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Anisotropic thermally conductive composites are very critical for precise thermal management of electronic devices. In this work, in order to prepare a composite with significant anisotropic thermal conductivity, polyamide 12/styrene–acrylic copolymer–boron nitride (PA12/SA–BN) composites with macro and micro double anisotropic structures were fabricated successfully using 3D printing and micro-shear methods. The morphologies and thermally conductive properties of composites were systematically characterized via SEM, XRD, and the laser flash method. Experimental results indicate that the through-plane thermal conductivity of the composite is 4.2 W/(m·K) with only 21.4 wt% BN, which is five times higher than that of the composite with randomly oriented BN. Simulation results show that the macro-anisotropic structure of the composite (caused by the selective distribution of BN) as well as the micro-anisotropic structure (caused by the orientation structure of BN) both play critical roles in spreading heat along the specified direction. Therefore, as-obtained composites with double anisotropic structures possess great potential for the application inefficient and controllable thermal management in various fields.

The development of semi-aromatic polyamides with excellent mechanical properties has always been a popular research avenue. In this work, the semi-aromatic polyamide 12T (PA12T) with the maximum tensile strength of 465.5 MPa was prepared after stretching at 210 °C 4.6 times. Wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) were used to characterize the structural evolution of semi-aromatic polyamide 12T (PA12T) after stretching at different stretching temperatures and stretching ratios. The formation mechanism of this change in mechanical properties was investigated from different aspects of the aggregated structure such as crystal morphology, crystal orientation and crystallinity. The relevant characterization results show that the crystal structure, crystal orientation and crystallinity of PA12T were the highest when the sample was pre-stretched at 210 °C, which is crucial for improving the mechanical properties of PA12T. These findings will provide important guidance for the preparation of polymer materials with excellent mechanical properties.

The rapid development of the polymeric materials market has created an urgent demand for the thermoplastic polyamide elastomer (TPAE) owing to its greater functionality, and ability to be synthesized via a facile and industrial route. In this work, a series of novel silicone-containing polyamides (PA1212/Si12) were successfully synthesized from 1,12-dodecarboxylic acid (LA), 1,12-dodecarbondiamine (DMDA), and 1,3-bis (amino-propyl) tetramethyldisiloxane (BATS), via a one-pot melt polycondensation method in the absence of a catalyst. FTIR, 1H-NMR, GPC and inherent viscosity results cohesively prove that the polymerization of monomers was well conducted, and the chemical structure was in high accordance with the design. As expected, the Si12 unit-content of the copolymers regulate the properties of the series. As the feeding ratio of BATS in the diamines increases from 5 mol% to 40 mol%, the thermal transition temperatures, Tg and Tm, decline steadily before finally stabilizing at ~6 °C and 160 °C, respectively, indicating that the co-polyamides possess improved chain flexibility but restricted crystallization ability. The conspicuous evolution in crystalline morphology of the series was observed by XRD and AFM. The increased PA Si12 phase induces the crystallized PA 1212 phase to transit from a thermally-favorable large and rigid crystal structure (α phase) to a kinetically-favorable small and ductile crystal structure (γ phase). Reflected in their stress–strain behavior, PA1212/Si12 copolymers are successfully tailored from rigid plastic to ductile elastomer. The tensile strength mildly drops from above 40 MPa to ~30 MPa while the reversible elongation increases from ~50% to approximately 350%. Accordingly, the moderate surface tension differences in the monomers facilitate the efficient conduction of the co-polymerization process, and the distributed short siloxane unit in the backbone fulfills the copolymer with desirable elasticity. Interestingly, the novel silicone-containing polyamides also display Si12 unit-content dependent flame retardancy, humidity stability, and unconventional solid-state fluorescence properties. The elastomers exhibit a low bibulous rate and anti-fouling characteristics to dye droplets and mud contamination, pass the V–1 rating (UL 94) with a constantly declining PHRR value, and emit blue luminescence under a 365 nm light source. Herein, we propose a new facile strategy for developing a high-performance and multifunctional silicone-modified polyamide, which bears promising industrialization potential. In addition, this first reported silicone-containing thermoplastic polyamide elastomer, which is self-extinguishing, anti-fouling and blue-luminescent, will further broaden the application potential of thermoplastic polyamide elastomers.