Weak Interfacial Interaction Research Articles

Constructing polymer/metal-organic framework nanohybrids to design compatible polymer-filler-polymer membranes for CO2 separation

Membrane technology is energy-saving and environmentally friendly for gas separation. Mixed matrix membranes containing filler-polymer two components and adjusted transport pathways are promising for carbon capture. However, weak filler-polymer interfacial interaction and filler agglomeration usually cause defect formation and performance deterioration. In this study, we report a concept of polymer-filler-polymer membranes for efficient CO2 separation, highlighted by polymer of intrinsic microporosity (PIM)-metal-organic framework (MOF)-PIM combination. Key point is that the membrane systems consist of polymer matrices, MOFs as fillers for membranes and as hosts for inserted polymers, and polymer guests in MOFs. With partial functionalization of PIM to generate linker-analogous segments and retain unmodified sections, the PIM derivative chains can be uniformly coordinated in MOF nanohybrids and service as interfacial binders to enhance filler-polymer compatibility and filler dispersibility. Meanwhile, the PIM incorporation can regulate the morphologies and inner channels of MOF nanohybrids. For CO2/N2 separation, the polymer-filler-polymer membranes exhibit substantially improved permeability of 9532 Barrer, selectivity of 63.2, and antiaging property. We envisage that this concept reported here provides an alternative route to design compatible and high-performance membranes and other composites for separations and other applications.

Ion transport, mechanical properties and relaxation dynamics in structural battery electrolytes consisting of an imidazolium protic ionic liquid confined into a methacrylate polymer

The effect of confining a liquid electrolyte into a polymer matrix was studied by means of Raman spectroscopy, differential scanning calorimetry, temperature-modulated differential scanning calorimetry, dielectric spectroscopy, and rheology. The polymer matrix was obtained from thermal curing ethoxylated bisphenol A dimethacrylate while the liquid electrolyte consisted of a protic ionic liquid based on the ethyl-imidazolium cation [C2HIm] and the bis(trifluoromethanesulfonyl)imide [TFSI] anion, doped with LiTFSI salt. We report that the confined liquid phase exhibits the following characteristics: (i) a distinctly reduced degree of crystallinity; (ii) a broader distribution of relaxation times; (iii) reduced dielectric strength; (iv) a reduced cooperativity length scale at the liquid-to-glass transition temperature (T g); and (v) up-speeded local T g-related ion dynamics. The latter is indicative of weak interfacial interactions between the two nanophases and a strong geometrical confinement effect, which dictates both the ion dynamics and the coupled structural relaxation, hence lowering Tg by about 4 K. We also find that at room temperature, the ionic conductivity of the structural electrolyte achieves a value of 0.13 mS/cm, one decade lower than the corresponding bulk electrolyte. Three mobile ions (Im+, TFSI-, and Li+) contribute to the measured ionic conductivity, implicitly reducing the Li+ transference number. In addition, we report that the investigated solid polymer electrolytes exhibit the shear modulus needed for transferring the mechanical load to the carbon fibers in a structural battery. Based on these findings, we conclude that optimized microphase-separated polymer electrolytes, including a protic ionic liquid, are promising for the development of novel multifunctional electrolytes for use in future structural batteries.

Tailoring flower-like Zn(OH)2 nanoarchitectures and stearic acid on cellulosic fibers for structurally robust superhydrophobic surface

Structurally robust nanostructures on the surface of matrix highly determine the durability of superhydrophobic surface of cellulosic materials. Traditionally, the hydrophobic inorganic-organic nanocomposites were physically coated on the surface of cellulose fibers, whereas the nanocomposite was easy to fall off under external force due to the weak interfacial interaction between inorganic materials and cellulose, restricting their practical application. In this work, a sort of structurally stable superhydrophobic cellulosic materials was elaborately designed by successive in situ synthesis of Zn(OH)2 nanoarchitectures and coating stearic acid (STA). The unique flower-like micro/nano structures as well as the presence of hydrophobic STA imparted the cellulosic materials with superhydrophobic behavior and the optimized water contact angle of synthesized STA@Zn(OH)2/paper nanocomposite was enhanced to 171°. Moreover, the resultant cellulosic nanocomposite also possesses excellent structural stability without STA and Zn(OH)2 fall off as well as hydrophobicity reduction after bending 100 times. Compared to bare filter paper, both tensile stress and elongation at break of optimized flower-like nanocomposite reached 14.04 MPa and 25.24% with 109.6% and 323.5% improvement, respectively. Furthermore, such superhydrophobic cellulose-based material also presented excellent anti-fouling and antibacterial performances. This work proposed a facial and efficient strategy to construct structurally stable superhydrophobic cellulose-based materials, displaying great potential application in food packaging and outdoor anti-fouling fields.

Curing kinetics and mechanical properties of magnetocured epoxy adhesive doped with magnetic nanoparticles

AbstractThe curing kinetics as well as the corresponding tensile properties of magnetocured epoxy adhesive doped with magnetic nanoparticles (MNPs) is investigated in this article, where the curing reaction process is depicted using an isoconversional model. It is found that the tensile modulus and strength strongly depend on the curing degree (CD) and mass fraction of MNPs when curing degree varies from 0.7 to 1.0. When curing degree is 0.7, the tensile modulus of the adhesive with 15%wt and 30%wt MNPs increases by 46% and 592% compared to that with 10%wt MNPs, respectively, but the increase is not obvious when curing degree is higher than 0.9. This difference is more significant in the tested tensile strength, where the samples with 15%wt and 30%wt MNPs are 7.08 and 20.83 times higher than the one with 10%wt MNPs under 0.7 curing degree. However, the corresponding tensile strength with 1.0 curing degree is reduced by 4% and 35%, respectively. Scanning electron microscopy observation reveals different fracture mechanisms caused by curing degree variation. Failure occurs in the adhesive region for curing degree below 0.9, while failure initiates and propagates at the interface between adhesive and MNPs for curing degree above 0.9. It can be concluded that the intrinsic property of the adhesive determines the tensile properties when the curing degree is lower than 0.9, while the weak interfacial interaction between adhesive and MNPs introduces reverse effect when the curing degree is higher than 0.9. This competitive relationship should be considered in the design of magnetocuring process.Highlights Enhancement in adhesive modulus from MNPs addition degrades as CD approaches 1. Intrinsic property of adhesive determines the tensile strength with CD < 0.9. Weak interface dominates the failure mechanism in adhesive with CD > 0.9.

Tailoring the interfacial interaction of collagen fiber/waterborne polyurethane composite via plant polyphenol for mechanically robust and breathable wearable substrate

Collagen fiber-waterborne polyurethane composites possess great potential applications in flexible wearable devices owing to their excellent biocompatibility, flexibility, and biodegradability. However, the weak interfacial interactions which result in poor mechanical strength and breathability, have significantly hindered their practical application. Herein, high-performance collagen fiber-based wearable substrates prepares by constructing a hydrogen-bonded cross-linked network structure using bayberry tannin, a natural plant polyphenol, as a coupling bridge to bind collagen fibers and waterborne polyurethane (WPU). The dynamic rupture and reformation of sacrificial hydrogen bonds on the molecular scale effectively dissipate energy under mechanical stress, endowing these composites with remarkable toughness and ultrahigh water vapor permeability (WVP). The resultant composite’s tensile strength and WVP are 100% and 60 times higher than WPU, respectively. Additionally, this cost-effective strategy enables easy large-scale composite production. This method guides the development of high-performance, multifunctional collagen fiber-based wearable composites while advancing the tannery solid waste circular economy.

High‐Strength, High‐Barrier Bio‐Based Polyester Nanocomposite Films by Binary Multiscale Boron Nitride Nanosheets

AbstractOwing to the inferior dispersibility of boron nitride nanosheets (BNNSs) and weak interfacial interaction with the matrix, the performance of BNNS‐based composites is usually far below theoretically predicted values. Here, binary multiscale BNNSs (LDH‐BNNSs) fillers are synthesized through in situ growth of layered double hydroxide (LDH) on the BNNSs’ surfaces. LDH‐BNNSs with a multiple mosaic interface show superior dispersion of nanosheets in matrix and extraordinary filler‐matrix bonding. Density functional theory simulations reveal the stable dispersion mechanism of LDH‐BNNSs. Moreover, the bio‐based poly(ethylene furandicarboxylate) composites with 0.2 wt% LDH‐BNNSs loading exhibit simultaneous improvements in tensile strength (≈140 MPa), Young's modulus (≈6.5 GPa), toughness (≈2.0 MJ m−3), and gas barrier properties. Regulation of the interfacial structures of binary multiscale BNNSs significantly increases the filler utilization of the nanosheets, leading to extraordinary stress transfer efficiency and a physical shielding effect. Therefore, this simple, efficient, and novel strategy has promised in enhancing composite performance, and it provides a novel way to develop strong, tough, and high‐barrier bio‐based polyester composites.

Developing a pachyman/polyvinyl alcohol-polylactic acid bilayer film as multifunctional packaging and its application in cherry tomato preservation

Polyvinyl alcohol (PVA) is a widely used biodegradable material, but its high solubility and water vapor permeability limit its applications in food packaging. To address this issue, bilayer films were developed based on the combination of blending and coating techniques in the study, which consisted of an inner pachyman (PM)/PVA blend layer and an outer polylactic acid (PLA) layer. Blending PVA with PM reduced the solubility and oxygen permeability of the film, and the blend matrix showed rapid self-healing capabilities. Loading of a thin PLA shell onto the PM/PVA layer improved the water resistance, tensile strength, stiffness and water vapor barrier of the developed bilayer films. The best overall performance of the bilayer film was achieved using 40 g/L PLA as the film-forming solution. Infrared spectroscopic and microscopic structure analysis revealed weak interfacial interaction of the bilayer film. Furthermore, this bilayer film showed a better preservation effect on cherry tomatoes compared with PVA, polyethylene, and PM/PVA films. The physicochemical quality of fruits could be effectively preserved for at least 10 days under ambient environment. It is anticipated that the bilayer film developed here serves as a promising candidate for food packaging materials to extend the shelf life.

Effects of functionalization and silane modification of hexagonal boron nitride on thermal/mechanical/morphological properties of silicon rubber nanocomposite

Hexagonal boron nitride (h-BN) nanoparticles could induce interesting properties to silicone rubber (SR) but, the weak filler-matrix interfacial interaction causes agglomeration of the nanoparticles and declines the performance of the nanocomposite. In this work, h-BN nanoparticles were surface modified using vinyltrimethoxysilane (VTMS) at different concentrations. Before silane modification, h-BN nanoparticles were hydroxylated using 5 molar sodium hydroxide. The nanoparticles were characterized to assess success of silane grafting. The pure and modified h-BN nanoparticles were applied at 1, 3 and 5 wt% to HTV silicon rubber (SR). The curing, thermal, mechanical and morphological properties and hydrophobicity of the nanocomposites were evaluated. The morphology of the SR nanocomposites was characterized using AFM and FE-SEM analysis. It was found that silane grafting on the h-BN nanoparticles improves crosslink density but declines curing rate index (CRI) of the SR nanocomposite (at 5 wt% loading content) by 0.7 (dN m) and 3.5%, respectively. It also increased water contact angle of the nanocomposites from 97.5° to 107°. The improved nanoparticle-rubber interfacial interactions caused better dispersion of h-BN nanoparticles in SR matrix (at 5 wt%) that enhanced the elongation at break, modulus at 300% and Tg of the SR nanocomposites.

A novel strategy to functionalize styrene butadiene rubber toward enhanced interfacial interaction with silica

AbstractIncorporation of nanofillers (such as silica) into elastomer matrix is the most common strategy to prepare high‐performance rubber products. However, the poor dispersion of nanofillers in non‐affinity rubber materials and the weak interfacial interaction significantly limit the processing and mechanical properties. To reduce the polarity difference and enhance the interfacial interaction between silica and styrene butadiene rubber (SBR), we prepared a hydroxyethyl acrylate‐grafted SBR (SBR‐g‐HEA) through the redox initiator system, and subsequently fabricated SBR‐g‐HEA/silica nanocomposites by simple mechanical blending. The effects of reaction conditions on the grafting rate were studied in detail. ATR‐FTIR and 1H‐NMR collectively confirmed the successful grafting of HEA groups on SBR molecular chains, and the grafting fraction could be regulated from 0% to 2.5%. Scanning electron microscope (SEM) and rubber processing analyzer (RPA) showed that the incorporation of HEA could significantly improve the dispersion of silica nanoparticles in SBR matrix. Notably, the resulting SBR‐g‐HEA exhibited significantly enhanced attributes when compared to their unmodified counterparts, including superior mechanical properties, improved wear resistance, and reduced heat generation. The strategy proposed here provided insights toward the fabrication of non‐affinity rubber/filler nanocomposites for high‐performance rubber products and green tire.

Ultralight, Heat-Insulated, and Tough PVA Hydrogel Hybridized with SiO2 @cellulose Nanoclaws Aerogel via the Synergy of Hydrophilic and Hydrophobic Interfacial Interactions.

Lightweight porous hydrogels provide a worldwide scope for functional soft mateirals. However, most porous hydrogels have weak mechanical strength, high density (>1g cm-3 ), and high heat absorption due to weak interfacial interactions and high solvent fill rates, which severely limit their application in wearable soft-electronic devices. Herein, an effective hybrid hydrogel-aerogel strategy to assemble ultralight, heat-insulated, and tough polyvinyl alcohol (PVA)/SiO2 @cellulose nanoclaws (CNCWs) hydrogels (PSCG) via strong interfacial interactions with hydrogen bonding and hydrophobic interaction is demonstrated. The resultant PSCG has an interesting hierarchical porous structure from bubble template (≈100 µm), PVA hydrogels networks introduced by ice crystals (≈10 µm), and hybrid SiO2 aerogels (<50nm), respectively. PSCG shows unprecedented low density (0.27g cm-3 ), high tensile strength (1.6MPa) & compressive strength (1.5MPa), excellent heat-insulated ability, and strain-sensitive conductivity. This lightweight porous and tough hydrogel with an ingenious design provides a new way for wearable soft-electronic devices.

Synergistic effect between tannic acid-Fe3+ and chitosan hydrogel-coated covalent organic framework: Endowing better nanofiltration performance and stability

The weak interfacial interaction of nanomaterials and substrate is an important factor affecting the stability and rejection of nanofiltration membranes. Herein, two materials of covalent organic framework modified by chitosan hydrogels (CH@COF) and tannic acid (TA)-Fe3+ served as an interlayer of the thin-film composite (TFC) membrane to overcome this problem. The synergistic effect between CH@COF and TA-Fe (such as constructing stable chemical bonds between the polyamide layer and substrate, increasing the degree of cross-linking of the polyamide layer, and decreasing its thickness) endows the TFC/TA-Fe(CH@COF) membrane with excellent nanofiltration performance and stability. Its water permeability was 16.17 L m−2 h−1 bar−1, which was 185% of that of the TFC-control membrane (8.74 L m−2 h−1 bar−1), and the rejections of the membrane for norfloxacin, ciprofloxacin, and ofloxacin were 94.89%, 99.07%, and 99.10%, respectively. In addition, its flux recovery rate (FRR) values for high-concentration sodium alginate and bovine serum albumin were 98.32% and 97.99%, respectively, indicating outstanding antifouling performance. This work emphasizes the synergy and potential of different materials as an interlayer in high-performance TFC membranes.

Multifunctional and magnetic MXene composite aerogels for electromagnetic interference shielding with low reflectivity

Lightweight and multifunctional compressible aerogels with low reflectivity are highly demanded to protect electronic devices from increasingly serious electromagnetic interference and radiation. Although simply incorporating magnetic particles can reduce the strong electromagnetic (EM) reflection caused by the high conductivity of MXene, high density, inhomogeneous dispersion and weak interfacial interactions may impede the potential applications. Here, we report the fabrication of three-dimensional magnetic MXene/Fe3O4@acidified-MWCNT (aMWCNT) composite aerogel by a directional freezing and subsequent freeze-drying process, and the shielding effectiveness of composite aerogel can be tuned from 32.5 to 51.6 dB in the X-band. At the same time, since the Fe3O4 nanoparticles are pre-decorated onto aMWCNTs, the heterogeneous interface polarization and magnetic loss are enhanced at low loadings. Therefore, the reflected power coefficient of the aerogel is as low as 0.31 with an ultra-light density of only 10 mg cm-3. Moreover, the good reversible compressibility, fatigue resistance, excellent heat insulation, and infrared stealth grant the aerogels great application prospects for anti-infrared detection and green shielding materials.

Improved interfacial interactions of modified graphene oxide/natural rubber composites with the low heat build‐up and good mechanical property for the green tire application

AbstractWith the rapid development of transportation system, the safety, reliability, and durability of green tires play an important role in modern transportation. While for the material preparation, the poor dispersion ability of reinforced filler and the weak interfacial interactions with polymer matrix seriously restricted the further application in the green tire field. Meanwhile, avoiding the use of organic solvents is also an environmental issue that needs to be considered in the preparation process. Herein, water‐soluble 2‐mercapto‐1‐methylimidazole (MMI) functionalized graphene oxide (GO‐MMI) was obtained through a simple, green and one‐step hydrothermal method. Additionally, the modified graphene oxide/natural rubber composites (GO‐MMI/NR) with different GO‐MMI content were prepared by the latex coprecipitation approach. As a result, the modified GO‐MMI could be evenly dispersed in the NR matrix through the mechanical blending and the obtained GO‐MMI/NR composites possessed the good comprehensive properties after vulcanization. Specifically, the tensile strength (26.8 MPa), elongation at break (801%), low heat build‐up (6.2°C), Deutsches Institute for Normung (DIN) abrasion loss volume (71.31 mm3) and heat resistance index (162.1°C) were synchronic‐lifting when compared with the GO/NR composites. The results demonstrated that obtained GO‐MMI/NR composites owned the promising application for the industrial‐scale green tires.

Flexible and mechanically strong MXene/cellulose-lamellae sheets for electromagnetic interference shielding

MXene, two-dimensional layered transition metal carbides, nitride, or carbonitrides, have shown promise for ultrahigh electromagnetic interference (EMI) shielding in flexible electronics and aerospace due to their intrinsic metallic conductivity and mechanical strength. However, weak interfacial interactions, void microstructure defects, and oxidative degradation can leave MXene sheets in a thermodynamically metastable state, resulting in poor EMI shielding and mechanical strength. Herein, we utilized abundant hydrogen-bonded ultrafine cellulose lamella (UCL) to sequentially bridging induced densification of MXene nanosheets. This resulted in improved the tensile strength, toughness, oxidative stability, resistance to ultrasonic decomposition, and super-foldable conductivity of MXene sheets. The resulting MXene@UCL sheets (MXCS) exhibited high electrical conductivity of up to 7649 S cm−1 and ultrahigh weight-normalized shielding efficiency (SSE/t, 53003.45 dB∙cm2 g−1), making them mechanically strong and highly conductive. The MXCS material has a tensile modulus of up to 10.9 ± 0.7 GPa and provides excellent weight-normalized shielding efficiency. Simultaneously, it is capable of enduring 100,000 repetitions of folding without experiencing any damage to its construction or fluctuations in conductivity. Furthermore, high-strength scalable MXCS sheets can be produced using doctor blade casting, commercial resin bonding, and aerogel calendering methods, without compromising their performance. This has significant scientific and practical application potential.

Interfacial interaction and intense interfacial ultraviolet light emission at an incoherent interface

Incoherent interfaces with large mismatches usually exhibit very weak interfacial interactions so that they rarely generate intriguing interfacial properties. Here we demonstrate unexpected strong interfacial interactions at the incoherent AlN/Al2O3 (0001) interface with a large mismatch by combining transmission electron microscopy, first-principles calculations, and cathodoluminescence spectroscopy. It is revealed that strong interfacial interactions have significantly tailored the interfacial atomic structure and electronic properties. Misfit dislocation networks and stacking faults are formed at this interface, which is rarely observed at other incoherent interfaces. The band gap of the interface reduces significantly to ~ 3.9 eV due to the competition between the elongated Al-N and Al-O bonds across the interface. Thus this incoherent interface can generate a very strong interfacial ultraviolet light emission. Our findings suggest that incoherent interfaces can exhibit strong interfacial interactions and unique interfacial properties, thereby opening an avenue for the development of related heterojunction materials and devices.

Single-Walled Carbon Nanotube/Copper Core-Shell Fibers with a High Specific Electrical Conductivity.

Carbon nanotube (CNT)/Cu core-shell fibers are a promising material for lightweight conductors due to their higher conductivity than pure CNT fibers and lower density than traditional Cu wires. However, the electrical properties of the hybrid fiber have been unsatisfactory, mainly because of the weak CNT-Cu interfacial interaction. Here we report the fabrication of a single-walled CNT (SWCNT)/Cu core-shell fiber that outperforms commercial Cu wires in terms of specific electrical conductivity and current carrying capacity. A dense and uniform Cu shell was coated on the surface of wet-spun SWCNT fibers using a combination of magnetron sputtering and electrochemical deposition. Our SWCNT/Cu core-shell fibers had an ultrahigh specific electrical conductivity of (1.01 ± 0.04) × 104 S m2 kg-1, 56% higher than Cu. Experimental and simulation results show that oxygen-containing functional groups on the surface of a wet-spun SWCNT fiber interact with the sputtered Cu atoms to produce strong bonding. Our hybrid fiber preserved its integrity and conductivity well after more than 5000 bending cycles. Furthermore, the current carrying capacity of the coaxial fiber reached 3.14 × 105 A cm-2, three times that of commercial Cu wires.

Flexible and Photo-responsive superwetting surfaces based on porous materials coated with Mussel-Inspired Azo-Copolymer

The decoration of porous materials with stimulus-responsive polymers is an efficient strategy for the fabrication of superwetting surfaces; however, the weak interfacial interaction between the polymers and the substrates limits their application. Herein, inspired by the molecular structure of the mussel foot protein, a series of catechol-functionalized azobenzene-containing copolymers with diverse chain structures are synthesized via solution radical polymerization and used for the preparation of smart superwetting surfaces. After dip-coating with the mussel-inspired azo-copolymers, the modified cotton fabrics and melamine sponges possessed smart surfaces with photo-switchable wettability. These as-prepared flexible smart surfaces exhibited rapid wettability transition between high hydrophobicity and superhydrophilicity with alternating ultraviolet (UV) and visible light irradiation. Meanwhile, these superwetting surfaces were also experimentally found to be robust without apparent degradation in their photo-responsiveness, even after being soaked in acid/base solutions and subjected to repetitive mechanical deformation. Especially, the functionalized melamine sponges as bulk superwetting materials have excellent mechanical stability, which can tolerate harsh abrasion cycles and repetitive compressive deformations. More importantly, it was also confirmed that the mussel-inspired azo-copolymers exhibited excellent adhesion properties at the interface of various substrates. This bioinspired strategy and developed functional copolymers paves the way for facile and large-scale fabrication of superwetting surfaces, which may find a wide range of advanced potential applications in microfluidic devices, biomedicine and sensors.

Improving the intrinsic activity of ultrathin 2D–2D heterostructures by bridge-bonded Ni–O–Ti ligands for efficient oxygen evolution

The integration of ultrathin two-dimensional (2D) semiconductors with other conductive 2D materials to form hybrid electrocatalysts with abundant heterointerfaces can enhance the electrocatalytic activity by facilitating interfacial charge transfer. However, the hybrid electrocatalysts with weak interfacial bonding have limited effect on the electrocatalytic performance because the intrinsic activity of interfacial sites cannot be altered by weak interfacial interactions. As a proof-of-concept, we design ultrathin 2D–2D heterostructures with bridge-bonded Ni–O–Ti ligands based on single-layered Ti3C2T x MXene and metal hydroxides, and further reveal the structure-activity correlation between interfacial bonding and electrocatalytic oxygen evolution reaction by combining theoretical and experimental studies. Density functional theory calculations reveal the modulation of the electronic structure of interfacial metal sites after the formation of bridged interfacial Ni–O–Ti bonding. Compared with the hydrogen-bond-linked heterostructure, the ultrathin 2D–2D heterostructure with bridge-bonded Ni–O–Ti ligands shows enhanced intrinsic activity and stability towards electrocatalytic oxygen evolution with a very low overpotential of 205 mV at 10 mA cm−2 and the long-term durability. This work provides a new understanding and approach for the design and development of 2D hybrid catalysts with highly efficient electrocatalytic activity.

In situ coating of energetic crystals: A compact core-shell structure with highly reduced sensitivity

The weak interfacial interaction and high sensitivity is a longstanding problem for nitramine explosives. Herein, polyhydroxyethyl acrylate nitrate (PANE) was adopted to passivate three nitramine explosives through a facile and efficient in situ polymerization method. The core-shell structure of the PANE-coated composites was confirmed after detailed morphological and structural characterization. As a result, we find that, the hydrophobic PANE shell improved the adhesion work between the explosives and fluoropolymer (F2314) binder because of the enriched interfacial interactions. Besides, 2% PANE can retard the crystal transformation of CL-20 and HMX explosives by 10.7 °C and 4.3 °C, but does not affect the thermal decomposition behavior. The mechanical sensitivity of PANE-coated composites decreased more significantly than raw explosives and the mixed samples. As a typical example, the impact and friction sensitivity of CL-20@PANE composite with 2.0% shell content is practically halved when compared to raw CL-20 with the characteristicheight (H50) of 32.2 cm and the explosionprobability (P) of 50%. This study offers a simple, effective and universal method for design and preparation of energetic composites with high safety performance.

Surface modification of carbon nanotubes by a bifunctional amine silane; effects on physical/mechanical/thermal properties of epoxy nanocomposite

Weak interfacial interactions between MWCNTs and epoxy matrix causes agglomeration of the nanotubes and declines in the nanocomposite performances. In this study, MWCNTs were surface modified by a bifunctional amino silane (i.e. Bis (3-triethoxysilylpropyl)amine) at different concentrations. The nanotubes were previously functionalized through acid oxidation to increase silane grafting ratio. The pure, functionalized and silanized carbon nanotubes were characterized to assess the success of silane grafting. The pure and modified nanotubes were applied at different contents (0.5, 1 and 2 wt%) to epoxy resin. The tensile, flexural and compressive properties of the nanocomposites were evaluated. The nanocomposites were also characterized using water contact angle test, DSC, DMTA and FE-SEM/EDS analysis. It was observed that silanization of nanotubes caused considerable increment (32°) in the water contact angle of epoxy films. The results showed that incorporating the pure nanotubes (at 0.5 wt%) to epoxy resin enhanced the mechanical strengths but decreased the modulus of the epoxy sample. It was found that incorporating 0.5 wt% of modified MWCNT into epoxy binder caused 33, 53 and 40 % improvement in the tensile, flexural and compressive strengths and 56, 85 and 110 % increment in the tensile, flexural and compressive modulus compared to the pure MWCNT containing nanocomposite. The modified MWCNTs participated in curing of epoxy resin through reaction of silane amide groups with resin epoxide groups that this increased enthalpy of curing up to 25 %.