Marine bacteria capable of enzymatic degrading of low- and high-density polyethylene: Toward sustainable mitigation of marine microplastic pollution

The accumulation of plastic waste, particularly from high-density polyethylene (HDPE) and polyethylene terephthalate (PET), poses significant environmental challenges due to their persistence and the complexity of recycling mixed polymer. Accordingly, this study was conducted to investigate the thermal degradation behavior and kinetic parameters of virgin HDPE, PET, and their binary mixture to support waste-to-energy applications. Thermogravimetric analysis (TGA) and Differential thermogravimetry (DTG) were performed under pyrolytic conditions using nitrogen as the carrier gas at multiple heating rates, and degradation kinetics were evaluated using five isoconversional methods: Friedman (FR), Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Starink (STK), and Vyazovkin (Vy). Results showed that both HDPE and PET undergo single-step degradation, with HDPE decomposing at higher temperatures in a narrower range (449–497 °C) than PET (394–471 °C) at 15 °C/min. The HDPE–PET blend showed a broader decomposition range (417–495 °C) with an onset temperature between PET and HDPE. Comparatively, the Friedman (FR) method provided reliable activation energies for HDPE and PET (259.55 ± 7.3 and 193.16 ± 17.07 kJ/mol), as it effectively captures the single-step degradation of individual polymers with minimal variation across conversion levels. For the HDPE–PET binary blend, the Vyazovkin (Vy) method yielded the most consistent activation energy profile (173.51–217.45 kJ/mol; average 210.47 ± 7.2 kJ/mol), demonstrating its robustness in handling the complex, overlapping decomposition behaviors of mixed polymer systems. Model-fitting via y(α)/y(0.5) analysis identified the autocatalytic model 1 − α n α m + α ∗ as the most appropriate for all samples, with simulated curves showing excellent agreement with experimental data (R 2 > 0.92). These findings demonstrate the feasibility of predicting pyrolysis behavior for both individual and mixed plastics, contributing to improved strategies for managing mixed plastic waste streams. • At β = 15 °C/min, the HDPE–PET blend showed a broader decomposition range (417–495 °C). • Eα by Fr averaged 259.55 kJ/mol for HDPE, 193.16 kJ/mol for PET, and Vyazovkin 210.47 kJ/mol for the blend. • The autocatalytic model obtained the f(α) for degradation kinetics for HDPE, PET, and their blend. • Simulated autocatalytic model curves matched experimental data (R 2 > 0.92),

Agricultural HDPE pyrolysis for environmental management: Feedstock complexity, reaction dynamics, and circular resource recovery.

Investigation of pipe–soil interface effects on the stress–deformation behavior of buried high-density polyethylene pipes: full-scale test and analytical solution

The accumulation of plastic waste poses severe environmental challenges, driving the need for efficient catalytic recycling technologies to enable a circular economy. High-density polyethylene (HDPE) is particularly challenging to catalytically upgrade due to its high crystallinity and the limited accessibility of its polymer chains. While zeolite catalysts offer shape selectivity advantages for product control, their practical application in polyolefin conversion has been constrained by low catalytic activity. Herein, we engineered a hierarchical ZSM-5 zeolite with a substantially enhanced external surface area and multilevel porosity to reduce mass-transfer limitations and improve catalytic efficiency. Pyridine and 2,6-di-tert-butylpyridine Fourier transform infrared spectroscopy studies confirmed that the synthesized ZSM-5 possesses significantly more external and macromolecule-accessible acid sites compared to commercial counterparts. The optimized ZSM-5 with a Si/Al ratio of 100 achieved an 86.8% HDPE conversion at a mild temperature of 250°C, exhibiting high selectivity toward C4-C12 unsaturated hydrocarbons. The mass-based activity was 1.5 times higher than that of the best-reported pure zeolite catalyst for polyethylene cracking. By engineering the external surface acidity and molecular transport pathways of zeolite catalysts, this work paves the way for efficient chemical valorization of waste polyolefins, demonstrating the power of rational catalyst design.

Physical modeling of high density polyethylene (HDPE) pipes buried in sand under lateral pulling loads

Anthropogenic stones on a remote oceanic island: formation, transport, and burial in a sea turtle nesting beach.

Effects of chemical treatments on mechanical properties of unidirectional flax fiber reinforced high density polyethylene composites

Retraction notice to“Improved Fresh and Hardened properties of Concrete with High Density Polyethylene aggregates: Role of Silica fume, Steel Fibers, Macro synthetic fibers and Variation of water cement ratio” [Mater. Chem. Phys.: Sustain. Energy 2 (2025) 100010

The aim of this study is to investigate human exposure to chemicals transference through ingestion of foods that are cooked in their plastic packaging. For this purpose, six different food types were analyzed before and after cooking in microwave and conventional oven, as well as their plastic containers. This approach allowed to tentatively identifying 35 intentionally added substances and 3 non-intentionally added substances. Several compounds already transferred upon contact and increased their transference after cooking. Conversely, decapropylene glycol, diisodecyl phthalate, undecaethylene glycol, 2-(14,15-epoxieicosatrienoyl)glycerol, 1-linoleoyl-glycerol and octyl 3,3,3-trifluoropropanoate only transferred during cooking. Low density polyethylene packaging exhibited a greater number of transferred plasticizers. In contrast, linear hydrocarbons that could transfer were prominent in high density polyethylene trays. Finally, obtained results will contribute to human exposure assessment of these chemicals. It has been tentatively identified 15 compounds to be considered of greatest safety concern, above all, benzylbutyl phthalate and butyl hydroxy toluene.

Improved properties of high-density polyethylene by integrating high content of bio-fillers based on green nanolignin for applications in plastic industry

In-situ hydrogen generation and hydrodeoxygenation via Ni-Mo alloy tandem catalysis: Co-liquefaction of high-density polyethylene and bamboo sawdust into hydrocarbon fuels

The role of graphene nanoplatelets and carbon black hybrid fillers on rheological and mechanical properties and sagging behavior of high-density polyethylene nanocomposite

Role of ex-situ hydrocarbons plasticization on high-density polyethylene slow crack growth

The increasing presence of microplastics (MPs) in wastewater sludge raises concerns about their potential interference with anaerobic digestion (AD), a key process for energy recovery and sludge stabilization. This study investigated the impact of three common MPs, polystyrene (PS), polyethylene terephthalate (PET), and high-density polyethylene (HDPE), on the anaerobic degradation of a synthetic, rapidly biodegradable substrate under controlled batch conditions with the biomass from an anaerobic digester as inoculum. Biogas production, intermediate metabolic parameters, and microbial community dynamics were comprehensively assessed. The results showed a moderate inhibition of methane yield in the presence of MPs, with HDPE causing the most significant reduction (up to 24%) in biogas generation. PS exhibited the lowest impact, independent of the concentration added (0.5 and 1.0 g·L−1). The microbial community structure demonstrated robustness, with Firmicutes and Bacteroidota maintaining dominance and methanogenic populations largely unaffected, except in the presence of HDPE. Raman spectroscopy indicated that none of the MPs underwent substantial structural degradation, but the subtle spectral shifts—particularly in PET—suggested the initial stages of physicochemical alteration. These findings offer new insights into the short-term resilience and adaptability of anaerobic microbiomes in the presence of MPs while revealing potential signals of process disruption.

Prosthetic foot design plays a critical role in restoring mo- bility and quality of life for individuals with lower- limb ampu- tation, particularly in low-resource settings where affordability, durability, and functional reliability are essential. The Jaipur- Foot prosthesis is widely used due to its low cost and cultural adaptability; however, its long-term structural performance is strongly influenced by material selection. Traditional micro- cellular rubber (MCR), while offering flexibility and shock absorption, has been associated with excessive deformation and limited fatigue resistance under repetitive loading. Despite the increasing clinical adoption of high-density polyethylene (HDPE) as an alternative prosthetic material, a direct component-level numerical comparison between HDPE and MCR for Jaipur-Foot applications remains limited. In this study, a Jaipur-Foot–inspired three-dimensional model was developed using computer-aided design and evaluated through finite element analysis. Static structural analysis was performed under physiological load levels ranging from 600 N to 1200 N, followed by fatigue life estimation and topology optimization using ANSYS Mechanical. The results indicate that HDPE exhibits a more uniform stress distribution and controlled deformation compared to MCR across all loading conditions. Under a 1200 N load, the maximum equivalent stress remained below 9 × 105 Pa for HDPE, while fatigue life predictions showed a significantly higher endurance compared to MCR. Topology optimization further demonstrated the potential for material reduction with- out compromising structural safety. Overall, the findings suggest that HDPE offers improved structural reliability and fatigue performance over conventional MCR, highlighting its suitability as a biomaterial for durable and cost-effective Jaipur-Foot prosthetic applications.

The increasing demand for sustainable materials has driven interest in biocomposites that incorporate low-value agricultural residues to offset the use of virgin plastics. The study investigated the production of blend pellets from raw and torrefied almond shells and post-consumer plastic waste as a potential feedstock for biocomposite and biofuels applications. Almond shells were torrefied in a lab-scale fixed-bed reactor at 300 °C for 30 min prior to the pelleting tests. High-density polyethylene (HDPE) and polypropylene (PP) wastes were size-reduced in a Crumbler (rotary shear grinder) fitted with a 2 mm head and a 2 mm screen to remove the fines. A portion of the crumbled HDPE, and torrefied almond shells were further ground in a Wiley mill fitted with 2 and 1 mm screens for flat die pelleting tests. The flat die pellet mill used for testing had a 6 mm die and a length-to-diameter (L/D) ratio of 2.0. The blend ratio consisted of 30% torrefied almond shells and 70% HDPE, with a 10% starch binder. The measured pellet properties include unit, bulk and tap densities, durability, and expansion ratio. The bulk density of the blend pellets ranged from 360 to 410 kg/m3, and durability ranged from 80% to 88%. The blend pellet unit density ranged from 830 to 880 kg/m3. The blend pellets produced using crumbled HDPE, PP and raw and torrefied almond shells in a ring die pilot-scale pellet mill with an L/D ratio of 6 and steam conditioning exhibit similar densities to those of HDPE pellets produced using a flat die pellet mill, albeit with lower durability. The study indicated that a smaller grind size and preheating the blend before pelleting produce blend pellets with higher density and greater durability.

The advancement of stab-resistant body armour is critical for law enforcement and military personnel operating in high-risk environments. Conventional armour systems, while effective, often impose excessive weight and restrict mobility, compromising wearer comfort and operational efficiency. This study evaluated the stab-resistant performance of novel composite configurations integrating high-density polyethylene (HDPE), Kevlar trauma liner, and polycarbonate, with the objective of meeting National Institute of Justice (NIJ) Standard 0115.00 Level II protection requirements. Five stacking sequences (A to E) were fabricated and tested against single-edged (P1) and double-edged (S1) knives under two impact energy levels: 33 J (E1) and 50 J (E2). Experimental trials were conducted using the Stab Apparatus and Measurement System at the Science and Technology Research Institute for Defence Ballistic Laboratory, Batu Arang, Selangor, Malaysia. Results demonstrated that Sequence E which comprising HDPE type II, polycarbonate, HDPE type II, Kevlar trauma liner, HDPE type I, and HDPE type II had successfully satisfied NIJ Level II criteria. Penetration depths were 6 mm at E1 and 10 mm at E2, both within NIJ limits (≤6 mm for E1 and ≤20 mm for E2). Finite Element Analysis (FEA) predictions closely aligned with experimental outcomes, with error values ranging from 5% to 10%, thereby validating the model’s reliability. The optimized hybrid configuration exhibited superior stab resistance and notable weight reduction compared to conventional titanium O-ring armour. These findings highlight the potential of multi-material composites to deliver lightweight, agile, and effective stab-resistant armour for urban patrol and high-risk security operations.

The accumulation of plastic waste represents a significant environmental challenge worldwide, and its reuse in construction materials offers a sustainable management alternative. This study investigates the use of recycled high-density polyethylene (HDPE) and polypropylene (PP) granules as partial volumetric replacements (10%, 20%, and 30%) for limestone aggregate in mortar mixtures. A total of seven mixtures were produced and evaluated in terms of flow value, unit weight, water absorption, porosity, compressive strength, flexural strength, and capillary water absorption. In comparison to the control mixture, it was found that the use of plastic aggregate improved the workability. It was found that the flexural and compressive strengths of mixtures decrease when plastic aggregate is added. Additionally, it was understood that utilization of plastic aggregate in mixtures caused an increase in water absorption rate and porosity values. HDPE and PP plastic aggregates increased flow by 9% to 13% and reduced unit weight by 15 to 15.3%, while compressive and flexural strengths decreased by 48 to 30% and 46 to 54%, respectively. The optimum replacement level was 10% for both HDPE and PP mixtures.

Nigeria generates about 2.5 million metric tons of plastic waste annually, but recycling plants processes only around 10% of this amount. Consequently, the rest of the plastic wastes are being dumped in terrestrial and aquatic systems with a huge negative effect human health and pollution problems. The most effective means to promote recycling is to introduce a low-cost plastic shredding machine that can help to reduce the size of the plastic to smaller pieces for convenient storage and transportation. However, the high price of foreign shredding equipment has made it hard for waste collectors to purchase. Hence,the main goals of this work are to design, to fabricate, and carry out performance evaluation of an affordable plastic shredding machine that can operate well and be suitable for small- and medium-sized recyclers. The design procedure was carried out using SolidWorks software which was in agreement with engineering design standards. A 2-mm thick mild steel pyramidal hopper, a shredding chamber with 6-mm thick cutting blades on a 30-mm diameter shaft, a structured mild-steel frame and a 6.5-hp gasoline engine were the main components of the manufactured machine. The 24-toothed spur gears were designed to allow for both clockwise and anticlockwise movement, and the shaft was built to endure the greatest shear and bending strains. Polyethylene terephthalate (PET) bottles, High-density polyethylene (HDPE) products, and polyvinyl chloride (PVC) pipes were used to measure the machine's throughput capacity and shredding efficiency. The shredding operation occurred within a 0.017 m³ shredding chamber, after which the shredded materials were discharged through an outlet chute.The shredding efficiencies for PET, HDPE, and PVC were 69.55, 85.67, and 71.85%, respectively, with throughput capacities of 14 kg/h, 17 kg/h, and 15 kg/h. The overall cost of the produced shredding machine was ₦350,000, which is significantly less than the ₦900,000–₦2,500,000 price range of similar-capacity machines that are frequently imported into Nigeria. The use of materials that could be found locally was the main reason for the reported cost savings.