Selective Laser Sintering (SLS) is a powder‐based 3D printing technology. It offers a new means of fabricating complex modules with special properties, such as mechanical, flame retardant, electrical and thermal properties. In this paper, the effect of an intumescent flame retardant (IFR) and montmorillonite (MMT) on the fire resistance of thermoplastic polyurethane (TPU) was investigated. TPU composites powders were prepared by mixing with a two‐step method and can be effectively applied to SLS. Morphology characters exhibited that the fillers disperse well in the TPU powder. The structure analysis and hydrophilia analysis of sodium montmorillonite (Na‐MMT) and organically modified montmorillonite (OMMT) demonstrates the different compatibility in TPU, which reflects diverse flame retardant behavior. With 22% IFR and 3% OMMT fillers, the LOI of TPU composites increased from 17.2% to 28% and subsequently a UL‐94 V‐0 ranking was obtained. In the CCT results, the formula of 22% IFR and 3% OMMT showed the lowest heat release and smoke production. The study also explored the effects of flame retardant fillers on the thermal stability of TPU composites and melting and crystallization behaviors in SLS processing. In addition, the char residues after heating were analyzed via scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy and laser Raman spectroscopy. The results demonstrate that the composites have favorable flame retardant properties, thermal stability, char forming performance, and SLS process properties. The TPU composites prepared via SLS in this study demonstrated extensive potential in fire protection materials.

A highly flame-retardant PP composite powder suitable for selective laser sintering (SLS) was prepared successfully by mechanical blending, which was composed of pure PP, piperazine pyrophosphate (PPAP), melamine polyphosphate (MPP), and triazine-based charring-foaming agent (CFA). The results showed that the flowability of PP composite powder decreased by about 40% and the DSC data indicated the sintering window decreased by about 2 C. Although the flame retardants influenced the processing of SLS, the PP composite powder was still able to be used for printing. The LOI value of PP composites prepared by SLS was 29.2% and the UL-94 grade was V-0 rating at the filler loading (16wt% PPAP, 4wt% MPP, 4wt% CFA). The cone calorimeter testing (CCT) data represented that the heat and smoke release significantly decreased. The synergistic effect among flame retardants promoted high-quality char layers, which is favorable for improving the flame retardancy and thermal stability of PP composites by the test of TGA, SEM, Raman spectra, and FT-IR. However, the flame retardancy and mechanical properties of PP composites made by SLS were both in varying degrees of decline compared to the ones made by thermo-compression (TC) because of the higher porosity. An air duct with complex structures was prepared by SLS at last.

Presently, layered double hydroxides (LDHs) are pervasively adopted as part of flame retardant polymer composite materials due to its favorable synergism effect with certain flame retardants. In addition, it is environmentally friendly. Meanwhile, selective laser sintering (SLS) is a powder‐based three‐dimensional (3D) printing technology, providing a novel path to manufacturing polymer composite materials with complex shapes. In this research, flame retardancy of thermoplastic polyurethane (TPU) was enhanced based on LDHs and intumescent flame retardant (IFR). Being prepared by SLS technology. First, TPU composite powders based on LDHs and IFR were obtained using a two‐stage mixing method. Morphology analysis revealed that IFR and LDHs were dispersed uniformly in TPU powder. Subsequently, flame retardant TPU composites were prepared with TPU composite powders using the SLS process under appropriate 3D printing parameters, thereby enabling flame retardant TPU parts to be obtained. With 23 wt% IFR and 2 wt% LDHs filler, the limiting oxygen index of TPU composite was reached to 31.7%, while passing the UL‐94 V‐0 level during the vertical burning test. The cone calorimeter test showed that the heat release rate, smoke production rate, as well as production of carbonic oxides, all decreased significantly following the addition of LDHs. Thermogravimetric analysis indicated that LDHs and IFR were characterized by a favorable synergism effect, with the TPU/23IFR/2LDHs possessing good thermal stability. Char residue analysis, including SEM, energy dispersive X‐ray, Fourier transform infrared, and Raman spectra, further testified that a synergism effect existed between LDHs and IFR in the TPU composite. Overall, in this study the TPU composites fabricated by SLS technology exhibited excellent flame retardant ability.

In recent years, with the rapid development of 5G communication technology and microelectronic chip integration technology, smart wearable devices with high thermal conductivity are becoming more and more important. The most common method to improve the thermal conductivity of polymers is to introduce fillers with high thermal conductivity for compounding and build a thermal conductivity network inside the system. At present, the main methods of preparing heat-conducting composites are hot pressing molding, injection molding, and casting molding, but these traditional molding processes are difficult to prepare heat-conducting composites with complex shapes and structures. Selective laser sintering (SLS) is a new 3D printing technology, which uses the energy provided by laser to melt polymer powder, then sinter layer by layer, stack layer by layer, and finally form printed products. Compared with the traditional molding process, the SLS process has the advantages of a simple manufacturing process, high molding precision, recyclable materials, and wide application, which can realize the design and development of complex structural parts. In this study, TPU composites were successfully prepared by using thermoplastic polyurethane (TPU) polymer as matrix material, AlN and h-BN as thermally conductive fillers, and SLS technology. When the content of AlN is 20 wt% and the content of h-BN is 15 wt%, the thermal conductivity of TPU composite is as high as 0.90 W/mK, which is 391% higher than that of pure TPU sintered parts. At this time, the tensile strength of the composite is 17.2 MPa and the elongation at break is 301%, and it still shows good mechanical properties. This work is devoted to proposing a preparation method of flexible and high thermal conductivity composite materials, which can be used to prepare thermal management materials with complex shapes and structures and carriers of smart wearable devices, and has broad application prospects.

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