S ound-Absorbing Evaluation on Nylon 6 /Low-Melting PET Nonwoven Fabric
Jia-Horng Lin
1,2, Ying-Hsuan Hsu
1, Chen-Hung Huang
3,a, Yu-Chun Chuang
1, Ting-Ting Li
4and Ching-Wen Lou
5,b1Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung City 407, Taiwan.
2School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan.
3Department of Aerospace and Systems Engineering, Feng Chia University, Taichung City 407, Taiwan.
4School of Textiles, Tianjin Polytechnic University, 63 Chenglin Road, Hedong District, Tianjin, 300160, China.
5Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taichung 406, Taiwan.
a[email protected], b[email protected] (corresponding author)
Keywords: Nylon 6, Low melting PET fiber, Nonwoven, Needle-punching, Absorption coefficient.
Abstract. In recent years, as quality life improves, people begin to focus on quiet environment.
Long-term noise pollution makes trouble of dysphoria and concentrating for people, thus noise- reduction has become an urgent project. This study uses Nylon 6 fibers, blended with different contents of low-melting PET fibers (10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt%), to fabricate Nylon6/ LPET nonwoven fabrics after needle-punching process. Afterwards, their maximum tensile strength, air permeability, sound absorption coefficient were all evaluated. When low-melting PET fibers contain 30 wt%, the nonwoven fabric has the better sound-absorbing property. Herein, the maximum tensile strength reaches 70.79 N and 31.01 N, respectively in CD and MD; the air permeability is about 116.5 [cm3/(cm2/s)].
Introduction
As rapid economic development in recent years, technology factory and residential area are built growingly. Relatively, human peoples’ quality life needs to be improved gradually. Noise pollution has become the common pollution in our daily life. Differences of the most severe noises that everyone suffers result in numerous hurts. For human people, 1 kHz- 3 kHz noises are more sensitive. Noises not only generate tired feeling to people, but also bring trouble to concentrate and working-efficiency. If these noises reduce, human health and working benefits would be greatly improved [1]. Noises also produce shielding effect, unable to feel the dangerous signal and thus easy to cause accident [2]. Textile fibers, especially for nonwovens, have widely used as sound-
absorbing materials. In general, porous media in saturated dry air can reduce environmental noise by transferring loss [3-4]. The best way is to transform sound energy into heat energy via reducing sound transfer and inhibiting sound vibration [5]. In this experiment, the sound-absorbing effect is achieved by fibrous pores, producing an energy change when noise transfers to sound-absorbing materials. As a kind of energy, according to energy conservation law, noise energy cannot disappear suddenly but can convert into different form of energy for sound-absorbing and sound-consuming effects [6]. In addition, main fibers —high-stiff Nylon fibers were combined with LPET fibers to increase the nonwovens stiffness.
Experimental Materials
Nylon 6 fiber: 3D (fineness)× 51 mm (length), provided by Ten Pow Chemical Industry Co., Ltd.; Low melting PET fiber (LPET): 4D (fineness) ×51 mm(length), offered by Far Eastern Textile., Ltd.
Apparatus
Maximum tensile strength testing: Instron5566, USA; Air permeability testing: Textest FX3300, Germany; Absorption coefficient testing: Double-microphone impedance tube tester.
Nonwoven Fabrication Process
Nylon 6 fibers blended with different ratios of LPET fibers (10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%) were made into Nylon 6/LPET nonwoven fabrics (basis weight:200±20 g/m2) via blending, carding, lapping, needle-punching (200 strokes/min ) and air-drying (130 ℃, 10 min).
Afterwards, their maximum tensile strength, air permeability and sound absorption coefficient were tested respectively according to ASTM D5035-11, ASTM D0730 and ASTM E1050-10, intended for finding the optimal nonwoven ratio.
Results and Discussion Maximum tensile strength
Figure 1 shows the maximum tensile strength of nonwoven fabrics with different ratios of LPET fibers (10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%). When LPET fibers include from 10 wt% from 30 wt%, their tensile strengths present hardly difference. But when LPET fibers content rises up at above 30 wt%, the tensile strength of nonwoven fabric tends to be down. This is because fiber tenacity of Nylon 6 is stronger than that of LPET. Tensile strength of nonwoven fabrics with 30 wt
% LPET fibers reaches the maximum of all, respectively 70.79 N in CD and 31.01N in MD, as indicated in Figure 1. Also, it is found that tensile strength in CD reveals to be higher than that in MD. This is due to fiber content in CD higher than that in MD after laying along CD from carding to lapping.
Air permeability
Most sound-absorbing materials depend on their porosity. The porosity is evaluated by air
permeability, revealing that the difficulty degree when sound is incident into inner sound-absorbing materials via air vibration. Table 2 shows air permeability of Nylon 6/LPET nonwoven fabrics with different ratios of LPET fibers (10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%). Nonwoven fabric with 30 wt% LPET fibers presents the lowest air permeability of 116.5 [cm3/(cm2/s)], because after melting uniform-dispersed LPET fibers bond nonwoven fibers and thus shield the inter-fiber pore.
However, when LPET fibers are rising to 50 wt%, the air permeability improves to 131.2 [cm3/
(cm2/s)]. This is attributed to the fact that too many LPET fibers influence the nonwoven manufacturing process, producing larger pores among fibers.
Figure 1. Maximum tensile strengths of Nylon 6/LPET nonwoven fabrics.
Table 2 Air permeability of Nylon 6/LPET nonwoven fabrics.
LPET content
(wt%) 10 20 30 40 50
Air permeability
[cm3/(cm2/s)] 128.4± 2.72 129.0± 4.69 104.1± 3.69 122.4± 2.63 137.0± 3.71
Figure 2. Sound-absorbing property of 1-layer Nylon 6/LPET nonwoven fabrics and 5-layer Nylon 6/LPET nonwoven fabrics.
Sound absorption coefficient
Figure 2 shows sound-absorbing property of 1-layer Nylon 6/LPET nonwoven fabric (LPET fibers ratio: 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%) and 5-layer Nylon 6/LPET nonwoven fabric (LPET fibers ratio: 10 wt%, 30 wt%, 50 wt%). 1-layer Nylon 6/LPET nonwoven fabrics all reveals worse sound-absorbing property due to their thinner thickness of 0.2 cm. Consequently, 5- layer nonwoven fabrics are performed to improve the sound-absorbing property. It is observed that both for 1-layer and 5-layer nonwoven fabrics, at frequency of 1000 Hz -2000 Hz, the sound
absorption coefficient is lower due to long wavelength at medium frequency; moreover, a trough is at 600 Hz-900 Hz, owing to resonance between samples and inner wall of impedance tube as indicated by Naoki Kino [7]. For 5-layer nonwoven fabrics, 30 wt% LPET fibers addition has higher sound absorption coefficient than the other two LPET fibers additions at testing frequency range, owing to different structure of three LPET fibers additions. 10 wt% LPET fibers addition shows lower absorption coefficient, attributed to too fluffy nonwoven fabrics. Moreover, because nonwoven fabric with 50 wt% LPET fibers has many larger pores, conversely the sound absorption coefficient reduces.
Conclusion
According to the experimental results, Nylon 6/LPET nonwoven fabric added in 30 wt% LPET fibers shows the highest tensile strength and lowest air permeability, respectively 70.79 N (CD) and 116.5 [cm3/(cm2/s)]. For sound-absorbing property, increasing one layer corresponds to improvement of 0.8 % sound-absorbing coefficient. When Nylon 6/LPET nonwoven fabrics are adding up to 5 layers (20 mm thickness), the mean absorption coefficient is 0.662. The optimum sound absorption produces when ratio of LPET fibers is 30 wt%. Therefore, in the following study, we will focus on properties of sandwiched structural composites composed of Nylon 6/LPET nonwoven fabrics (30 wt% LPET fibers) and other materials.
Acknowledgement
This work would especially like to thank National Science Council of the Taiwan, for financially supporting this research under Contract NSC 99-2621-M-035-001.
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