Advanced Industrial and Engineering Polymer Research最新文献

The sustainable processing of recycled products requires veritable testing during quality control for commercial application. In this research work, mechanical (ASTM D3039), compression (ASTM D5467) and impact (ASTM A370) are utilized to observe the usability, diversity, and suitability of the developed polypropylene-postconsumer cotton fibers (PP-PCCF) composites for industrial applications. The cotton waste was ground using a grinding machine. The ground fibers were introduced to manufacture composites from 0 to 40% fiber loading variations. The fine cotton fibers and synthesized composites were characterized by scanning electron microscope before and after mechanical testing. The fiber length, diameter and area were in the range of 2.5 mm–5.5 mm, 12.5 μm–22 μm and 200.15 μm²–250.50 μm², respectively. The engineering and design values were tensile strength (31.16 MPa–22.77 MPa), breaking strength (26.69 MPa–22.77 MPa), modulus of elasticity (2223.79 MPa–2770.77 MPa), and extension (17.48–3.21). Similarly, flexural strength, modulus, energy, and fracture force are also enhanced with an increase in fiber loading. The impact energies of pure polypropylene and PP-PCCF composites (with 10, 30, and 40% PCCF contents) were 50 kJ/m², 48 kJ/m², 43 kJ/m², and 58 kJ/m². The micrographs of PP-PCCF composites prove that the density of voids is enhanced with an increase in fiber contents. The PP-PCCF composites with 0%–30% fiber loadings showed minimum defects and were observed to be suitable for structural applications. On the other hand, the PP-PCCF composites with 30%–40% fiber loading are acceptable for environmental applications.

The development of innovative coatings with advanced multifunctional properties can lead the way to a more sustainable future. During the last decade, the global use of solar energy has been accelerating while there is a growing need for more energy-efficient buildings. Recent research efforts have focused on developing smart coatings that can rectify and amplify the role of protective glass surfaces which are mainly used in photovoltaic panels and in building windows. These surfaces suffer from the deposition of dirt, which compromises the power output of photovoltaic panels and stains the building facades. The application of novel self-cleaning, antifouling coatings on these surfaces can offer a proactive solution. Many research groups have suggested the use of antireflective coatings that can improve the transparency of glass, as well. Furthermore, the concept of radiative cooling coatings has been gaining attention as a method to lower the operating temperature of solar panels and to improve the temperature management of indoor spaces. In recent years, many hybrid polymer-based coatings have been proposed for these purposes, and the goal of this review is to summarize them and to assess their performance. The first part of this article is concerned with the selection of materials and the manufacturing processes. The second part is focused on the properties of these coatings, namely their optical transparency, their self-cleaning ability, their antireflective and radiative cooling performance, as well as their mechanical and chemical durability. The connection between the selection of materials, the coating formulation and the desired properties will be highlighted. Finally, future directions in this research field will be proposed.

The treatment of wastewater requires the use of eco-friendly and cost-efficient adsorbents. A hybrid adsorbent film based on biodegradable polymers (poly(vinyl alcohol) (PVA) and chitosan (Ch) was developed to remove Acid Orange 7 (AO7), an azo dye from the textile industry present in industrial wastewaters. The polymeric absorbent material was submitted to a curing process with different time-temperature combinations which improved its physical stability in aqueous media. This result was supported by modulated differential scanning calorimetry (MDSC) and thermogravimetric analysis (TGA). ATR-FTIR also confirmed the electrostatic interactions by hydrogen bonds between PVA and Ch, as well as among the polymers and the dye. The best curing condition to reach a high removal without weight loss was the combination of 160°C-1h.

Dye adsorption depended mainly on pH, adsorbent dose, contact time, temperature, and coexisting anions. The maximum removal efficiency (>91%) was achieved at pH = 2.5. The adsorption kinetics followed the Lagergren pseudo first-order rate equation and the adsorption isotherm was best described by the Redlich-Peterson model. As far as the authors know, the maximum adsorption capacity (Q_m) of the adsorbent film obtained in the present work is the highest value reported in literature (Q_m = 678 mg/g at 298 K and pH = 2.5). Physisorption would be the dominant mechanism at pH 4.0 while at pH 2.5 the process was conducted by chemisorption. Regeneration studies showed that composites could be used for five consecutive cycles without losing their adsorption capacity.

Thus, the use of the developed eco-compatible biodegradable materials would allow easy regeneration without losing removal selectivity, a key feature in the development of environmentally friendly sorbent materials.

Waste rubbers are environmental pollutants that could not be easily recycled. Devulcanization (i.e. as a reverse process of rubber vulcanization) is considered as a promising method for recycling of rubber wastes. In this study, a simple and effective chemo-mechanical devulcanization for waste nitrile rubber (WNBR) was introduced and compared to the mechanical, thermo-chemo-mechanical and radio-chemo-mechanical methods. The mechanical stress was applied to crumbed waste rubbers using a two roll mill in presence of different chemical agents (i.e. N-cyclohexyl-2- benzothiazole sulfonamide (CBS), tetra methyl thiuram disulfide (TMTD), diphenyl disulfide (DPDS), VitaX and a mixture of VitaX and DPDS). The sheet formation time on two roll mill, crosslink density (CLD) and sol/gel contents of waste rubber powders were measured before and after devulcanization. The devulcanized rubbers were characterized using TGA, DSC and GPC analysis. Finally, the properties of devulcanized nitrile rubber (i.e. the tensile, hardness and curing properties) were evaluated and compared to pristine NBR. It was found that VitaX is the most efficient chemical agent among the chemical agents. It caused 43, 87 and 98% decrement in the sheet formation time of chemo-mechanically, thermo-chemo-mechanically and radio-chemo-mechanically devulcanized samples compared to the mechanically devulcanized NBR, respectively. The samples also showed 24, 33 and 100% increment in the sol content, devulcanization percent and tensile strength compared to the mechanically devulcanized NBR, respectively.

In this research, the manufacturing of completely biodegradable composites with a unique single-step sheet consolidation method was discussed. Layers of unidirectional, coarse twill, and fine twill flax; and poly lactic acid (PLA) were used as the material system to manufacture cylindrical and spherical composite half-shells. The three processing parameters were vacuum pressure, temperature and time. Thickness, mass fraction, tensile strength, shear strength, shape conformance and biodegradability of the manufactured composites were experimentally determined. The composite specimens’ cross-sections were also observed under an optical microscope, to assess, the consolidation quality of the manufactured composites, that was represented by the composite thickness, and primarily governed by the polymer viscosity, and the transverse and in-plane fibre reinforcement permeability. Biodegradable Flax-PLA composites were successfully consolidated, within 5% tolerance of the targeted mass fractions and thickness values, conforming within 8% tolerance to the shape of the mould. The highest achieved shear strength, flexural modulus, tensile strength and elastic modulus, were 22 MPa, 19.9 GPa, 179 MPa and 19.5 GPa, respectively. This research will be valuable to develop, flat and curved biodegradable composites, for one-off or small scale productions, at a relatively low capital cost.

Shape memory polymers (SMPs) are a class of smart materials that can be programmed to recover from temporary shape to permanent shape by applying external stimuli (temperature, magnetic field, light, electric field, and moisture, etc.). This unique property of SMPs makes them an appealing candidate in application for soft robotics, such as smart actuators, artificial muscles, and biomedical devices. In this contribution, we have developed multi-stimuli-responsive SMPs from bio-based benzoxazine resin and iron oxide nanoparticles (Fe₃O₄ NPs) that could be actuated by magnetic field and light. The nanocomposites were characterized by infrared spectroscopy, in which molecular interaction between benzoxazine/epoxy copolymers and Fe₃O₄ NPs was observed. Effects of nanoparticle content (0–5 wt%) on magnetic, mechanical, thermal, and thermo-mechanical properties of nanocomposites were investigated. Shape memory performance of nanocomposites was significantly improved with incorporation of Fe₃O₄ NPs. Shape fixity increased from 85% of neat copolymers to 93% of copolymers filled with 3 wt% Fe₃O₄ NPs, while shape recovery increased from 94% to 98%. Moreover, shape fixity could be done without external force contact by 808 nm-light actuation and magnetic attraction, due to photothermal and magnetic properties of nanocomposites. Shape recovery was tested under actuation by magnetic field. The highest shape recovery ratio was 99% within 26 s for copolymers filled with 5 wt% Fe₃O₄ NPs. Lastly, preliminary application of nanocomposites was demonstrated as they could push a 1 g-object within 10 s of actuation by magnetic field. In overall, these nanocomposites with multi-stimuli-responsive shape memory property had a good potential to be applied for soft robotics.

The interesting thermomechanical properties of rubber materials have favored their widespread application in many fields, with a consequent increase in the amount of worn synthetic and natural rubber discarded every year. However, the complex three-dimensional molecular structure of rubber complicates the recycling and degradation process, and the current rubber waste management measures (i.e., landfilling, incineration, rubber grinding) are found to be unsustainable or substantially inadequate. On the other hand, devulcanization technologies, thanks to the selective cleavage of crosslinks, represent a sustainable and feasible approach to obtain a material that can be reintroduced into the rubber value chain or reused in novel eco-sustainable thermoplastic or elastomeric blends. Hence, this review provides an overview of the current rubber waste management techniques and devulcanization technologies, highlighting the underlying devulcanization mechanisms, describing the pros and cons of each method, and presenting some literature examples. Since most of the research on devulcanization has been made on waste tires, this review mainly focuses on the most widely used rubber classes for this application, i.e., natural rubber (NR) and styrene-butadiene rubber (SBR), and the most common vulcanization technique, i.e., sulfur vulcanization. Considering the importance of the application of a circular economy approach, this work also reviews the applications of rubber devulcanizates, focusing on how devulcanized rubber can be compounded with different polymeric matrices to develop eco-sustainable polymer blends with suitable physical properties.

In the last decade, growing efforts were made to replace crosslinked XLPE insulations with thermoplastic ones in high-voltage DC cables. The main reason for these development projects is the injection and trapping of charge carriers under DC conditions, leading to a field distribution within the insulation layer different from HVAC cables. Thermoplastic cable insulation is favorable in many respects, except for its thermal stability. So far, HDPE/LDPE and binary or ternary PP-based blends have been tried. The former offers a limited advantage in heat resistance, while the latter is too hard at high PP contents and loses thermomechanical properties at high elastomer contents. In this paper, the compatibility of binary polyolefin blends is first briefly reviewed; then, the cable-specific properties are presented together with examples taken from the literature. Deep trap formation, low conductivity, and optimum breakdown properties are observed in HDPE/LDPE blends under specific crystallization conditions where a fine-grained structure is formed. It results in a proper concentration of the traps, but these are not accumulated at the spherulite boundaries. Trap density and energy are also modulated by the relaxation processes. The future belongs to the PP-based blends, where several compatibilizing agents (copolymers, elastomers, in situ reactions) have been tried to find the balance between electrical, mechanical, and thermal properties. In these materials, again, fine, close to co-continuous structures should be achieved to reach the required properties, but the aromatic and polar comonomer content also contributes to the formation of deep traps in relatively uniform distribution. The PP phase must remain continuous to maintain the necessary thermomechanical properties above the Tg of the soft components.

In this paper, a green method of modifying high flame retardant and high mechanical properties MH was proposed, gallic acid (GA)-Fe³⁺ complex was employed to modify the surface of magnesium hydroxide (MH), aiming to achieve novel functionalized MH-based flame retardant for ethylene-vinyl acetate copolymer (EVA). The structural and morphological characterization of the newly designed flame retardant were studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscope and X-ray Diffraction. The flame retardancy of EVA, EVA/MH, EVA/MH@Fe-GA was investigated via Limiting oxygen index, UL-94 vertical combustion tests, and cone calorimeter test. The LOI and UL94 results showed that EVA/MH@Fe-GA (01) achieved an LOI of 38.5% and UL-94 passed the V-0 grade. The CCT results showed that compared with neat EVA, the peak heat release rate (pHRR) of EVA/MH@Fe-GA decreased by 90.83%, and TSP decreased by 86%, as compared to neat EVA. The mechanical properties of EVA/MH, EVA/MH@Fe-GA were investigated via tensile and impact tests. Compared with EVA/MH, MH@GA-Fe shows good tensile property and impact resistance, the impact strength of EVA/MH@Fe-GA increased by more than 28%, and the elongation at break increased by 145%.

Over the last few years, transition metal based LDHs are drawing more and more attention. This is especially true for tri-metal LDHs due to their wide range of applications. This research work highlights four types of tri-metal layered double hydroxide (t-LDH) that were synthesized and used in polypropylene (PP) nanocomposites. The effect and interaction of cobalt (Co), nickel (Ni), copper (Cu) and zinc (Zn) containing MgAl LDHs in PP nanocomposite were prepared and tested. These t-LDHs (MgCoAl, MgNiAl, MgCuAl, MgZnAl) were synthesized using the urea hydrolysis method. The t-LDH/PP nanocomposites were prepared using melt mixing in a small-scale compounder. Structural and morphological analysis of t-LDH and their PP nanocomposites were done using XRD spectroscopy and SEM. The thermal behaviour of the nanocomposites was studied using DSC and TGA. Rheological analysis was done using a rheometer, flammability was analysed using limiting oxygen index (LOI) and UL94 testing. Mechanical properties were compared by a UTM and Charpy impact test. The thermal stability, flame retardancy and mechanical strength are increased with the addition of these t-LDHs. MgCuAl/PP nanocomposites showed superior thermal and mechanical properties as compared to MgAl/PP, MgCoAl/PP, MgNiAl/PP, MgZnAl/PP nanocomposites. In comparison to pure PP with the addition of only 5 wt.% of MgCuAl-LDH the degradation temperature was 43 °C higher.