Xing Liu’s research while affiliated with Gannan Normal University and other places

Glass fiber reinforced nylon 66 (GF/PA66) composites have been widely used in a range of industrial applications, but it is still a challenge to design and manufacture GF/PA66 composites with simultaneously improved processability, thermal, and mechanical properties. Here, a novel imide oligomer (FPI) was synthesized and used as a multifunctional modifier. Thanks to trifluoromethyl (CF3) and anhydride groups, FPI was located at the interface between GF and the PA66 matrix, and enhanced the interfacial interactions via covalent interactions and hydrogen bonds (H bonds), leading to the homogeneous dispersion of GF in composites and the improved processability. In addition, the results were confirmed by molecular dynamics (MD) simulations. The equilibrium torque of GF30/PA‐FPI3 (30 wt% GF and 3 wt% FPI) was decreased by 54.2% compared to that of GF30/PA, attributed to the rigid‐flexible structure of FPI. Furthermore, unlike conventional flow modifiers that have a negative effect on the thermal, mechanical, and hydrophobic properties of GF/PA66 composites, the glass transition temperature (Tg), heat deflection temperature (HDT), fracture energy, flexural modulus, and water contact angle of GF30/PA‐FPI3 were increased by 10.6°C, 40.3°C, 67.8%, 20.1%, and 26.9° respectively, compared to those of GF30/PA. Therefore, this study demonstrated the potential application of FPI for GF/PA66 composites and provided a promising avenue for preparing high performance GFRP composites as advanced engineering composites.

The preparation of phase change materials (PCMs) with excellent heat storage capacity, shape stability, and working durability is of vital importance for their popularization and application. In this work, a series of form‐stable PCMs was prepared via blending diglycidyl ether of bisphenol A (DGEBA), aliphatic anhydride with octadecyl side chains (MNAO), and paraffin together followed by thermal curing. Thanks to the plasticizing effect and self‐assembly of paraffin, the crystalline behavior of paraffin and MNAO was hardly limited by the epoxy network, and the latent heat of EP/Pa‐50 with 50 wt% paraffin content was high, up to 92.3 J/g. Meanwhile, EP/Pa‐50 had a low supercooling extent of 11.0°C. Instead of the significant reduction in other properties of most PCMs after being blended with paraffin, the overall performance of EP/Pa‐50 remained good due to the strong intermolecular interactions between paraffin and MNAO (based on their good compatibility) and the reliable epoxy network, and EP/Pa‐50 exhibited excellent shape stability without the leakage problem, high thermal stability (remain stable below 170°C) and good mechanical properties (tensile strength up to 10.5 MPa). This work provides a facile strategy to prepare form‐stable PCMs, which have promising application prospects in the field of thermal regulation.

Metal-organic frameworks (MOFs) hold great promise for diverse applications when combined with polymers. However, a persistent challenge lies in the susceptibility of exposed MOF pores to molecule and polymer penetration, compromising the porosity and overall performance. Here, we design a molecular-caged MOF (MC-MOF) to achieve contracted window without sacrificing the MOF porosity by torsional conjugated ligands. These molecular cages effectively shield against the undesired molecule penetration during polymerization, thereby preserving the pristine porosity of MC-MOF and providing outstanding light and thermal management to the composites. The polymer containing 0.5 wt % MC-MOF achieves an 83% transmittance and an exceptional haze of 93% at 550 nanometers, coupled with remarkable thermal insulation. These MC-MOF/polymer composites offer the potential for more uniform daylighting and reduced energy consumption in sustainable buildings when compared to traditional glass materials. This work delivers a general method to uphold MOF porosity in polymers through molecular cage design, advancing MOF-polymer applications in energy and sustainability.

Polyamide 6 (PA6) is a widely used thermoplastic engineering polymer, and the toughening modification for PA6 is always a main research topic. Meanwhile, the rigidity and heat resistance of PA6 usually deteriorate. To address this conflict, an epoxy compound (EGDE‐GA) was designed and synthesized and used to modify PA6 by dynamic vulcanization in twin‐screw extruder. EGDE‐GA is a linear molecule with a flexible molecular structure, which is favorable to toughening of PA6, and epoxy groups of EGDE‐GA can form local cross‐linked structure to improve the rigidity and retain the heat resistance of PA6. At the loading of 20 wt% of EGDE‐GA, the modified PA6 (PA6/EGDE‐GA 20) exhibited very high elongation at break and notched impact strength, which were increased by 413% and 520%, respectively, compared to those of PA6. The tensile strength was 61.4 MPa, which was higher than that of PA6. The heat deflection temperature remained almost unchanged. The results showed that the modified polymers may possess the high toughness without sacrificing the original rigidity by building the local crosslinked structure using dynamic vulcanization. The findings provide a feasible method for reusing and upcycling PA6 and other polymers with higher value and wider use in the industry. Highlights The polyamide 6 (PA6) is toughened via dynamic vulcanization. The toughness of modified PA6 is increased by 520% compared with pure PA6. The toughened PA6 exhibits higher tensile strength than that of pure PA6. The toughened PA6 maintains its rigidity and heat resistance.

Conventional base-catalyzed epoxy/aliphatic thiol systems have a poor storage stability, and are impossible to be one-pot systems. A widely accepted solution is to use the latent catalysts, which are usually insoluble anionic initiators sensitive to impurities and moisture, and have many limitations in practical use. In this work, a soluble thiol-terminated imidothioether oligomer (TPI) was synthesized and used as a latent hardener and modifier to prepare one-pot epoxy/thiol systems without the latent catalysts. The latent behavior and curing mechanism of epoxy systems (EP/TPI series), consisted of bisphenol A diglycidyl ether (DGEBA), pentaerythritol tetrakis(mercaptoacetate) (PETMP) and TPI, were proposed. The thiol exchange reaction between TPI and PETMP preceded the curing reaction of DGEBA, and produced aromatic thiols, which were unreactive at ambient conditions and reacted with DGEBA to form the thermosets at temperatures above 130 °C. At the loading of 24.4 wt% TPI, the epoxy system (EP/TPI-3)had a shelf life of 13 days and was completely cured within 20 min at 180 °C. Meanwhile, the catalyst-free curing process of EP/TPI-3 system was insensitive to impurities and moisture. Furthermore, the thermal and mechanical properties of EP/TPI-3 thermoset were simultaneously improved, thereinto, the glass transition temperature, Young’s modulus and ultimate tensile strength were increased by 16.7 °C, 12.9%, and 13.6%, respectively, compared with those of the commercial DGEBA/PETMP thermoset. This work shows that TPI has the potential to be a powerful alternative to commercial latent catalysts, and EP/TPI thermosets with high performance have broad application prospects.