Abstract:

Objective Under the background of national carbon peak and carbon neutralization, the use of waste corncobs to prepare sound-absorbing composites can not only reduce the greenhouse gases generated by the combustion of waste corncobs, but would also help meet the current carbon peak and carbon neutralization goals, effectively promoting China's green development to a new level.

Method The morphological structure, aggregation structure and macromolecular structure of waste corncob were characterized by scanning electron microscopy, X-ray diffractometer and Fourier transform infrared spectrometer, and the relationship between its structure and sound absorption performance was clarified. The sound-absorbing composites of waste corncob/polycaprolactone were prepared by hot pressing method using waste corncob as the reinforcement and polycaprolactone as the matrix. The effects of the particle size of waste corncob, the mass fraction of waste corncob, the hot pressing pressure, the hot pressing time, the hot pressing temperature and the thickness of the back air layer on the sound absorption performance were investigated and study its sound absorption mechanism.

Result Corncobs had a hollow structure with undulating surface and irregular connection, which was similar to the hollow tubular structure composed of waist circular sheet structure stacked together. These holes were stacked and interspersed with each other, and the hollow structure would form a pore structure. When the sound wave contacted the sound-absorbing composites, a part of the sound wave would enter the composites, reflect and diffuse in the pores, causing the vibration and friction of the gas, thus converting part of the sound energy into heat energy, so that the sound wave can be absorbed. In addition, due to the low crystallinity of waste corncob, the macromolecules were not closely arranged, the distance between molecules is large and the interaction was weak, and the molecular chain was easy to move. When sound wave were incident, the vibration of molecular chains and bonds would be caused, and the energy of some sound waves would be weakened. When the sound energy acts on the macromolecular structure of the waste corncob, the force between the segments made the sound wave energy attenuate during the propagation process and converted into other forms of energy to achieved the effect of sound absorption. Through single factor experiments, the parameters were optimized, and the average sound absorption coefficient and noise reduction coefficient were used as indicators. when the particle size of waste corncob was 0.1 mm, the mass fraction of waste corncob was 30%, the hot pressing time was 20 min, the hot pressing pressure was 10 MPa, the hot pressing temperature was 130 ℃, and the thickness of the back air layer was 2.0 cm, the average sound absorption coefficient of the corncob/polycaprolactone sound-absorbing composites prepared was 0.50, the noise reduction coefficient can be up to 0.57, the maximum sound absorption coefficient was increased to to 0.82.

Conclusion The use of waste corncob to prepare sound-absorbing materials solves the problem of resource waste and environmental pollution caused by a large number of waste corncobs as garbage burial and incineration, and has good social benefits. At the same time, it provides experimental and theoretical basis for the development of waste corncob/ polycaprolactone sound-absorbing composites, and provides a new idea for the recycling of waste corncob.

Key words: waste corncob, structural characteristic, sound absorption performance, sound absorption mechanism, composite material