrations of MPs promoted the enrichment of tetracycline antibiotic resistance genes in rhizosphere soil. MPs treatment promoted the enrichment of ARGs and mobile genetic elements (MGEs) in lettuce tissues, and the overall abundance of ARGs in root after 0.5 %, 1 %, and 2 % (w/w, dry weight) polyethylene (PE) administration was considerably higher compared to that in the untreated group (p < 0.05). At the same time, high PE concentrations promoted the spread of sulfa ARGs from root to leaf. MPs also impacted the bacterial communities in the soil-plant system, and the changes in ARGs as well as MGEs in each part of the soil-vegetable system were significantly correlated with the bacterial diversity index (p < 0.05). Correlation analysis and network analysis showed that bacterial communities and MGEs were the main drivers of ARGs variation in soil-lettuce systems.

Modeling of soluble solid content of PE-packaged blueberries based on near-infrared spectroscopy with back propagation neural network and partial least squares (BP-PLS) algorithm.

Blueberries are a nutritious and popular berry worldwide. The physical and chemical properties of blueberries constantly change through the cycle of the supply chain (from harvest to sale). The purpose of this study was to develop a rapid method for detecting the properties of packaged blueberries based on near-infrared (NIR) spectroscopy. NIR was applied to quantitatively determine the soluble solid content (SSC) of polyethylene (PE)-packaged blueberries. An orthogonal partial least squares discriminant analysis model was established to show the correlation between spectral data and the measured SSC. Multiplicative scattering correction, standard normal variable, Savitzky-Golay convolution first derivative, and normalization (Normalize) were used for spectra preprocessing. Uninformative variables elimination, competitive adaptive reweighted sampling, and iteratively retaining informative variables were jointly used for wavelength optimization. NIR-based SSC prediction models for unpacked blueberries and PE-packaged blueberries were developed using partial least squares (PLS). The prediction model for PE-packaged samples (RP 2 =0.876, root mean square error of prediction [RMSEP]=0.632) had less precision than the model for unpacked samples (RP 2 =0.953, RMSEP=0.611). To reduce the effect of PE, the back propagation (BP) neural network and PLS were combined into the BP-PLS algorithm based on the residual learning algorithm. The model of BP-PLS (RP 2 =0.947, RMSEP=0.414) was successfully developed to improve the prediction accuracy of SSC for PE-packaged blueberries. The results suggested a promising way of using the BP-PLS method in tandem with NIR for the rapid detection of the SSC of PE-packaged blueberries. PRACTICAL APPLICATION: Most of the NIR-based research used unpacked blueberries as samples, while the use of packaged blueberries would provide researchers with a better understanding of the crucial factors at different phases of the blueberry supply chain (from harvest to sale). To meet market demands and minimize losses, NIR spectroscopy has been proven to be a rapid and nondestructive method for the determination of the SSC of PE-packaged blueberries. This study provides an effective method for monitoring the properties of blueberries in the entire supply chain.

Hydrophobic organic contaminants affiliated with polymer-specific microplastics in urban river tributaries and estuaries

Exposure to microplastics (MPs) and hydrophobic organic contaminants (HOCs) combined at high concentrations may induce adverse effects to aquatic organisms in laboratory-scale studies. To determine environmentally relevant concentrations of HOCs in MPs, it is essential to understand the occurrence of MP-affiliated HOCs in the aquatic environment. Here we report the occurrences of HOCs affiliated with polymer-specific floating MPs from 12 tributaries and three estuaries in the Pearl River Delta, South China. Target HOCs include nine synthetic musks (SMs), 14 ultraviolet adsorbents (UVAs), 15 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). Average concentrations of MP-affiliated ∑9SM, ∑14UVA, ∑15PAH, ∑8PBDE, and ∑14PCB were 1790, 5550, 1090, 412, and 107 ng g−1, respectively. The average concentrations of HOCs affiliated with MPs of different polymer types were 9790, 7220, 72,500, and 55,800 ng g−1 for polyethylene (PE), polypropylene, polystyrene, and other MPs, respectively. As the concentration of PE was the highest among all MPs at the average concentration of 0.77 mg m−3, the monthly outflow of PE-affiliated HOCs accounted for the largest proportion (46 %) in the outflow of MP-affiliated HOCs (2.8 g) to the coastal ocean via three estuaries. These results suggest that HOCs were highly concentrated in MPs and varied among different chemicals and polymer types. Due to the differences of polymer characteristics and half-life of affiliated chemicals, future toxicology studies concerning exposure to these combined pollutants may need to specify polymer types and their affiliated chemicals.

Modification Mechanism and Technical Performance of Recycled PE-Modified Asphalt

Waste plastic pollution is a serious issue. In order to adhere to the concept of green development and rationally dispose of polyethylene waste plastic products, polyethylene (PE)-modified asphalt was prepared using recycled polyethylene (RPE) and low-density polyethylene (LDPE) as raw materials. The chemical structures of the RPE- and LDPE-modified asphalt were studied using a Fourier transform infrared spectrometer (FTIR), and the dispersion of RPE was studied using a fluorescence microscope (FM). Subsequently, the modification mechanism of the PE-modified asphalt was revealed. The physical properties and high- and low-temperature rheological characteristics of the PE-modified asphalt were examined using physical property tests, a dynamic shear rheometer (DSR), and a bending beam rheometer (BBR). The creep performance of the PE-modified asphalt was analyzed using multiple-stress creep recovery (MSCR). In addition, a laboratory-made inexpensive inorganic stabilizer was added to enhance the storability of the PE-modified asphalt. The results show that PE and asphalt are similarly compatible and form an S-C bond with an inorganic stabilizer. The resulting product’s storage stability is enhanced via the cross linking between the PE and asphalt and the subsequent formation of a network structure. The segregation softening point increased from 2 °C to 45 °C with the increase in PE content, and the increase in RPE was more obvious than that of LDPE. The high-temperature failure of the 2–6% RPE-modified asphalt can reach 70 °C, while that of the 8% RPE-modified asphalt can reach 76 °C. Low-temperature performance was reduced slightly: the 8% PE-doping low-temperature failure temperature was −14.7 °C. The low-temperature performance was somewhat reduced, but it was still within a PG rating.

Effects of Combined Pollution of Microplastics and Lead on Maize Seed Germination and Growth

Microplastics are a new contaminant that are causing worldwide concern. However, an understanding of their impact on agricultural seed germination remains inadequate. To investigate the effects of combined microplastic and heavy metal contamination on crop seed germination and growth, the effects of exposure to different single and combined concentrations of lead (Pb) and three microplastics[polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC)] on maize seed germination and growth were investigated using maize seeds. The results showed that:the inhibition of maize seed germination by Pb single exposure generally increased with Pb concentration. Compared with that in CK, 500, 1000, and 1500 mg·L-1 PE exposure significantly inhibited maize seed germination, but 100 and 300 mg·L-1 exposure had no significant effect (except at d 5). All PP concentration exposures significantly inhibited maize seed germination, with higher concentrations resulting in stronger inhibition. Compared to that under PP and PE exposure, PVC single exposure inhibited maize germination less, and 500, 1000, and 1500 mg·L-1 exposures produced a facilitative effect at the later stages of germination. The germination index, germination potential, and vigor index of maize seeds decreased with the increase in the single exposure concentration of lead and three types of microplastics, significantly decreased compared with that of CK under the combined exposure of Pb and PE, and did not change significantly under the combined exposure of PP and Pb or PVC and Pb. Among the three types of microplastics, PVC had the least effect on corn seed vigor. Both single exposures of 10 mg·L-1Pb and 100 mg·L-1 of the three microplastics promoted maize stalk and root growth, whereas other concentrations showed mostly inhibitory effects. When the PE concentration was 500 mg·L-1, the 10 and 20 mg·L-1Pb exposures both promoted maize seed stalk and root growth; however, the combined PP and Pb exposures did not produce significant inhibition, whereas 500 mg·L-1PVC and 10 mg·L-1Pb showed the strongest inhibition of maize stalk and root growth under combined PVC and Pb exposures. The effects of combined exposure to microplastics and Pb on the germination and growth of maize seeds were essentially antagonistic, thus slowing down the toxic effects of their respective single exposures on maize seeds.

Mitigating Stripping in Asphalt Mixtures: Pretreatment of Aggregate by Thermoplastic Polyethylene Powder Coating

Thermoplastic polyethylene (PE) powder coating is proposed as a new technique to pretreat the aggregate of asphalt mixtures and improve the corresponding moisture resistance. In this paper, ethanol solution is investigated as a fluidized bed to disperse the PE powder. The surface tension of the solution, indicating the wettability of the liquid phase, decreases with increasing ethanol concentration and temperature. The PE powder could be stably dispersed into the solution when 15% ethanol solution heated to 40 to 50°C is used to reduce the surface tension of liquid to less than 40 mN/m. The suspension carrying the PE particles could be uniformly sprayed onto a hot aggregate surface (180–190°C) where the liquid phase evaporates fast while the PE powder melts and stays. The powder coating technique could prevent the aggregate from lumping and achieve a high-quality and efficient coating for aggregate. The PE monolayer model considering a hexagonal close packing of PE on aggregate surface is tentatively proposed to determine the theoretical amount of PE required to perfectly coat the aggregate. The predicted PE content was reasonably lower than that determined by the experimental results considering the ideal monolayer coating was hard to achieve. However, the modeling results could be used to determine the lower bound of the required PE content. The optimum PE content significantly increased with increasing particle size of PE and specific surface area of aggregate. The use of high-density polyethylene (HDPE) powder with a smaller particle size was more effective in the coating process. In addition, excessive PE could not further enhance the moisture resistance of asphalt mixtures efficiently. This study can contribute to both the recycling of waste plastic and the construction of durable asphalt pavements.

Microplastic transport dynamics in surcharging and overflowing manholes

The transport of microplastics within urban water systems remains poorly understood, with little prior research on their behaviour within manhole configurations. This study represents the first to measure and model the transport dynamics of microplastics within circular and square manholes under different hydraulic scenarios. The transport and fate of polyethylene (PE) was quantified and compared to solutes (Rhodamine WT dye) using energy losses, residence time distributions (RTDs), and mixing models within surcharging and overflowing manholes. The bulk mass of solute and PE concentrations followed similar flow paths across all conditions except for 17.3 ± 7.9 % of PE mass that was immobilized in a dead zone above the inlet pipe for manholes with a surcharge to pipe diameter ratio ≥2. Consequently, these microplastics only exit after a significant change in hydraulic regime occurs, causing microplastics to be at risk of being contaminated over a prolonged duration. No significant mixing differences for PE and solutes were found between manhole geometries. The deconvolution method outperformed the ADZ model with goodness of fit (Rt2) values of 0.99 (0.60) and 1.00 (0.89) for PE and solute mixing, respectively. This establishes the deconvolution method as the most accurate and appropriate model to accurately predict microplastic mixing in manholes and urban drainage systems.

Recycled polyethylene waste as binder stabilizer for SMA mix in gulf environment

Each year, millions of tons of household and industrial waste, including plastic, are responsible for harming the environment through burning, landfilling, or going to dump in open water. Waste plastic disposal is a critical issue faced by municipalities in modern cities. In addition, the development of hundreds of kilometers of roads worldwide leads to the consumption of vast quantities of raw materials and the depletion of valuable natural resources. The high expense of virgin polymers and rising plastic waste have shifted the research focus toward green pavements that utilize waste plastics. Therefore, this research aims to investigate the use of recycled plastic waste as a binder modifier for Stone Mastic Asphalt mix (SMA). The high-temperature performance of the Recycled Polyethylene Modified Binder (RPMB) has been evaluated with various percentage dosages to satisfy the environment of the Gulf region. In addition, the impact of RPMB on the SMA mix was studied through three performance tests, drain down resistance, moisture damage resistance, and rutting performance. The results showed continuous improvement in rheological properties with increased recycled polyethylene (RP) content by up to 6%. The RP enhances the binder properties such as the rutting parameter, non-recoverable compliance, and viscosity to meet the high-temperature performance requirement for heavy traffic (UPG 76 H) of most roads in the gulf environment. However, the results showed that RPMB could not meet the recovery requirement set by AASHTO TP 70. That is due to RP's plastomer nature. Therefore, it is necessary to supplement some proportion of the RP with an elastomeric polymer. Further, the results of SMA mix properties with RPMB showed remarkable improvement over than control mixture in terms of resistance to drain down, moisture damage, and rutting by 55.1%, 52.6%, and 96.4, respectively.

Fabrication of highly porous and adhesive thick Y2O3 film by room-temperature spray process for thermal insulation coating

An effective strategy for manufacturing ceramic thick films with high porosity and robustness was proposed by aerosol deposition (AD). The agglomeration of the Y2O3 and polyethylene powder composites was investigated to prepare porous films. After exploring a suitable particle distribution, Y2O3 and polyethylene composite powder were prepared using two different mixing methods with various polyethylene contents. During the transportation in vacuum, easily separated mixture powders of Y2O3 and polyethylene caused insufficient energy result in partially delaminated films. In contrast, the appropriate agglomeration of the Y2O3–polyethylene composite powders can be crushed with higher kinetic energy by increased mass, resulting in uniform and robust porous films with high adhesive strength. After burning, the Y2O3–polyethylene (8 wt% polyethylene) thick film (∼100 μm) exhibited high porosity (66%), low thermal conductivity (∼0.15 W/m·K at room temperature), and good adhesion strength (8.4 MPa). In this study, we provide effective guidelines for fabricating AD-based porous ceramic films deposited at room temperature with low thermal conductivity and high adhesive strength.

The influence of high molecular weight polyethylene and basalt content on the mechanical risks of protective three-dimensional weft-knitted fabrics designed to wear next to skin

This study examines the resistance of three-dimensional (3D) weft-knitted fabrics to mechanical risks to determine the influence of varying percentage contents of high molecular weight polyethylene and basalt on cut, puncture, abrasion, and tear resistance. The three-dimensional weft-knitted fabrics are designed by separating functional layers: the outer (protective) layer contains varying percentage contents of high molecular weight polyethylene and basalt; the inner layer (suitable for contact with the skin) contains polyester; both layers are connected using polyamide. The strength properties of knits in response to mechanical impact were evaluated by performing cut, puncture, abrasion, and tear resistance tests. Basalt was found to improve the cut resistance of knits significantly, even with its content as low as 5% in the outer layer. The knit with the highest high molecular weight polyethylene content in the outer layer demonstrated the best puncture and tear resistance. No correlation was established between the varying percentage contents of high molecular weight polyethylene and basalt and the maximum number of abrasion cycles, as the three-dimensional weft-knitted fabrics showed no noticeable wear. The test results show that the structure of three-dimensional weft-knitted fabric with the outer layer designed to withstand mechanical impact and the inner layer suitable for direct contact with the skin protects against a wide range of mechanical impacts. This applies even when varying percentage contents of high molecular weight polyethylene and basalt are used only in the outer layer.

Comparison of NIR and Raman spectrometries as quantitative methods to monitor polyethylene content in recycled polypropylene

Recycled polypropylene (rPP) often contains a small amount of polyethylene (PE), which frequently compromises the performance of the material and needs to be monitored. In the current work, near-infrared (NIR) and Raman spectrometries were investigated to establish convenient and accurate methods to analyze PE content in rPP. Various spectrum pretreatment methods, including multivariate scattering correction (MSC), standard normal variate transformation (SNV), baseline correction, normalization, smoothing, and first derivative, were tested to reduce noise and improve spectrum quality for partial least squares (PLS) regression. Forward and backward interval partial least squares (FiPLS/BiPLS) methods were employed to optimize spectral range selection. The best NIR model had an R2 of 0.9971 and a root-mean-square error of prediction (RMSEP) of 0.2761 PE wt% in independent validation, and the best Raman model achieved an R2 of 0.9945 and an RMSEP of 0.3818 wt%. The models were further validated with rPP samples. The best Raman model obtained an R2 of 0.9954 and an RMSEP of 0.2404 wt% on non-colored rPP, but it failed to be applied to colored rPP. The best NIR model had a slightly weaker performance on non-colored rPP (R2: 0.9246; RMSEP: 0.9710 wt%), but it was successfully applied to grey commercial rPP samples. This work would help quality assurance of recycled PP materials.

Effects of microplastic combined with Cr(III) on apoptosis and energy pathway of coral endosymbiont.

The combined effect of polyethylene (PE) microplastics and chromium (Cr(III)) on the scleractinian coral Acropora pruinosa (A. pruinosa) was investigated. The endpoints analysed in this study included the endosymbiont density, the chlorophyll a + c content, and the activity of enzymes involved in apoptosis (caspase-1, caspase-3), glycolysis (lactate dehydrogenase, LDH), the pentose phosphate pathway (glucose-6-phosphate dehydrogenase, G6PDH) and electron transfer coenzyme (nicotinamide adenine dinucleotide, NAD+/NADH). During the 7-day exposure to PE and Cr(III) stress, the endosymbiont density and chlorophyll content decreased gradually. The caspase-1 and caspase-3 activities increased in the high-concentration Cr(III) exposure group. Furthermore, the LDH and G6PDH activities decreased significantly, and the NAD+/NADH was decreased significantly. In summary, the results showed that PE and Cr(III) stress inhibited the endosymbiont energy metabolism enzymes and further led to endosymbiont apoptosis in coral. In addition, under exposure to the combination of stressors, when the concentration of Cr(III) remained at 1 × 10-2mg/L, the toxic effects of heavy metals on the endosymbiont were temporarily relieved with elevated PE concentrations. In contrast, when coral polyps were exposed to 5mg/L PE and increasing Cr(III) concentrations, their metabolic activities were seriously disturbed, which increased the burden of energy consumption. In the short term, the toxic effect of Cr(III) was more obvious than that of PE because Cr(III) exposure leads to endosymbiont apoptosis and irreversible damage. This is the first study to provide insights into the combined effect of microplastic and Cr(III) stress on the apoptosis and energy pathways of coral endosymbionts. This study suggested that microplastics combined with Cr(III) are an important factor affecting the apoptosis and energy metabolism of endosymbionts, accelerating the collapse of the balance between the coral host and symbiotic endosymbiont.