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This paper presents a comprehensive investigation into the manufacturing of high-performance wood-crosslinked high-density polyethylene composites (WxHDPEC). In particular, the effect of maleated polyethylene (MAPE) treatment and concentration (0-50 wt%) of maple wood fibers is investigated. The samples were produced via dry-blending followed by compression molding and a set of characterization was performed including chemical, morphological, mechanical, thermal, and physical properties. The gel content was found to increase with increasing wood fiber content, while the surface modification significantly improved the tensile strength (11%), tensile modulus (298%), flexural strength (138%), and flexural modulus (81%). Thermal analyses also showed improved thermal stability and higher thermal resistance for the treated composites. Finally, the Shore D hardness increased by 11.0 (from 61.5 to 72.5) and 12.1 (from 61.5 to 73.6) points, while the Shore A hardness increased by 7.5 (from 91.5 to 99.0) and 8.1 (from 91.5 to 99.6) points for the untreated and treated composites, respectively. These improvements are attributed to effective adhesion between MAPE-treated wood fibers and the xHDPE matrix. The findings not only advance our understanding of these complex materials but also provide alternatives for various applications from construction to automotive engineering. Highlights * High-performance wood-reinforced crosslinked high-density polyethylene was produced. * The effect of maleated polyethylene (MAPE) treatment and maple wood fibers was studied. * Higher crosslink density in MAPE-treated wood-xHDPE was obtained. * Wood-crosslinked high-density polyethylene composites have better properties. KEYWORDS composites, crosslinking, high-density polyethylene, maple wood fibers, mechanical properties, surface treatment, 1 | INTRODUCTION Crosslinked polyethylene (xPE) has gained significant attention in various industries due to its important properties such as higher thermal stability, higher impact resistance, and better thermal insulation [...]

One of the most used resins in the plastics industry is polyethylene (PE). Although PE has good impact resistance and ductility, its low maximum use temperature and mechanical strength limit some commercial development, especially for load-bearing applications. To get better overall performances, crosslinking is performed to improve the chemical, mechanical, and thermal properties of PE. A though PE can be crosslinked by using various chemical and physical methods, this makes the resulting polymers more difficult to recycle since a three-dimensional (3D) network is created. In this review, we first describe the different crosslinking techniques for PE to manufacture crosslinked PE (XLPE) parts. Then, as more than half of the XLPE-based products are disposed directly after use, we present several options to reuse and recycle these products to overcome this environmental issue and find a sustainable solution. A focus is made on mechanical recycling and de-crosslinking techniques for XLPE to generate recycled-XLPE (r-XLPE). Finally, a conclusion is presented on the current situation and research gaps that must be filled by future works. KEYWORDS crosslinking, polyethylene, processing, properties, recycling, 1 | INTRODUCTION Polymers have surpassed all other materials in the modern era in terms of the amount produced every year. This is due to their lightweight, easy processing, and [...]

Polyethylene (PE), including high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE), makes up a significant part of post‐consumer plastics in municipal solid waste, presenting challenges for traditional recycling methods due to a wide range of melt flow properties and poor interfacial adhesion between the different resin, which often leads to low quality products (downcycling). In this study, a method is proposed to modify the molecular structure of post‐consumer PE (rHDPE and rLDPE) and their blends by using a straightforward organic peroxide crosslinking technique with 1 phr of dicumyl peroxide (DCP). Different rHDPE/rLDPE blend weight ratios (0/100, 20/80, 40/60, 50/50, 60/40, 80/20, and 100/0) were prepared using a combination of co‐rotating twin‐screw extrusion and pulverization. The final parts were produced via rotomolding where both the forming and crosslinking processes occurred concurrently. Subsequently, the materials were characterized in terms of chemical, thermal, and mechanical properties. It was found that the tensile strength (228%), tensile modulus (345%), flexural strength (145%), and flexural modulus (251%) increased by crosslinking the 80% wt. rHDPE (x‐rHDPE). Conversely, the gel content increased by 17%, thermal resistance by 37.2%, and the impact strength by 93% with 80% wt. rLDPE (x‐rLDPE). It can be concluded that a balance between the properties occurs as the addition of DCP improved both the interfacial adhesion and melt properties of rHDPE/rLDPE blends. This innovative approach represents a simple and straightforward method to upcycle mixed plastics (PE) streams, especially for rotomolding applications. It also offers promising avenues for sustainable waste management and material reuse. [ABSTRACT FROM AUTHOR]

In this work, natural fibers extracted from the medicinal aromatic plant Deverra tortuosa, with different sizes (S1 = 2 mm and S2 = 500 μm), were incorporated into recycled low density polyethylene (rLDPE) to produce sustainable biocomposites. Compounding was performed with different fiber concentrations (0 to 30% wt.) via twin-screw extrusion followed by injection molding. Based on the samples obtained, a comprehensive series of characterization was conducted, encompassing morphological and mechanical (flexural, tensile, hardness, and impact) properties. Additionally, thermal properties were assessed via differential scanning calorimetry (DSC), while Fourier transform infrared spectroscopy (FTIR) was used to elucidate potential chemical interactions and changes with processing. Across the range of conditions investigated, substantial improvements were observed in the rLDPE properties, in particular for the tensile modulus (23% for S1 and 104% for S2), flexural modulus (47% for S1 and 61% for S2), and flexural strength (31% for S1 and 65% for S2). Nevertheless, the tensile strength decreased (15% for S1 and 46% for S2) due to poor fiber–matrix interfacial adhesion. These preliminary results can be used for further development in sustainable packaging materials. [ABSTRACT FROM AUTHOR]

In the past decades, natural rubber (NR) foams became popular in the automotive, construction and aerospace industries because of their lightweight, flexibility and shock-absorbing properties. The selection of optimal formulation and processing parameters is critical to produce foam with specific properties depending on the application. In this study, the effect of foaming agent concentration, foaming temperature and time on the morphological and mechanical properties of NR foams was investigated. First, increasing the foaming agent content from 5 to 9 phr (parts per hundred rubber) increased the cell size (16%), while decreasing the compression modulus (28%). In the second part, increasing the foaming temperature (145 to 155°C) resulted in larger cell size (163%); while decreasing the cell density (28%), compression modulus (2%), and hardness (1%). In the third part, increasing the foaming time (25 to 45 min) led to smaller cell size (63%) combined with higher cell density (100%), compression modulus (16%), and hardness (3%). Based on all the results obtained, the best NR foam was obtained with 7 phr of foaming agent and produced at 150°C for 35 min leading to superior morphological and mechanical performance: the smallest cell size (25 µm) and the most uniform cell size distribution (Đ = 1.03) generating the highest compression modulus (3.36 MPa). Finally, the experimental compression results were combined to build a nonlinear regression model to optimize the formulation and processing conditions leading to 6.5 phr of OBSH molded at 150°C for 36 min. The model showed good agreement with a validation test with less than 2% deviation observed for both compression modulus and strength. [ABSTRACT FROM AUTHOR]

In this study, high density polyethylene (HDPE) was combined with dicumyl peroxide (DCP) to produce crosslinked parts via rotational molding. The effect of DCP content (0.1–2.5 phr) on the crosslinking degree was investigated to determine its effect on the chemical, mechanical, physical, and thermal properties of HDPE. The gel content and crosslink density was found to increase with DCP content. These trends led to a reduction in the degree of crystallinity, melting, and crystallization temperature. Thermogravimetric analysis (TGA) showed that crosslinked HDPE (xHDPE) has higher thermal stability than the neat matrix in both air and nitrogen atmosphere. In addition, a direct relationship was observed between improved thermal resistance and higher impact strength. Finally, relationships between the tensile properties of xHDPE and the degree of crystallinity were observed, which were all controlled by the level of crosslinking. These results have the potential to advance the manufacturing of high performance materials suitable for a wide range of applications such as automotive parts, agricultural products, chemical storage tanks, large waste containers, and fuel tanks in general. [ABSTRACT FROM AUTHOR]

Sustainable natural rubber foams were prepared by replacing petroleum‐based carbon black (CB) with recycled silica (SiO2) nanoparticles. The total nanofiller concentration was fixed at 40 phr, while the CB/silica ratio was changed from 40/0 to 0/40. The results showed that increasing the silica content increased the curing characteristics, such as delta torque (ΔM) by 54%, scorch time (ts) by 50% and optimum curing time (t90) by 65%. But foams based on a hybrid system (20/20) produced a more homogeneous structure improving the cell nucleation step and leading to the smallest cell size (18 μm) and highest cell density (8.8 × 103 cells mm−3) due to reduced filler−filler interactions and better particle dispersion. This improved cellular morphology generated superior mechanical and thermal insulation performance, including the highest compression modulus (2.7 MPa), compressive strength (1.9 MPa) and recoverability (96.6%) combined with the lowest thermal conductivity (0.114 W m−1 K−1) at a density of 0.652 g cm−3. Nevertheless, the foam with 40 phr silica showed higher compressive modulus (26%) and compression strength (15%) compared to the reference sample having 40 phr CB, mainly due to its higher crosslink density. As a final comparison, the recycled silica, being a suitable and sustainable alternative to petroleum‐based CB, showed superior mechanical and thermal insulation properties compared to a commercial grade of silica for natural rubber foams. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

In recent years, small drones have been used in agriculture, for spraying water and pesticides. Although spraying systems affect the efficiency of agricultural drones considerably, research on the spraying system of drones is insufficient. In this paper, a new nozzle with a feedback channel is proposed for agricultural drones. The proposed nozzle was manufactured through 3D printing, and its performance was compared with that of the nozzle used in commercial agricultural drones. Images taken with a high-speed camera were digitally processed, to track the area and location of spray particles, and the spraying characteristics were evaluated based on the size and uniformity of the droplets obtained from the images. The proposed nozzle provided a better performance, as it could spray smaller droplets more uniformly. Commercial nozzle droplets have an average diameter of 1.76 mm, and the proposed nozzle has been reduced to a maximum of 215 μm. In addition, the full width at half maximum (FWHM) of the commercial nozzle is 0.233, but the proposed nozzle is up to 1.519; the proposed nozzle provided better performance, as it could spray smaller droplets more uniformly. Under the condition of 30 kg, the best performance in the proposed nozzle, the minimum value of the average droplet diameter of the nozzle without feedback channel is 595 μm and the maximum value of FWHM is 1.329. Therefore, a comparison of the performance of the proposed nozzle with that of a nozzle with no feedback channel indicates that the feedback channel effectively reduces the droplet diameter and improves the spraying uniformity. It is expected that the proposed nozzle can be useful for designing the spraying systems of agricultural drones. [ABSTRACT FROM AUTHOR]

This paper reports the results of an experimental study when a closed-loop pulsating heat pipe (CLPHP) was subjected to active and passive cooling for its thermal performance and flow regimes. The active cooling was done using forced convection while the passive cooling was done by free convection. The results take into account the effect of convection sources on the start-up pulsations, dry-out conditions, critical heat flux, thermal performances, flow regimes, and bubble behaviors of CLPHP using a uniform heating pattern. The experiments are performed under normal gravity conditions, with methanol employed as a working fluid. A high-speed camera is used to record the internal flows for various values of heat input (Q in). Experimental results indicate that the free convective CLPHP exhibits delayed start-up pulsation and early evaporator dry-out, while the forced convective CLPHP has an early start-up pulsation and delayed dry-out condition. Slug-plug flow and oscillatory annular flow are dominant for the free convective CLPHP, while slug-plug flow, elongated plug flow along with higher amplitude, and oscillatory annular flow are dominant for the forced convective CLPHP. Liquid thin films are dominant for both free and forced convection at high Q in. The bubbles are arranged in irregular patterns for free convection, while active oscillations with regular bubble patterns are observed for the forced convective CLPHP. The condenser temperature affects bubble displacement, thereby leading to higher velocity for the free convective CLPHP. The time-averaged acceleration of the bubbles increases with an increase in Q in. The present analysis will be helpful to design and develop a CLPHP based on its thermo-hydrodynamics properties for engineering applications. [ABSTRACT FROM AUTHOR]

• A fill ratio of 50% resulted in an optimum thermal performance. • Thermally driven flow regimes for 50%, as 50% give an optimum thermal performance. • Oscillation of vapor plug and liquid slug are observed at Q in 10 W. • Annular and semi-annular flow is dominant at high Q in. • Liquid thin-film evaporation and condensations play an important role in the heat transfer coefficient. A two-turn closed-loop pulsating heat pipe (CLPHP) with a transparent glass tube (borosilicate glass) having an inner diameter of 2 mm is manufactured and designed. The manufactured CLPHP is tested under ambient environmental conditions, mounted in the bottom heat vertical mode position and charged with various filling ratios (FRs), using ethanol as a working fluid. The overall length of the device is 210 mm, the length of the evaporator section is 50 mm, and the remainder of the device consists of the condenser section, which is fully exposed to the ambient room temperature. A series of experiments are performed to investigate the thermal performance and observe the corresponding flow patterns. The thermal resistance (R th) results indicate that the optimal FR is 50%, and the R th significantly decreases with an increase in the heat input power (Q in) for an FR of 50% ethanol. The initial flow motions of the liquid slugs (LSs) and vapor plugs (VPs) are observed at a Q in of 10 W for all FRs. Notably, oscillations of small VPs and LSs appear, along with the contributions of dispersed bubbles and large VPs at lower heat loads, while the oscillations of annular VPs, semi-annular VPs, and bulk circulations are larger at higher Q in values. Liquid thin films are observed in the evaporator and condenser at high Q in values. The present experimental approach facilitates the design of a glass-tube CLPHP that operates under ambient conditions. The ambient temperature provides the necessary cooling source for recondensing the fluid to operate the device successfully. [ABSTRACT FROM AUTHOR]