This work focuses on the influence of chain structure on properties such as the structural, thermal, morphological, and mechanical properties of polyimide foams (PIFs) which were prepared by polyester ammonium salt powder foaming process. Results showed that the melt viscosity of PEAS is affected by the structure of dianhydrides, which can greatly determine the foaming process, cell structure, and final properties of PIFs. PIF which was derived from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-diaminodiphenylmethane exhibited the highest compressive strength (0.374 MPa-RT, 0.194 MPa-200 °C) and compressive modulus (9.24 MPa-RT, 7.37 MPa-200 °C). All PIFs exhibited excellent thermal stability as the initial thermal decomposition temperature reached as high as 544 °C. In addition, the thermal conductivity of the as-prepared PIFs fell in a range of 38−42 mW m −1 K −1 , which show potential applications in areas of aerospace, aeronautics, marine use, and transportation among others.
Conductive polymer composites (CPCs) play an important role in various industrial applications including anti-static materials, electromagnetic interference shielding, sensors, and so forth. However, the contradiction between high conductivity and mechanical properties, especially tensile strength, is hard to balance many CPCs. In this paper, a self-reinforced polypropylene (PP)/graphene composite with segregated structures was fabricated by a novel coating-reducing-pressing method. By controlling the hot-pressing parameters, a special structure consisting of both an interconnected conductive graphene network and an unmolten fiber phase in a PP matrix can be obtained. PP/ graphene composites with such a structure showed not only excellent electric properties but also outstanding mechanical properties. A super-low electrical percolation threshold of 0.0043 vol % was reached for the composites because of an effective formation of the conductive graphene network. The conductivity of composites with only 1.85 wt % graphene reached to 4.09 S/m. The composites also showed good electromagnetic shielding effectiveness under an X band with the highest EMI of 29.3 dB at 10 GHz. The existence of the PP fiber phase contributed to the improved mechanical strength and toughness of the self-reinforcing conductive composites compared to the blending samples, which made it even stimuli-responsive for bending deformation. These results were believed helpful in the design and fabrication of a new kind of conductive self-reinforced polymer composites.
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