Manufacturing Techniques and Mechanical Properties of Recycle
Kevlar®/PET Composite Nonwoven
Ching-Wen Lou
1, b, An-Pang Chen
2, Ya-Yuan Chuang
2, Jan-Yi Lin
2, Mei-Chen
Lin
2and Jia-Horng Lin
2,3,a1Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taichung 406, Taiwan, R.O.C.
2Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung City 407, Taiwan, R.O.C.
3School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan, R.O.C. a[email protected] , b[email protected],
Keywords: Recycle Kevlar® fiber, low melting polyester fiber, stab resistance, burst strength,
nonwoven Abstract.
Kevlar® fiber has characteristics of thermostability, high modulus, low elongation, impact resistance, chemical resistance and high performance. Therefore, in this study Kevlar® fiber was used to reinforce the nonwoven fabrics.
In this research, the content of the Kevlar® fiber was varied as 0 wt%, 5 wt%, 10 wt%, 20 wt%, and that of 15D PET fiber was changed as 70 wt%, 65 wt%, 60 wt%, 50 wt% accordingly when the Low-Tm polyester fibers was constant as 30 wt%. These fibers were used to manufacture the Kevlar®/PET composite nonwoven by nonwoven processing. Afterwards, the mechanical properties of the Kevlar®/PET composite nonwoven was measured both at cross direction and machine direction.
1. Introduction
Kevlar® fiber is the trade name made by Du Pont company. After the terephthalic acid and phenylenediamine monomer undergo the reaction of the condensation polymerization at low temperature, the Poly-p-phenylene terephthalamide fiber, abbreviated as PPTA fiber, was made whose chemical structure was shown in figure 1. The common solvents can’t solve the PPTA due to its rigid molecular. Thus it was spinned by dry/wet spinning at liquid crystal phase. For mechanical property, the Kevlar® fiber has tenacity of 19.4 cN/dex, modulus of 430~970 cN/dex. It has 1.44gw/cc specific gravity and decomposed at 550 oC. At present, the Kevlar® fiber was not only applied in bulletproof field but also sports equipment and aerospace conveyor [1-2]. In many research, the kevlar® fiber was used as the reinforced materials. In bulletproof field, it has ability of absorbing the impact energy and cushion [3-5].
Figure 1. The molecular structure of Kevlar® fiber. In this research, the combined Kevlar® fiber, PET fiber and Low-T
m polyester fibers were used to manufacture the Kevlar®/PET nonwoven fabrics by nonwoven process [6-10]. In the experiment,
the ratio of Kevlar® fiber was changed to evaluate the mechanical properties of Kevlar®/PET nonwoven fabrics at cross direction (CD) and machine direction (MD).
2. Experimental
Recycled Kevlar® fibers with a length of 50-60 mm were taken from Kevlar unidirectional selvages which were supplied by DuPont Company, America. Low-Tm polyester fibers had the fineness of 4D, length of 51 mm (provided by Huvis Chemical Fiber Co., South Korea). And the PET fiber had the fineness of 15D. Recycled Kevlar® fibers, Low-T
m polyester fibers and 15D PET fiber with variety of weight ratio (0:30:70, 5: 30:65, 10:30:60, 20:30:50) underwent the nonwoven manufacturing process consisting of opening, mixing, carding, laying, and needle-punching, forming the Kevlar®/PET composite nonwoven fabric. Afterwards, the tensile strength (ASTM D 5035-11), tearing strength (ASTM D5035-06), static puncture test (ASTM F1342-05) and bursting strength(ASTM 1883-07) of the Kevlar®/PET composite nonwoven fabric was measured respectively. Two orientations of nonwoven fabrics, MD and CD, was defined.
3. Results and Discussion
3.1 The effect of Kevlar® fibers content, as well as CD and MD on maximum tensile strength of Kevlar®/PET composite nonwoven fabric
In this test, the Low-Tm polyester fibers had content of 30wt%. And the content of Kevlar® fibers (0 wt%, 5 wt%, 10 wt% and 20 wt%) and 15D PET fiber (70 wt%, 65 wt%, 60 wt% and 50 wt%) were changed.
It is shown from figure 1 that when the ratio of the Kevlar® fibers was added, the tensile strength was increased. This is due to the fact that the Kevlar® fibers have benzene structure, and bonding between molecular has the high compactness and stiffness.
When Kevlar® fibers were not added in the nonwovens, composite nonwoven fabrics has higher tensile strength at CD than that at MD, because the fiber in CD has higher orientation than in MD. This phenomena was obviously displayed at higher content of Kevlar® fibers. This is because the Kevlar® fibers have high tensile strength and shearing strength, which reinforced Kevlar®/PET composite nonwoven fabrics especially at CD. Therefore , the Kevlar®/PET composite nonwoven fabrics have the optimum tensile strength when the ratio of Kevlar® fibers was 20 wt% and at CD.
Figure 1. The effect of content of Kevlar® fibers, and CD and MD on maximum tensile strength of Kevlar®/PET composite nonwoven fabric on (Kevlar® fibers: 0-20 wt%, 15D PET fiber: 70 wt%-50 wt%, Low-Tm polyester fibers: 30 wt%).
3.2 The effect of Kevlar® fibers content, as well as CD and MD on maximum tearing strength of Kevlar®/PET composite nonwoven fabric
Figure 2 shows the influence of Kevlar® fiber mass fractions on the maximum tearing strength of Kevlar®/PET composite nonwoven fabrics. While the ratio of the Kevlar® fibers was accelerated, the tearing strength was increased. This may be because Kevlar® fiber has the
microfibrillar structure. The fibrillar is composed of tabular crystal that was assembled by microfibrillar. In addition, the existence of microfiber connects with microfibrillar on various crystal faces. This leads to the high modulus and strength for Kevlar® fiber. Therefore, Kevlar®/PET composite nonwoven fabrics have the maximum tearing strength at CD when the Kevlar® fiber contained 20 wt%.
Figure 2. The effect of content of Kevlar® fibers, and CD and MD on maximum tear strength of Kevlar®/PET composite nonwoven fabric (Kevlar® fibers: 0-20 wt%, 15D PET fiber: 70 wt%-50 wt%, Low-Tm polyester fibers: 30 wt%).
3.3 The effect of Kevlar® fibers content on bursting strength of Kevlar®/PET composite nonwoven fabric
Figure 3 shows that the ratio of the Kevlar® fibers was added, the burst strength tends to be increased. This is due to the fact that the kevlar® fibers have benzene structure, and bonding between the molecular is compact and stiff. The rigid structure of Kevlar® fibers makes nonwoven fabrics difficult to deform when nonwoven is suffered from bursting force. Ultimately, the Kevlar®/PET composite nonwoven fabrics have the maximum bursting strength when Kevlar® fibers contained 20 wt%.
Figure 3. Effect of content of Kevlar® fibers on maximum bursting strength of kevlar®/PET composite nonwoven fabric (Kevlar® fibers: 0-20 wt%, 15D PET fiber: 70 wt%-50 wt%, Low-Tm polyester fibers: 30 wt%).
3.4 The effect of Kevlar® fibers content on stab resistance of Kevlar®/PET composite nonwoven fabric
The stab resistance is mainly due to the friction among fibers or pressure between probe and materials, so the increase of fiber fineness and strength increased is beneficial to improve the stab resistance.
Figure 4 shows that as the ratio of kevlar® fibers increases, the stab resistance improves. This trend is because the kevlar® fibers have benzene structure, and bonding between the molecular possesses higher compactness and stiffness. When probe impact penetrates the fibers, the rigid-structure fiber would resist against the probe energy. Therefore, the kevlar®/PET composite nonwoven fabrics have the maximum stab resistance strength when the ratio of kevlar® fibers was
20 wt%.
Figure 4. Effect of the content of kevlar® fibers on maximum stab resistance of kevlar®/PET composite nonwoven fabric (kevlar® fibers: 0-20 wt%, 15D PET fiber: 70 wt%-50 wt%, Low-Tm polyester fibers: 30 wt%).
4. Summary
In this research, the kevlar® fibers, Low-Tm polyester fibers and 15D PET fiber were used to manufacture the kevlar®/PET composite nonwoven fabrics through the nonwoven processing. The result shows that the CD tensile strength increased from 2 N to 27.4 N with the ratio of the kevlar® fibers increasing from 0 wt% to 20 wt%; and improved by 1270 % as compared to that of PET/low-Tm polyester composite nonwoven fabrics (0 wt% Kevlar® fiber). The maximum tearing strength at CD also increased from 3.8 N to 39 N at ratio of kevlar® fibers from 0 wt% to 20 wt%, improving by 926.3 %. The resulting Kevlar®/PET composite nonwoven fabrics would apply in the excellent stab resistance and high mechanical strength demanding fileds.
Acknowledgements
This work would especially like to thank National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract NSC 100-2621-M-166-001.
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