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[Display omitted] • Mechanical and tribological properties of PAA/EP composites were enhanced by HSiNH 2. • Compatibility of PAA and EP was improved by using HSiNH 2 as "bridging structure". • PAA was prepared by ball milling method based on the friction chemistry principle. Despite the great application potential of epoxy resin (EP) modified with polyamic acid (PAA), the large amount of high-boiling-point non-protonic polar solvents used to promote their compatibility cannot be completely eliminated, which affects the fabrication and application of epoxy composites in practical engineering. Herein, PAA was prepared by solvent-free ball milling method, and then the primary amine hyperbranched polysiloxane (HSiNH 2) was prepared by "one-pot" method as the "bridging structure" to improve the compatibility between PAA and EP. Compared to neat EP, the flexural, impact and tensile shear strength of the epoxy composite are increased by 22.2 %, 30.0 % and 23.2 %, while the average friction coefficient and volume wear rate are reduced by 26.5% and 20.6% under the contents of PAA and HSiNH 2 are 1.50 wt% and 2.0 wt%, respectively. Moreover, the material exhibits excellent thermal properties. By comprehensively analyzing the structure and properties of the epoxy composite, it is mainly ascribed to the fact that HSiNH 2 with a large number of reactive groups acted as a "bridging structure" to enhance the compatibility of PAA and EP, which results in the epoxy composite having excellent mechanical, tribological and thermal properties. This research also lays the theoretical foundation for the development of high-performance epoxy composites in aerospace. [ABSTRACT FROM AUTHOR]

Graphical abstract Densely interconnected 3D BNNS networks for isotropically thermal conductivity epoxy composites with reduced filler-filler thermal resistance via a novel thermally AgNPs welding strategy. Highlights • BNNS@AgNPs are prepared via a ball milling method and in-situ reduction treatment. • Interconnected 3D BNNS networks formed by thermally sintered AgNPs structures. • The silver bridges serve as thermal transport junctions in the 3D filler network. • The mechanical and thermal stability of composites are improved simultaneously. Abstract Polymer-based thermal conductive composites (PTCs) with good thermal and mechanical properties are highly appreciated in the thermal management of modern electronic devices. However, the heat transfer property of particle-filled PTCs is severely limited by the thermal resistance at both filler-matrix and filler-filler interfaces. Intensive efforts have been taken to enhance the filler-matrix interface, however, the effect of filler-filler thermal contact resistance on the heat transfer properties of PTCs is still not very clear. In this work, continuous thermal conductive networks with good filler-filler interface contact are formed in epoxy composites via the in-situ sintering of silver nanoparticles on the surface of boron nitride nanosheets (BNNS). In this composites, homogeneously dispersed and well exfoliated BN nanosheets are bridged to each other via the sintered AgNPs located at the BNNS and a 3D boron nitride nanosheets network is formed with solid Ag junctions lying in between. After thermal sintering process, the thermal conductivity of EP/BNNS@AgNPs composite with the 3D boron nitride nanosheets network increase from 0.95 W/m·K to 1.13 W/m·K at the filler loading of 20 wt%, which indicates that merged AgNPs are used as thermal transport junctions to reduce the thermal contact resistance within 3D BNNS networks. The present strategy provides an effective route for developing high-performance PTCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel phosphorus-containing tertiary amine hardener (DCM) is synthesized. • DCM endows epoxy resin with desired heat resistance and char-forming capacity. • DCM improves the mechanical stiffness, robustness and toughness of epoxy resin. • DCM imparts superior flame retardancy and smoke suppression to epoxy resin. Although current phosphorus (P)-based hardeners endowed epoxy resins (EPs) with intrinsic flame retardancy, their addition usually reduced thermal and mechanical properties. In this work, a novel phosphorus-containing tertiary amine hardener (DCM) was synthesized using diphenylphosphinic chloride and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), and applied to fabricate high-performance EP/DCM. Introducing P-containing group reduced the reactivity of tertiary amine of DCM, but EP/DCM gelled at 100 °C within 11.3 min, showing modest-temperature curing character. EP/DCM exhibited higher glass-transition temperature (T g) and char yield than virgin EP/DMP-30. Moreover, EP/DCM featured superior mechanical properties, of which the tensile strength, elongation at break and impact strength increased by 61.2%, 72.0% and 198.5%, respectively, relative to those of EP/DMP-30. DCM endowed EP thermosets with remarkable flame retardancy and smoke suppression. The limiting oxygen index (LOI) and UL-94 rating of EP/DCM reached 35.7% and V-0, respectively, with 36.2% and 22.6% reductions in peak heat release rate (PHRR) and peak smoke production rate (PSPR) compared with those of EP/DMP-30. This work pioneers an innovative strategy for creating high-performance EPs with satisfactory heat resistance, fire safety, and mechanical properties by curing with P-containing tertiary amine hardeners. [ABSTRACT FROM AUTHOR]

• Flexible, healable and degradable polyurethane phase change materials (PU-PCMs) were synthesized. • The PU-PCMs exhibit high tensile strength (∼39.0 MPa), tensile strain (∼1425 %), and toughness (∼324.0 MJ/m3). • The h -BN enhanced PU-PCM film with excellent thermal regulation for the working CPU. Materials with multifunctionality, especially polymers based on dynamic covalent bonds, have attracted considerable interest due to their technological innovation. Nowadays, phase change materials (PCMs) are widely used in various cutting-edge fields, while strategies for simultaneous realization of their flexibility, self-healing, high mechanical properties and degradability are still highly anticipated. In this work, we have designed and constructed a multifunctional polyurethane phase change material (PU-PCM) by the incorporation of isocyanate-hydroxy coupling reaction, where the soft phase polyethylene glycol (PEG6K) serves as latent heat storage sectors, and triple boron-urethane bonds (t -BUBs) as dynamic cross-linkers in the hard segment provide healable ability, excellent mechanical properties, and degradability through the cooperative effect of ordered H-bonding interactions. As a result, the well-designed PU-PCM exhibits high flexibility, superior tensile strength (∼39.0 MPa), tensile strain (∼1425%), and toughness (∼324.0 MJ/m3), as well as excellent healable efficiency (∼90% at room temperature), and degradability in a mildly acidic solution. Also, the h -BN enhanced PU-PCM composite film can be used to cool the working CPU as the PEG6K chains embedded in the soft segments can work as a smart thermal-regulator to harvest the undesired heat from the surroundings. [ABSTRACT FROM AUTHOR]

• Gibbs free energy mainly dominates the formation of bixbyite-structured five-principal rare-earth element HEOs. • Cooling rate is the second factor on the phase structure formation of HEOs. • HEO4 exhibits higher fracture toughness and lower thermal conductivity than Y 2 O 3. • HEO4 shows a superior oxygen barrier property than 8YSZ. Cubic bixbyite-structured high-entropy oxides (HEOs) are regarded as potential candidates in high temperature thermal insulation field in recent years. However, their relevant properties are still needed to be explored for possible applications. In this work, twelve new high-entropy oxides (HEO1-12) of (5Re 0.2) 2 O 3 (Re represents five elements selected from Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) are prepared by solution combustion synthesis method combined with conventional sintering. Except HEO10 with a single monoclinic phase, other samples have a single bixbyite phase. The average grain size of bixbyite-structured samples is within 0.76 ∼ 4.96 μm. Then, the samples of HEO4, 5, 7–9 are chosen to study their mechanical and thermal properties. Their nano-modulus, nano-hardness, fracture toughness K IC , brittleness M and surface fracture energy are in the range of 152.42 ∼ 237.33 GPa, 9.22 ∼ 12.65 GPa, 1.77 ∼ 2.51 MPa·m1/2, 2.35 ∼ 3.09 μm−1/2 and 9.00 ∼ 22.49 J m−2, respectively. HEO4, i.e., (Ce 0.2 Nd 0.2 Sm 0.2 Dy 0.2 Gd 0.2) 2 O 3 , exhibits higher K IC (1.92 MPa·m1/2) and lower M (2.71 μm−1/2) than another reported cubic bixbyite-structured HEO of (Eu 0.2 Er 0.2 Lu 0.2 Y 0.2 Yb 0.2) 2 O 3. Among the five samples, HEO4 has the lowest thermal conductivity κ (1.88 ∼ 2.55 W·m−1·K−1 in 25 ∼ 500 °C), which is much lower than bixbyite-structured Y 2 O 3. In addition, HEO4 possesses a lower oxygen diffusion compared with 8YSZ in 600 ∼ 700 °C, which endows it the better oxygen barrier property. To sum up, HEO4 could be a promising candidate for high temperature thermal insulation applications due to its excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multifunctional P/Ni-doped g-C 3 N 4 (Ni-P-C 3 N 4) nanoflakes were synthesized. • Ni-P-C 3 N 4 can be homogeneously dispersed in ABS by simple melt-blending. • Ni-P-C 3 N 4 endowed ABS with enhanced thermal stability and mechanical strength. • Ni-P-C 3 N 4 significantly improved the flame retardancy and smoke suppression of ABS. The ubiquitous application of highly flammable acrylonitrile–butadienestyrene (ABS) resin has brought great fire threat to human and environment. Unfortunately, current flame retardants often improve flame retardancy but reduce mechanical and thermal properties, seriously affecting their practical application. We herein reported novel multifunctional, high-efficiency, phosphorus and nickel co-doped graphitic carbon nitride (Ni-P-C 3 N 4) nanoflakes to address the trade-off between flame retardancy and mechanical/thermal properties. The addition of 2.0wt% of Ni-P-C 3 N 4 increased the initial degradation temperature and tensile strength of ABS composite (ABS/Ni-P-CN2) by 15 °C and 24.3% relative to virgin ABS, indicating its positive effect on thermal and mechanical properties. Compared with ABS, ABS/Ni-P-CN2 exhibited a notable increase in time to ignition, along with 32.4% and 33.8% reductions in peak heat release rate (PHRR) and peak smoke production rate (PSPR), demonstrating excellent anti-ignition, flame-retardant and smoke-suppressive performances. The increased fire safety was mainly due to the physical barrier effect of g-C 3 N 4 nanosheets and the catalytic charring effect of P and Ni. This work offers a novel design strategy to create multifunctional flame retardants for fabricating fire-safe polymer composites with superior thermal and mechanical properties, holding great potential in industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel eugenol-functionalized and cage-like EG-POSS is synthesized. • EG-POSS is conducive to reduce dielectric constant and loss of BD resin. • The mechanical and thermal properties of BD resin are also improved. • Well-dispersed and covalently bonded Si-O-Si cages in resin led to enhancements. Introducing porous materials into resin matrix is effective to achieve low dielectric constant (low- k) value but challenge for simultaneously improving mechanical and thermal properties due to the heterogeneous dispersion of these fillers. Herein, a novel eugenol-functionalized cage-like (pore size, 1–2 nm) polyhedral oligomeric silsesquioxane (EG-POSS) was designed and synthesized, which exhibits excellent solubility and reactivity with BD-type bismaleimide resin. Thus, 4 wt% incorporated EG-POSS is uniformly dispersed in resin matrix and the resultant hybrid (BDEP- 0.04) shows outstanding comprehensive performance, especially on dielectric, mechanical and thermal properties. Specifically, the dielectric constant (k) and loss (tan δ) at 1 MHz are reduced to 2.88 and 0.010 from 3.33 and 0.013. Meanwhile, the corresponding impact strength and flexural strength are improved to 18.75 KJ/m2 and 159.01 MPa, increased by 63.63 % and 27.29 %. In addition, BDEP -0.04 also exhibits the excellent thermal stability with glass transition temperature (T g) of 290 °C, which is 8 °C higher than BD resin. Based on the lower k and t a n δ value of BDEP -0.04 hybrid resin, as well as its better adhesion with silica fiber, the wave-transparent and mechanical properties of silica fiber reinforced composites (SF/BDEP -0.04) are further improved, showing that the wave transmission efficiency (94.2%), flexural strength (309.99 MPa), flexural modulus (15.70 GPa) and interlaminar shear strength (35.41 MPa) are all greatly higher than those of SF/BD. It's concluded that EG-POSS is effective to optimize and balance the dielectric, mechanical and thermal properties of BD-type bismaleimide resin and SFs/BD composites, which is valuable for practical application in wave-transparent field. [ABSTRACT FROM AUTHOR]

Balanced strength and toughness is always the goal of high-performance polymer materials for practical applications. In this work, a series of transparent poly(lactic acid) (PLA) nanocomposite films incorporated with fully exfoliated octadecylamine-functionalized graphene (ODAG) as effective nanofiller were prepared by solution blending and casting method. Because of the good hydrophobic compatibility between ODAG and PLA, a homogeneous dispersion of ODAG into PLA matrix and improved interfacial adhesion between them can be achieved. The obtained PLA/ODAG nanocomposite films present markedly improved crystallization behavior, mechanical properties and thermal stability. Compared to neat PLA, the nanocomposite films show a 34% increase in tensile strength, 44% increase in Young’s modulus, and 300% improvement in tensile toughness by the addition of only 0.4 wt% of ODAG. The simultaneous improvement in both strength and toughness could be attributed to homogeneous dispersion of ODAG in PLA matrix, improved interfacial interaction due to unique interphase structure, as well as enhanced crystallization. [ABSTRACT FROM AUTHOR]

A masterbatch of graphene oxide (GO) in polyol was prepared and used for the preparation of polyurethane (PU)/GO nanocomposites by bulk in-situ polymerization. The prepared nanocomposites were characterized in terms of their thermal, mechanical, and morphological properties as a function of GO loading. Here, grafted PU chains on the surface of GO facilitated the beneficial stress transfer from the PU matrix to GO. This stress transfer occurs due to the reaction of the hydroxyl and carboxyl groups of GO with the isocyanate groups of 4,4'-methylene diphenyl diisocyanate (MDI) and the PU pre-polymer. The Young's modulus of the PU was improved by 280.5% through the incorporation of 3 wt% GO. Additionally, an improvement of 40.5% in the tensile strength and 19% in the elasticity was achieved at 1 wt% GO. Strain hardening of PU was improved with GO loadings up to 1 wt% due to the synergetic orientation of the soft segment and the PU-grafted GO in the strain direction. However, the large increase in cross-link density that occurred at 2 wt% GO prevented strain hardening, and the ultimate tensile strength decreased. The Halpin-Tsai model was used to predict the orientation of GO in PU nanocomposites. The randomly oriented 3D arrangement of GO in PU showed better agreement between the theoretically calculated and experimentally determined moduli compared to the 2D alignment. These results demonstrate that the preparation of PU nanocomposites using masterbatch dilution is an excellent method to attain well-dispersed GO. This technique can also be used to overcome the environmental problems associated with volatile organic compound (VOC) emission, as well as addressing some of the difficulties found in the plastics processing industry. [ABSTRACT FROM AUTHOR]

• Highly flexible CNTs based monolithic support was constructed via a directional freezing method. • Monolithic CNTs based composite PCM exhibits superior mechanical and thermal properties. • Flexible mechanism of monolithic CNTs based composite PCM is proposed. • This design strategy provides a new direction for future wearable fitting-skin temperature-controlled materials. Currently, most reported composite phase change materials (PCMs) are powdery shape, which require secondary processing for practical applications. Although some monolithic composite PCMs have been developed, their flexibility usually undergoes a remarkable reduction or even complete disappearance when supporting material s are infiltrated with PCMs. To solve this problem, we fabricated a flexible supporting material with a folded layer-bridge network structure by dispersing carbon nanotubes (CNTs) in acetic acid solution of chitosan (CS) with poly(vinyl alcohol) (PVA) using a directional freezing method. Then CS/PVA/CNTs (CPC) scaffold was infiltrated with polyethylene glycol (PEG) to prepare PEG@CPC composite PCM. The resulting flexible composite PCM displays excellent mechanical properties, such as high tensile strength of 2.42 MPa and bending resistance of >100 cycles. Moreover, it displays outstanding thermal properties, such as high crystallinity of close to 100% and encapsulation ratio of 92.6 wt%. This work provides a simple method for preparation of flexible monolithic composite PCMs for many potential applications, such as wearable fitting-skin temperature-controlled materials. [ABSTRACT FROM AUTHOR]

• Waste tissue paper was successfully utilized for the preparation of WTP-PVA CAs. • The WTP-PVA CAs displayed low density and superior mechanical properties with specific Young's modulus 1246.8 MPa cm3 g−1. • The WTP-PVA CAs showed good electrical and thermal properties. • The average EMI shielding effectiveness of WTP-PVA is ~40.8 dB with an absorption-dominant shielding feature. • WTP-PVA CAs showed considerable capacity to CO 2 adsorption with excellent selectivity and recyclability. Carbon aerogels (CAs) have always shown great potential for multifunctional applications. However, simultaneous improvement of mechanical, electrical and thermal properties of CAs with low density is still a big challenge due to their structural defects, disordered microstructure, and colossal oxygen containing functional groups. Herein, a subtle approach is developed to prepare CAs from waste tissue paper (WTP) and poly(vinyl alcohol) (PVA) as the basic ingredients. The WTP-PVA CAs possessed a highly interconnected three-dimensional porous structure with low density (0.057 g cm−3), high porosity (~97%) and specific surface area (1384 m2 g−1). Albeit with low density, the resultant CA displayed superior mechanical properties (specific Young's modulus up to 1246.8 MPa cm3 g−1) and thermal stability. Besides, they also featured high electrical conductivity (1.35 S cm−1) and low thermal conductivity (0.087 W m−1 K−1). These properties provided an opportunity for some advanced applications such as electromagnetic interference (EMI) shielding and CO 2 gas capture. The highest shielding effectiveness (SE), specific SE and thickness-averaged specific SE of WTP-PVA in the X-band are 40 dB, 700 dB cm3 g−1 and 1818 dB cm2 g−1 respectively, with an absorption-dominant shielding mechanism. More importantly, the WTP-PVA CA with abundant ultramicropores showed great potential for CO 2 adsorption (5.14 mmol g−1 at 0 °C) with good selectivity and regeneration capability even without the aid of any chemical activation, functionalization or heteroatom doping. [ABSTRACT FROM AUTHOR]