Intumescent coatings, which swell and form a protective char when exposed to flame, are key for fire protection. This study evaluates the Heat Blocking Efficiency (HBE) of epoxy resin coatings, incorporating eco-friendly tannic acid (TA) and ammonium polyphosphate (APP) on hot-rolled carbon steel (HRCS). Using a methane torch, a 6.3-mm thick HRCS plate was subjected to 130 kW/m2 heat flux. To predict heat transfer and estimate HBE, we combined experimental methods and numerical simulations involving a two-dimensional heat conduction model via finite element analysis (FEA), considering thermal insulation, heat flux boundary conditions, convection, and radiation. The results aligned closely with experimental data, confirming the coatings' efficacy in keeping steel temperature below the critical range of 550-600°C for up to 20 minutes, with the minimum temperature observed under 250°C. The coatings' HBE successfully reduced the substrate temperature by 90%, demonstrating their potential for advancing fire safety in coatings technology.

With the accelerating advancement of wearable electronics, electronic skin (e-skin) has emerged as a promising technology for applications in health monitoring, prosthetics, and human-machine interfaces. Nonetheless, achieving simultaneous breathability, antibacterial properties, and high sensing fidelity presents a formidable challenge. In this study, we report a multifunctional electronic skin (e-skin) constructed from a modified Tecoflex (thermoplastic polyether-based polyurethane) electrospun nanofiber membrane (T-eNFM), integrating breathability, antibacterial activity, and high-fidelity sensing capabilities. The T-eNFM substrate promotes wearer comfort via its innate breathability while simultaneously inhibiting bacterial colonization through robust antimicrobial functionality. A composite of multi-walled carbon nanotubes (MWCNTs) and silver paste (Ag powder) was printed onto T-eNFM-3 to form a conductive, mechanically compliant sensing layer. The fabricated strain sensor exhibited a gauge factor of 5.81, while the multilayer pressure sensor displayed a sensitivity of 2.83 kPa-1, rendering it ideally suited for monitoring cardiovascular physiological signals. This work outlines a blueprint for next-generation electronic skin devices by addressing the critical challenges of comfort, safety and multifunctionality.

This study investigated the thermal performance of reduced super intumescent (RSI) coating, focusing on the correlation between porosity evolution and thermal conductivity under elevated temperature conditions. Porosity development was quantified using scanning electron microscopy (SEM) combined with MATLAB-based image analysis, achieving a maximum porosity of 62% after 60 min of exposure. Thermal degradation was characterized using thermogravimetric analysis (TGA), which recorded a mass loss of 35% between 250 °C and 400 °C, capturing the decomposition kinetics and correlating degradation stages with char formation. Fire protection efficiency was evaluated by employing heat flow meter tests (thermal conductivity reduced from 0.15 W/mK to 0.05 W/mK), methane torch experiments (backside temperature increase delayed by up to 50% compared to uncoated steel), and COMSOL-based heat transfer simulations. The results revealed that the RSI coating’s thermal conductivity decreased as its porosity increased, enhancing its insulation effectiveness. Additionally, the formation of a thermally stable char layer at 400 °C significantly reduced heat transfer to the metal substrate by 66%. These findings support the optimization of bio-derived fire-retardant coatings for passive fire protection applications.

Solid-state processing of semi-crystalline polymers is an attractive, environmentally friendly, and scalable methodology that can be used to produce high-value-added products. In this study, we applied a two-stage scrapless, solventless, and low-energy-consuming solid-state process with special emphasis on isotactic polypropylene (PP). In Stage 1, cross-rolling, we report the production of tough sheets both at room temperature and under cryogenic conditions (-40 degrees C), well below the T-g of PP. In Stage 2, the PP was oriented below T-m to a draw ratio of 25 into thin rods with outstanding mechanical properties. The oriented thin rod, that is, the product, exhibited moduli of approximately 30 GPa and tensile strength values greater than 1 GPa. These mechanical properties compare favorably with those of gel-spun fibers of ultra-high-molecular-weight PP, which are more than 30 times thinner. The solid-state structure of the product comprises a taut network with a profuse crazing configuration and a highly fibrillated structure. A complex hierarchical structure is proposed to elucidate the evolution of these properties as a function of orientation. Highlights A two-stage solid-state process for polypropylene was successfully developed. The product exhibited a high stiffness of 29 GPa and strength >1 GPa. Product tensile properties compare favorably with gel-spun PP fibers. A complex hierarchical structure was established.

The competition between mono- and divalent counterions in polyelectrolyte gels can lead to reversible transitions between swollen and collapsed phases. In this study, we investigate the emergence of a propagating boundary that separates the two phases in cylindrical polyacrylate gels, where it moves along the gel's longitudinal axis. We emphasize the distinction between an overall calcium-induced contraction and the axial progression phenomenon and use an object detection algorithm to determine the boundary propagation rate. Additionally, we investigate how calcium concentration, external voltage, and gel diameter influence the formation time and propagation velocity of the phase boundary. Our findings reveal that an increased calcium concentration in the adjacent bath, the application of an external voltage, and a decreased gel diameter contribute to a shorter formation time and a higher propagation velocity of the phase boundary. These results provide important insights into the complex dynamics of phase boundaries in cylindrical polyelectrolyte gels.

The oil and gas industry is subject to significant fire hazards due to the flammability of hydrocarbons and the extreme conditions of operational facilities. Intumescent coatings (ICs) serve as a crucial passive fire protection strategy, forming an insulating char layer when exposed to heat, thereby reducing heat transfer and delaying structural failure. This review article provides an overview of recent developments in the effectiveness of ICs in mitigating fire risks, enhancing structural resilience, and reducing environmental impacts within the oil and gas industry. The literature surveyed shows that analytical techniques, such as thermogravimetric analysis, scanning electron microscopy, and large-scale fire testing, have been used to evaluate the thermal insulation performances of the coatings. The results indicate significant temperature reductions on protected steel surfaces that extend critical failure times under hydrocarbon fire conditions. Recent advancements in nano-enhanced and bio-derived ICs have also improved thermal stability and mechanical durability. Furthermore, numerical modeling based on heat transfer, mass conservation, and kinetic equations aids in optimizing formulations for real-world applications. Nevertheless, challenges remain in terms of standardizing modeling frameworks and enhancing the environmental sustainability of ICs. This review highlights the progress made and the opportunities for continuous advances and innovation in IC technologies to meet the ever-evolving challenges and complexities in oil and gas industry operations. Consequently, the need to enhance fire protection by utilizing a combination of tools improves predictive modeling and supports regulatory compliance in high-risk industrial environments.

Poly(hydroxyalkanoates) (PHAs) are a class of sustainable, bio-based thermoplastic polymers with attractive physiochemical properties, including non-toxicity, biocompatibility, elastomeric behavior by design, and piezoelectric characteristics. In the ongoing effort to reduce plastics waste, PHAs can play a substantial role due to their inherent biodegradability free of microplastics, customizable properties, and versatile applications. This includes their tremendous potential in a broad range of biomedical applications. Biomass-based materials have recently gained great interest in the health sector, given the vast amount of interdisciplinary research in bioengineering and medicine. Implantable biomaterials should not elicit any negative response at the implantation site, which differentiates them from general-purpose polymers. PHAs do not induce any thrombosis or antigenic response even after being in contact with blood in the human body during long-term use. The biocompatibility of PHAs is also a key factor in the rapid growth and proliferation of tissues onto and within these materials when served as tissue engineering scaffolds. By application, the biomedical field was estimated to be the second-largest market share for PHAs, in terms of volume, in 2022. While PHA-based materials bring forth a broad range of opportunities, they also present challenges that have limited their widespread use and a greater market share. A better understanding of their physiochemical properties and biodegradation rates, production challenges, and the need for cost-effective strategies are some of the hurdles that need to be addressed. This review paper provides an overview of the commonly used PHA homopolymers and copolymers in biomedical fields and packaging industries. The introduction of the manuscript presents the concept of bioplastics and their environmental significance, highlighting the urgent need for alternatives to conventional fossil-based plastics. The next sections briefly cover the synthesis, properties, as well as homopolymer and copolymer formulations, followed by the application of PHA-based materials in the biomedical field. Current opportunities and challenges, together with some insight into the future gathered from the published studies, have been brought in the concluding section of this paper.

Poly(hydroxyalkanoates) (PHAs) are emerging as sustainable materials in packaging and medical device industries. Nevertheless, the high cost and the need to improve the mechanical properties have limited their widespread use. Blending with other bio-based polymers, such as poly(lactic acid) (PLA), has been proposed in previous studies. This study investigates the effects of temperature, azodicarbonamide (AZ, foaming agent), boron nitride (BN, filler), and multilayer film/foam coextrusion on the properties of a blend containing an amorphous PHA and PLA. The effect of twin-screw micro-compounder temperature (185 degrees C & 205 degrees C) and BN concentrations of 1, 2, 3, 5, and 10 wt% (185 degrees C) on the properties of the PHA/PLA blend were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. Design of experiments (DoE) was used to find the optimal concentrations of AZ and BN (205 degrees C) using JMP (R) software. The response surface analysis predicted an optimal design based on the target response levels (modulus, tensile strength, strain at break, and toughness). This formulation was prepared and characterized using DSC, TGA, tensile, and melt flow index (MFI) measurements. Finally, this formulation was processed via film/foam coextrusion and examined using scanning electron microscopy (SEM) and density measurements. This study demonstrated that AZ and BN can be used to manipulate the mechanical properties and crystallinity of PHA/PLA blends, while reducing the overall material cost via density reduction (20-21% for the optimal formulation). Furthermore, reducing the concentration of AZ using the I-optimal design in this study could alleviate the toxicity concerns for food packaging.

AbstractPrevious studies have shown that gel‐spun‐ultra‐high‐molecular‐weight polyethylene (UHMWPE) produces thin fibril products that exhibit high tensile moduli (35–200 GPa). The elaborate gel‐spinning process involves complex drawing stages with solvent incorporation. In this study, a previously proposed two‐stage, environmentally friendly solventless methodology was optimized. The two‐stage process included cross‐rolling (Stage 1) and orientation (Stage 2) to obtain oriented HDPE thin rods with an impressively high modulus using conventional HDPE. The optimization of the process was successfully achieved by thoroughly investigating the voiding mechanism. In addition, rapid relaxation during orientation supports the cavitation mechanism. Owing to this optimization, a modulus of 75 GPa was readily attained. The significant enhancement in the mechanical properties was a direct result of the optimization of our processing methodology to achieve a high degree of orientation. Notably, the fabricated oriented HDPE thin rods showed moduli comparable to those of the gel‐spun UHMWPE fibers but were at least 40 times thicker. Our comprehensive characterization of the voiding process and stress relaxation during our two‐stage process indicated the formation of a highly taut network structure and craze‐like configuration with controlled delamination. Thus, our proposed hierarchical model was refined to elucidate the process‐structure‐property relationships in greater detail.Highlights An optimized two‐stage environmentally friendly solventless process has been developed to create oriented polyethylene thin rods with impressively high modulus (75 GPa). The optimization was achieved by thoroughly investigating the voiding effect during cross‐rolling and crystalline relaxation during orientation. Comparison of the modulus from our process are similar to various commercial, gel‐spun fibers. Our thin rod products are at least 40 times thicker than commercial gel‐spun fibers. The thin rod product has impressively high modulus‐to‐weight and strength‐to‐weight ratios for future study in composite systems.

Abstract A novel intumescent fire‐retardant coating formulation has been developed by taking advantage of the inherent stability of large cyclic polyphenols (e.g., tannic acid) to remove the need for a dedicated blowing agent, specifically melamine. Cone calorimetry data indicate a lower fire growth rate (FIGRA) (5.0 ± 1.3 vs. 2.4 ± 0.7 kW m−2 s−1) upon removal of melamine. Total smoke release (TSR) increases following this removal (178 ± 21.4 vs. 305 ± 13.2 m2 m−2), which indicates the role of tannic acid in gas generation. Thermogravimetric analysis resulted in similar residue yield from the examined systems (36 ± 1.3% vs. 34 ± 1.7%) despite removal of a dedicated blowing agent. These results indicate that tannic acids multistep degradation allows it to behave as both a char forming and blowing agent in intumescent systems. The observed reduction of acid loading between the melamine‐tannin system and the melamine‐free composition (15.6% vs. 10.6% wt. ammonium polyphosphate, respectively) is also significant. Tannic acid occurs in agricultural waste products, which is encouraging for the pursuit of sustainable chemistry and addressing potential adverse health effects in humans combined with reducing the overall phosphorous loading. Highlights Melamine was removed from the intumescent without compromising stability. The resulting intumescent char was stronger despite less expansion. Tannic acid is attributed as both the charring and blowing agent. The tannin‐based coating requires a lower acid loading for similar performance.

The use of polymers in the fabrication of bilayers for stimuli-responsive systems is well-known, yet viscoelasticity and viscoelastic models representing bilayer behavior have received surprisingly little attention. Of particular recent interest to us are simple polymeric bilayers in which one material, such as styrene-ethylene-propylene-styrene (SEPS) or styrene-isobutylene-styrene (SIBS), shows typical rubbery elastic response upon extension and retraction, and the other, an unvulcanized, low-Tg polymer such as butyl rubber (butyl), exhibits a viscoelastic response. When such a bilayer strip is extended to a fixed strain and held for several seconds followed by sudden release of this strain, rapid curling is observed, achieving a maximum curvature within 1 second, with a gradual uncurling, typically taking 300-600 seconds to eventually return to a flat strip. Attention has been directed to modeling the observed bilayer behavior. We compare predicted curvature and relaxation time constants from finite element analysis (FEA) simulations using Maxwell, Zener, Generalized Maxwell, and Parallel Rheological Framework (PRF) viscoelastic models to the experimentally measured values. We find that the Generalized Maxwell model predicts curvature over time with the lowest overall mean absolute scaled error (MASE) of 0.519, corresponding to a 4.9% difference from the second lowest error model and a 76.8% difference from the highest error model. Building upon an understanding of the material mechanics in simple bilayer strips, more complex bilayer systems can be designed. Samples of cross and weave geometries were fabricated from bilayer films and initial testing demonstrates how these materials can be used in potential applications.

The all-iron flow battery is currently being developed for grid scale energy storage. As with all flow batteries, the membrane in these systems must meet stringent demands for ionic conductivity while limiting unwanted reactant (Fe3+) crossover. In addition, for the all-iron chemistry proton transport across the membrane is highly desirable to maintain the pH levels in the negative and positive electrolytes. Two membranes are considered, Nafion and an in-house developed composite based on Daramic (a commercial microporous separator) and poly(vinyl alcohol). Their performance is compared for various metrics specific to the all-iron flow battery chemistry.

The effect of thermal treatment on the mechanical performance of biaxially oriented poly(p-phenylene sulfide) by cold roll milling was studied. It was found that the ductility of the cross-rolled material could be further enhanced by annealing at temperatures above Tg and the yield strength could be enhanced by annealing at temperatures below Tg with a partial loss in ductility. Two-dimensional wide-angle X-ray diffraction patterns suggested a reduced crystallinity in the rolled material and showed that the crystal structure of the unrolled material could be partially recovered by annealing above Tg; however, scattering patterns adjacent to the crystalline reflections persisted with heat treatment. Modulated differential scanning calorimetry (MDSC) and broadband dielectric spectroscopy indicated that cross-rolling altered the kinetics of the cold-crystallization process. MDSC and dynamic mechanical analysis measured a reduction in Tg suggesting enhanced molecular mobility as an outcome of cross-rolling. After annealing at temperatures well beyond Tg, a large reduction in elongation to failure was observed, and the material could not cold draw. These results suggest that a two-stage process involving plastic deformation by roll milling followed by annealing treatment may be used to commercially produce high toughness and yield strength sheet products from commercially available resins.

We report a low-temperature inkjet printing and plasma treatment method using silver nitrate ink that allows the fabrication of conductive silver traces on poly(vinyl alcohol) (PVA) film with good fidelity and without degrading the polymer substrate. In doing so, we also identify a critical salt loading in the film that is necessary to prevent the polymer from reacting with the silver nitrate-based ink, which improves the resolution of the silver trace while simultaneously lowering its sheet resistance. Silver lines printed on PVA film using this method have sheet resistances of around 0.2 Ω/□ under wet/dry and stretched/unstretched conditions, while PVA films without prior treatment double in sheet resistance upon wetting or stretching the substrate. This low resistance of printed lines on salt-treated films can be preserved under multiple bending cycles of 0–90° and stretching cycles of 0–6% strain if the polymer is prestretched prior to inkjet printing.

Deformation of polyethylene by bidirectional cold rolling was investigated. The objective was to better understand the evolution of the hierarchical structure with thickness reduction and the effect on mechanical properties. At a 60% thickness reduction, the thickness recovery after rolling peaked, and the density and crystallinity decreased rapidly resulting in greater optical clarity. Tensile specimens were deformed in uniaxial tension, and it was observed that the yield mechanism shifted from necking and whitening to a diffuse yielding process with extent of rolling. Concomitant greater work hardening, fracture stress, and elastic recovery were also observed upon fracture at both 25 degrees C and -40 degrees C. Scanning electron micrographs of the fracture surface revealed discrete buckled microlayers. Furthermore, dynamic mechanical analysis (DMA) revealed the loss tangent peaks associated with the beta and alpha relaxations shifted, suggesting that dilatation rather than compaction was the dominant mode of deformation at 60% thickness reduction.

This study conducted a comprehensive characterization and analyses on the fire-resistant behaviors of novel fungal fibers grown with substrate containing Silica (Si) source at multiple scales. At micro-scale, the results of SEM showed that silica affected the physiological activities of fungi, with the extent of effects depending upon its concentration. Fourier-transform infrared (FTIR) spectra displayed the existence of Si–O–C chemical bonds in fungal fibers grown with Si source, indicating that Si source becomes a part of the structure of fungal fibers. Thermogravimetric analysis (TGA) and Microscale combustion calorimetry (MCC) of fungal fibers exhibit an early thermal decomposition of non-combustible components, which will potentially help release the thermal stress and mitigation of spalling when used in concrete. Compared with polypropylene (PP) fibers, fungal fibers have a lower thermal degradation rate, a higher residual weight, a lower heat release peak temperature, and less total heat of combustion; all of these indicate improved thermal stability and fire resistance, and a lower rate of function loss in case of a fire. Additionally, the thermal stability and fire resistance of fungal fibers were improved with the increase of Si source concentration in the nutrition medium. For example, addition of 2% Si source in the feeding substrate leads to a 23.21% increase in residual weight in TGA, and a 23.66 W/g decrease in peak heat release rate as well as a 2.44 kJ/g reduction in total heat of combustion in MCC. At laboratory scale, compared with PP fibers, fungal fibers grown with 2% Si source have a higher residual weight of 40.40%, a higher ignition temperature of 200.50 °C, and a declined flame height of 11.64 mm in real fire scenarios. Furthermore, only in the fungal fibers grown with Si source, partial burning occurred. In post-fire conditions, the microstructure of residual char from fungal fibers grown with higher content of Si source became denser, which would lead to a reduction of the fuel vapor release and heat transfer. FTIR spectra of residual char demonstrated that fungal fibers grown with Si source formed more stable chemical bonds with higher heat of chemical bond formation, contributing to improved thermal stability and fire resistance. Therefore, compared with traditional fibers used for fiber reinforced concrete, incorporating the new natural grown fibers will potentially further improve the fire resistance of concrete and mitigate the concrete spalling.

In this study, we propose a novel two-stage solid-state processing technique to fabricate thin-oriented high-density polyethylene (HDPE) rods with enhanced mechanical properties. This unique solvent-free technology involves biaxial rolling (Stage 1) followed by a uniaxial orientation procedure (Stage 2). The oriented thin HDPE rods exhibit an impressive modulus of 37 GPa. This is a result of a complex, oriented composite structure containing crazes with a network of interlocking fibers. Surprisingly, the high-modulus thin rods were created under relative low uniaxial tensile orientation conditions having draw ratio of eleven. Gel-spun ultra-high-molecular-weight fiber processing requires orientations greater than thirty. A corresponding scaled hierarchical model was proposed to summarize the process-structure-property relationships. This study demonstrates a strategy for creating high-modulus polymeric materials via controlled solid-state processing.

Abstract Production of biopolymer for packaging applications is still a burgeoning demand with the rising environmental concern about pollution due to non‐degradable plastic waste materials. This paper introduces a novel approach, yet a continuous production method, to produce PLA multilayer film/foams structures having 16, 32, and 64 alternating layers which were developed by multilayer coextrusion technique, and the morphology, density, mechanical properties and oxygen transmission of the as‐extruded film/foams were characterized. The lightweight multilayered PLA film/foam has a unique solid/porous alternating horizontal architecture, in which the film layers can effectively control the growth of the cells and suppress the premature rupture of cells during coextrusion process. Tensile properties at elevated temperatures of the PLA film/foam were used to optimize thermoforming conditions. The effects of annealing temperature and time on the crystallinity and oxygen permeability of PLA multilayer film/foams were investigated. Oxygen transmission showed a strong correlation with the crystallinity of PLA multilayer film/foam. The material with 32 layers 50/50 film/foam achieved extremely high barrier after 30 min annealing, which is 35 times better than the control.

Electrical excitability of cells, tissues and organs is a fundamental phenomenon in biology and physiology. Signatures of excitability include transient currents resulting from a constant or varying voltage gradient across compartments. Interestingly, such signatures can be observed with non-biologically-derived, macromolecular systems. Initial key literature, dating to roughly the late 1960's into the early 1990's, is reviewed here. We suggest that excitability in response to electrical stimulation is a material phenomenon that is exploited by living organisms, but that is not exclusive to living systems. Furthermore, given the ubiquity of biological hydrogels, we also speculate that excitability in protocells of primordial organisms might have shared some of the same molecular mechanisms seen in non-biological macromolecular systems, and that vestigial traces of such mechanisms may still play important roles in modern organisms' biological hydrogels. Finally, we also speculate that bio-mimicking excitability of synthetic macromolecular systems might have practical biomedical applications.