•Low environmental stress cracking resistance (ESCR) in recycled HDPE hinders their use in rigid packaging.•Higher concentrations of HDPE from milk bottles in PCR notably impair their ...ESCR.•Prioritizing sorting based on bottle types over separating bottles and caps is recommended.•Comprehending the root causes of low ESCR in PCR is essential to devise strategies to improve this property.•Optimized sorting processes are the key to increasing PCR uptake in new products.
High-density polyethylene (HDPE) is widely used in products such as bottles for cleaning products, in which Environmental Stress Cracking Resistance (ESCR) is required. This property is typically inferior in post-consumer recycled plastics (PCR), thus limiting their uptake in the rigid packaging industry. This study evaluated two PCR HDPE grades and the root causes of their low ESCR. Effects of sourcing the waste from detergent bottles (BPE) or milk bottles (UPE), Polypropylene (PP) contamination from bottle caps, and multiple recycling steps were all investigated. The findings revealed that ESCR is reduced by adding UPE, PP, and consecutive extrusion cycles. Unexpectedly, the presence of a high content of milk bottle grades in a given PCR hinders their uptake in detergent bottle production much more than the presence of PP caps, inferring that sorting based on bottle types instead of separating bottles and caps should be prioritized.
Display omitted
Display omitted
•Microplastics (MPs) with adsorbed hazardous chemicals threat humans and fauna.•Photocatalytic degradation of MPs by C,N-TiO2 was proposed to fight MPs pollution.•Photocatalysis of ...HDPE MPs was studied at different pH and temperature values.•A combined effect of low pH and temperature resulted in 70 % of MPs’ degradation.•Photocatalysis of HDPE MPs in aqueous medium can reduce MPs marine pollution.
Microplastics (MPs) are pollutants formed by plastics ≤ 5 mm and are present in marine and terrestrial environments. Due to their large surface to volume ratio and chemical surface properties, MPs adsorb hazardous chemicals from their surrounding environment. When MPs are consumed by fauna, they transfer those substances through the trophic chain. An essential issue of MPs is their disposal. Due to their size, the disposal methods commonly used for plastic items are not suited for MPs. Here, photocatalysis in an aqueous medium is proposed as an alternative to fight MPs pollution. Although the photocatalysis of MPs has been reported, the effect of operating variables in the process has not been investigated. To fill this gap, the impact of pH and temperature on the degradation process of HDPE MPs was investigated using C,N-TiO2 and visible light. Degradation was followed by mass loss, carbonyl index calculation and microscopy. It was found that photocatalysis at low temperature (0 °C) increases MPs’ surface area by fragmentation, and low pH value (pH 3) favours hydroperoxide formation during photooxidation. By using the design of experiments tool, it was demonstrated that there is a combined effect of pH and temperature in the photocatalysis of HDPE MPs.
This paper reports on the photocatalytic activity showed by nanocomposites of TiO2 with low density polyethylene (LDPE) and high density polyethylene (HDPE) (10, 20 wt%) for the degradation of methyl ...orange in aqueous medium under visible light irradiation. TiO2 was synthetized by sol-gel process, and the polymers were incorporated by impregnation. Both the pure TiO2 and the nanocomposites were characterized using different physico-chemical techniques including specific surface area analysis, X-ray diffraction analysis, transmission electron microscopy, ultraviolet-visible and photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. All the prepared nanocomposites showed an absorption edge in the visible region. TiO2(90)/LDPE photocatalyst showed the best degradation efficiency after 180 minutes of reaction, without notorious decrease of degradation efficiency after three consecutive uses. Photoluminescence and X-ray photoelectron spectroscopy analyses suggested the presence of vacancies in the TiO2 structure promoted by a Ti–O–C interaction being responsible for the photocatalytic activity enhancement under visible light irradiation.
•Replacing PP with MAPP in 50/50w/w blend composites with different amounts of wood powder (WP).•Separation between PP and MAPP crystallization more resolved with increasing WP content.•Cooling rate ...had a stronger influence on MAPP than on PP crystallization in the presence of WP.•Replacement of PP with MAPP in the blend composites had an appreciable influence on the tensile properties.
The morphology and properties of blends of PP/HDPE and MAPP/HDPE blends, and their composites with wood powder, were investigated in this paper. The blends showed two-phase morphologies, and MAPP interacted better than PP with HDPE, while the WP interacted more strongly with MAPP. Although the different components in the blends were immiscible, they showed one crystallization peak. MAPP and HDPE showed separate crystallization peaks in the composites, and this separation of the crystallization became more resolved with increasing WP content and at lower cooling rates. This was also observed for PP and HDPE in their composites, but to a lesser extent. Young’s modulus increased and the stress at break decreased with increasing WP content, and these were more pronounced in the PP/HDPE/WP composites. Interaction between WP and MAPP also had an influence on elongation at break. The presence of WP increased the thermal stability of the MAPP/HDPE and PP/HDPE.
Soil erosion is a potentially important source of microplastic (MP) entering aquatic ecosystems. However, little is known regarding the erosion and transport processes of MP from agricultural ...topsoils. The aim of this study is to analyze the erosion and transport behavior of MP during heavy rainfall events, whereas a specific focus is set to preferential MP transport and MP-soil interactions potentially leading to a more conservative transport behavior. The study is based on a series of rainfall simulations on paired-plots (4.5 m × 1.6 m) of silty loam and loamy sand located in Southern Germany. The simulations (rainfall intensity 60 mm h−1) were repeated 3 times within 1.5 years. An amount of 10 g m−2 of fine (MPf, size 53–100 μm) and 50 g m−2 of coarse (MPc, size 250–300 μm) high-density polyethylene as common polymer was added to the topsoil (<10 cm) of the plots. The experiments show a preferential erosion and transport of the MP leading to a mean enrichment ratio of 3.95 ± 3.71 (MPc) and 3.17 ± 2.58 (MPf) in the eroded sediment. There was a higher MP enrichment on the loamy sand but a higher sediment delivery on the silty loam resulting in nearly equal MP deliveries from both soil types. An increasing interaction with mineral soil particles or aggregates leads to a decreasing MP delivery over time. Within 1.5 years, up to 64% of the eroded MP particles were bound to soil particles. Overall, more of the MPc was laterally lost via soil erosion, while for the MPf the vertical transport below the plough layer was more important. In general, our study indicates that arable land susceptible to soil erosion can be a substantial MP source for aquatic ecosystems.
Display omitted
•Coarse HDPE-MP is preferentially eroded and hence enriched in delivered sediments•HDPE-MP erosion decreases over time due to increasing soil-MP interactions•Lateral HDPE-MP fluxes increase and vertical fluxes decrease with MP particle size
The fabricated multifunctional composite PCMs possesses high energy storage density, excellent light-to-thermal conversion and electro-to-thermal conversion effect.
Display omitted
•The HDPE/CNTs ...porous scaffolds were successfully fabricated via sacrificial template method.•HDPE/CNTs/PW-3:7 obtained possesses high melting enthalpy (153.95 J/g).•The thermal conductivity and electrical conductivity of HDPE/CNTs/PW-3:7 are increased greatly.•HDPE/CNTs/PW-3:7 possesses huge potential in the field of multifunctional thermal energy storage.
The risk of leakage and low thermal conductivity severely hinder the wide application of phase change materials (PCMs). In this work, the high-density polyethylene/carbon nanotubes (HDPE/CNTs) porous scaffolds were successfully fabricated via a sacrificial template method followed by the general melt blending and water solvent etching. Subsequently, a series of paraffin wax HDPE/CNTs/PW composite PCMs were obtained combined with the simple vacuum impregnation method. The obtained HDPE/CNTs porous scaffolds can effectively avoid the leakage of PW, meanwhile, the thermal conductivity and electrical conductivity of HDPE/CNTs/PW-3:7 are increased by 2.94 times and 13 orders of magnitude compared with the HDPE/PW-3:7 respectively, also, it exhibits high phase change enthalpy (153.95 J/g for melting enthalpy and 152.82 J/g for crystallization enthalpy). From the above perspectives, the HDPE/CNTs/PW-3:7 has promising potential value in the application of light-to-thermal conversion, electro-to-thermal conversion and thermal energy storage.
•Developed pipe-swallowing technique for pipe replacement in sand.•Evaluated it by monitoring stress, pulling force, and vertical displacement.•Established an equation to predict vertical ...displacement.
Pipe bursting, a trenchless technique for replacing underground pipes, may induce ground movements that potentially harm nearby structures. To address this issue, the innovative pipe-swallowing method has been developed. Compared to pipe bursting, this method reduces surface disturbances and offers better protection for the newly installed pipes. In this study, a uniaxial test machine was employed in preliminary tests to enhance the structural design of the pipe-swallowing device. Follow-up experiments conducted in a 3.0 m × 1.8 m × 1.5 m test box measured the pulling forces and three-dimensional surface displacements involved in replacing a buried HDPE pipe, 315 mm in diameter, with another of the same size. The most effective pipe splitting force, determined as 32 kN, was achieved using three blades with 30° V-edges and 120° intersection angles, leading to the lowest observed peak pulling force. This force predominantly offsets the friction between the new pipe and the soil, the interaction of the swallower with the soil, and the force required for pipe splitting. The pipe-swallowing process leads to persistent alterations in the pressure distribution around the pipe, causing ground disturbances extending roughly ± 650 mm. The maximum vertical displacement measured was 21 mm, aligning with the modified Gaussian distribution model. These findings affirm the practicality of the pipe-swallowing method and pave the way for future improvements in finite element models for this application. Furthermore, expanded research exploring a range of soil types and pipe materials, including both flexible and brittle varieties, is crucial for advancing the efficiency of this technology.
•SSPCM’s based on HDPE/paraffin waxes can be prepared using twin-screw extrusion.•The waxes were uniformly dispersed and distributed in the polymer matrix.•SSPCM’s with a high melting point wax ...(Tm=56–58°C) had latent heats up to 89J/g.•The waxes had a strong plasticising effect on the HDPE.•SSPCM’s with the higher melting point wax were mechanically superior.
Shape stabilised phase change materials (SSPCMs) based on a high density poly(ethylene)(hv-HDPE) with high (H-PW, Tm=56–58°C) and low (L-PW, Tm=18–23°C) melting point paraffin waxes were readily prepared using twin-screw extrusion. The thermo-physical properties of these materials were assessed using a combination of techniques and their suitability for latent heat thermal energy storage (LHTES) assessed. The melt processing temperature (160°C) of the HDPE used was well below the onset of thermal decomposition of H-PW (220°C), but above that for L-PW (130°C), although the decomposition process extended over a range of 120°C and the residence time of L-PW in the extruder was <30s. The SSPCMs prepared had latent heats up to 89J/g and the enthalpy values for H-PW in the respective blends decreased with increasing H-PW loading, as a consequence of co-crystallisation of H-PW and hv-HDPE. Static and dynamic mechanical analysis confirmed both waxes have a plasticisation effect on this HDPE. Irrespective of the mode of deformation (tension, flexural, compression) modulus and stress decreased with increased wax loading in the blend, but the H-PW blends were mechanically superior to those with L-PW.
PDF
