Macromolecular Materials and Engineering最新文献

Sustainable hybrid composites, made of two different natural plant fiber types, are increasingly being attracted by composite researchers, for their cost effectiveness and ability to control mechanical performances through varying weight ratios of different fibers. In contrast, their lower mechanical properties are reported in the literature, because of strength variations of different fiber types and an improper fiber-matrix stress distribution. Therefore, it is aimed to develop sustainable hybrid composites from two dry fiber preforms—woven fabric and short fiber preform—originated from same fiber type (jute). A highly packed short fiber preform is used as the core layer, while woven fabrics (plain/twill–rib/twill–diamond) are used in the skin layers for producing sandwiched hybrid jute composites. Mechanical tests and scanning electron microscopy images show that hybridized plain fabric/short fiber preform composites have better mechanical properties (≈58 MPa tensile strength/≈117 MPa flexural strength/≈112.12 kJm⁻² impact strength with an ≈487.4% improvement) compared to other fabric structures hybrid/nonhybrid composites. This enhancement is related to the interlocking of short fibers with long plain fabric leading to a strong fiber-matrix interfacial bonding. Thus, this developed hybrid composites, can be applied in many semi-structural applications, wherein composites’ low cost and mechanical performances are primary concerns.

In recent years, the demand for filter media has increased dramatically, driven by the need to manufacture personal protective equipment and for various applications in the industrial and civil sectors. Nanofiber-based membranes are proposed as potential alternatives to commercial filtration devices. This study presents the design and implementation of an innovative pre-industrial electrospinning setup, combining a negatively charged spinneret and a positively charged counter-electrode, capable of producing polyvinylidene fluoride (PVDF) nanofibers with an average diameter of 410 nm and electrostatic surface potential values 3.7 times higher compared to a conventional electrospinning process, eliminating the need for further post-treatment. These properties are essential for improving mechanical and electrostatic filtration of small particles, including infectious droplets. The surface potential of the membranes is also long-lasting, as evidenced by tests one year after manufacture. As a case-study, these filters are used to manufacture surgical masks, reporting excellent performance in terms of bacterial filtration efficiency (BFE) up to 99.9%, and breathability (29.8±4.5 Pa cm⁻²) when compared to commercially available meltblown polypropylene (PP) face masks, and also complied with the stringent European standard (EN14683:2019) for type-II surgical masks. Furthermore, the pre-industrial setup allows for increased production capacity of up to 42 000 m² per year, suitable for large-scale production.

Isaac Newton once contemplated the fall of an apple, setting in motion a revolution in the understanding of gravity. In a similar spirit of curiosity and inquiry, here a journey is embarked upon to explore the intricate world of viscoelastic damping for polydimethylsiloxanes (PDMS). Inspired by the notion that even the simplest of phenomena can yield profound insights, a novel approach to study damping in silicone elastomers through a simple ball drop test is introduced. This novel solution allowes for precise measuring and analyzing the material's damping characteristics under various conditions. By carefully controlling the release and monitoring, the response of the falling ball by simple video tracking, valuable insights into the key viscoelastic properties of silicone blends are extracted, including rebound resilience, Young's modulus, and complex modulus. Through the analysis of trajectory data generated during the sphere's interaction with the silicone damper, dynamic and static material parameters are determined. Remarkably, these outcomes closely align with results obtained from cost-intensive and high-maintenance industrial measurement setups such as dynamic thermomechanical analysis (DTMA) or tensile testing. This approach not only simplifies the complexity of the system but also offers a cost-effective and efficient means of gaining essential knowledge in material science.

Petroleum-derived plastics are harmful to ecosystems because they are not decomposed in the natural environment. Therefore, the replacement of petroleum-derived plastics with biodegradable plastics has attracted considerable attention. UV-barrier films in the agricultural and packaging fields are mainly composed of petroleum-derived plastics, which have a negative impact on the ecosystem when they leak into the environment. Thermoplastic starch (TPS) is an inexpensive and sustainable biodegradable plastic that has recently attracted considerable attention. In this study, the addition of UV barrier properties and remolding ability to TPS for replacing petroleum-derived UV barrier films are investigated. Also, a biodegradable polyester coating is studied to improve the water resistance of the prepared UV-barrier TPS (U-TPS). To prepare U-TPS, a conjugated enamine structure is formed by reacting starch acetoacetate with diamine monomers during melt kneading. U-TPS exhibits high UV barrier properties across the UV regions (200–400 nm) owing to the presence of acetoacetyl groups and enamines. These results indicate the possibility of increasing the utilization of TPS in agriculture and as a packaging material.

Front Cover: The cover image of article 2400038 by Mostafa Baghani and co-workers shows the free shape recovery process of 3D printed PETG-ABS blend in terms of time at a recovery temperature of about 100 °C. This blend is prepared by melt mixing in the internal mixer at a temperature of 200 °C and 60 rpm for 6 minutes, and the final part is 3D printed by granule-based material extrusion method.

This study presents the development and 4D printing of magnetic shape memory polymers (MSMPs) utilizing a composite of polylactic acid (PLA), polymethyl methacrylate (PMMA), and Fe₃O₄ nanoparticles. The dynamic mechanical analysis reveals that the integration of Fe₃O₄ maintains the broad thermal transition without significantly affecting α-relaxation time, indicating high compatibility and homogeneous distribution of the nanoparticles within the polymer matrix. Field emission scanning electron microscopy further confirms the high compatibility of PLA and PMMA phases as well as uniform dispersion of Fe₃O₄ nanoparticles, essential for the effective transfer of heat during the shape memory process. Significantly, the incorporation of magnetic nanoparticles enables remote actuation capabilities, presenting a substantial advancement for biomedical applications. 4D-printed MSMP nanocomposites exhibit exceptional mechanical properties and rapid, efficient shape memory responses under both inductive and direct heating stimuli, achieving 100% shape fixity and 100% recovery within ≈85 s. They are proposed as promising candidates for biomedical implants, specifically for minimally invasive implantation of bone scaffolds, due to their rapid remote actuation, biocompatibility, and mechanical robustness. This research not only demonstrates the 4D printability of high-performance MSMPs but also introduces new possibilities for the application of MSMPs in regenerative medicine.

The spherulitic morphology of isotactic polypropylene can be transformed into the oriented fibrillar morphology through hot stretching processes with varying temperature (T_s) or altering strain (ε_t). The effects of T_s and ε_t on the structural characteristics of fibrillar crystals are comprehensively investigated with respect to crystal orientation, long periodic spacing, lamellar thickness (L_c), crystallinity (X_c), melting point, and chain relaxation behavior. Small-angle X-ray scattering patterns illustrate that the fibrillar crystals consist of alternated stacks of crystalline lamellae and amorphous layers. High T_s leads to a low orientation degree of lamellae, whereas large ε_t facilitates a high orientation level. The X_c and mean L_c are improved continuously with the increasing of T_s or ε_t, indicating a stretching-enhanced crystallization behavior driven by the two factors. The endothermic profiles reveal that new chain-folded lamellae with relatively thinner thickness form during the hot stretching process. The formation of thinner lamellae is dominated by the melting–recrystallization mechanism. This work would provide guidance for optimizing process conditions to manipulate the microstructure of hot-stretched semicrystalline polymers.

Sustainable functionalization of bacterial cellulose for cost-effective bionanocomposites with desired properties has received growing attention in recent years. This article presents the results of work aimed at obtaining bionanocomposite materials based on bacterial cellulose, a natural and eco-friendly material. Bacterial cellulose obtained from the Kombucha symbiotic culture of bacteria and yeast (SCOBY) fermentation process is functionalized by embedding with diatom frustules, silver nanoparticles (AgNPs), and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The effects of functionalization on mechanical, optical, plasmonic, electrical, chemiluminescent, and antimicrobial properties are evaluated. Morphological characteristics of the nanocomposites are studied using electron microscopy. Addition of diatom frustules introduced into the SCOBY culture media results in bionanocomposite materials with enhanced tensile strength and increased ultraviolet (UV) blockage properties. In situ functionalization of bacterial cellulose with AgNPs tunes plasmonic and chemiluminescent properties, revealing the biosensing potential of the material. Modified bacterial cellulose shows antimicrobial activity in experiments with gram-positive and gram-negative bacteria. Dual functionalization of bacterial cellulose with PEDOT:PSS and AgNPs results in improved electrical conductivity of the bionanocomposite. Overall, bottom-up physical functionalization approaches and the resulting bionanocomposite materials will open up new opportunities for the low-cost production of green materials and contribute to the development of a sustainable economy.