Abstract:

Objective Noise pollution is listed as one of the four major pollutants in the world, along with water pollution, air pollution, and solid waste pollution, which seriously endangers human health. Therefore, it is of great importance to study sound absorption materials with simple processes and universal applicability. PET/ES fiber porous sound absorption nonwoven materials were prepared by using polyethylene terephthalate fiber (PET) and polyethylene/polypropylene bicomponent fiber (ES) as raw materials, using the needling process in combination with hot air bonding technology.

Method PET and ES fibers of different ratios (9∶1, 8∶2, 7∶3, 6∶4, 5∶5 for PET/ES fibers) were mixed, and the fibers were weighed in different qualities (20 g, 40 g, 60 g, 80 g, 100 g), and the fibers were opened, carded, and then needled to obtain the PET/ES composite fiber mesh. The PET/ES composite fiber porous sound absorption nonwoven material was prepared by the hot air bonding with regulated hot melt temperature (135 ℃ and 145 ℃) and bonding time (10, 20, and 30 min). With a scanning electron microscope, pore size analyzer, electronic fabric strength machine, and noise vibration test system, the morphological characteristics, pore size and its distribution, mechanical properties, and sound absorption properties of the PET/ES fiber porous sound absorption nonwoven materials were characterized.

Results PET and ES fibers had good microscopic morphology, no obvious cross-linking between fibers, and the distribution of fiber diameters was more concentrated. The melting point of PET fibers was at 250 ℃, and the ES fibers had two melting points at 129 ℃ and 160 ℃, respectively, which indicated that in the ES fibers with the skin-core structure the polyethylene fibers (PE) were on the surface layer and polypropylene fibers (PP) were in the core layer. The mechanical properties of the sound absorption materials were significantly improved with the increase of hot air bonding temperature and bonding time (2 044% compared to the pre-hot reinforcement). The prepared sound absorption materials all had high porosity (above 80%, up to 91.22%), and the porosity tended to increase with the increase of fiber feeding and ES fiber content. In addition, the average pore size and standard deviation of pore size of the sound absorption materials decreased with the increase of fiber feeding and ES fiber content (up to 83.16% for pore size and 82.26% for standard deviation of pore size). The mechanical properties of the material are affected by the ratio and feeding amount of PET/ES fibers. An increase in fiber feeding caused increase in the surface density and thickness of the material, resulting in a significant increase in tensile stress of the sound absorption material. The increase in ES fiber content resulted in an increase in the number of bonding points between neighboring fibers within the fiber network, which led improvement of the structural stability of the fiber network, and enhancement of the tensile stress of the material. The ratio of PET/ES fibers and the amount of feeding had a significant effect on the sound absorption coefficient of the material, which was more obvious at low frequencies when the proportion of ES fibers was low, and the sound absorption coefficient of the material at high frequencies was significantly improved with the increase of ES fiber content.

Conclusion In summary, the prepared PET/ES fiber porous sound absorption materials demonstrated high porosity, and the mechanical properties of the sound absorption materials are significantly improved with the increase of the hot air bonding temperature and bonding time. In addition, the ratio of PET/ES fibers and the amount of feeding had a significant effect on the sound absorption coefficient of the material, which was better at low frequencies when the proportion of ES fibers was low, and the sound absorption coefficient of the material at high frequencies was significantly improved with the increase of ES fiber content. The materials developed in this study require a simple preparation process and demonstrate strong universality, which provide reference significance for the development of new multi-frequency band sound absorption materials.

Key words: polyester fiber, polyethylene/polypropylene bicomponent fiber, porous structure, nonwoven material, sound absorption performance, hot air bonding technology