Strong Mechanical Properties Research Articles

A multifunctional sensor for real-time monitoring and pro-healing of frostbite wounds

Flexible epidermal sensors based on conductive hydrogels hold great promise for various applications, such as wearable electronics and personal healthcare monitoring. However, the integration of conductive hydrogel epidermal sensors into multiple applications remains challenging. In this study, a multifunctional PAAm/PEG/hydrolyzed keratin (Hereinafter referred to as HK)/MXene conductive hydrogel (PPHM hydrogel) was designed as a high-performance therapeutic all-in-one epidermal sensor. This sensor not only accelerates wound healing but also provides wearable human-computer interaction. The developed sensor possesses highly sensitive sensing properties (Gauge Factor = 4.82 at high strain), strong mechanical tensile properties (capable of achieving a maximum elongation at break of 600 %), rapid self-healing capability, stable self-adhesive capability, biocompatibility, freeze resistance at −20 °C, and adjustable photo-thermal conversion capability. This therapeutic all-in-one sensor can sensitively monitor human movements, enabling the detection of small electrophysiological signals for diagnosing relevant activities and diseases. Furthermore, using a rat frostbite model, we demonstrated that the composite hydrogel sensor can serve as an effective wound dressing to accelerate the healing process. This study serves as a valuable reference for the development of multifunctional flexible epidermal sensors for personal smart health monitoring. Statement of significanceAccelerated wound healing reduces the risk of wound infection, and conductive hydrogel-based sensors can monitor physiological signals. The multifunctional application of conductive hydrogel sensors combined with wound diagnostic and therapeutic capabilities can meet personalized medical requirements for wound healing and sensor monitoring. The aim of this study is to develop a multifunctional hydrogel patch. The multifunctional hydrogel can be assembled into a flexible wearable high-performance diagnostic and therapeutic integrated sensor that can effectively accelerate the healing of frostbite wounds and satisfy the real-time monitoring of multi-application scenarios. We expect that this study will inform efforts to integrate wound therapy and sensor monitoring.

Thermally stable 3D cross-linked fluorinated polyimide/PVDF-HFP hybrid separator for lithium battery applications

Commercial Celgard 2325 separators suffer from poor flexibility, poor electrolyte wettability, and thermal instability, which can cause internal short circuits and thermal runaway in lithium rechargeable batteries. A novel 3D cross-linked and thermotolerant fluorinated polyimide (PI) / PVDF-HFP (PV) hybrid nanofiber separator rich in polar functional groups was fabricated using an electrospinning technique. PI and PV polymers are joined by a hydrogen bond through their exposed amide (–NH) and fluorinated (-CF) functional groups to build a supramolecular polymer cross-linked system. The separator exhibited high porosity (75 %), outstanding electrolyte uptake ability (775 %), strong mechanical properties (15.7 MPa), excellent thermal stability, and flexibility. As a result, the separator showed excellent Li+-conductivity (3.3 mS cm−1) and high Li+-transference number (tLi+ = 0.7) and maintained a proper-contacted electrolyte/electrode interaction for stable Li plating/stripping. Furthermore, when the PI/PV hybrid separator was applied in anode-free Li-metal batteries (a protocol of Cu/NMC cell), or Li-ion (MCMB /NMC) batteries, the cells achieved a high capacity and long lifetime. Remarkably, the Cu/NMC cell fabricated with a PI/PV hybrid separator is more robust and continues to function even after being heated at a high temperature of 140 °C for 1 h.

A strategy for synthesis of silane terminated polyether triggered by click reaction and its application in preparation of modified silane sealants

A new hydroxy-silane coupling agent was synthesized from 3-butene-1-alcohol and mercaptopropyl-3-methoxysilane based on a click reaction between double bonds and sulfhydryl groups and was successfully used in the synthesis of silane-modified polyether (STPE). The effect of molecular weight of polypropylene glycol (PPG) on the properties of silane-modified polyether was studied. It was found that with the increase in PPG molecular weight, the initial thermal decomposition temperature and hardness of STPE elastomers decreased, but the molecular structure hardly changed. In addition, with the increase in molecular weight, the elongation at break of the elastomer will gradually increase, but the tensile strength of the elastomer does not change much. When the molecular weight reaches 20 000 g/mol, the resin with a viscosity of 1.6 × 105 mPa s can be obtained, and the elongation at break of the cured elastomer reaches 383.4% and the tensile strength is 0.25 MPa. After the STPE resin was prepared into a silane modified sealant, the tensile strength reached 1.31 MPa and the elongation at break reached 406.2%, which had the best mechanical properties among the prepared sealants. This shows that the sealant prepared from high molecular weight resin has stronger mechanical properties, which provides a new idea for the preparation of sealants.

Multifunctional carbon dots reinforced gelatin-based coating film for strawberry preservation

The development of safe, non-toxic, multifunctional nano preserved materials with excellent performance has become a hot research topic. Multifunctional Sophora Japonica extract (95% rutin)-derived carbon dots (R-CDs) were prepared by hydrothermal method. The π-π conjugation structure of R-CDs enabled them UV broadband absorption properties. The excellent antioxidant properties of R-CDs were attributed to the presence of the sp2 carbon in core and a large number of hydroxyl groups at the edges, and their degradation rate of potassium permanganate and scavenging activity of superoxide anion radical were better than that of ascorbic acid. The presence of CO bond may be the site for the generation of reactive oxygen species (ROS) and thus they could kill Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis) and Listeria monocytogenes (L. monocytogenes) at a concentration of 2 mg/mL and inhibited the growth of fungi (Botrytis cinerea). Then R-CDs were uniformly dispersed in gelatin-based solution, and the as-prepared films had smooth surface, good hydrophilicity, strong mechanical properties and good biocompatibility. With the increase of R-CDs addition, the tensile strength increased and then decreased, and the elongation at break rose to 358%. The film inherited the broadband UV absorption, antioxidant and antibacterial properties of R-CDs. The storage period of strawberries was prolonged after coating. The variety and abundance of microorganisms on the surface of strawberries was reduced and the growth of harmful bacteria was inhibited. This work provides more possibilities for the application of nanomaterials in fruit preservation.

Guar Gum-based multifunctional hydrogels with high sensitivity and negligible hysteresis for wearable electronics

As a classic flexible material, hydrogel shows great potential in wearable electronics. However, it remains a challenge to prepare hydrogels that simultaneously have robust toughness, strong mechanical properties, high conductivity, fit to human skin, and strain sensitivity. In this work, oxidized guar gum (OGG) and acrylamide (AM) were used to create a novel hydrogel that is highly strain-sensitive. The hydrogel reveals a skin-like elastic modulus (∼ 29 kPa), high toughness (732.3 kJ·m−3), high breaking elongation (1060%), high adhesion, high self-healing efficiency (96%), and negligible lag (η = 3.9%, energy loss coefficient). Meanwhile, it has good biocompatibility and outstanding antimicrobial qualities. In addition, the introduction of iron ions may increase the conductivity (1.1 S·m−1) while maintaining high transparency, and the gel-based sensor exhibits high sensitivity (GF=11.82). The highly sensitive sensors exhibit very fast response time (55–60 ms) and adequate stability (2000 cycles). Interestingly, hydrogel sensors can monitor a variety of human movements, including large-scale joint bending and tiny facial expressions, gesture recognition and handwriting. In addition, it has been successfully used to transmit encrypted information, human-machine interaction and wireless sensing.

Bio-Waste Argan Nut Shell-Derived Porous Activated Carbon for High Performance Supercapacitor Electrode Material

The supercapacitors (SCs) have become a great candidate for high power applications in energy storage units which bridge the gap between conventional capacitors and batteries fuels cells. This is because of their relatively higher specific energy compared to normal parallel plate capacitors, and higher power density and longer cycling stability, fast charge–discharge time, low level of heating, appropriate dimension/weight and low cost. The Carbon materials are considered as ideal electrode materials for supercapacitors, they play an important role in energy storage devices due to their large specific surface area, tunable pore size, high electrical conductivity and strong mechanical property, nevertheless most of the commercial activated carbons are produced from fossil fuel-based precursor (petroleum and coal) which made them to be expensive and environmentally non-friendly. hence the increasing focus on biomass precursors which are cheaper, readily available, renewable, structurally porous and environmentally friendly. Agriculture production and agro-industrial processes generate a large amount of waste. That can potentially be used to obtain important functional materials. Thus, it is possible to prepare activated carbon with high specific surface from various type of biomass. Taking all this into account, our work has focused on the use of Argan residues, very abundant in Morocco, for the production of activated carbons with developed porosity. The resulting material was evaluated as electrode material for the supercapacitor, Valuable strategies are the use of aqueous electrolytes and activated carbon that enable the valorization of wastes in a circular economy approach.The Argan residues (ANS, Argan Nut Shell) were ground to obtain a particle size of 1-3 mm The ACs were prepared by chemical activation with KOH in two steps: carbonization of the precursor followed by activation of the biochar. In the two-stage process, carbonization was carried out at 500 °C and in all cases, KOH is used in lentils. The following process variables were studied: activation temperature (700, 800 and 850 °C) and KOH/AS ratio (3/1 and 4/1). After the heat treatment, the samples were washed with 5 M HCl solution until neutral pH and dried (110 °C, 12 h). Activated carbons were characterized by N2 -196 °C and CO2 adsorption at 0 °C, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).The symmetric SC was assembled with the two identical electrodes (positive/negative) by sandwiching a filter paper as a separator (Whatman). Then, few drops of aqueous 1M H2SO4 dropped in between the electrodes. The electrochemical techniques used were Cyclic voltammetry and galvanostatic charge/discharge cycling. Cyclic voltammetry (CV) was scanned from 5 to 80 mV/s. Galvanostatic charge−discharge experiment was performed with a specific current from 0.125 to 12A.g-1. The study showed that the new mechanism used to produce the activated carbon from Argan Nut shell lead to high surface area. The optimum activated carbon obtained by operating carbonization temperature as 500°C and activation temperature at 800°C with KOH activation, with these conditions the results were (SBET =3091 m2.g-1, VT=1.52 cm3.g-1), In contrast, the symmetric two electrode system exhibits outstanding charge storage capacity, reaching a high specific capacitance ranging between 512-320 F.g−1 at 0.125 A g−1. Remarkable electrochemical performance is further demonstrated using Argan Nut Shell, with an excellent rate performance after 2500 cycles, the capacitance still remained at 92 %, indicating great cycle stability.This study demonstrated the interesting nature of Argan Nut shell to develop cost effective electrode materials for supercapacitors with high performance. To conclude, high surface area and porosity of the prepared ACs can serve as a flexible backbone for constructing wearable energy storage devices. Clearly, using biomasses are definitely the right track towards making renewable carbon materials and energy storage. Figure 1

Plasma Modification of Interfaces in Ceramic Nanofiber–Polymer Electrolytes for Lithium Metal Batteries

Ceramic–polymer composite electrolytes hold a great promise as next-generation electrolytes because of strong mechanical properties and wide electrochemical stability window. However, it remains challenges in improving ionic conductivity and lithium ion transference numbers. In this work, plasma treatment has been performed on Li0.33La0.557Ti0.995Al0.005O3 (LLATO) nanofibers. The treated nanofibers are then incorporated with a polymer matrix to form a composite electrolyte. Plasma treatment has modulated oxygen vacancies, functional groups, polarity, and interfacial interaction of LLATO-polymer. This has improved lithium ion transport at interface of LLATO-polymer electrolyte. As a result, the LLATO-polymer electrolyte shows enhanced ionic conductivity and mechanical performance. This work has implication in design of ceramic-polymer composite electrolytes for solid state lithium metal batteries.

Strong Bioactive Glass-Based Hybrid Implants with Good Biomineralization Activity Used to Reduce Formation Duration and Improve Biomechanics of Bone Regeneration.

Developing bioactive implants with strong mechanical properties and biomineralization activity is critical in bone repair. In this work, modified cellulose nanofiber (mCNF)-reinforced bioactive glass (BG)-polycaprolactone (PCL) hybrids (mCNF-BP) with strong biomechanics and good apatite formation ability were reported. Incorporating mCNFs shortens the forming duration of the hybrid films and enhances the biomechanical performance and in vitro apatite-formation capability. The optimized biomechanical performance of the optimal hybrid materials is produced at a relatively high mCNF content (1.0 wt%), including a considerably higher modulus of elasticity (948.65 ± 74.06 MPa). In addition, the biomineralization activity of mCNF-BP hybrids is also tailored with the increase in the mCNF contents. The mCNF-BP with 1.5 wt% and 2.0 wt% mCNFs demonstrate the best biomineralization activity after immersing in simulated body fluid for 3 days. This study suggests that mCNFs are efficient bioactive additive to reinforce BG-based hybrids' mechanical properties and biomineralization activity.

A Novel Methacryloyl Chitosan Hydrogel Microneedles Patch with Sustainable Drug Release Property for Effective Treatment of Psoriasis.

Psoriasis is a chronic and recurrent skin disease that often requires long-term treatment, and topical transdermal drug delivery can reduce systemic side effects. However, it is still a challenge in efficient transdermal drug delivery for psoriasis treatment due to low penetration efficiency of most drugs and the abnormal skin conditions of psoriasis patients. Here, a safe and effective methacryloyl chitosan hydrogel microneedles (CSMA hMNs) patch is developed and served as a sustained drug release platform for the treatment of psoriasis. By systematically optimizing the CSMA preparation, CSMA hMNs with excellent morphological characteristics and strong mechanical properties (0.7 Nneedle-1 ) are prepared with a concentration of only 3% (w/v) CSMA. As a proof-of-concept, methotrexate (MTX) and nicotinamide (NIC) are loaded into CSMA hMNs patch, which can produce a sustained drug release of 80% within 24h in vitro. In vivo experiments demonstrated that the CSMA hMNs patch can effectively inhibit the skin thickening and spleen enlargement of psoriatic mice and has a good biosafety profile at sufficient therapeutic doses. This study provides a new idea for the preparation of hMN systems using modified CS or other biocompatible materials and offers an effective therapeutic option for psoriasis treatment. This article is protected by copyright. All rights reserved.

A critical review of recent advances in the aerospace materials

The pursuit for improved performance in the aerospace and aviation industries has inspired the development, investigation, and research of advanced materials. Since the last few years, a lot of research on different alloys, composites and some other advanced materials has been performed to perfectly meet the needs of the aerospace field such as basic frames of aircraft, fuselages, engine parts, wings etc. Various aluminium, magnesium, titanium, and nickel-based alloys have been developed with certain advantages like strength-to-weight ratio, corrosion resistance, wear resistance etc. However, there are major challenges to aerospace materials such as insufficient mechanical and chemical properties, overall weight of aircraft, fretting wear, stress corrosion cracking, incapability at high temperatures, and low oxidation resistance. Therefore, vast studies have been conducted for the development of next-generation aerospace materials. In the present article, attention has been made to study the contemporary materials, current research going on and future trends on advanced materials in the field of aerospace engineering. Aluminium-based alloys are found as the most widely used metal alloys in the aerospace sector for their strong mechanical properties. However, polymer matrix composites and metal matrix composites have gained popularity due to their exceptional strength and stiffness. Titanium-based alloys are favoured for their strength and corrosion resistance, leading to increased adoption.

Preparation of lignin-based personal multifunctional protective mask interlayer with antibacterial, anti-UV and iodine trapping effects and exploration of its iodine trapping mechanism

Personal multifunctional protective mask is becoming an effective and convenient device for maintaining human health. When used in a normal environment, it can prevent the spread of respiratory viruses and bacteria, and absorb UV rays. When used in extreme environments full of iodine vapor, it can effectively absorb iodine vapor. Herein, an eco-friendly multifunctional nanofiber membrane with rapid sterilization ability, ultraviolet absorption and iodine vapor trapping capacity was prepared using lignin and polyvinylpyrrolidone as raw materials through electrostatic spinning technology. The results showed that PVP-WSL and PVP-IL have bactericidal rates of 21.86% and 34.08% for E. coli, 30.27% and 52.64% for S. aureus, respectively. These mask barriers have good UV resistance performance (the UV transmittance was lower than 0.015%) and effective trapping capacity of iodine vapor (the iodine maximum trapping capacity of the PVP-WSL and PVP-IL nanofiber membranes were equally determined to be 294 mg/g and 225 mg/g, respectively). In addition, these membranes have strong thermal stability (initial thermal decomposition temperature was higher than 350 °C) and mechanical properties (tensile strength higher than 1.07 MPa). This work fully meets the requirements of public health protection for degradable and high-performance media and is ideal for multifunctional personal protective equipment.

Delignified wood biocomposites as sustainable and transparent materials for passive cooling applications

ABSTRACT Wood possesses unique structural and functional properties that make it a promising material for the development of windows. In this study, the potential use of wood biocomposites as a window materials was explored by delignification of local Indonesian woods, such as mahogany (Swietenia macrophylla), sungkai (Peronema canescens), mindi (Melia azedarach), and maple (Acer laurinum), using NaOH and H2O2 followed by epoxy resin impregnation. Macroscopic observations, optical transmittance (τ), tensile and bending strength tests were performed to evaluate their optical and mechanical properties. An infrared exposure simulation was also conducted to assess the material passive cooling capabilities in a room model. The results revealed that mahogany and maple had the highest τ values (86.03% and 81.43%, respectively). Transparent mahogany wood exhibited haze due to optical scattering but showed strong mechanical properties with an ultimate tensile strength (UTS) of 78.83 MPa and a strain (ϵ) of 2.67%. Transparent maple wood had UTS of 84.67 MPa and ϵ of 2.32%. The use of transparent mahogany and maple in room model reduced the temperature difference between indoor and outdoor environments by up to 11.5°C and 10.5°C, respectively, which suggests that transparent wood can be used as a window material for sustainable passive cooling applications.

Multifunctional Flexible Sensor Based on PU-TA@MXene Janus Architecture for Selective Direction Recognition.

Multifunctional selectivity and mechanical properties are always a focus of attention in the field of flexible sensors. In particular, the construction of biomimetic architecture for sensing materials can endow the fabricated sensors with intrinsic response features and extra-derived functions. Here, inspired by the asymmetric structural features of human skin, a novel tannic acid (TA)-modified MXene-polyurethane film with a bionic Janus architecture is proposed, which is prepared by gravity-driven self-assembly for the gradient dispersion of 2D TA@MXene nanosheets into a PU network. This obtained film reveals strong mechanical properties of a superior elongation at a break of 2056.67% and an ultimate tensile strength of 50.78MPa with self-healing performance. Moreover, the Janus architecture can lead to a selective multifunctional response of flexible sensors to directional bending, pressure, and stretching. Combined with a machine learning module, the sensor is endowed with high recognition rates for force detection (96.1%). Meanwhile, direction identification in rescue operations and human movement monitoring can be realized by this sensor. This work offers essential research value and practical significance for the material structures, mechanical properties, and application platforms of flexible sensors.

Protein-Stabilized Emulsion Gels with Improved Emulsifying and Gelling Properties for the Delivery of Bioactive Ingredients: A Review.

In today's food industry, the potential of bioactive compounds in preventing many chronic diseases has garnered significant attention. Many delivery systems have been developed to encapsulate these unstable bioactive compounds. Emulsion gels, as colloidal soft-solid materials, with their unique three-dimensional network structure and strong mechanical properties, are believed to provide excellent protection for bioactive substances. In the context of constructing carriers for bioactive materials, proteins are frequently employed as emulsifiers or gelling agents in emulsions or protein gels. However, in emulsion gels, when protein is used as an emulsifier to stabilize the oil/water interface, the gelling properties of proteins can also have a great influence on the functionality of the emulsion gels. Therefore, this paper aims to focus on the role of proteins' emulsifying and gelling properties in emulsion gels, providing a comprehensive review of the formation and modification of protein-based emulsion gels to build high-quality emulsion gel systems, thereby improving the stability and bioavailability of embedded bioactive substances.

Fabrication of recyclable high-barrier water- and oil-proof paper by sodium alginate/cellulose nanofiber/ethyl cellulose/ polyvinyl butyral

Paper-based packaging materials have seen explosive growth in recent years as consumers become more aware of the environmental and health hazards created by traditional food packaging materials. Even yet, there is a significant opportunity for improvement in the production of fluorine-free, water- and oil-proof, recyclable food packaging papers made from ecologically friendly polymers. In this study, we used sodium alginate (SA), cellulose nanofibers (CNF), ethyl cellulose (EC), and polyvinyl butyral (PVB) to create coatings that are impervious to water and oil. The paper was first impregnated with CaCl2 solution before SA and CNF were evenly mixed and applied to the paper. Ca2+ ion cross-linking strengthened the connection between the SA/CNF coating and the paper, which increased its oil-proof properties. The hydrogen bonding force in EC/PVB solution enhanced the water-proof performance and mechanical qualities of the paper. Finally, the water- and oil-proof paper showed excellent water repellency (Cobb value: 1.1 g/m2), oil repellency (kit rating: 12/12), low air permeability (0.2 µm/Pa·s), and stronger mechanical properties (4.21 kN/m). There is a great need for this fluorine-free, biodegradable, and recyclable paper-based material in the food packaging market due to its excellent barrier qualities.

Temperature-Mediated Phase Separation Enables Strong yet Reversible Mechanical and Adhesive Hydrogels.

Hydrogels with strong yet reversible mechanical and adhesive properties fabricated in a facile and friendly manner are important for engineering and intelligent electronics applications but are challenging to create and control. Existing approaches for preparing hydrogels involve complicated pretreatments and produce hydrogels that suffer from limited skin applicability. Copolymerized hydrogels are expected to present an intriguing target in this field by means of thermoresponsive features, while the perceived intrinsic flaws of brittleness, easy fracture, and weak adhesion enervate the development prospects. Herein, we report a hydrogel with strong yet reversible mechanical and adhesive properties using cellulose nanofibrils to simultaneously address multiple dilemmas inspired by a temperature-mediated phase separation strategy. This strategy applies temperature-driven formation and dissociation of hydrogen bonds between common copolymers and cellulose nanofibrils to trigger the onset and termination of phase separation for dynamically reversible on-demand properties. The resulting hydrogel exhibits up to 96.0% (117.2 J/m2 vs 4.8 J/m2 for interfacial toughness) and 85.7% (0.02 MPa vs 0.14 MPa for mechanical stiffness) adhesive and mechanical tunability when worked on skin, respectively. Our strategy offers a promising, simple, and efficient way to directly achieve robust adhesion performance in one step using common copolymers and biomass resources, with implications that could go beyond strong yet adhesive hydrogels.

A highly strong PEDOT modified wood towards efficient electromagnetic interference shielding

In the development of the modern electronics industry, the high mechanical performance, the green, and high-performance electromagnetic interference (EMI) shielding materials need to urgently be developed. Herein, polythiophene/Wood (PEDOT/wood) was fabricated through in situ polymerizing thiophene in the delignified paulownia wood. The results indicated that PEDOT were evenly distributed on the carbohydrates framework of the wood, endowing the composite with a highly electrical conductivity of 112.8 S m−1 and a superior electromagnetic shielding effectiveness of 46.2 dB at 2 mm thickness. The normalized SE (EMI SE/thickness) of the composite calculated as 213 dB/cm. Meanwhile, a high compressive strength and tensile strength of the prepared PEDOT/wood composite were tested as 50.9 MPa and 67.8 MPa, respectively. Such a high conductivity, strong mechanical properties and renewable PEDOT/wood suggests it as a potential candidate for the application in electromagnetic interference shielding and paves a new way for the biomass-based electromagnetic shielding materials.

Polyvinyl alcohol flame retardant film based on halloysite nanotubes, chitosan and phytic acid with strong mechanical and anti-ultraviolet properties

The research of additive biomass flame retardants is becoming more and more popular. In this work, amino modified halloysite nanotubes (A-HNTs), chitosan (CS) and phytic acid (PA) were introduced into polyvinyl alcohol (PVA) matrix to construct PA/A-HNT/CS/PVA organic-inorganic composite film with hydrogen bond and covalent bond cross-linking network structure. Adding PA/A-HNT/CS can remarkably improve the mechanical strength, UV resistance and thermal stability of PVA film. Compared with control PVA film, the transmittance of composite film in ultraviolet region decreases from 90 % to <15 %, and the tensile strength raises from 19.8 MPa to 31.0 MPa. The thermal decomposition temperature of the composite film increases, the weight loss rate decreases obviously, and the carbon residue can reach 26 wt% at 700 °C. The limiting oxygen index increases from 18.5 % to 32.2 %. Furthermore, the addition of this flame-retardant system can obviously reduce the combustion intensity of PVA, and its flame-retardant grade can reach V-0. It is of great significance to expand the application of PVA and the development of biomass flame retardant.

Low-temperature self-healing polyurethane adhesives via dual synergetic crosslinking strategy

Abstract Damage to polymer adhesives is one of the most common reasons for structural integrity damage of composite solid propellants. The introduction of self-repairing technology into the adhesive is expected to solve this problem. However, at low temperatures, the self-repairing and mechanical properties of the materials are greatly impaired, thereby limiting the application of self-repairing adhesives in composite solid propellants. In this study, based on the dual synergistic crosslinking strategy, a polyurethane adhesive exhibiting excellent self-healing and mechanical properties at low temperatures was successfully prepared. The adhesive exhibited high self-repairing efficiency and ultra-long elongation at break at low temperatures. Specifically, at a low temperature of −40°C, the self-repair efficiency was over 70% and the elongation at break was over 1,400%, which were much higher than the results of the control group. Moreover, the strength was comparable to that of the control group. This polyurethane adhesive shows excellent self-healing and mechanical properties at low temperatures and is expected to provide the strong self-healing ability and mechanical properties for composite solid propellants, alleviating the problem of structural integrity damage.

Tough and strong sustainable thermoplastic elastomers nanocomposite with self-assembly of SI-ATRP modified cellulose nanofibers

The ingenious design of sustainable thermoplastic elastomers (STPEs) is of great significance for the goal of the sustainable development. However, the preparation of STPEs with good mechanical performance is still complicated and challenging. Herein, to achieve a simple preparation of STPEs with strong mechanical properties, two biobased monomers (tetrahydrofurfuryl methacrylate (THFMA) and lauryl methacrylate (LMA)) were copolymerized into poly (THFMA-co-LMA) (PTL) and grafted onto TEMPO oxidized cellulose nanofiber (TOCN) via one-pot surface-initiated atom transfer radical polymerization (SI ATRP). The grafting modified TOCN could be self-assembled into nano-enhanced phases in STPEs, which are conducive to the double enhancement of the strength and toughness of the STPEs, and the size of nano-enhanced phases is mainly affected by TOCN fiber length and molecular weight of grafting chains. Especially, with the addition of 7 wt% TOCN, tensile strength, tensile strain, toughness, and glass transition temperature (Tg) of TOCN based STPEs (TOCN@PTL) exhibited 140 %, 36 %, 215 %, and 6.8 °C increase respectively, which confirmed the leading level in the field of bio-based elastomers. In general, this work constitutes a proof for the chemical modification and self-assembly behavior of TOCN by one-pot SI ATRP, and provides an alternative strategy for the preparation of high-performance STPEs.