Preparation and properties of nonwoven flame retardant sound-absorbing material from Hu sheep wool

Objective The scale of Hu sheep breeding continues to grow, but due to the low quality of fiber, Hu sheep wool is not suitable for preparing medium and high-grade wool yarns, resulting in the low price and low industrial demand. Based on the performance and structural characteristics of Hu sheep wool, this paper explores the development of sound-absorbing material by needle punching Hu sheep wool, which represents an effort to best use natural resources. Method Hu sheep wool sound-absorbing materials were prepared by needling, milled finishing and flame retardant finishing. The processing process involves scouring → weighing → opening → carding → lapping→ fleece formation → pre-needling → needling → rolling → milled-finishing → drying → flame retardant finishing → drying → finished product. The effects of structural parameters, milled process and flame retardant process on sound absorption performance were explored. Results Hu sheep wool has a distinct medullary cavity, which is a loose porous structure (Fig.2). The Hu sheep wool scales are covered with craze, and the scales are wide and cocked up obviously (Fig.3). The fibers of Hu sheep wool were entangled with each other to form a three-dimensional fiber network (Figs.4-6). The fibers winding of Hu sheep wool needled fabric after milled finishing was more compact than that before milled finishing. After flame retardant finishing, the flame retardant was attached to the fiber surface of the Hu sheep wool needle fabric. When the sound wave range was in the middle and high frequency range, the sound absorption effect of the Hu sheep wool sound absorption material was good (Fig.7). The structural parameters (thickness, surface density and average pore size) of needled sound absorbing materials had influence on sound absorption performance (Tab.3). The horizontal burning performance of the Hu sheep wool needled fabric before flame retardant finishing reached the flame retardant standard requirements, but the vertical burning speed was 276 mm/min, failing meeting the standard requirements(Fig.8). After flame retardant finishing, the horizontal burning performance exceeded the standard requirements, and the vertical burning speed became 0 mm/min, meeting the standard requirements. Conclusion Hu sheep wool has an obvious medullary layer, and the porous structure of its medullary cavity makes Hu sheep wool have good sound absorption performance. The Hu sheep wool scales are covered with craze, and the scales were very wide and cocked up obviously. This scale structure makes the Hu sheep wool have good milling power. For Hu sheep wool needled fabric, thickness and surface density are the main factors affecting its sound absorption performance. On the premise of not affecting the lightweight of the vehicle and meeting the requirements of sound absorption performance, the Hu sheep wool needled fabric with a thickness of 3.5-5 mm and a surface density of 350-450 g/m2 can be selected as the sound absorption material for the interior of the vehicle to meet the requirements of noise reduction. © 2023 China Textile Engineering Society. All rights reserved.