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Low-density polyethylene (LDPE)/multiwalled carbon nanotubes (MWCNTs) nanocomposites with different foaming agent (OBSH) contents were innovatively prepared via In Situ Bubble Stretching (ISBS) and synergistic cyclic volume stretching. The cyclic convergent and divergent flow makes the MWCNTs repeatedly subjected to bubble stretching, which is conducive to the efficient dispersion of MWCNTs in the matrix. The thermal weight loss of neat OBSH and nanocomposite were characterized by thermal gravimetric analyzer (TGA), which indicated that the OBSH in the nanocomposite had been completely decomposed into gas during the plasticizing transport process. The results of morphology showed that the moderate content of OBSH had better dispersion effect on MWCNTs. At optimal OBSH content, the OBSH could generate enough gas and larger bubbles per unit time to provide greater expansion forces to do much for the dispersion of MWCNTs. The dynamic mechanical analysis (DMA) was further carried out and also proved that the content of OSBH was an important factor for the dispersion of MWCNTs. Moreover, the relationship between the OBSH content and conductivity was discussed in details. The improvement in conductive properties of nanocomposites associated with the use of the method can be attributed to a more homogeneous dispersion of MWCNTs., 1. INTRODUCTION Carbon nanotubes (CNTs), as good nanofillers with unique structure and good performance [1, 2]. are usually dispersed into various polymeric matrixes to prepare polymer/CNTs nanocomposites. The polymer/CNTs nanocomposites [...]

Under extreme conditions, the polymer dielectric materials are expected to have good dielectric properties and heat resistance. Polyimide (PI) has high service temperature (>250°C) and low dielectric loss, but its low dielectric constant limits its further application. The addition of MXene can significantly improve the dielectric constant of PI, but the poor compatibility between MXene and weak polar matrix leads to Bénard‐Marangoni (BM) instability in the process of thermal imidization. This issue can be solved by the surface modification of MXene. Therefore, in this work, a new cetyltrimethylammonium bromide (CTAB) decorated MXene/PI nanocomposite film was prepared by in‐situ polymerization. With the addition of 7 wt% MXene@CTAB, the PI nanocomposite shows improved dielectric constant (k = 7.8 at 100 Hz), which is 2.4 times that of pure PI due to the formation of micro‐capacitors structure and Maxwell‐Wagner‐Sillars (MWS) interfacial polarization. Its dielectric loss keeps at an ultra‐low level (0.027 at 100 Hz) while that of 7 wt% MXene/PI nanocomposite is 3.027. It is owing that CTAB inhibits the agglomeration of MXene. In addition, MXene@CTAB/PI composites have excellent thermal stability, good hydrophobicity, and low water absorption. The above properties ensure MXene@CTAB/PI composites wide application in various extreme situations. [ABSTRACT FROM AUTHOR]

Biodegradable polylactide (PLA) has been widely utilized in people's daily lives. In order to improve the fire safety of PLA, ammonium polyphosphate (APP) was self-assembled onto the surface of serpentine Ni3Si2O5(OH)4 through the electrostatic method, followed by mixing with PLA by melt compounding. The APP-modified serpentine (serpentine@APP) dispersed uniformly in the PLA matrix. Compared with pure PLA, the PLA composite with 2 wt% serpentine@APP reduced the peak heat release rate (pHRR) and total heat release (THR) by 43.9% and 16.3%, respectively. The combination of APP and serpentine exhibited suitable synergistic flame-retardant effects on the fire safety enhancement of PLA. In addition, the dynamical rheological tests revealed that the presence of APP and serpentine could reduce the viscosity of PLA composites. The plasticizing effects of APP and serpentine benefited the processing of PLA. The mechanical properties of PLA/serpentine@APP maintained suitable performance as pure PLA. This study provided a feasible way to enhance the fire safety of PLA without sacrificing its mechanical properties. [ABSTRACT FROM AUTHOR]

Thermoplastic polyurethane (TPU) is widely used in daily life due to its characteristics of light weight, high impact strength, and compression resistance. However, TPU products are extremely flammable and will generate toxic fumes under fire attack, threatening human life and safety. In this article, a nanohybrid flame retardant was designed for the fire safety of TPU. Herein, Co3O4 was anchored on the surface of exfoliated ultra-thin boron nitride nanosheets (BNNO@Co3O4) via coprecipitation and subsequent calcination. Then, a polyphosphazene (PPZ) layer was coated onto BNNO@Co3O4 by high temperature polymerization to generate a nanohybrid flame retardant named BNNO@Co3O4@PPZ. The cone calorimeter results exhibited that the heat release and smoke production during TPU combustion were remarkably restrained after the incorporation of the nanohybrid flame retardant. Compared with pure TPU, the peak heat release rate (PHRR) decreased by 44.1%, the peak smoke production rate (PSPR) decreased by 51.2%, and the peak CO production rate (PCOPR) decreased by 72.5%. Based on the analysis of carbon residues after combustion, the significant improvement in fire resistance of TPU by BNNO@Co3O4@PPZ was attributed to the combination of quenching effect, catalytic carbonization effect, and barrier effect. In addition, the intrinsic mechanical properties of TPU were well maintained due to the existence of the PPZ organic layer. [ABSTRACT FROM AUTHOR]

Phase change materials store and release heat energy in the process of phase change, so as to realize the effective recovery and utilization of heat energy. In this work, ultra‐high molecular weight polyethylene (UHMWPE)@carbon nanotubes (CNT) 3D porous matrix were fabricated by rotary sintering. By vacuum adsorbing paraffin wax (PW) into UHMWPE@CNT porous matrix, composite phase change materials (CPCM) with excellent shape stability and mechanical properties were obtained. In addition, thermal gravimetric analysis (TG) results showed that the thermal stability of PW in CPCM was significantly improved. Moreover, the highest thermal conductivity of CPCM was 0.31 W m−1 K−1 at a relatively low content of CNT, which was 1.71 times that of CPCM without CNT. CNT was uniformly dispersed in the porous matrix of UHMWPE to enhance the thermal properties of CPCM. Especially when the CNT content was 1.5%, the thermal storage performance and photothermal conversion efficiency of CPCM were effectively improved. Therefore, the CPCM prepared by this method with excellent combination property, had great application prospect in energy storage. [ABSTRACT FROM AUTHOR]