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To explore thermal and mechanical properties of epoxy material, difunctional aromatic epoxy--divinylbenzene dioxide (DVBDO) had been synthesized by epoxidizing divinylbenzene, using the metal acetylacetone compound grafted Fe3O4 particles as the catalyst. The catalyet had high conversion and epoxy selectivity and could be recyclable. Then the polymerization of DVBDO with different diamine curing agents were reported. The structure and viscosity of DVBDO were firstly characterized. Because it had low molecular weight and viscosity, DVBDO had excellent liquidity and formability. Subsequently to clarify the properties of epoxy thermosets, experiments to determine thermal and mechanical performances were carried out, such as differential scanning calorimetry (DSC), thermal gravimetric (TGA), dynamic mechanical analysis (DMA) and tensile test. It could be observed that the thermoset polymers using DVBDO as epoxy matrix had excellent thermal (Tg was about 201°C) and mechanical properties (tensile strength was 131.99Mpa). Possibly considering that this kind of thermoset polymers had higher rigidity and crosslink density. In conclusion, a new type of one-component liquid epoxy encapsulant material with low viscosity, good filling fluidity, strong heat resistance and excellent storage performance had been developed.

Design and development of intelligent fire warning materials with rapid response capabilities has always been an urgent need for the safety of many flammable materials in their applications. Herein...

The alpine wetlands in the Tibetan Plateau (TP) account for more than 30% of the wetlands in China. As an ecosystem that is particularly sensitive to the changing climate, the rapid warming of the TP may have a significant impact on the growth of vegetation in these cold wetlands. However, due to the lack of ground observations, it remains unclear how the land-atmosphere exchanges of water and energy develop in such special alpine ecosystems. This limits the understanding of how eco-hydrological processes respond to environmental changes. In this study, we used ground measured data to investigate the dynamics of energy partitioning and water budget over a typical wetland in the central TP over two hydrological years. The results demonstrate that the seasonal variations in land-atmosphere energy exchange were significant during the observation period. In the growing season, the available energy was mainly consumed by latent heat flux (LE), with the mean ratio of LE to net radiation (Rn) exhibiting values of 0.68 and 0.76 in 2019 and 2020, respectively. During the freezing period, the available energy was primarily consumed by sensible heat flux (H), with mean ratio of H to Rn values of 0.69 and 0.68 in 2019 and 2020, respectively. The total annual evapotranspiration (ET) (include sublimation) in 2019 and 2020 were 652.5 mm and 706.6 mm, respectively. Annual ET was found to be higher than precipitation (P), indicating that soil water was supplied via lateral flow from the melting of upstream glaciers and snow, supporting ET from the wetland. During the growing season, ET was mainly controlled by solar radiation but became more strongly coupled with soil water during the freezing period. Evaluations of four typical gridded ET products suggest that the Penman–Monteith–Leuning (PML) model showed the best performance with the highest Nash-Sutcliffe Efficiency (NSE) when compared with the ground-measured ET rates, indicating that this product may be appropriate for use in similar data-scarce regions. The land-atmosphere energy and water exchanges in the alpine wetland are important for an improved understanding of the hydrological cycle of the Asian Water Tower and could be used as a reference for further ET model parameterizations and validations.

Design and exploitation of smart fire-warning devices with ultrasensitive response capability are always an urgent need for effective fire protection. Herein, a nano-filler (BP-MoS2) is prepared by ball milling black phosphorene and molybdenum disulfide and added into the graphene oxide (GO) film to fabricate a multifunctional film with high fire resistance and rapid response ability. When the addition of BP-MoS2 is 20.0 wt%, the GO/BP-MoS2 20.0 shows an excellent flame retardancy. The residual char rate is improved from 46.60% to 66.65%, and its peak of heat release rate (pHRR) value has reduced from 599.92 W g−1 to 274.00 W g−1, resulting in a 54.33% decrease, which is attributed to the ultra-fast catalytic char formation and synergistic flame retardancy of BP and MoS2. Meanwhile, the composite film can still maintain the original shape within 15 s of ignition. More interestingly, when encountering a flame attack, it reveals an ultra-fast fire warning response (about 1 s), which is attributed to the fast carbonization after contacting with flame. Such approach offers a novel perspective for the preparation of intelligent fire alarm devices with ultra-fast response ability.

Owing to the high interface thermal resistance and aggregation in polymer-based materials, the thermal conductivity of multi-walled carbon nanotubes (MWCNTs) has been severely decreased in practical applications. In this work, an amino-functionalized black phosphorene (BP–NH2) fabricated by ball milling has been employed to react with carboxylated multi-wall carbon nanotubes (MWCNTs–COOH) via covalent bonds to prepare a nanofiller (BP–MWCNTs) with high thermal conductivity and excellent flame retardancy. When incorporating 20.0 wt% BP–MWCNTs into cellulose nanofiber (CNF), the CNF/BP–MWCNTs 20.0 shows an in-plane thermal conductivity of 22.38 ± 0.39 W m−1 K−1 and a cross-plane thermal conductivity of 0.36 ± 0.03 W m−1 K−1, resulting in an anisotropy index of 62.17. The effective medium theory (EMT) calculation demonstrates the interface thermal resistance is reduced to 1/39 that of pure MWCNTs, which is ascribed to the covalent bond between BP–NH2 and MWCNTs–COOH. Simultaneously, the CNF/BP–MWCNTs 20.0 can pass the testing of UL-94 V-0 grade and the limiting oxygen index (LOI) value can be increased from 18.1% to 29.9%. Its peak of heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), CO generated per second (COP) and CO2 generated per second (CO2P) are decreased by 37.47%, 43.51%, 50.00%, 35.29%, 50.00% and 19.70%, respectively, which is due to the formation of an intumescent flame-retardant system rich in carbon source (MWCNTs), acid source (BP) and gas source (amino groups). This covalent linkage strategy offers a new thought for the preparation of flexible materials to enhance the thermal conductivity and fire resistance.

The conductivity and thermal stability of traditional polymers are generally not ideal, consequently endowing polymer-based pressure-sensitive adhesives (PSAs) with certain conductivity and heat resistance has become a popular design idea. Although multi-walled carbon nanotubes (CNTs) possess good electrical conductivity and thermal stability, their adhesion to the substrate is poor. Inspired by mussel chemistry, polydopamine (PDA) is adopted to modify CNTs to improve their adhesion to substrates. Eventually, polydopamine-modified multi-walled carbon nanotubes (PDA-CNTs) are added into the polyurethane/polysiloxane matrix, and a series of self-adhesive and heat-resistant conductive adhesives are successfully prepared under UV irradiation. As a result, the conductivity and thermal stability of PSAs are refined as expected. Especially when the content of PDA-CNTs is 4 wt%, the conductivity reaches 1.2 × 10−5 S/cm. Comparing to pure polymer (PUA), the conductivity of PUATS4 is increased by six orders of magnitude. In addition, its heat resistance is also improved, and the carbon residue rate is up to 14.5 wt% at 750 °C. These excellent performances of PSAs will be beneficial to the applications in conductivity and thermal stability in the future.