In this study, a facial method of fabricating hexagonal boron nitride nanosheet (BNNS) was proposed. Isopropyl alcohol was employed as the solvent to obtain the BNNS via exfoliation of the pristine hexagonal boron nitride. The yield of the exfoliated BNNS with thickness less than 20 nm was as high as 0.17-0.2 mg mL À1 . The BN-and BNNS-filled polyamide 6 (PA6) composites were subsequently prepared by melt blending, and a comparison of thermal conductivity and mechanical properties of the resultant composites were demonstrated. Results indicated that the PA6/BNNS composites showed superior mechanical and thermal conductive properties when compared with that of neat PA6 and PA6/BN composites. At a filler-loading fraction of 40 wt%, thermal conductivity of the PA6/BNNS composite reached 2.496 W mK À1 , which was 21.8% higher than that of PA6/BN composites at the same filler-loading concentration. In addition, the tensile strength of PA6/BNNS composites was invariably higher than that of neat PA6, with a 6.23% increment at a filler concentration of 30 wt%. Based on the results of differential scanning calorimetry, a new crystallization peak (T CC , 2) was observed at higher temperature region for the filler-containing composites and the position of the new peak gradually shifted to higher temperatures with an incremental loading concentration of BN and BNNS.
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 50.78 MPa 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.
In this study, flake graphite was dispersed in immiscible polyamide 6/polypropylene (PA6/PP) blends to improve their thermal conductivity. Blends of PA6/PP were prepared in different relative fractions and thermal conductivity of the graphite-containing blends showed enhanced values for immiscible blends when compared with those of mono-PA6-based composites at the same graphite loading fractions. Moreover, a PA6/PP mass ratio of 8/2 showed better dispersion of graphite and less interfacial defects, resulting in better heat conduction ability when compared with other immiscible blends. At graphite loading of 40 wt%, thermal conductivity of PA6/PP/graphite composite reached 2.896 W/mK, which is nearly 40% higher than that of mono-PA6/graphite composite. Morphology and melt rheology measurements confirmed that flake graphite began to form thermally conductive network at 30 wt% in immiscible blends which is crucial to the improvement of thermal conductivity.
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