Preparation and Characterization of High Strength Anti-Aging Geotextile
Abstract: In order to improve the durability and safety of geosynthetics in practical engineering applications, an anti-aging polypropylene/high modulus and high strength polyvinyl alcohol short fiber mixed wholesale polypropylene nonwoven geotextile was prepared. The content of polyvinyl alcohol fiber was discussed on polypropylene nonwoven geotextile manufacturers. The effects of mechanical and filtration properties were observed by scanning electron microscopy. The weathering resistance and metal ion resistance were characterized by correlation tests. The results show that the polyvinyl alcohol fiber is uniformly dispersed in the polypropylene nonwoven geotextile factory price, which makes the inter-fiber entanglement tighter. When the content of high modulus and high-strength polyvinyl alcohol fiber is 60%, the mechanical and filtration properties of the polypropylene nonwoven geotextile for sale are significantly improved. Wet rupture strength is 29.7, 34.8kN / m, respectively; equivalent pore diameter is 0.1093mm; at the same time, weather resistance and metal ion resistance are improved, after 90d photo-oxidation aging and 18d thermal oxygen aging (after immersion in copper nitrate solution) After the experiment, the strength retention rates were 73.7% and 64.3%, respectively.
Keywords: composite wholesale polypropylene nonwoven geotextile; weather resistance; metal ion resistance; anti-aging polypropylene fiber; high modulus high strength polyvinyl alcohol fiber
polypropylene nonwoven geotextile manufacturers is an industrial textile used in civil engineering, water conservancy and other projects . Since the Netherlands was first used in dam construction in 1926, it has been widely used worldwide. Since the 1990s, China has used a large number of high quality polypropylene nonwoven geotextile in water conservancy, roads, railways, mines, landfills, and other engineering fields, mainly for drainage, filtration, isolation, protection, and anti-seepage . To meet the engineering design period (such as the design life of modern landfills is 30 to 50a), long-term and stable function is one of the main requirements of polypropylene nonwoven geotextile for sale, but in practical applications, complex and harsh environments tend to It causes certain damage to the wholesale polypropylene nonwoven geotextile and greatly shortens its service life, which does not meet the engineering design requirements .
At present, the raw materials for preparing high quality polypropylene nonwoven geotextile are mainly polyester (PET) and polypropylene (PP), accounting for more than 90% of the total output. Polypropylene has good acid and alkali resistance, but it is not resistant to ultraviolet radiation. Photocatalytic degradation occurs under intense ultraviolet light for a long time, causing macromolecular chain breakage. At the same time, the metal ions present in the waste liquid of mines and landfills will also catalyze and accelerate the heat aging process of polypropylene, and the temperature and humidity will cause the mechanical properties to drop drastically, thus losing the role that should be exerted. The UV resistance of polyester is slightly better than that of polypropylene, but it is resistant to acid and alkali, and moisture and temperature will also have a certain effect on it. Both types of fibers are defective and are often associated with greater safety risks in complex and variable environments [4-5].
High modulus high strength polyvinyl alcohol (PVA) fiber  has a linear density of 2.2 dtex, a strength of more than 15.3 CN/dtex, elongation at break of 6%, a modulus of 30 GPa, and good acid and alkali resistance/heat. Anti-radiation properties, filaments are often used in cable and fishing nets for marine applications . At the same time, high modulus and high strength PVA has higher cost performance and good engineering application value compared with other high-performance fibers [8-9], such as aramid and carbon fiber.
In this paper, a certain proportion of anti-aging polypropylene and high-modulus high-strength polyvinyl alcohol mixed acupuncture to prepare short-fiber wholesale polypropylene nonwoven geotextile, in order to improve the product’s strength, acid and alkali / metal ions and anti-ultraviolet radiation performance, enhance its complex and harsh environment The safety and long-term effectiveness provide theoretical basis and guidance for future research.
1.1 Raw materials
Anti-aging polypropylene staple fiber, breaking strength is 6.2cN/dtex, elongation at break is 16%, purchased from Yizheng Chemical Fiber Co., Ltd.; high modulus and high strength polyvinyl alcohol staple fiber, breaking strength is 15.3cN/dtex, elongation at break The long rate is 6% and is provided by Anhui Weiwei Group Co., Ltd.
Figure 1 shows the preparation process of anti-aging PP/high modulus high strength PVA wholesale polypropylene nonwoven geotextile. In the production and preparation process, it is necessary to pay attention to 1) Due to the high rigidity of the high modulus and high strength PVA fiber, the linear density is small, the carding and the needling process should be as soft as possible, especially in the process of acupuncture, excessive needle density. And the depth of acupuncture is easy to damage the fiber and even cause breakage. The depth of acupuncture used in this experiment is 8mm, the density of acupuncture is 300 thorns/m2; 2) the density of high-mode high-strength PVA fiber is small, during the reciprocating laying process It is easy to cause drift, which causes the uniformity of the nonwoven polypropylene nonwoven geotextile for sale to decrease. The distance between the reciprocating and the bottom curtain should be properly adjusted, preferably 40 cm.
Figure 1PP/PVA polypropylene nonwoven geotextile manufacturers preparation process
1.3 Performance test
1.3.1 Microscopic observation
The internal microscopic morphology of the anti-aging PP/high modulus and high strength PVA staple fiber needled wholesale polypropylene nonwoven geotextile was observed using a Quanta 200 scanning electron microscope (Netherlands) with an operating voltage of 20 kV.
1.3.2 Filter performance test
The equivalent pore size (O95) was tested on an XSB-88 vibrating screen.
1.3.3 Dry/wet strength test
According to GB/T17638—20017 “Geosynthetic Synthetic Short-staple Needle Nonwoven polypropylene nonwoven geotextile for sale”, the breaking strength of the dry state and wet sample soaked in water for 24h was tested.
1.3.4 Weatherability test
Refer to GB/T3681—2000 “Test Methods for Natural Weather Exposure of Plastics” for weather resistance testing.
1.3.5 Copper ion resistance test
The sample was immersed in a copper nitrate solution at 25 ° C, taken out after 72 h, and then placed in a constant temperature oven at 120 ° C for 18 d, and the change in strength was tested to characterize the copper ion resistance of the wholesale polypropylene nonwoven geotextile .
2. Results and discussion
2.1 Analysis of mechanical properties
Table 1 shows the effect of high modulus and high strength PVA short fiber content on the dry and wet strength of high quality polypropylene nonwoven geotextile (area density 400 g/m2). It can be seen that with the increase of PVA content, the dry strength and wet strength of the mixed polypropylene nonwoven geotextile manufacturers are greatly improved. The dry/wet breaking strength of pure polypropylene nonwoven geotextile factory price was 17.2 and 13.5 kN/m, respectively. When the PVA content is 60%, the dry/wet breaking strength of the geotextile is as high as 29.7 and 34.8 kN/m, respectively. On the one hand, the high modulus and high strength polyvinyl alcohol has high strength and is not easily broken under the action of external force, and the mixed acupuncture with PP staple fiber can enhance the effect; on the other hand, the linear density of polypropylene staple fiber in general geotextile is 6.7. Dtex, while the high modulus high strength PVA has a linear density of 2.2 dtex, as shown in Figure 2. In the wholesale polypropylene nonwoven geotextile, a large number of high-modulus high-strength polyvinyl alcohol fibers exist, and the linear density thereof is small, so that the entanglement is tight with each other, thereby improving the mechanical properties of the polypropylene nonwoven geotextile for sale.
Table 1 Effect of PVA content on dry/wet fracture strength of polypropylene nonwoven geotextile manufacturers
Figure 2 SEM photo of PP/PVA geotextile
In addition, it can be seen from Table 1 that the dry strength of pure polypropylene high quality polypropylene nonwoven geotextile is higher than the wet strength; but in PP/PVA polypropylene nonwoven geotextile for sale, with the increase of PVA content, starting from about 35%, Its wet strength is higher than the dry strength, and is more pronounced when the PVA content is 60%. This can be explained by the fact that the high-modulus high-strength polyvinyl alcohol fiber is a highly crystalline, highly oriented material. In the wet state, the water molecules enter the fiber interior, weakening the force between the macromolecular chains, and enhancing the macromolecular chain. The slipping ability and the uniformity of the tension increase the number of macromolecules and improve the mechanical properties . Although PP is also a kind of polymer material, its crystallinity is low, and the entry of water molecules will destroy the arrangement and bonding between the macromolecules, thereby deteriorating the mechanical properties. This makes the anti-aging PP/high-modulus high-strength PVA staple fiber mixed wholesale polypropylene nonwoven geotextile has unique engineering application advantages in water conservancy projects or in high humidity environments.
2.2 Analysis of filtration performance
Table 2 shows the effect of PVA content on high quality polypropylene nonwoven geotextile filtration performance. It can be seen that as the PVA content in the mixed polypropylene nonwoven geotextile manufacturers increases, the equivalent pore diameter O95 decreases, indicating that the vertical permeability coefficient decreases. Geotextiles play a role infiltration in many practical engineering applications, such as Yangtze River channel management and soft foundation treatment. Due to the low strength of fine denier polypropylene, it is easy to cause serious fiber damage during high-speed carding and needle punching. It is difficult to meet the requirements of engineering on the mechanical properties of polypropylene nonwoven geotextile factory price. Therefore, 6.7dtex polypropylene is generally used as the raw material of short fiber needled polypropylene nonwoven geotextile factory price. To ensure that the mechanical properties meet engineering standards. In addition, the coarser fiber also makes the geotextile larger in diameter and larger in vertical permeability coefficient, which affects its filtration performance, especially in the soft foundation treatment project, the size of the wholesale polypropylene nonwoven geotextile coated on the outer layer of the drainage board. The requirements are more stringent.
Table 2 Effect of PVA Content on the Performance of polypropylene nonwoven geotextile manufacturers Filtration
PP/PVA mixed polypropylene nonwoven geotextile for sale not only has high strength but also has the characteristics of small equivalent pore size and small vertical permeability coefficient. Compared with pure PP high quality polypropylene nonwoven geotextile, its filtration performance is better.
2.3 Weathering performance analysis
Geotextiles are exposed to the natural environment, and their mechanical properties will decrease rapidly under the long-term effects of ultraviolet light, rain, temperature (high temperature or high cold) . Among them, the effect of ultraviolet light on polypropylene fibers is particularly significant. After the PP molecule absorbs the light energy, it is exciting to the electronically excited state. If it does not jump from the excited state back to the ground state in time, it will generate free radicals, which will react with the oxygen in the air, that is, photo-oxygen reaction occurs; therefore, polypropylene Fiber aging does not react with light, but by absorbing light energy and reacting with oxygen. Figure 3 shows the regularity of the breaking strength of pure PP, anti-aging PP and anti-aging PP/PVA polypropylene nonwoven geotextile for sale in the natural exposure aging experiment.
Figure 3 Weather resistance of polypropylene nonwoven geotextile manufacturers
It can be seen from Fig. 3 that after 90 days of natural exposure aging test, the mechanical properties of pure PP high quality polypropylene nonwoven geotextile are most obvious, the strength retention rate is about 37%; the strength retention rate of anti-aging PP polypropylene nonwoven geotextile manufacturers is about 58%, which is better than Pure PP wholesale polypropylene nonwoven geotextile. This shows that the addition of an anti-aging agent can partially alleviate and prevent photo-oxidative aging of the polypropylene material, but the effect is not very satisfactory. In addition, the strength retention rate of the anti-aging PP/PVA mixed polypropylene nonwoven geotextile factory price after the natural exposure aging test is about 73%, which is significantly higher than that of the anti-aging PP polypropylene nonwoven geotextile factory price. High-mode high-strength PVA fibers are exposed to ultraviolet light for a long time and are less affected. Therefore, the use of polypropylene nonwoven geotextile manufacturers mixed with anti-aging PP can improve the weather resistance of nonwoven polypropylene nonwoven geotextile for sale.
2.4 Surface morphology analysis
Figure 4 shows the surface topography of anti-aging PP and high modulus high strength PVA after 90 days weathering test. It can be clearly seen that the anti-aging PP has undergone photooxidation reaction under ultraviolet irradiation for a long time, the macromolecular chain is broken, the fiber is damaged, and the surface exhibits various forms of cracks, depressions, flaking and other forms of damage, thereby making the fiber The mechanical properties are greatly affected; on the contrary, the damage form of the high modulus high strength polyvinyl alcohol fiber surface is mainly concave, and the damage is small. Therefore, the original mechanical properties of the fiber can be basically maintained after the weather resistance test for 90 days.
Figure 4 SEM photograph of anti-aging PP/PVA high quality polypropylene nonwoven geotextile (after natural exposure for 90d)
2.5 Copper ion resistance analysis
Polypropylene reacts under the action of temperature, which is the same as the principle of photooxidation. The absorption of thermal energy causes the polypropylene molecules to be excited from the ground state to the excited state, thereby reacting with oxygen, in which copper ions accelerate this as a catalyst. The reaction accelerates the aging of the anti-aging polypropylene fiber, and the catalytic action of the copper ion can be expressed by the following reaction formula :
Figure 5 shows the copper ion resistance of pure PP, anti-aging PP, and anti-aging PP/PVA polypropylene nonwoven geotextile for sale. Sample No. 1 is a pure PP polypropylene nonwoven geotextile manufacturers that have not been soaked in a copper nitrate solution, and No. 2 is a high quality polypropylene nonwoven geotextile that has been immersed in a copper nitrate solution for 72 hours. It can be seen from the figure that after 18 days of heat treatment at the same temperature, the breaking strength retention rates of samples No.1 and No.2 were 77.2% and 42.3%, respectively, indicating that copper ions have a significant catalytic effect on the thermal oxidation reaction of polypropylene materials. Sample No. 3 was treated with high temperature for 18 days, and the breaking strength retention rate was 44.6%, which was not much different from that of No. 2 sample, indicating that the anti-aging agent could not effectively prevent the thermal oxidation of polypropylene fibers under the catalytic action of copper ions.
Figure 5: Copper ion resistance of polypropylene nonwoven geotextile factory price
The No. 4 sample is an anti-aging PP/high modulus and high strength PVA mixed wholesale polypropylene nonwoven geotextile. After 18 days of high strength treatment, the breaking strength retention rate is 64.3%, which is better than the No. 2 and No. 3 samples. This is due to the high crystallization and high degree of orientation of the high modulus high strength polyvinyl alcohol fiber, which makes it excellent in high-temperature resistance. Only when it is above 80 ° C and the humidity is high, it will show significant mechanical properties degradation; In the case of heat, it can withstand a high temperature of 150 ° C or more for a long time, and there is almost no such situation in the practical application of the high quality polypropylene nonwoven geotextile: therefore, in the process of immersing and heating the copper nitrate solution, both copper ions and high temperature are almost Without affecting its performance, the fiber can still maintain high mechanical properties, which makes the copper-resistant performance of polypropylene nonwoven geotextile manufacturers improved compared to pure PP and anti-aging PP polypropylene nonwoven geotextile for sale.
(1) The high modulus and high strength PVA is applied to the polypropylene nonwoven geotextile factory price, which can obviously improve the mechanical properties of the non-woven short fiber polypropylene nonwoven geotextile factory price. When the PVA content is 60%, the dry/wet strength is 29.7 and 34.8 kN/m, respectively. They are 1.7 and 2.6 times of the same surface density anti-aging polypropylene high quality polypropylene nonwoven geotextile, and the wet strength is greater than the dry strength; at the same time, the equivalent pore diameter is small and the filtration performance is excellent.
(2) Anti-aging PP/high modulus and high strength PVA short fiber mixed polypropylene nonwoven geotextile factory price has better weather resistance and metal ion resistance than anti-aging PP and pure PP high quality polypropylene nonwoven geotextile, and the mechanical properties and long-term safety have been improved significantly.
(3) Anti-aging PP/high modulus and high strength PVA short fiber mixed polypropylene nonwoven geotextile for sale in areas with strong ultraviolet radiation (such as Xinjiang, Tibet, Sichuan, etc.) and water conservancy projects, projects containing metal ion waste liquid (such as landfills, tailings) Fields such as processing engineering have their unique advantages.