Polyethylene Content Research Articles

Effect of polyethylene microplastics on anammox sludge characteristics and microbial communities

Microplastics (MPs), a class of emerging pollutants, pose significant potential risks to microbial metabolism and ecology. By adding different concentration gradients of polyethylene (PE), the effects of PE on the nitrogen removal efficiency and bacterial colony structure of anammox granular sludge (AnGS) were examined. The results of the 40 d experiment with various concentrations (0.05~1.0g/L) of PE MPs on AnGS showed that the elimination of ammonia and nitrite nitrogen was less affected than in the control group. Analysis of extracellular polymer (EPS) content revealed a decreasing trend in EPS content under high stress concentrations (0.2~1.0g/L) compared to the control, and protein/polysaccharide (PN/PS) showed a similar situation, suggesting that the stability of AnGS was compromised by elevated PE concentrations. Specific anammox activity (SAA) indicated a declining trend with increasing polyethylene microplastic (PE MP) concentrations between 0.2 and 1.0g/L, and the nitrogen removal performance of AnGS decreased. From the micro-morphological point of view, the AnGS subjected to 0.5g/L stress formed blocky large particle aggregates. PE MPs were adsorbed on the surface of AnGS and combined with it to form dense particles, and both particle size and mechanical strength of the granular sludge increased proportionally the concentration of PE MPs. High-throughput sequencing data indicated that exposure to 0.5g/L PE MPs stress enhanced the complexity of the microbial community structure in AnGS, while reduced the relative abundance of the anammox bacteria Candidatus Brocadia and Planctomycetes by 2.2% and 4.2%, respectively.

Polyethylene microplastic pollution changes the electrical resistance and thermal conductivity of loess soil.

While plastics provide convenience, they also endanger the safety of the natural environment. Microplastic pollution caused by plastic aging has become an urgent concern in public places. In order to study the effects of microplastics on soil physical properties, the electrical resistance and thermal conductivity of soils containing different polyethylene and moisture content were tested. The results show that polyethylene have two effects on soil electrical resistance: one is that the plastic particles increase electrical resistance, and the other is that the electrostatic field carried by the plastic particles reduces electrical resistance. The effect of the two factors is balanced by the content of polyethylene at 6-8%. When the polyethylene content of the soil was 6% and 10%, the coefficients of electrical resistance variation were 0.89, 0.67, 0.85, 0.96, 0.97, 0.99 and 0.95, 0.68, 0.71, 0.93, 0.95, 0.96, respectively. Polyethylene alters soil properties by affecting water distribution through hydrophobicity. The water content gradually increases to 10%, the liquid conduction area inside the soil increases, and the higher the soil's ability to conduct electricity and heat. The results can provide theoretical reference for evaluating and controlling soil microplastic pollution.

Blood-brain barrier damage accelerates the accumulation of micro- and nanoplastics in the human central nervous system

The widespread use of plastics has led to increased micro- and nanoplastics (MNPs) pollution, resulting in significant environmental challenges and concerns about potential harm to human health. This study investigated whether certain types of MNPs can accumulate in the human central nervous system (CNS) and trigger inflammatory responses, particularly after CNS infection. Our analysis of 28 cerebrospinal fluid (CSF) samples from 28 patients with or without CNS infection revealed that only polystyrene (PS), polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) were capable of selectively entering the human CNS. Concentrations of PP and PE were positively correlated with the CSF albumin index. The levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) were significantly increased in patients with CNS infections. However, concentrations of MNPs were not significantly associated with CSF levels of IL-6 or IL-8. Overall, these findings suggest that specific MNPs can penetrate the human CNS, especially after impairment of the blood-brain barrier. Notably, MNPs derived from commonly used plastics did not significantly induce or exacerbate inflammation in the human CNS.

Experimental study on co-gasification of cellulose and high-density polyethylene with CO2

Co-gasification of biomass and waste plastic with CO2 presents an effective strategy for integrating biomass conversion, waste utilization and carbon recycling. In this study, the co-gasification of cellulose and high-density polyethylene with CO2 was investigated experimentally. The effects of mixing ratio and temperature on co-gasification characteristics, including gas yield, product gas composition, lower heating value of syngas and gasification efficiency, were comprehensively evaluated. Additionally, the interaction between cellulose and high-density polyethylene was analyzed. The results suggested that increasing the polyethylene content in feedstock resulted in decreased yields of H2 and CO, increased CH4 yield, increased lower heating value of syngas and reduced gasification efficiency. The interaction between cellulose and high-density polyethylene enhanced the gas yield, with the most significant effect at 40 % polyethylene content. In the range of 900 °C–1000 °C, increasing the temperature resulted in increased gas yield, reduced lower heating value of syngas and increased gasification efficiency. The positive interaction between cellulose and high-density polyethylene on gas yield was more significant at higher temperatures. This work shed light on reaction characteristics for co-gasification of biomass and high-density polyethylene with CO2, laying the foundation for the design and application of this technology.

Structure characteristics and gasification reactivity of co-pyrolysis char from lignocellulosic biomass and waste plastics: Effect of polyethylene

The rate limiting stage is char reactivity during gasification that can be influenced by its physicochemical structural characteristics. In this study, the effects of feedstock share, rice straw (RS) and polyethylene (PE), on the physicochemical properties and gasification reactivity of chars were investigated and their relationships were discussed. The char gasification reactivity was investigated via isothermal experiments using a thermal analyzer. The results indicated that the PE addition improved the specific surface area (SSA) and pore volume (Vp) of the char obtained from co-pyrolysis RS with PE. The SSA of the char increased by 1.31 times when the PE content was 60 wt%, compared with that of RS char. The order degree and gasification reactivity of the co-pyrolysis char samples increased with increasing PE content beyond 40 wt%. The char reactivity in the early stage of co-gasification was primarily determined by the order degree of carbonaceous and pore structure. The char reactivity in the later stage was influenced by these two factors and the silicon dioxide content could inhibit the char co-gasification reactivity.

Effect of solvothermal-treated polyethylene on the mechanical properties of sandcrete blocks and concrete

In building construction, seepage and dampness in walls present serious problems since they can cause structural failures and damage in both residential and commercial contexts. Finding more affordable options is necessary as mitigating these problems frequently requires expensive fixes. This study aims to evaluate the effects of solvothermal-treated polyethylene added at concentrations ranging from 0 to 1.0% on the mechanical properties of concrete and sandcrete blocks. In addition to assessing the workability, split tensile strength, and compressive strength of concrete samples at different levels of the polyethylene (PE) inclusion, the study looked into the water absorption capacity, density, and compressive strength of sandcrete blocks. The blocks’ compressive strength and water absorption capacity reduced as the amount of polyethylene additives rose, although there was a slight increase in the density. These changes remain well within the Nigerian Industrial Standards’ specified limits. Hardened concrete shows a drop in density, compressive strength, and split tensile strength with increasing polyethylene content, while fresh concrete's workability decreases as the percentage increases. 0.4% incorporation of the treated polyethylene achieved the target strength of 20 N/mm2 while Sandcrete blocks with up to 1% of the solvothermal treated polyethylene had compressive strengths more than the 2.5 N/mm2 minimum required for non-load-bearing walls. About 61% reduction in water absorption was achieved in 48 h by the blocks, presenting a promising and cost-effective solution for seepage-related issues in building construction.

Lower concentration polyethylene microplastics can influence free-floating macrophyte interactions by combined effects of many weak interactions: A nonnegligible ecological impact

Microplastics (MPs) are ubiquitous in freshwater ecosystems and their accumulation has been considered an emerging threat. Early research on the effects of MPs on macrophytes primarily focused on the toxicological impacts on individual macrophytes, with several studies suggesting that lower concentrations of MPs have little impact on macrophytes. However, the ecological implications of lower MP concentrations on macrophyte communities remain largely unexplored. Here, we experimented to assess the effects of lower concentrations including 25 mg/L, 50 mg/L, 75 mg/L, and 100 mg/L of polyethylene (PE) microplastics on Spirodela polyrhiza and Lemna minor, and their community. Our results also indicated that PE concentrations below 100 mg/L had no significant effect on relative growth rate, specific leaf area, Chlorophyll a, Chlorophyll b, Chlorophyll a + b, carotenoid, malondialdehyde (MDA), catalase, and soluble sugar of monocultural S. polyrhiza. However, a lower concentration of PE significantly decreased the MDA of monocultural L. minor and significantly affected the comprehensive index of S. polyrhiza. These findings suggested that lower concentrations of PE can influence interactions between macrophytes maybe due to the cumulative effects of many weak interactions. Additionally, our study showed that 75 mg/L and 100 mg/L PE additions decreased the competitive balance index value of two macrophytes under mixed-culture condition. This result implied that the ecological influence of lower concentration MPs on macrophytes may manifest at the community level rather than at the population level, due to species-specific responses and varying degrees of sensitivity of macrophytes to PE concentrations. Thus, our study emphasizes the need to closely monitor the ecological consequences of emerging contaminants such as MPs accumulation on macrophyte communities, rather than focusing solely on the morphology and physiology of individual macrophytes.

Microplastic polyethylene induced inner ear dysfunction in murine model

While the hazardous effects of microplastics (MPs) are increasingly reported, it remains uncertain if MPs induce inner ear dysfunction. Nonetheless, prevalence of inner ear dysfunction was observed across all age groups. In this study, we investigated whether MP polyethylene affect inner ear function in a murine model. To detect hearing loss and balance defect after polyethylene (PE) exposure, we evaluated hearing threshold levels, assessed cerebral glucose metabolism, conducted transcriptome analysis, and performed behavioral studies. C57BL/6 J mice (5-week-old) were grouped into control (n = 10) and PE-fed groups (n = 10). Mice were orally administered 100 ppm/100 μL (equivalent to 10 μg) of PE every day for 4 months. We identified the accumulation of PE in the cochlea and vestibular region. The fragmented PE in inner ear was 3.00 ± 0.38 µm in size; the administered PE concentration was 1.14 ± 1.06 mg/g. Fourier transform infrared spectrometry confirmed that the properties of the MP were identical with those of PE fed to the mice. Transcriptomic analysis showed up-regulation of PER1, NR4A3 and CEBPB at the PE exposed inner ear tissue and it was confirmed using qRT-PCR, western blotting, and immunofluorescence staining. We observed abnormalities in balance related behavior assessment in the PE group. Exposure to PE increased the hearing thresholds and decreased glucose metabolism in the bilateral lateral entorhinal cortex, right primary auditory cortex, and right secondary auditory cortex. We can conclude that PE exposure induced inner ear dysfunction such as hearing loss and balance disorder.

Correction: Tsai et al. Polyethylene (PE) Waste Minimization Study of Cement Mortar with Adding PE Content under Different W/B Ratios. Buildings 2022, 12, 2117

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Pemanfaatan Limbah High Density Polyetylene (HDPE) Geomembrane Sebagai Campuran Beton Normal

High-Density Polyethylene (HDPE) is a thermoplastic polymer material processed by the heating process of petroleum. One processed product is geomembrane sheets, commonly used to construct ponds in geothermal areas. This Final Project researched High-Density Polyethylene geomembrane waste as an additional material mixed into ordinary or everyday concrete mixtures with fc' = 25 MPa quality. The added waste material from the geomembrane (HDPE) is 0.5 x 0.5 cm and has been cut or chopped with a particular machine. High-density polyethylene (HDPE) content is included in the mixture in regular concrete with a volume composition of 0.00%, 0.25%, 0.50%, 0.75%, and 1.00%. The method for calculating the composition of the concrete mixture uses the American Concrete Institute (ACI) standard. The results showed that the most optimum value for obtaining the compressive strength of concrete fc' 25 MPa with the highest value of split tensile strength (3.54 MPa) was a mixture with 0.50% chopped geomembrane (HDPE). Based on these results, waste in geothermal areas is expected to be reduced by using concrete and a mixture of chopped geomembrane (HDPE).

Identification of the recyclable content of polyethylene films in the Upper Austrian waste streams

ABSTRACT The European Union (EU) has set ambitious recycling targets for plastic packaging waste of 50% and 55% by the end of 2025 and 2030, respectively. Austria’s recycling rate is currently below 30%, necessitating significant improvements in collection, sorting, and recycling efficiencies. To enhance the sorting efficiency, understanding the composition and condition of waste is crucial. Our study focuses on the identification of the recyclable content of polyethylene (PE) films in Upper Austrian waste streams for plastics recycling. This involved the manual sorting of three waste streams through various steps. As a result, the occurrences of monolayer PE films in the post-consumer waste streams were obtained. Based on the apprehended data, a circularity indicator (CI), which is a rough estimation of material circularity that takes into account the losses in both quantity and quality when reprocessing materials, together with a sensitivity analysis was calculated for Austria, which revealed that reducing demand and increasing the amount of recycled materials is more beneficial to the CI than improving energy efficiency. This research fills knowledge gaps on the availability of PE film waste in the various waste streams and can be used as a basis for enhancing the recycling rate in PE film recycling.

Unlocking interfacial synergies: In situ multi-step reaction-induced control for high-performance and functional polybutylene terephthalate/polyolefin blends from recycled sources

This investigation employed free radical melt grafting technology for the synthesis of (POE/R-LLDPE)-g-(GMA-co-St) graft copolymers. Subsequently, this graft copolymer was applied as a modifier for poly (butylene terephthalate) (PBT) resin. The effects of varying recycled linear low-density polyethylene (R-LLDPE) contents in the graft on the rheological behavior, thermal properties, mechanical properties, and toughening mechanism of PBT/(POE/R-LLDPE)-g-(GMA-co-St) blends were exhaustively explored. The findings revealed that glycidyl methacrylate (GMA) and styrene (St) were effectively grafted onto the poly (ethylene-octene) (POE) and R-LLDPE molecular chains. This process enabled the epoxy groups in the GMA of the graft to react with the terminal groups of the PBT resin, thereby enhancing its compatibility with PBT. The use of R-LLDPE-g-(GMA-co-St) or POE-g-(GMA-co-St) as singular modifiers did not produce optimal modification results. Conversely, the most effective modification of the PBT resin was observed when both were combined, indicating a pronounced synergistic modification effect. The optimal overall performance of the blend was noted when the R-LLDPE content in the graft copolymer was 50 wt%. This method significantly enhanced the toughness of the blend while preserving excellent thermal stability and mechanical strength, concurrently reducing the product cost. At this point, a high concentration of voids was observed in the stress-whitening area of the impact specimens. The PBT matrix displayed conspicuous shear yielding with a notably rough impact fracture surface, manifesting highly significant tough fracture characteristics.

Microplastic ingestion in mussels from the East Mediterranean Sea: Exploring its impacts in nature and controlled conditions

Microplastic ingestion poses a significant concern for a plethora of marine organisms due to its widespread presence in marine ecosystems. Despite growing scientific interest, the effects on marine biota are not yet well understood. This study investigates the ingestion of microplastics (MPs) by mussels from various marine environments and assesses the associated effects that can be induced by MPs and associated toxic chemicals. Biomarkers of oxidative stress (catalase, lipid peroxidation), biotransformation (glutathione S-transferase), genotoxicity (micronuclei frequency) and neurotoxicity (acetylcholinesterase) were employed. Mussels, considered reliable bioindicators of MPs pollution, were sampled by hand from diverse locations under varied anthropogenic pressures, including a highly touristic Marine Protected Area (MPA) in the Ionian Sea, a mussel farm and a fish farm in the Aegean Sea. The results revealed the highest MP ingestion in mussels from the fish farm [0.21 ± 0.04 (SE) MPs/g or 0.63 ± 0.12 (SE) MPs/Ind.], likely due to plastic aquaculture equipment use. Stereoscopic observation revealed fibers, as the predominant shape of ingested MPs across all sites, and μFTIR polymer identification revealed the presence of various types, with polyethylene (PE) and polyamide (PA) being the most abundant. Significant physiological alterations in mussels related to MP ingestion levels were observed through biomarkers indicative of oxidative stress and biotransformation, as well as the Integrated Biomarker Response (IBR index). However, laboratory experiments with mussels exposed to controlled increasing PE concentrations for four weeks, did not show significant effects triggered by the PE ingestion, possibly indicating other environmental factors, such as contaminants from aquaculture environments, may influence biomarker levels in the field. Despite the observed effects, MP ingestion rates in mussels from the field were relatively low compared to other studies. Future research should continue to investigate the interactions between MPs and marine organisms in diverse environments to better understand and mitigate their impacts.

Role of light microplastics in the dispersion process of spilled crude oil in the marine environment

Oil spill and microplastic (MP) pollution are the main problems in the marine environment. After an oil spill, the oil film may be dispersed into the water column in the form of droplets under the action of ocean waves. In this study, the sea condition was simulated through the batch conical flask oscillation experiment. Merey crude oil was selected as experimental oil, and polyethylene (PE) and polystyrene (PS) were used as experimental MP. The effects of MP properties (type, concentration and size) on the dispersion of spilled oil were investigated. It is found that for each MP, the oil dispersion efficiency (ODE) increased rapidly at first and then tended to be stable, which all reached the maximum at 360 min. When the concentrations of PE and PS increased from 0 to 100 mg/L, the maximum ODE decreased from 32.64 % to 13.72 % and 10.75 %, respectively, indicating that the presence of MP inhibits the oil dispersion. At the same oscillation time, the volumetric mean diameter (VMD) of dispersed oil increased with the MP concentration. When the particle size of PE and PS increased from 13 to 1000 μm, the maximum ODE increased from 24.74 % to 31.49 % and 28.60 %, respectively. However, the VMD decreased with the size of MP. In addition, the time series of the oil adsorption rate by the MP were well fitted by the kinetic models. The results of this research deepen the understanding of the migration law of spilled oil to the marine environment in the presence of MP, and may further improve the ability of marine environmental scientists to predict the fate of oil spill.

#2767 Micro(nano)plastics are exposed and bioaccumulated in human fetus—the first evidence from neonatal umbilical cord blood and urine

Abstract Background and Aims At present, the world population problem is increasingly serious, and the impact of environmental pollution on the health of pregnant women and fetuses is a global research focus. Among them, micro(nano)plastics (MNPs), as an emerging pollutant, has been confirmed by several animal experiments and in vitro human cell experiments to have biotoxic effects. Recent studies have shown that MNPs are found in human placenta, amniotic fluid, meconium, and other samples, but there is still a lack of direct evidence that MNPs can enter and bioaccumulate in the fetus. Method To initially explore the actual situation of neonatal exposure to MNPs, this study collected umbilical cord blood samples and postnatal urine samples from 6 healthy fetuses in Chengdu, Sichuan, China, and used pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and laser direct infrared spectroscopy (LDIR) to detect and analyze MNPs in samples. Results With an average abundance of 81.15 (40.71) μg/g, MNPs were found in 6 umbilical cord blood samples by Py-GC/MS. Polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS) and polyamide 66 (PA66), 4 different types of MNPs were found, with PE content being the highest among them. By using LDIR, MNPs were found in 5 umbilical cord blood samples, with an average abundance of 17.39 (18.91) particles/g. Three different types of MNPs were found, they are acrylates (ACR), polyethylene terephthalate (PET) and polypropylene (PP). MNPs particles were detected in 6 urine samples by PY-GC/MS, and the average abundance was 8.42 (4.70) μg/g. Two kinds of MNPs, PE and PVC, were detected, and the content of PE was higher. Conclusion The findings demonstrated that the contents and types of MNPs in umbilical cord blood samples were higher than those in urine samples. The levels of MNPs were correlated with the living habits of pregnant mothers, such as the frequency of ordering take-out food. In this study, through the detection of MNPs in umbilical cord blood and neonatal urine samples, we found the direct evidence of MNPs in the fetus for the first time, further confirmed that MNPs can enter the urine through renal metabolism, preliminarily explored the exposure and bioaccumulation effect of MNPs in the fetus, and analyzed the possible risks and related factors of exposure of MNPs during pregnancy, which provided a theoretical basis for in-depth study of the health impact of MNPs on pregnant women and fetuses.

#2550 Micro(nano)plastics in human urine: a surprising contrast between Chongqing's urban and rural regions

Abstract Background and Aims Microplastics (100 nm-5 mm) and nanoplastics (<100 nm) collectively referred to as micro(nano)plastics (MNPs), which are emerging pollutants all over the world. Environmental differences affect its distribution. The content of MNPs differs between urban and rural environments, according to previous studies. Method To understand the actual situation of human exposure to MNPs in various environments, this study collected 12 urine samples from volunteers in urban and rural regions of Chongqing and used pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and laser direct infrared spectroscopy (LDIR) to detect and analyze MNPs in urine. Results With an average abundance of 1.50 (2.31) mg/kg, MNPs were found in 9 samples by Py-GC/MS. Polyethylene (PE), polyvinyl chloride (PVC) and polyamide 66 (PA66), three different types of MNPs were found, with PE content being the highest among them. By using LDIR, MNPs were found in 7 samples, with an average abundance of 15.17 (23.13) particles/kg. Five different types of MNPs were found, with acrylates (ACR) being the main type, followed by polymethylmethacrylate (PMMA), polyurethane (PU), polypropylene (PP), polyethylene terephthalate (PET). Conclusion The findings demonstrated that urban region had much greater levels and more types of MNPs in human urine than rural. Additionally, regular contact with plastic toys and the use of personal care products are linked to the presence of MNPs. The influence of environmental factors on the actual exposure of the human body to MNPs was preliminary explored in this study, and two different methods were used for the first time to simultaneously detect and analyze MNPs in human urine. This allowed for the feasibility of comprehensively and effectively quantitatively analyzing the actual exposure of the human body to MNPs, and also provided the theoretical foundation for further research on the harm of MNPs to human health in different environments.

Energy-efficient scientific-technological approaches to the processing of plastic waste PET, PE, PP, PS to produce hydrogen-containing gas and titanium carbide powder

The paper considers gaseous products, structure and phase composition of hard products resulting from high-temperature exothermic reactions between Ti–PET–(PE, PP, PS) system components, depending on the content of oxygen-free polymers polyethylene (PE), polypropylene (PP), and polystyrene (PS) in the initial blend. It is found that the addition of PE, PP, PS polymers to the Ti–PET system increases the hydrogen content from 45 to 62 vol% and reduces the carbon monoxide content from 38 to 20 vol% in gaseous products. According to calculations, the adiabatic flame temperature of the synthesized gas in air is very close to that of pure hydrogen. The synthesized gas can therefore be used as ecological fuel for energy sources. On the other hand, oxygen-free polymers presenting in the system provide the formation of substoichiometric carbide TiC0.75. Its hardness is not lower than that of stoichiometric TiC and even exceeds widely used carbides and borides of transition metals. In addition, the agglomerate structure of synthesized TiC0.75 allows to apply it as a promising ecological basis for highly-efficient abrasive pastes, in particular for polishing and finishing fabricated metal products.

Study on CO2 co-gasification of cellulose and high-density polyethylene via TG-FTIR and ReaxFF MD

CO2 co-gasification of solid waste and biomass presents an approach for the comprehensive utilization of waste materials, biomass and carbon dioxide. In this study, the CO2 co-gasification of cellulose and high-density polyethylene was explored utilizing TG-FTIR method and ReaxFF MD simulation. The thermal behavior, synergistic effect, volatile release characteristics, activation energy and reaction mechanism were thoroughly analyzed. The experimental findings indicated that CO2 co-gasification involved four stages: drying, cellulose pyrolysis, polyethylene pyrolysis and semi-coke gasification. Co-gasification inhibited cellulose pyrolysis but promoted polyethylene pyrolysis, with the most pronounced promoting effect occurring at 40% polyethylene content. The absorbance curve suggested that CO release was associated with cellulose pyrolysis and the reaction between cellulose coke and CO2, and C-H release was related to the pyrolysis of cellulose and polyethylene. Co-gasification alleviated the energy barrier, with the greatest effect occurring at 40% polyethylene content. The simulated results confirmed that the promotion of polyethylene pyrolysis was attributed to the connection of radicals from cellulose with polyethylene. Additionally, the combination of hydrocarbon radicals and hydrogen from polyethylene and cellulose contributed to gas production. This investigation provides insights into the thermochemical conversion characteristics for CO2 co-gasification of biomass and high-density polyethylene.

Durability and performance of wood flour/polyethylene composites containing fire retardants after weathering via ASTM D2565

Wood–plastic composites are composite materials consisting of wood particles, thermoplastic polymer, and small amounts of other performance additives to increase performance in exterior construction applications such as decking and siding. Three best-performing fire retardants, determined from a previous study, which were brominated, magnesium hydroxide, and ammonium polyphosphate, were selected for this weathering study and more detailed analysis with color analysis, thermogravimetric analysis/differential scanning calorimetry, and the cone calorimeter. With the rapid surface heating condition at cone calorimeter irradiance of 50 kW m−2, modest surface leaching of fire retardant was detected as caused by weathering via increased first peak heat-release rate and reduced time to ignition values. Otherwise, the weathering had minimal effect on the remaining heat-release rate profile, and results confirmed ammonium polyphosphate as top performing fire retardant, even better than Ipe wood, with magnesium hydroxide and brominated slightly worse than Ipe. This suggests that 35% high-density polyethylene content reduced fire retardant bulk leaching.

Effects of process conditions and nano-fillers on the cell structure and mechanical properties of co-injection molded polypropylene-polyethylene composites

Compared with traditional injection foaming, co-injection foaming serves as a method to prepare products with high-quality surfaces and enhanced mechanical properties, demonstrating excellent technical advantages and economic benefits. The effects of high-density polyethylene (HDPE) content, foaming agent content, melting temperature of core material, and nano-organic montmorillonite (OMMT) content on the cell structure, mechanical properties, and crystallization behavior of isotactic polypropylene (iPP)/HDPE composite foam prepared by co-injection foaming were systematically studied. At a foaming agent content of 2 wt.%, HDPE content of 30 wt.%, OMMT content of 3 wt.%, and the melting temperature of core material of 190 °C, the composite foam exhibited a cell size measuring 85 μm, a cell density of 2.5 × 105 cells/cm3, a tensile strength of 25.8 MPa, and an impact strength of 12.5 kJ/m2. The addition of HDPE reduced the crystallinity of iPP matrix, while enhancing the solubility of carbon dioxide within the matrix. The non-miscible interface between HDPE and iPP helped reduce the energy barrier for cell nucleation. Furthermore, the introduction of OMMT as a nucleating agent in iPP/HDPE composite material dramatically decreased the energy barrier for cell nucleation. These synergistic effects result in foam with the smaller cell size and the higher cell density, exhibiting excellent comprehensive mechanical properties. This work provides a feasible method for preparing composite foam with excellent comprehensive performance.