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Lightweight polyimide foams (PIFs) with exceptional thermal resistance and compressive properties are fabricated by heating polyester ammonium salts (PEASs) which are prepared by copolymerizing 4, 4'‐diaminobenzanilide (DABA), 4, 4'‐diaminodiphenyl methane (MDA) and 3, 3', 4, 4'‐benzophenone tetracarboxylic dianhydride (BTDA). Hydrogen bonds are formed between CONH and CO in the PI chains due to the addition of DABA and the melt viscosity of PEAS precursors increase with increasing content of DABA, which is advantageous to bind the foaming gases for cell expansion. The expansion ratio of PEAS precursors is increased from 633% to 1133% when the molar ratio of MDA/DABA is changed from 10:0 to 6:4. The compressive strength and modulus of PIFM9D1 (i.e., the molar ratio of MDA/DABA is 9:1, foam density: 120.8 kg m−3) reach as high as 0.59 and 15.0 MPa, respectively. The PIFs possess prominent thermal performance with the initial thermal degradation temperatures (under both nitrogen and air atmosphere) and glass transition temperatures (as assessed by DSC and DMA) exceeding 511 and 292 °C, respectively. The thermal conductivity of PIFs is lower than 0.049 W m−1 K−1, which exhibits promising applications for serving as high‐temperature thermal insulation materials in the fields of aerospace, marine, and nuclear sectors among others. [ABSTRACT FROM AUTHOR]

Polyimide hollow microspheres (PIHMs) possess lightweight and excellent thermal resistance, making them highly valuable for various applications in aerospace, catalysis, and irradiation. Co‐polymerized PIHMs (PIHMBMDs) are fabricated through powder foaming combined with a gradient heating strategy in this work. The diameter of PIHMBMDs ranged from 364 to 1230 µm, which can be designed by regulating the size of polyester ammonium salts (PEASs). The PIHMBMDs possess intact morphology with a breakage rate of 3%–10% and low bulk density with a density ranging from 28.3 to 62.9 kg m−3. Furthermore, PIHMBMDs exhibit excellent thermal properties with a 5% weight loss temperature and glass transition temperature of 525.0 and 282.5 °C, respectively, making it an ideal material for fabricating lightweight and high‐temperature‐resistant multifunctional composites. Moreover, the proposed method is simple, efficient, and easily scalable, which is suitable for industrial applications to manufacture large quantities of PIHMs. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) with excellent mechanical and thermal properties were fabricated by thermal foaming of active cross-linkable units terminated polyester ammonium salts (PEAS) precursor powders. The active cross-linking strategy was realized by breaking C C bonds in maleic anhydride under heating treatment. Results showed that the formation of cross-linked structure before complete imidization effectively resisted matrix shrinkage and endowed PIFs with outstanding mechanical properties. The room temperature compressive strength and modulus of PIFs with four repeating units reached as high as 2.34 and 56.1 MPa, respectively. Moreover, the PIFs exhibited excellent thermal properties with onset decomposition temperatures ranging from 490 to 550 °C and the glass transition temperatures exceeding 290 °C. The PIFs displayed better thermal insulation, and the values of thermal conductivity fell within a range of 0.056–0.090 W m−1 K−1, which demonstrates potential application as high temperature resistant structural materials in aerospace and energy sectors. [Display omitted] • Rigid PIFs were fabricated by thermal foaming of active cross-linkable units terminated PEAS precursor powders. • Cross-linking structure was formed before complete imidization which endowed PIFs with outstanding mechanical properties. • Relationship between chain structure and properties of rigid PIFs were investigated. [ABSTRACT FROM AUTHOR]

Polyimide foam (PIF) has been extensively used as structural and thermal insulation materials. Five semi-rigid PIFs with different diamine structures were fabricated by unrestricted foaming process with polyester ammonium salt (PEAS) precursor powders. All PIFs exhibited a nearly homogeneous spherical closed pore structure with an average pore size of 123–335 μm and a high closed-cell rate (87.4–95.5%). Results indicated that the molecular structure, melt viscosity and foaming temperature were important factors that affected the foaming process and pore structure. The values of 10% compression strength of PIFs at both 25 and 200 °C were in the range of 0.16–0.35 and 0.09–0.16 MPa, respectively, with PIF BTDA-MDA and PIF BTDA-DMBZ exhibiting the best mechanical performance. All PIFs exhibited outstanding thermal stability, with glass transition temperatures of 312–378 °C and 5% weight loss temperatures of 504.5–564.5 °C in nitrogen and 501.8–562.0 °C in air, respectively. The prepared PIFs exhibited extremely low thermal conductivity and thermal diffusivity, which can be used as thermal insulation materials. Based on above findings, the prepared semi-rigid PIFs demonstrate a great potential for being utilized as thermal insulation and structural support materials in high-tech fields such as aerospace, marine transportation, and microelectronics. [Display omitted] • Lightweight semi-rigid PIFs were prepared using PEAS precursor foaming method. • The foaming behavior was affected by molecular structure and foaming temperature. • The melt viscosity of PEAS determined the cell structure of PIFs. • All PIFs exhibited superior mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Epoxy resin has gained significant attention in aviation equipment, coatings and electronic packaging materials due to its exceptional processability, adhesion and mechanical properties. However, its thermal resistance property and glass transition temperature (Tg) were relatively lower than cyanate resin (CE), polyimides (PI) and phenolic resins (PF), which largely restricts its application range. In this work, we had developed a new structural heat-and-shielding integrated epoxy resin via the design of carboranes-epoxy network. Benefiting from the structure of carborane, the thermal residual weight of the obtained epoxy reached 64.57 %, with a carbon atom protection rate of 45.47 % in air atmosphere at 800 °C, showing better thermal resistance property than most CE, PI and PF. And the Tg of the new epoxy was not observed within the tested temperature range (50–250 °C). Additionally, the introduction of carborane structures enhances the neutron shielding performance of the material (38.46 % enhanced). The reinforcement mechanisms of these above properties are systematically investigated. It's excepted that our work could provide some ideas to prepare structural -functional integrated epoxy and promote the development of carborane related materials. • Large-scale synthesis of CBOH was achieved using aqueous extraction method. • The mechanism underlying the improved thermal resistance of epoxy resin modified with carborane was elucidated. • Simultaneously, the content of B and H atoms in the material was increased. [ABSTRACT FROM AUTHOR]

Rigid polyimide foams (PIFs) were successfully fabricated through thermal foaming of polyester ammonium salt precursors (PEASs) with the addition of a pararosaniline base (PA) as a crosslinker. These foams exhibited good mechanical properties and thermal resistance. The construction of crosslinked structure derived from PA could improve melt viscosity and provide cell walls with sufficient strength to prevent shrinkage, which was conducive to elevating compressive properties. PIF BMP -2 (i.e., repeating unit was 2) exhibited optimal compressive strength of 1.76 and 1.25 MPa at room temperature (RT) and 200 °C, which were increased by 6.6 and 7.9 times compared to PIF BM (0.17 MPa (RT) and 0.11 MPa (200 °C)). Furthermore, a relationship between compressive strength and density was established, showing that the compressive strength is proportional to 2.34 and 2.13 powers of density at RT and 200 °C, respectively. Moreover, PIFs owned excellent thermal properties, the 5% weight loss temperature was higher than 458.9 °C in a nitrogen (N 2) atmosphere, and the glass transition temperature was up to 291.3 °C. Additionally, the thermal conductivities of the rigid polyimide foams (PIFs) ranged from 0.058 to 0.094 W m−1 K−1, which makes them highly suitable for potential applications in the fabrication of high-temperature resistant multifunctional composites, particularly in aerospace, defense, and transportation industries. [Display omitted] • Rigid polyimide foams were fabricated with pararosaniline base as a crosslinker. • Crosslinked structure could significantly improve mechanical properties of fabricated foams. • Relationship between PI chains and properties was investigated. [ABSTRACT FROM AUTHOR]