Co-continuous Structure Research Articles

Comprehensive and Robust Anti-Jamming Dual-Electrode Pair Sensor.

Capacitive flexible sensors often encounter instability caused by temperature fluctuations, electromagnetic interference, stray capacitance effects, and signal noise induced by ubiquitous vibrations. The challenge lies in achieving comprehensive anti-jamming abilities while preserving a simplistic structure and manufacturing process. To tackle this dilemma, a straightforward and effective design is utilized to achieve comprehensive and robust anti-jamming properties in capacitive sensors. Electrospinning thermoplastic polyurethane (TPU) fiber mats soak with ionic liquid (IL) to create a co-continuous structure (TPU@IL) with high ionic conductivity and dielectric constant, which acts as the sensing units. The sensing mechanism of the TPU@IL with multiple electrode pairs encapsulated by polyethylene terephthalate (PET) is systematically elucidated. The optimal dual-electrode pair design for capacitive and resistive sensors, which have different sensitivities to temperature and stress, simultaneous realizes temperature-stress dual-mode sensing. Remarkably, the sensitivity curve of the TPU@IL/PET capacitive sensor exhibits an intriguing rarely reported S-shape with an adjustable step stress point. No liquid leakage even during extensive stress-strain cycling (>4000 cycles). Despite a slight compromise in sensitivity and response time, the TPU@IL/PET sensor demonstrates exceptional electromechanical stability, reliability, and powerful anti-jamming abilities against various interferences. A simple yet innovative sensor design enhances the performance and applicability of capacitive sensors in challenging environments.

Effect of thermoplastic starch/poly(lactic acid) weight fraction on phase morphology and performance of biodegradable blends and their jute fiber composites.

The present work investigates the phase morphology and properties of biodegradable thermoplastic starch (TPS)-poly(lactic acid) (PLA) blends and their jute fiber (JF) biocomposites. The TPS/PLA blends and TPS/PLA/JF composites were fabricated using a twin-screw extruder and then injection molded into the test specimens, varying the TPS/PLA weight fractions (80/20, 60/40, 40/60, and 20/80) while keeping the JF content constant (10 wt%). At 80 wt% TPS, the TPS/PLA blend showed a co-continuous structure, whereas the remaining blends (20, 40, and 60 wt% TPS) exhibited a TPS droplets-PLA matrix structure. The TPS/PLA/JF composites displayed a PLA droplets-TPS matrix structure at 80 wt% TPS, a co-continuous structure at 60 wt% TPS, and a TPS droplets-PLA matrix structure at 20 and 40 wt% TPS. Increasing the proportion of PLA increased the melt flow ability, tensile strength, Young's modulus, storage modulus, thermal stability, and water contact angle of the blends and composites. The addition of jute fibers altered the phase morphology of the blends, enhanced their strength and stiffness, increased PLA nucleation, and improved the TPS-PLA phase compatibility. The blends and composites herein exhibit great potential in developing environmentally friendly injection-molded products, such as stationery, toys, gardening supplies, etc.

3D Printing of solvent-free PEO-Polyolefin solid polymer electrolyte by Fused Filament Fabrication

ABSTRACT 3D printing of energy storage systems is at the heart of In-Space Manufacturing strategy. Within this context, Li-ion polymer batteries printing through Fused Filament Fabrication (FFF) is envisaged. This study is devoted to optimising the extruded solid polymer electrolyte filament properties. As the poly(ethylene oxide) (PEO) – lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) electrolyte offers the best Li+ conductivities but suffers from poor mechanical behaviour, poly(propylene) (PP) is added to ensure filament printability. An exhaustive investigation highlights the impact of the PEO molar weight and the LiTFSI and PP proportions. Fine-tuning these parameters alters molten phase viscosity, which affects the electrolyte morphology and ionic conductivity. Best formulations feature a co-continuous structure that provides effective mechanical reinforcement and exhibits the best ionic conductivity reported so far for an FFF-printed solvent-free polymer electrolyte of 1.2 × 10−4 S.cm−1 at 70°C. Therefore, it opens the way towards polymer battery printing, on the Earth and in microgravity conditions.

Preparation and 3D printing parameters of thermo/electrically shape memory PLA/SEBS-g-MA/CB composites

In this work, novel thermo-responsive shape memory blends PLA/SEBS-g-MA and electro-responsive PLA/SEBS-g-MA/carbon black (CB) composites were prepared by melt blending, and were extruded into filaments for 3D printing. SEM images illustrate that the blends possess co-continuous structure at SEBS-g-MA ratio of 30 wt% and showcase remarkable shape memory properties (Rf 100%, Rr 85.3%), which were attributed to effective stress transfer. In the second part, PLA/SEBS-g-MA/CB composites were produced with different amounts of CB nanoparticles. The volume resistivity of composites with CB additions of 13 phr and above is maintained at about 102 Ω.cm, and the printed samples showed superior electro-responsive performance, with response completed in about 40 s at 60 volts DC. In addition, the effect of printing parameters on the mechanical properties was investigated and it was found that the choice of layer thickness was strongly related to tensile and flexural strength.

Conductivity of PLA/PBAT blends with carbon black as a conductive filler

Conductive composites of PLA/PBAT/CB were prepared by melt blending. CB selectively distributes in the PBAT matrix, and at a PLA to PBAT ratio of 1:1, the composite achieves a conductivity of 1.01 × 10−6 S/m with a percolation threshold of 0.42 wt%. Compared to PLA/CB and PBAT/CB, the PLA/PBAT/CB composite has a lower percolation threshold. The E2 processing sequence most effectively enhanced conductivity by optimizing carbon black distribution in the PBAT phase, promoting a co-continuous structure and improving conductive pathways and electrical properties. Key methods used include contact angle measurements, polarized light microscopy, scanning electron microscopy, and a high-resistance meter.

Preparation of Self-healing Thermoplastic Polysiloxane-Polyurea/Polyether-Polyurea Elastomer Blends with a Co-continuous Microphase Structure and In-Depth Research on Their Synergistic Effects.

Polymer blending has been an important method to create materials with specific properties that have synergistic effects. However, there are few reports on the mechanism of synergistic effects. It is well known that it is quite difficult to obtain ideal blends composed of nonpolar organosilicon polymers and polar polymers. In this paper, thermoplastic polyurea elastomer blends with a co-continuous microphase structure consisting of polysiloxane-polyurea (PDMS-PUA), polyether amine-polyurea (PEA-PUA), and compatibilizer PDMS-PUA-grafted PEA-PUA (PDMS-PUA-g-PEA-PUA) were prepared for the first time. For the first time, introduction of polysiloxane does not sacrifice mechanical properties of thermoplastic polyurea elastomers. For example, the tensile strength of the elastomer blend with 30 wt % PDMS-PUA content reached 25.7 MPa, which is higher than those of PEA-PUA and PDMS-PUA. The blends also show typical outstanding characters such as exceptional heat and water resistance. The mechanism of the synergistic effect on mechanical properties is revealed based on in-depth studies on mutual interphase interaction. In situ variable temperature infrared spectroscopic analysis (VTIR) shows that compatibilization facilitates the construction of a denser hydrogen bonding network at the blend interface, which is thought to play a key role in the co-continuous microphase structure. Microscopic morphological characterization shows that PDMS-PUA and PEA-PUA phases are deformed and oriented together during the stretching process, thus jointly resisting external forces. Moreover, the blends show an exceptional self-healing ability due to their strong and reversible hydrogen bonding network.

Non-isothermal crystallization kinetics of biocomposites based on PLA/PHBV and spent coffee grounds

AbstractThis study deals with the modification of a predominantly amorphous poly(lactic acid) (PLA) by blending it with a semi-crystalline biopolymer, polyhydroxybutyrate-co-valerate (PHBV), which has a high crystallinity. The blends with different concentrations of PLA and PHBV were compounded with spent coffee grounds (SCGs) and processed by injection moulding. The structural, thermal and mechanical properties of the produced samples were investigated. Particular attention was paid to the effect of the presence of SCG and the concentration of PHBV in the blend on the crystallization kinetics and the heat deflection temperature (HDT). For equimolar blends, only a slight increase in HDT (about 5 °C) was observed, but the addition of PHBV suppressed the cold crystallization of PLA, which otherwise negatively affects the dimensional stability of injection moulded parts. A similar effect, but to a lesser extent, was achieved by adding SCG to the PLA matrix. Thus, it is clear that the material structures of PLA/PHBV blends and composites help to minimize additional shrinkage of the parts and increase their dimensional stability. Due to the co-continuous structure of the symmetric PLA/PHBV blends and the increase in the degree of crystallinity from 36 to 47% by annealing the produced samples, the heat deflection temperature increased from 65 up to 90 °C.

Microphase separation regulation of polyurethane modified phenolic resin aerogel to enhance mechanical properties and thermal insulation

Applications of aerogels are commonly restricted by their complicated preparation route, high energy cost, brittleness and poor mechanical properties. Herein, a facile synthesis route for mechanical robust polyurethane (PU) modified phenolic resin (PF) aerogel was developed. The aerogel was prepared via polymerization of PU and phenolic resin (PF) followed by direct ambient pressure drying, sub-10 nm scale co-continuous phase structure was realized via control of kinetics of sol–gel reaction. The regulation of phase structure significantly enhanced mechanical properties of aerogels, which showed compressive strength and modulus of 29 MPa and 112 MPa, respectively, at 60 % strain without notable collapse. Furthermore, these aerogels showed excellent thermal insulation properties at both room temperature and high temperature. They exhibited superior dynamic ablative thermal protection at 1200℃ in oxygen-acetylene ablation test. This facile, inexpensive, environment-friendly methodology for aerogel preparation expands the application scope of aerogels in the field of thermal insulation under harsh environments.

Bioinspired Nanolayered Structure Tuned by Extensional Stress: A Scalable Way to High-Performance Biodegradable Polyesters.

The nacre-inspired multi-nanolayer structure offers a unique combination of advanced mechanical properties, such as strength and crack tolerance, making them highly versatile for various applications. Nevertheless, a significant challenge lies in the current fabrication methods, which is difficult to create a scalable manufacturing process with precise control of hierarchical structure. In this work, a novel strategy is presented to regulate nacre-like multi-nanolayer films with the balance mechanical properties of stiffness and toughness. By utilizing a co-continuous phase structure and an extensional stress field, the hierarchical nanolayers is successfully constructed with tunable sizes using a scalable processing technique. This strategic modification allows the robust phase to function as nacre-like platelets, while the soft phase acts as a ductile connection layer, resulting in exceptional comprehensive properties. The nanolayer-structured films demonstrate excellent isotropic properties, including a tensile strength of 113.5MPa in the machine direction and 106.3MPa in a transverse direction. More interestingly, these films unprecedentedly exhibit a remarkable puncture resistance at the same time, up to 324.8Nmm-1, surpassing the performance of other biodegradable films. The scalable fabrication strategy holds significant promise in designing advanced bioinspired materials for diverse applications.

Highly thermally stable Ti/Si/B modified bisphenol A-phenolic resins with co-continuous structure

Highly thermally stable Ti/Si/B modified bisphenol A-phenolic resins with co-continuous structure

Porous Melt Blown Poly(butylene terephthalate) Fibers with High Ductility and High-Temperature Structural Stability.

In this study, porous poly(butylene terephthalate) (PBT) fibers were produced by melt blowing cocontinuous blends of PBT and polystyrene (PS) and selectively extracting the interconnected PS domains. Small amounts of hydroxyl terminated PS additives that can undergo transesterification with the ester units in PBT were added to stabilize the cocontinuous structure during melt processing. The resulting fibers are highly ductile and display fine porous structural features, which persist at temperatures over 150 °C. Single fiber tensile testing and electron microscopy are presented to demonstrate the role of rapid quenching and drawing of the melt blowing process in defining the fiber properties. The templated highly aligned pore structure, which is not easily produced in solvent-based fiber spinning methods, leads to remarkable mechanical properties of the porous fibers and overcomes the notoriously poor tensile properties common to other cellular materials like foams.

Fluorinated semi-interpenetrating polymer networks for enhancing the mechanical performance and storage stability of polymer-bonded explosives by controlling curing and phase separation rates

Herein, the effect of fluoropolymer binders on the properties of polymer-bonded explosives (PBXs) was comprehensively investigated. To this end, fluorinated semi-interpenetrating polymer networks (semi-IPNs) were prepared using different catalyst amounts (denoted as F23-CLF-30-D). The involved curing and phase separation processes were monitored using Fourier-transform infrared spectroscopy, differential scanning calorimetry, a haze meter and a rheometer. Curing rate constant and activation energy were calculated using a theoretical model and numerical method, respectively. Results revealed that owing to its co-continuous micro-phase separation structure, the F23-CLF-30-D3 semi-IPN exhibited considerably higher tensile strength and elongation at break than pure fluororubber F2314 and the F23-CLF-30-D0 semi-IPN because the phase separation and curing rates matched in the initial stage of curing. An arc Brazilian test revealed that F23-CLF-30-D-based composites used as mock materials for PBXs exhibited excellent mechanical performance and storage stability. Thus, the matched curing and phase separation rates play a crucial role during the fabrication of high-performance semi-IPNs; these factors can be feasibly controlled using an appropriate catalyst amount.

A three-dimensional co-continuous network structure polymer electrolyte with efficient ion transport channels enabling ultralong-life all solid-state lithium metal batteries

Solid polymer electrolytes (SPEs) have emerged as one of the most promising candidates for the construction of solid-state lithium batteries due to their excellent flexibility, scalability, and interface compatibility with electrodes. Herein, a novel all-solid polymer electrolyte (PPLCE) was fabricated by the copolymer network of liquid crystalline monomers and poly(ethylene glycol) dimethacrylate (PEGDMA) acts as a structural frame, combined with poly(ethylene glycol) diglycidyl ether short chain interspersed serving as mobile ion transport entities. The preparaed PPLCEs exhibit excellent mechanical property and outstanding electrochemical performances, which is attributed to their unique three-dimensional co-continuous structure, characterized by a cross-linked semi-interpenetrating network and an ionic liquid phase, resulting in a distinctive nanostructure with short-range order and long-range disorder. Remarkably, the addition of PEGDMA is proved to be critical to the comprehensive performance of the PPLCEs, which effectively modulates the microscopic morphology of polymer networks and improves the mechanical properties as well as cycling stability of the solid electrolyte. When used in a lithium-ion symmetrical battery configuration, the 6 wt%-PPLCE exhibites super stability, sustaining operation for over 2000 h at 30 °C, with minimal and consistent overpotential of 50 mV. The resulting Li|PPLCE|LFP solid-state battery demonstrates high discharge specific capacities of 160.9 and 120.1 mA h g−1 at current densities of 0.2 and 1 C, respectively. Even after more than 300 cycles at a current density of 0.2 C, it retaines an impressive 73.5% capacity. Moreover, it displayes stable cycling for over 180 cycles at a high current density of 0.5 C. The super cycle stability may promote the application for ultralong-life all solid-state lithium metal batteries.

Layered co-continuous structure in bone scaffold fabricated by laser additive manufacturing for enhancing electro-responsive shape memory properties

Porous scaffold based on electro-responsive shape memory polymers (ESMPs) possesses great potential applications in minimally invasive surgery for bone defect repair because it provides the ability for remote control and internal heating. However, it's difficult to obtain co-continuous structure in bone scaffold for achieving excellent electro-responsive shape memory properties. In this study, layered co-continuous structure with thermoplastic polyurethane (TPU) loaded with multi-walled carbon nanotubes (MWCNTs) (referred to as cTPU) layer and l-polylactic acid (PLLA) layer alternate stacking was obtained via layer-by-layer fabrication technology, and the porous scaffold was fabricated via selective laser sintering (SLS). The thermal and electrical shape memory properties of the scaffolds with different contents of MWCNT were evaluated by dynamic mechanical analysis (DMA) and U-bending experiments. The results indicated that the layered co-continuous structure improved phase continuity and confined MWCNTs to one side, enhancing the electrically driven properties and shape memory properties. The scaffold with 1.5 wt% MWCNTs achieved shape fixed and recovery rates of 95.6% and 90.2%, respectively. With the further increasing of MWCNTs content, the shape memory properties decreased due to the agglomeration of MWCNTs in the cTPU phase, which affected the phase continuity of cTPU. The DMA results confirmed the good mechanical properties of the scaffold, and the cell culture experiment results demonstrated excellent cytocompatibility for cell attachment and growth. This work provides a feasible method to fabricate electro-responsive shape memory bone scaffold with layered co-continuous structure, which exhibits great potential in applications of bone defect repair.

Facile preparation of SAN/NBR TPV with balanced stiffness-toughness via metal-ligand coordination-induced dynamic vulcanization and in situ interfacial compatibilization

In this work, metal-ligand coordination interaction was utilized to induce the dynamic vulcanization (DV) of styrene-acrylonitrile copolymer (SAN)/butadiene acrylonitrile rubber (NBR)/cupric sulfate (CuSO4) TPVs. The TPVs exhibited co-continuous structure, in which the CuSO4 particles distributed in continuous NBR network to cross-link NBR phase through interaction between Cu2+ and nitrile groups (-CN), enhancing the mechanical strength and thickness of NBR network. CuSO4 particles were refined to nanoparticles during DV, and then migrated to SAN/NBR interface and interacted with SAN and NBR simultaneously to realize in-situ compatibilization, resulting in efficient toughening of SAN without sacrificing its stiffness. With 20 phr CuSO4, the TPVs showed excellent impact toughness of 104.51 kJ/m2, which was 58 times that of the neat SAN. Meanwhile, the TPVs exhibited improved tensile strength, elongation at break, tensile toughness and Young's modulus, revealing the balanced stiffness-toughness properties of TPVs. We propose a feasible approach to fabricate high-performance TPVs, and it may expand the research scope of dynamic vulcanization.

Fabricating biomimetic porous PEEK scaffolds for bone implants

Poly-ether-ether-ketone (PEEK) is a high strength polymer with strong potential for medical use, especially for bone implants. In this research, a novel method of making biomimetic porous PEEK scaffolds is developed. PEEK and polyethersulfone (PES) are blended at a proper ratio to generate a co-continuous phase structure. With solid-state foaming, PES is efficiently removed by leaching to yield interconnected porous PEEK scaffolds. The pore size and pore gradient of the PEEK scaffolds can be easily controlled by controlling the annealing time and temperature of the PEEK/PES blend. This study presents the conditions of the proposed fabrication process and compares the fabricated porous PEEK scaffolds with those fabricated using other methods. It is shown that the structural morphology and mechanical properties of the fabricated porous PEEK is generally comparable to those of trabecular bones, suggesting these scaffolds could be excellent candidates for bone implant applications.

A Novel Functional Compatibilization Strategy for Poly(lactic acid) and Poly(butylene adipate-co-butylene terephthalate) Blends to Achieve a Stable Co-continuous Structure and Excellent Antibacterial Performance

Blends of poly(lactic acid) (PLA) and poly(butylene adipate-co-butylene terephthalate) (PBAT) are currently the most widely studied biodegradable blends and have great potential to replace conventional polyolefin and polyester materials. However, PLA/PBAT blends still face the challenges of poor compatibility and antibacterial performance in the practice applications. In this study, antibacterial functional PLA/PBAT blends were fabricated using an alternative copolymer (PSM-D) composed of reactive maleic anhydride segments and imidazolium cations. The results revealed that PSM-D, with long alkyl chains, improved the compatibility, antibacterial properties, and mechanical properties of the PLA/PBAT blends. Under the optimized conditions, the elongation at break of PLA/PBAT blends was increased by 750%. Detailed analysis demonstrated that these outstanding improvements could be ascribed to the formation of a stable co-continuous structure in the PLA/PBAT matrix. Furthermore, the PLA/PBAT blends exhibited excellent antibacterial properties against both gram-positive Staphylococcus aureus and gram-negative Escherichia coli, which was attributed to the presence of imidazolium cations with long alkyl chains. This study provides a new “two-in-one” platform for fabricating functional compatibilization strategies for biodegradable polymer blends and is expected to have broad implications and practical relevance for packaging and medical devices.

Improving flame retardant and electromagnetic interference shielding properties of poly(lactic acid)/poly(ε-caprolactone) composites using catalytic imidazolium modified CNTs and ammonium polyphosphate

The flame retardants and electromagnetic interference (EMI) shielding performance were enhanced by using imidazolium-functionalized polyurethane (IPU) modified multi-walled carbon nanotubes (CNTs) and ammonium polyphosphate (APP) for polylactic acid (PLA)/polycaprolactone (PCL) composites. The PLA/PCL/10APP/8CNT/1.6IPU composite containing 10 wt% APP and 8 wt% imidazolium modified CNTs reached the limiting oxygen index (LOI) value of 30.3 % and passed the V-0 rating in UL-94 tests. Moreover, the peak of the heat release rate (pHRR) and total heat release (THR) for this composite reached around 302 kW/m2 and 64 KJ/m2, which were decreased by 39.1 % and 15.8 % compared with that of PLA/PCL/10APP composite. The improved flame retardancy was attributed to the interplay of catalytic, barrier, and condensed char forming of imidazolium-modified CNTs and APP. IPU catalyzed the charring effect of the polymer matrix during combustion and regulated the migration of more CNTs to disperse at the two-phase interface. The dispersion of imidazolium-modified CNTs and co-continuous phase structure of the composites can establish continuous conductive pathways. The PLA/PCL/APP/CNT/IPU composite obtained a higher conductivity compared to the PLA/PCL/APP/CNT composite and whose EMI SE reached 33.9 dB, which is a promising candidate for next-generation sustainable and protective plastics.

Synergistic enhancement of thermomechanical properties and oxidation resistance in aligned Co-continuous carbon-ceramic hybrid fibers.

Carbon fibers are highly valued for their lightweight characteristics, outstanding mechanical properties, and cost-efficiency. However, their limited oxidation resistance and low thermomechanical stability in hot air impose constraints on their utilization. Here, we present an approach to simultaneously achieve high thermomechanical properties and high-temperature oxidation resistance in carbon-ceramic hybrid fibers featuring a highly aligned co-continuous topological structure through a continuous process. These hybrid fibers exhibit superior mechanical properties compared to pure carbon fibers with the same diameter (20 μm), including a tensile strength of 2.0 ± 0.2 GPa, Young's modulus of 175 ± 34 GPa, and elongation at break of 1.3 ± 0.2%. Moreover, when subjected to thermal exposure under stress loading conditions in air, the ceramic constituents form a protective oxidized ceramic layer that effectively mitigates thermal oxidation and mechanical loading effects at elevated temperatures, surpassing the performance of carbon fibers. Our discovery offers a promising avenue for bridging the performance gap between cost-effective high-strength carbon fibers and expensive SiC counterparts with exceptional oxidation resistance, which can be applied in many fields wherever high thermomechanical loading and oxidation-resistant properties are important.

A comparative study of the cryogenic performance of CFRP composites with polyethersulfone/epoxy blends and electrospun polyethersulfone interleaves

Thermoslastic-modifers are used to enhance the fracture toughness of epoxy resins for cryogenic applications. This study presents a comparative analysis of the cryogenic performance of laminated fibre-reinforced composites, focusing on two different toughening approaches: interleaving electrospun polyethersulfone (PES) veils or epoxy/PES blends with varying PES loadings. In casted epoxy/PES blends, the particulate phase structure was formed with a PES content of 2.5–10 phr, transitioning to a co-continuous structure beyond 10 phr. Electrospun PES interleaves effectively enhanced interlaminar fracture toughness at both 293 and 77 K by 76 % and 48 %, respectively. These improvement levels achieved were comparable to those of laminates toughened with 7.5 phr PES/epoxy blend. The results presented suggest that interleaving composite laminates offers great potential in enhancing the durability of cryogenic tanks while being seamlessly integrated into manufacturing processes.