Macromolecular Materials and Engineering最新文献

The rising widespread oil-impacted wastewater warrants an urgent call for innovative approaches to the handling of oily wastewater. A variety of techniques has been investigated to treat oil-impacted water, and they are found to be inefficient. Electrospun nanofibers emerge as the viable technique to treat oily wastewater precisely owing to their high specific surface areas and interconnected nanoscale pore structures. In this review, a brief background on the study is provided followed by the environmental pollution by the oily wastewater. Subsequent to that, the polyvinylidene fluoride (PVDF) modification methods are also presented followed by the physicochemical properties of both the electrospun PVDF blends and the PVDF-based composites. Furthermore, the performances of the PVDF-based composites in oil/water separation are described. It is concluded with the future prospects for using PVDF-based composites for oil/water separation.

This study investigates the mechanical properties of nonwoven hybrid composites made from recycled cotton/polyethylene terephthalate (PET) with various fiber weight percentages (100/0, 0/100, 75/25, 60/40, 50/70, 60/40, and 25/75). The multilayered nonwoven carded webs are manufactured by the carding machine, while the manual lay-up technique is used to fabricate nonwoven-reinforced composites. Their tensile, flexural, and impact properties and microstructure are then examined. It is found that the tensile modulus and strength increase with the increase in cotton, while the impact strength improves with the increase in PET. The composite of 75% cotton/25% PET offers 92.13% and 67.87% higher tensile modulus and strength than the composite of 25% cotton/75% PET; however, the composite of 25% cotton/75% PET shows 83.09% and 36.22% higher flexural modulus and strength, and 187% more impact strength, respectively, than the composite of 75% cotton/25% PET. The outcome of this study indicates that nonwoven composites with higher contents of recycled cotton can potentially be applied in building and construction sectors where substantial tensile strength is necessary, while composites with comparatively higher contents of recycled PET may be used for various potential applications (e.g., helmets, surfboards, and automotive interiors) where significant flexural and impact strengths are required.

Polylactic acid (PLA) composites having 1 wt% of MoS₂ particles are prepared by solvent (SM) and melt mixing (MM) methods and their main thermal and mechanical properties are characterized. Coated films from SM samples and 3D-printed filaments from MM samples are tested as active layers in reversible bilayer actuators using a paper sheet as a passive layer. The thermal properties depend on the method used to prepare the composites with MM samples presenting a cold crystallization and a glass transition during the first and second heating and SM samples displaying a standard melt process during the first heating and a small cold crystallization and a glass transition during second heating. Regarding the stiffness, MoS₂ increases this property confirming its reinforcement effect. Both kinds of bilayers show reversible actuation under heating either by putting the actuator on a hot plate or by remotely irradiating the sample with near-infrared light (NIR). Under NIR, the 3D printed composites present a much higher actuation. The higher remote actuation in composited bilayers is explained by the NIR light absorption of the MoS₂ photoactive particles. This actuator can be used for the design of a smart façade or blind that closes under NIR stimulus.

To facilitate the ongoing transition toward a circular economy, renewable 3D print materials that are both sustainable and competitive must be accessible. However, the growing demand for bio-based thermosetting resins, which are used as ink for vat photopolymerization, gives rise to environmental concerns in terms of plastic waste management. Therefore, photocurable materials that are renewable and recyclable at the same time are needed. In this work, a mechanically robust and reprocessable 3D printed photopolymer is developed from renewable feedstock. Reaction of malic acid with glycidyl methacrylate introduces both methacrylate moieties that can undergo photopolymerization in the 3D printer, and β-hydroxyester linkages that can act as dynamic crosslinks via bond exchange reactions. By combining modified malic acid with reactive diluents, a photoinitiator, and phosphate catalyst, three distinct resins are formulated, resulting in bio-based contents ranging from 43% to 49%. The formulations demonstrate good layer fusion and accurate print quality, while the 3D printed specimens are robust and thermally stable. Notably, the printed object with shortest relaxation time displayed Arrhenius flow behavior with an activation energy of 36.0 kJ mol⁻¹, and its mechanical performance is maintained after being recycled three times. This contributes to the end-of-life perspective of photocurable resins in additive manufacturing.

Biodegradable poly(butylene succinate-co-adipate)/Poly(3-hydroxybutyrate-co-3-hydoxyvalerate) (PBSA/PHBV) filled with lignocellulosic sidestream/fibers from cowpea, a neglected and underutilized African crop are produced by injection molding and extrusion film casting. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) suggests that the fibers have more affinity and interfacial interaction with PBSA than PHBV. This is shown by a decrease in dampening of PBSA and an increase in dampening of PHBV with fiber addition. In addition, fiber addition results in more homogeneous crystal morphology of PBSA, while resulting in more heterogeneous crystal morphology of PHBV. The tensile strength of injection molded bio-composites increases with fiber addition due to good interfacial adhesion between the matrix and fibers revealed by scanning electron microscope. In contrast, the tensile strength of bio-composite films decreases with fiber addition due to the high-volume fraction of pores in bio-composite films that act as stress raisers. The stiffness of both injection molded, and bio-composite films increase with fiber addition, as revealed by an increase in Young's modulus and storage modulus, while the tensile strain decreases. In conclusion, low-value cowpea sidestream can be used as a filler to produce injection molded bio-composites and bio-composite films for potential application as rigid and flexible packaging.

Magnetochromic materials change color upon variation in an external magnetic field. A magnetochromic elastomer resulting from the dispersion of magnetic nanoparticles (MNPs) in a liquid and subsequent emulsification in a crosslinkable polydimethylsiloxane (PDMS) is presented. The MNPs form rod-like structures under an external magnetic field, aligning with the field and allowing light to pass through the elastomer. The elastomer thus changes from dark grey to transparent/light grey. Polyethylene glycol 200 (PEG200) is selected as carrier liquid due to the faster movement of MNPs herein than in glycerol, leading to more rapid color changes in the films. The influence of magnetic particle types (commercial, superparamagnetic, and surfactant-coated) on the magnetochromic effects is investigated. All films exhibit optical density changes upon exposure to a magnetic field. Moreover, the films retain their color-changing ability after cycles of 40 times exposure to a magnetic field. Compared to the synthesized superparamagnetic particles, the films with commercial particles display superior optical density change abilities, suggesting commercial MNPs are more suitable for magnetochromic films. The obtained films have promising applications as magnetical field sensors due to their simple storage requirements, rapid response, and excellent repeatability.

Electrospun sponges with electrical conductivity are promising materials for electrodes with applications in pressure sensors, flexible wearable sensors, and supercapacitors. However, electrospun sponges display poor electric conductivity, which can be increased by the addition of silver nanowire (AgNW). The resulting electric conductivity may depend strongly on the distribution of the AgNW in and on the sponges. A straightforward assembly method for an elastic conductive sponge, composed of 3D structures and metal nanowires, using a synergistic strategy which involves modified impregnation and deposition processes assisted by polyethyleneimine (PEI) impregnation, is presented. The resulting changes in the material properties are also explored, and it is under specific conditions, that percolation, leading to significantly enhanced electrical conductivity in the sponges, is achieved.

Over the past years, poly(lactic acid) or polylactide (PLA) is commonly researched as a possible replacement for traditional fossil-based polymers because of its compostability, biocompatibility, and high mechanical properties. PLA has a variety of applications in packaging, biomedical, and structural. However, PLA has limitations, such as high brittleness, low thermal stability, and a slow crystallization rate, which limits the wide range of applications. To overcome these limitations, the literature reports that blending PLA with other polymers, such as poly(ε-caprolactone) (PCL), is an economically viable approach. Although blending PLA with PCL is considered a feasible approach, the blend system still suffers from immiscibility, depending on the blend composition. This review aims to highlight recent developments from 2014 to date on the processing of PLA/PCL blends, including their composites, with a primary focus on morphological characteristics and mechanical and thermal properties, including their potential applications in various sectors.

To elucidate the specific mechanical impact of carbon black (CB) filler–rubber interactions on reinforcement, CB particles are subjected to graphitization at 1300 °C and oxidation through concentrated nitric acid treatment to modulate their surface activity. Alongside untreated CB particles, the influence of surface activity and the oxygen distribution are investigated to assess their role in shaping CB aggregate structures using X-ray absorption spectrum (XAS) and X-ray computed tomography (CT) with spatial resolution of 30 nm. Meanwhile, virgin and modified CBs are blended in natural rubber with varying amounts (10, 30, 50 phr) and the aggregates distributions in rubber are investigated by nano-CT. Combined with the mechanical properties of rubber composites and parameters of filler networks, the mechanical contributions arising from filler–rubber interactions are quantified. The findings underscore the robust interactions between oxidized CB and rubber matrix, exhibiting a mechanical property enhancement ratio of ≈59.2% at low strains in comparison to normal CB filler. The results indicate the synergies encompass of filler network, rubber chains, and filler–rubber interactions all play important roles for reinforcement, which aligns with the broader understanding of filler–rubber interactions and CB reinforcement mechanisms.

Biodegradable polymers play a crucial role in the development of materials for biomedical applications. This study investigates the enzymatic biodegradation, bioactivity, and cytotoxicity of poly(butylene succinate-dilinoleic succinate) (PBS-DLS) copolymers modified with poly(ethylene glycol) (PEG). Two copolymer variations with different segmental compositions (70 wt.% and 60 wt.% of hard segments) are synthesized. After modifying the copolymers with PEG, the presence of a lipase catalyst accelerated degradation after 20 days, evidenced by reduced residual content. Gel permeation chromatography analysis showed up to 40% decrease in molecular weight, while gravimetric analysis indicated a mass loss of up to 10%. Morphological examination revealed that the enzymatic breakdown, facilitated by hydrolase activity (boosted by the presence of PEG), resulted in surface erosion, holes, and changes in spherulitic morphology. Bioactivity studies demonstrated the formation of biomimetic calcium/phosphate (Ca/P) crystals. Copolymers with higher crystallinity (70 wt.% hard segments) favored tricalcium phosphate-like crystal formation, while those with lower crystallinity (60 wt.% hard segments) are more susceptible to hydroxyapatite precipitation. In vitro cytotoxicity tests exhibited excellent cell viability and attachment for all copolymers. The ability to control degradation through PEG modification, along with their bioactivity and cell compatibility, positions them as promising candidates for diverse biomedical applications.