In extreme environments, protective devices need to be designed to take into account a variety of potential external threats. Kevlar and Nomex® were used in Apollo-era spacesuits, for example, to cope with varying temperatures in space, dust storms and meteor hazards, and intense solar radiation.

Among them, the mechanical strength of Kelvar® is derived from its rigid para-aromatic polyamide skeleton, which is spontaneously arranged and crystallized by ordered liquid crystal solution under stress. Nomex® thermal insulation is derived from the intermediate aromatic polyamide skeleton, where the kinked polymer backbone inhibits the accumulation of polymer and thus the slow transfer of heat across the disordered polymer chain. The realization of this kind of versatility is mostly based on the design of multi-layer structure, but in fact, it is difficult to construct bulletproof insulation materials through multi-layer structure due to the competition between adiabatic process and mechanical energy dissipation process. However, it has been found that nanoscale Kevlar can build multifunctional materials by dispersing ordered microcrystals in randomly arranged ordered films.

Limitations of traditional materials

Based on this, a team of scientists at the university of harvard combining porous mesh structure and directional fiber, developed a new type of material, the material has two kinds of adiabatic and bulletproof performance at the same time, to overcome the traditional protective material limitation of design cannot meet the demand of a variety of functions, in the military, aerospace and other fields has important application value.

The researchers synthesized a para - arylon fiber using an immersive rotary air - jet spinning platform. It arranges the counterpoint aramid fibers along the direction of mechanical load of aerogel. Directional counterpoint arylon fiber can effectively cope with mechanical stress, while porous network structure can reduce heat diffusion without damaging structural function.

The preparation methods

To study the material's bullet-proof properties, the researchers used a simulated bullet test to evaluate whether the bullet penetrated the material. The test results show that the anti - ballistic properties of aramid fiber are comparable to those of commercial anti - ballistic textiles.

Ballistic performance test

It was found that the thermal conductivity of the counterpoint aramide material was much lower than that of the commercial fiber Twaron®, and its thermal insulation performance was improved by 20 times compared with the commercially available counterpoint aromatic polyamide material.