Increase In Tensile Strength Research Articles

Enhancing fruit preservation with sodium alginate films incorporating propolis extract and graphene oxide.

In this work, sodium alginate (SA) composite films containing propolis extract (PRO) and graphene oxide (GO) were developed. Subsequently, the effects of PRO and GO on different properties of SA composite films were studied, and the films were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The PRO release properties and fruit preservation performance of the developed composite films were also investigated. The results showed that the incorporation of PRO resulted in a 51.16% increase in tensile strength. The simultaneous incorporation of PRO and GO reduced water vapor permeability (WVP) by 22.56% compared to the SA film. The temperatures at which the SA/GO/PRO film lost 5% of its weight were 8.0°C higher than those of the SA film. The incorporation of GO into the SA/PRO composite film also modulates the release of PRO. Furthermore, the incorporation of PRO and GO improved the tensile strength of the SA film, as reflected in the microstructure of the films. The reduced WVP of the SA composite film allowed the packaged blueberries to exhibit less weight loss and shrinkage, thereby prolonging their shelf life.

Evaluation of mechanical and wear properties of LM24/fly ash/titanium diboride hybrid metal matrix composites using stir casting

This study focuses on the development of novel hybrid composites based on the LM24 alloy, utilizing liquid metallurgy stir casting to incorporate dual reinforcements (titanium diboride (TiB2) and fly ash (FA)). The weight percentage of TiB2 was maintained at levels of 2.5%, 5%, and 7.5%, keeping the FA at 2.5% during the course of fabrication. The introduction of 7.5 wt% TiB2 and 2.5 wt% FA displayed a very notable 43.18% increase in hardness and a 21.53% increase in tensile strength of the hybrid composite compared to the LM24 alloy. Furthermore, hybrid composites with a total reinforcement of 10 wt% exhibited superior wear resistance across the entire range of applied loads. Tensile fractography revealed ductile fracture mode for the LM24 alloy, while hybrid composites displayed a mixed-mode fracture. High-load-induced abrasive wear with little plastic deformation was seen on worn surfaces of hybrid composites, whereas adhesive wear was the dominant type of wear in the LM24 alloy. The results show that hybrid composites have better mechanical and tribological properties because the reinforcement particles are well distributed and the load is transmitted optimally. However, it is noted that increased reinforcement levels lead to a reduction in ductility, resulting in decreased impact resistance for the hybrid composites.

Heat-Responsive PLA/PU/MXene Shape Memory Polymer Blend Nanocomposite: Mechanical, Thermal, and Shape Memory Properties

This study investigates the fabrication and characterization of heat-responsive PLA/PU/MXene shape memory polymer blend nanocomposites with varying PLA content (10, 20, 30, and 50%) and a fixed MXene content of 0.5 wt.%. The results indicate significant improvements in mechanical properties, with the 50% PLA/PU/MXene blend showing a 300% increase in ultimate tensile strength and a 90% decrease in % elongation compared to pure PU. Additionally, the 50% blend exhibited a 400% increase in flexural strength. Microstructural analysis revealed dispersed pores and sea–island morphology in pure PU and the 50% PLA/PU/MXene blend. Thermal analysis using DSC showed an increase in crystallinity from 33% (pure PU) to 45% for the 50% PLA/PU/MXene blend, indicating enhanced crystalline domains due to the semi-crystalline nature of PLA and MXene’s influence on molecular ordering. TGA demonstrated a significant improvement in thermal stability, with the onset temperature rising from 185 °C (pure PU) to 212 °C and the degradation temperature increasing from 370 °C to 425 °C for the 50% blend, attributed to the rigid structure of PLA and MXene’s stabilizing effect. Shape memory testing revealed that the 30% PLA/PU/MXene blend achieved the best shape fixity and recovery with optimal performance, whereas higher PLA content diminished shape memory behavior.

Two‐dimensional layered MoS2/lignin as additives for epoxy composites with improved mechanical and tribological properties

AbstractThe MoS2/lignin hybrid material was successfully synthesized and incorporated into an epoxy resin to fabricate composite coatings. The results demonstrate that MoS2 is uniformly attached to the surface of lignin sheets. Compared to adding lignin alone, the MoS2/lignin hybrid‐epoxy resin (EP) composite coatings exhibited enhanced friction‐reducing and wear‐resistant properties. Specifically, the 1 wt% MoS2/lignin hybrid displayed excellent dispersion and high interfacial compatibility within the resin matrix, leading to a 66.7% increase in Vickers hardness, a 27.5% increase in tensile strength, and a 73.9% improvement in char yield. Furthermore, the friction coefficient and wear rate were reduced by 63.2% and 75.8%, respectively. As a uniformly dispersed hybrid structure, the MoS2/lignin material can endure higher loads, autonomously repair defects, and form a stable and complete transfer film on the worn surface, demonstrating synergistic friction‐reducing and wear‐resistant effects within the epoxy resin matrix. Integrating MoS2 into a two‐dimensional material can provide a practical reference for designing polymer‐based hybrid materials with outstanding comprehensive properties.Highlights The MoS2/lignin hybrid material was successfully synthesized. MoS2 is uniformly attached to the surface of lignin sheets. The hybrid significantly enhances friction‐reducing and wear‐resistant properties. Vickers hardness increased by 66.7%, and tensile strength increased by 27.5%. The friction coefficient was reduced by 63.2%, and the wear rate was reduced by 75.8%.

Welding speed effects in underwater and conventional friction stir welding of dissimilar aluminum alloy 6061-T6 and 5083-H12 joints

This study investigates the influence of welding speed on the mechanical and microstructural properties of dissimilar aluminum alloy joints (AA6061-T6 and AA5083-H12) joined using Underwater Friction Stir Welding (UFSW) and Conventional Friction Stir Welding (CFSW). The experiments were conducted at a constant tool rotation speed of 1120 rpm and varying welding speeds (20 to 80 mm/min). Results showed that UFSW achieved peak temperatures 13% lower than CFSW. Moreover, the generated peak welding temperature was inversely proportional to welding speed in UFSW and CFSW. Optimal performance was observed at 63 mm/min, where UFSW produced an 89% reduction in intermetallic compound (IMC) thickness and a 21% finer grain size compared to CFSW. Additionally, UFSW joints exhibited a 10.20% increase in tensile strength and a 7% increase in hardness over CFSW. The enhanced cooling effect in UFSW contributed to these improvements, yielding more uniform material flow, refined microstructure, and reduced IMC formation. These findings suggest UFSW as a superior technique for achieving high-quality dissimilar aluminum alloy joints, with significant enhancements in mechanical properties and microstructural refinement.

Effect of friction stir processing on wire arc additively manufactured ER70S-6/SS308L bimetallic FGM

In this research, wire arc additive manufacturing (WAAM) is employed to fabricate a bimetallic steels component using ER70S-6 and SS308L. However, this process involves high power densities and significant heat inputs, which elevate the risk of unfavorable grain structures and defects. To mitigate this issue, friction stir processing (FSP) is applied, utilizing a unique tool featuring a flat shoulder without a pin. The resulting samples undergo testing for mechanical and metallurgical properties. The microstructure of ER70S-6 reveals ferrite with small amounts of pearlite at the grain boundaries. The upper portion of the deposited sample exhibits more pronounced grain refinement compared to the lower section, largely due to the rapid cooling rate and thermal cycling effects during layer deposition. This grain refinement is attributed to dynamic recrystallization, which enhances the hardness of the FSP-treated sample relative to its initial as-deposited state. Tensile tests indicate a significant increase in tensile strength, accompanied by a reduction in percentage elongation after FSP. The fatigue crack growth rate is higher along the longitudinal direction of bi-metallic joint as compare to transverse to the joint.

Enhancing performance of in-situ synthesized biocompatible shape memory polyurethane acrylate by cellulose nanocrystals.

This study presents the development of biocompatible and biodegradable nanocomposites utilizing renewable cellulose nanocrystals (CNCs) in polycaprolactone (PCL)-based polyurethane acrylates (PUA) through in situ polymerization. First, CNCs were derived from cotton linter via acid hydrolysis; then functionalized with 3-methacryloxypropyltrimethoxysilane to produce silane-modified CNCs (S-CNCs). CNCs offered uniform dispersion in PUA up to 2 wt% loading, resulting in significant property enhancements, including ~60 % increase in tensile strength and ~25 % increase in Young's modulus. Despite the chemical interaction of S-CNCs with PUA, they tended to agglomerate beyond 0.5 wt% loading due to the promotion of chemical interactions between S-CNC particles at higher concentrations. Despite this, comparable improvements (e.g. ~50 % in tensile strength and ~25 % in Young's modulus) were observed at just 0.5 wt% S-CNC loading. Both neat PUA and PUA nanocomposites demonstrated exceptional shape memory properties, with shape fixity exceeding 95 % and shape recovery approaching 100 %. However, S-CNCs also halved the shape recovery time compared to neat PUA, a critical advancement for time-sensitive applications. Meanwhile, the biocompatibility of PUA was largely preserved in the presence of the nanoparticles, particularly for S-CNC.

Extraction of lignin from Duabanga grandiflora and its valorization for nanocomposite development with enhanced mechanical and UV shielding properties

Abstract In this study, we report on extracting lignin (EL) from Duabanga grandiflora (Khukon), an untapped wood source, and its transformation into nano-lignin (NL) to create durable and thermally stable composites. Utilizing ultrasonication, we synthesized spherical lignin nanoparticles with an average size of 8 nm, as verified by High-Resolution Transmission Electron Microscopy (HRTEM). These nanoparticles were integrated into a polyvinyl alcohol (PVA) and guar gum (GG) matrix, resulting in PVA-GG-nano-lignin (PGNL) composites. Polyvinyl alcohol (PVA)-Guar gum (GG) nanocomposite films containing various contents of lignin nano-particles (1, 2 and 3 wt%) were formulated by a simple solvent cast method and cross-linked by adding borax. Addition of 1wt% lignin nanoparticles brought in the composite films with 29.8MPa tensile strength and 139.3% elongation at break. Compared to PVA-GG-lignin (PGL) composites, the PGNL composites exhibited a 59.4% increase in tensile strength and enhanced elongation at break and good thermal degradation properties. Notably, the PGNL composite films were transparent but could shield 99.9% of the UV-A (320-400 nm) and UV-B (280-320 nm) radiations, marking a significant advancement in UV protective materials. Our innovative use of Duabanga grandiflora-derived nano-lignin in a dual-polymer network not only underscores the potential of renewable resources in high-performance applications but also aligns with the principles of a circular bioeconomy by offering a sustainable solution for effective UV protection.

Mechanical Properties and Prediction Based on ANN Model of Basalt and Polypropylene Fiber Reinforced Concrete

Objectives: Utilization of steel fiber increases concrete strength and ductility however, the cost of steel fiber is high and ultimately leads to an increase in the cost of concrete. Basalt fiber is a new type of fiber with high strength and toughness and can effectively replace the place of steel fibers. In this paper, concrete reinforced with polypropylene fibers and basalt fibers was tested for its mechanical properties and compared with the same predicted through a simulated model created by the Artificial Neural Network. Methods: The percentage of polypropylene fiber was kept at 0.25%, and different amounts of basalt fiber were added as 0%, 0.25%, 0.5%, 0.75%, and 1%. Based on traditional testing methods compressive strength, tensile strength, and flexural strength of normal concrete, Fiber reinforced concrete and Hybrid fiber reinforced concrete have been found. To forecast the concrete qualities, the model was simulated after the datasets were trained using a neural network fitting tool. Findings: In comparison to concrete that had only 0.25% polypropylene fiber, a hybrid fiber-reinforced concrete mix including 0.5% basalt fiber and 0.25% polypropylene fiber demonstrated a 9.69% improvement in compressive strength. In comparison to the concrete made only of polypropylene, the mix containing 0.25% polypropylene fiber and 0.75% basalt fiber showed a 26.12% increase in flexural strength and a 39.25% increase in split tensile strength. The error percentage between predicted and experimental values is below 10%. Novelty: Utilization of basalt fiber in concrete is very rare and this proposed work focused on the hybridization of basalt fiber in the place of steel fibers, which is prone to corrosion and reduces the cost of material effectively. The concrete's flexural and tensile strengths were significantly increased by the addition of basalt fibers. The mechanical characteristics of hybrid fiber-reinforced concrete are well predicted by the simulated ANN model. Keywords: Basalt fiber, Polypropylene fiber, Artificial Neural network, Fiber reinforced concrete, Hybridization

Improvement adhesion durability of epoxy adhesive for steel/carbon fiber-reinforced polymer adhesive joint using imidazole-treated halloysite nanotube

Surface treatment is essential for enhancing adhesion durability and minimizing substrate damage in hybrid structural materials. This study focuses on developing a hybrid adhesive lap joint by incorporating halloysite nanotube (HNT) with imidazole-functionalized surfaces (IM-HNT) into epoxy adhesives to improve adhesion performance and thermal shock resistance. The surface treatment of HNT with imidazole (IM) introduced a curing catalyst effect, reducing activation energy by 50% and accelerating curing time by 90%, as confirmed by Kissinger’s plot and permittivity measurements. The optimized IM-HNT content improved thermal stability by controlling thermal expansion and enhanced mechanical properties, achieving a 15% increase in tensile strength and a 50% enhancement in fracture toughness. The adhesion performance of steel/carbon fiber-reinforced polymer (CFRP) hybrid joints was evaluated through single-lap shear tests, demonstrating a 25% improvement in shear strength. Adhesion durability was tested under cyclic thermal shock conditions, showing a 30% increase as IM-HNT content increased. Finite element analysis (FEA) revealed reduced residual stress at the adhesive interface, supporting the enhanced thermal and mechanical robustness. This study highlights the potential of surface-treated halloysite nanotubes in hybrid adhesive lap joints to significantly improve adhesion durability and thermal shock resistance, addressing critical requirements for hybrid structural materials.

Enhancing black mulberry storage with sodium caseinate and gum tragacanth edible films

A bright future lies ahead for the application of natural biocomposites in the food industry. In this research, edible biocomposite films were created using sodium caseinate (SC)-gum tragacanth (GT) and incorporating carum carvi seed essential oil (EO) as a nanoemulsion. Different ratios of oil were used as variables. The physical properties, structural morphology, mechanical characteristics, and thermal behavior of the films were evaluated. Furthermore, the preservative effects of these edible films were studied to prolong the shelf life of black mulberries over a period of 10 days at 4 °C. The findings indicated that the increase of EO content to the edible films resulted in a significant increase in thickness, tensile strength, opacity and water vapor permeability. Conversely, the elongation at break, water solubility and moisture content decreased with the rise in oil content up to 3.9%. Also the visual appearance and sensory evaluation of the fruits revealed that black mulberries covered with edible films containing 2.6 and 3.9% oil were more preferred compared to the other groups. The integration of caraway oil into the SC-GT biocomposite has been investigated for the first time, demonstrating that the resulting films are effective in prolonging the shelf life of black mulberries.

Synthesis of multi‐element flame retardant hydrazides and its modification to epoxy resin

AbstractWhen flame retardants are added to epoxy resins (EP) to enhance their flame retardancy, it often results in a negative impact on the mechanical properties of itself. In order to solve this problem, a new reactive flame retardant multi‐element hydrazides (BSD) is synthesized by using benzenesulfonohydrazide and diphenylphosphinic chloride as raw materials, it can play a flame retardant effect through the synergistic effect of P\N\S multi‐elements, and at the same time, a large number of secondary amine groups in the structure of BSD can produce strong hydrogen bonding interactions with the hydroxyl groups of the molecular chain of EP. The experimental results proved that the incorporation of only 3 wt% of BSD enabled EP to achieve a UL‐94 V‐0 rating. Furthermore, when the amount of BSD is increased to 5 wt%, the values for peak heat release rate (PHRR) and total heat release showed a reduction of 26% and 20.8%, ultimately maximizing the limiting oxygen index to 34.9%, showing exceptional efficiency. In the meantime, it showed a 37.3% increase in flexural strength and a 21.4% increase in tensile strength, and the transparency of the modified epoxy resin was still maintained at this time. In summary, introducing BSD into EP obtains a highly efficient reinforced flame retardant epoxy resin (FREP).Highlights A P/N/S‐containing hydrazide to improve the flame retardant of EP. When the P content is 0.25 wt%, the FREP reaches UL‐94 V‐0 grade. Tensile and flexural strength increased by up to 21.4% and 37.3%. With the addition of BSD, the FREP still show high transparency.

Zero Waste Concept in Production of PLA Biocomposites Reinforced with Fibers Derived from Wild Plant (Spartium junceum L.) and Energy Crop (Sida hermaphrodita (L.) Rusby).

This research follows the principles of circular economy through the zero waste concept and cascade approach performed in two steps. Our paper focuses on the first step and explores the characteristics of developed biocomposite materials made from a biodegradable poly(lactic acid) polymer (PLA) reinforced with natural fibers isolated from the second generation of biomass (agricultural biomass and weeds). Two plants, Spartium junceum L. (SJL) and Sida hermaphrodita (SH), were applied. To enhance their mechanical, thermal, and antimicrobial properties, their modification was performed with environmentally friendly additives-linseed oil (LO), organo-modified montmorillonite nanoclay (MMT), milled cork (MC), and zinc oxide (ZnO). The results revealed that SH fibers exhibited 38.92% higher tensile strength than SJL fibers. Composites reinforced with SH fibers modified only with LO displayed a 27.33% increase in tensile strength compared to neat PLA. The addition of LO improved the thermal stability of both biocomposites by approximately 5-7 °C. Furthermore, the inclusion of MMT filler significantly reduced the flammability, lowering the heat release rate to 30.25%, and enabling the categorization of developed biocomposite in a group of flame retardants. In the second step, all waste streams generated during the fibers extraction process are repurposed into the production of solid biofuels (pellets, briquettes) or biogas (bio)methane.

Preparation of high-performance red fluorescent epoxy resin films guided by rare earth europium

Epoxy resins offer broad applications but are limited by their mechanical strength. This study enhances the properties of an indole-based epoxy resin (EPI) through the incorporation of europium ions (Eu3+), leveraging their cation-π interactions. A red fluorescent indole-based epoxy resin (Eu@HEr) was synthesized, emitting at 616 nm under Ultraviolet (UV) light. Eu@HEr exhibited a 42% increase in tensile strength (86 MPa) and a 114% improvement in elongation at break (10.9%) compared to EPI. The thermal decomposition temperature of Eu@HEr rose by 64 °C, indicating superior thermal stability. These findings highlight the potential for high-performance epoxy resins with dual mechanical and luminescent properties.

Recyclable Millable PolyureThane based on Enaminone Bonds With Upcycled Mechanical Performance.

Thermoplastic polyurethane (TPU) exhibits re-processable properties, but the properties of TPU is deteriorated during the reprocessing for the oxidation and degradation of polymer chains. Meanwhile, although thermoset polyurethane exhibits excellent mechanical properties, it cannot be recycled for permanent crosslinking. Hence, it's still a challenge to obtain PU which exhibits the balance between the recyclability and mechanical properties. In this work, a new dynamic bond obtained from the reaction between enaminone and isocyanate is used to prepare re-processable millable polyurethane, and the morphology of network can be tuned via the dissociation of the cross-linked sites of PU. Interestingly, the cross-linked network can transform into a linear polymer by adding the amine which can be used when reacted with isocyanate to generate new re-crosslinked PU. This process can be carried out in a Haake mixer without any solvents. The mechanical properties of the re-crosslinked polyurethane can be tuned via the controlling of the amine and isocyanate addition, and the maximum tensile strength increase by 178.4% after processing for four times, realizing mechanical reinforcement after recycling. This kind of recycling achieves through one-step melting method in solvent-free conditions provides a feasible way to prepare recyclable PU with good mechanical performance and customizable properties.

Multiscale analysis of the mechanical properties and interface damage mechanisms of carbon fiber reinforced polypropylene composites

AbstractIn this article, the mechanical properties of carbon fiber reinforced polypropylene (CF/PP) composites at different carbon fiber (CF) mass fractions were systematically investigated. A comprehensive examination is provided through the integration of experimental testing, numerical simulation, and theoretical analysis, revealing the enhancement effects of CF on the polypropylene (PP) matrix across multiple scales. Experimental results demonstrated that the incorporation of CF significantly impedes crack propagation and enhances the fracture resistance of the composites. Specifically, at a CF mass fraction of 15%, the elastic modulus of the composites is enhanced by 21.7% compared with pure PP, while the tensile strength increases by 40.9%–43.2%. The addition of maleic anhydride grafted polypropylene (MAH‐g‐PP) as a compatibilizer significantly improves the interfacial compatibility between CF/PP. Furthermore, finite element simulations revealed the damage evolution process at the CF/PP interface during tensile loading. Based on the Mori‐Tanaka model, the elastic modulus was predicted, aligning well with experimental and simulated results. This research offers a scientific basis for the design and application of CF/PP composites and contributes to the advancement of high‐performance composites.Highlights CF/PP composites show enhancements in mechanical properties with CF addition MAH improves interfacial adhesion between CF and PP, boosting tensile strength Multiscale experimental and FEA studies reveal CF/PP interface damage mechanisms Mori‐Tanaka model accurately predicts the elastic modulus of CF/PP composites

Critical Role of Rubber Functionalities on the Mechanical and Electrical Responses of Carbon Nanotube-Based Electroactive Rubber Composites.

Carbon nanomaterials, particularly carbon nanotubes (CNTs), are widely used as reinforcing fillers in rubber composites for advanced mechanical and electrical applications. However, the influence of rubber functionality and its interactions with CNTs remains underexplored. This study investigates electroactive elastomeric composites fabricated with CNTs in two common diene rubbers: natural rubber (NR) and acrylonitrile-butadiene rubber (NBR), each with distinct functionalities. For NR-based composites containing 2 vol% CNTs, mechanical properties, such as elastic modulus (2.24 MPa), tensile strength (12.48 MPa), and fracture toughness (26.92 MJ/m3), show significant improvements of 125%, 215%, and 164%, respectively, compared to unfilled rubber. Similarly, for NBR-based composites, the elastic modulus (5.46 MPa), tensile strength (13.47 MPa), and fracture toughness (82.89 MJ/m3) increase by 94%, 22%, and 65%, respectively, over the unfilled system. Although NBR-based composites exhibit higher mechanical properties, NR systems show more significant improvements, suggesting stronger chemical bonding between NR chains and CNTs, as evidenced by dynamic mechanical, X-ray diffraction, thermogravimetric, and thermodynamic analyses. The NBR-based composite at 1 vol% CNT content exhibits 261% higher piezoresistive strain sensitivity (GF = 65 at 0% ≤ Δε ≤ 200%) compared to the NR-based composite (GF = 18 at 0% ≤ Δε ≤ 200%). The highest gauge factor of 39,125 (1000% ≤ Δε ≤ 1220) was achieved in NBR-based composites with 1 vol% CNT content. However, 1.5 vol% CNT content in NBR provides better strain sensitivity and linearity than other composites. Additionally, NBR demonstrates superior electromechanical actuation properties, with 1317% higher actuation displacement and 276% higher electromechanical pressure compared to NR at an applied electric field of 12 kV. Due to the stronger chemical bonding between the rubber and CNT, NR-based composites are more suitable for dynamic mechanical applications. In contrast, NBR-based CNT composites are ideal for stretchable electromechanical sensors and actuators, owing to the high dielectric constant and polarizable functional groups in NBR.

Evaluation of facings and sandwich properties of carbon fiber/epoxy-PVC foam sandwich composites: Comparison of VARI co-cure and precure manufacturing methods

The manufacturing process of sandwich composites using vacuum-assisted resin infusion (VARI) can be achieved in a one-step infusion process (co-cure). The purpose of this study is to evaluate the properties of the facing and sandwich composites manufactured by the VARI co-cure method. The sandwich composite was fabricated by VARI co-cure and precure for comparison using carbon fiber-epoxy as the facing and PVC foam as the core material. Thickness measurement, fiber volume fraction test, and tensile test were conducted to evaluate the facing properties. The flexural properties of the sandwiches and the effect of different plies on the facing and sandwich properties were also analyzed. The thickness of the co-cure facing is thicker and more varied than the precure. In addition, for the co-cure sandwich, the vacuum bag side (upper) facing has higher thickness and thickness variation than the mold side (lower) facing. The tensile strength of the co-cure facing is lower than the precure facing, which is 433–490 MPa (upper) and 455–521 MPa (lower) compared to 467–538 MPa (precure). The flexural and shear rigidity of the co-cure sandwich is affected by the side of the facing (upper/lower) exposed to tension or compression normal stress as a result of differences in facing properties on both sides. The specific flexural stiffness of the co-cure sandwich was lower by 17.09–45.19 MN-cm5/g compared to the precure of 16.86–46.83 MN-cm5/g due to a combination of increased flexural rigidity and the addition of density to the co-cure sandwich. Increasing facing plies from 2 to 6 plies results in an increase in facing thickness (166%) and thickness variation (477%), an increase in the fiber volume fraction of facing (11%), resulting in an increase in tensile modulus (12%) and strength (14%) of facing as well as increased stiffness of flexural (339%) and shear (42%) of sandwich.

Pullulan fermented by Aureobasidium melanogenum TZ-FC3 for the preparation of self-healing, adhesive, injectable and antibacterial pullulan/PVA/borax hydrogel.

Natural polymer hydrogels, such as pullulan-based hydrogels, offer significant advantages over synthetic materials due to their thermal stability, film-forming capacity, solubility, adhesiveness, and antioxidant properties. In this study, the strain Aureobasidium melanogenum TZ-FC3, which produces a high level of pullulan, was successfully isolated from the mangrove ecosystems of Guangdong Province, China. 66.01 ± 1.10 g/L pullulan without melanin was produced by the TZ-FC3 strain within 120 h at flask level. Pullulan fermented by A. melanogenum TZ-FC3 was added to enhance the hydrogen bond network within the pullulan/PVA/borax hydrogels (P-2, P-3 and P-4 hydrogels) to improve mechanical strength and crosslinking density of PVA/borax hydrogel (P-1 hydrogel). Compared to the P-1 hydrogel, the P-2 hydrogel exhibited a 65.4 % increase in tensile strain, a remarkable 694.03 % increase in tensile strength and improved the degree of internal crosslinking. Additionally, the pullulan/PVA/borax hydrogels demonstrated excellent self-healing properties, adhesion, injectability, and antibacterial activity. The preparation process of pullulan/PVA/borax hydrogels is straightforward and effective, suggesting broad industrial applicability and underscoring their potential as next-generation materials for advanced healthcare solutions.

Effect of cryogenic treatment on the mechanical properties of 3D-printed polylactic acid part

The article investigates the effect of cryogenic treatment on the 3-D printed Polylactic Acid (PLA) specimen. It was found that exposure of PLA specimens to the cryogenic temperature (10 K) using a cryocooler led to a 35 % increase in tensile strength in 5 h, with most improvement occurring within the first hour. The cryogenic treatment enhanced the PLA specimen’s strength and ductility due to increased crystallinity and better molecular alignment. It is likely due to the interaction of the cooling medium (helium) used in the cryocooler with the PLA specimens. Towards this, EDS analysis is performed on cryo-treated PLA specimens. The EDS analysis reveals that nickel and iron compounds were detected on the surface of the cryogenic-treated PLA specimen. These findings highlight that cryogenic treatment significantly improves PLA specimen’s mechanical properties and tensile strength. However, challenges arise, including delamination-layer separation caused by internal stresses, and must be addressed. This work will be helpful for researchers working in polymer 3-D printing.