Fabrication and Characterization of a High-Strength Polyimide/Thermoplastic Polyurethane Composite Aerogel with Hydrophobicity and Low Thermal Conductivity

Abstract

Polyimide (PI) aerogel has surfaced in research and development as a result of its heat resistance, flame retardancy, and low dielectric constant. However, it is still a challenge to reduce the thermal conductivity while improving its mechanical strength and retaining hydrophobicity. Herein, the PI/thermoplastic polyurethane (TPU) composite aerogel was synthesized by coupling TPU with PI via a novel method of chemical imidization combined with freeze-drying technology. With this technique, PI aerogel with excellent comprehensive performance is produced. Interestingly, the volume shrinkage of the composite aerogel decreased from 24.14 to 5.47%, which leads to low density (0.095 g/cm3) and elevated porosity (92.4%). In addition, strong mechanical strength (1.29 MPa) and high hydrophobicity (123.6°) were achieved. More importantly, PI/TPU composite aerogel demonstrated a low thermal conductivity of 29.51 mW m–1 K–1 at ambient temperature. Therefore, PI/TPU composite aerogel can be a promising material for hydrophobic and thermal insulation applications.

Surface Modification of Polyimide Aerogel by Thermoplastic Polyurethane for Enhanced Mechanical Strength and Thermal Insulation Performance

“…As for PI aerogel, the compressive strength cannot be tested because the block is prone to be destroyed as shown in the video. In our previous work, 7 PI/ TPU aerogels were constructed by adding TPU into the sol− gel solution before the gel formed. In that work, the compressive strength of PI aerogel can also be enhanced from 0.77 to 1.29 MPa with the addition of 8.87 wt % TPU, but the value is decreased to 0.79 MPa when the TPU content is increased to 12.73 wt %.…”

“…The PI gel was synthesized according to our previous method reported in ref . At 25 °C, 0.843 g of ODA was dissolved in 15 mL of NMP solution, and then 1.278 g of BPDA was added into the solution.…”

“…In our previous work, the chemical imide method coupled with freeze-drying technology is used to synthesize PI aerogel; the calcination process is removed by this method, and the contraction of the aerogel is small. 7 But the aerogel is still fragile, and it is not easy to get an intact bulk material. To solve this problem, thermoplastic polyurethane (TPU) was added in the synthesis of PI aerogel; the flexibility of TPU can enhance the mechanical strength of PI aerogel to a certain extent.…”

“…In our previous work, the chemical imide method coupled with freeze-drying technology is used to synthesize PI aerogel; the calcination process is removed by this method, and the contraction of the aerogel is small . But the aerogel is still fragile, and it is not easy to get an intact bulk material.…”