Research on tear strength of coated fabrics
Research on tear strength of coated fabrics
The main polymer types currently used as fabric coating agents include polyurethane resin, polyacrylate resin and polyvinyl chloride resin. Among them, the latter has a long history of application and is used in large quantities. Polyvinyl chloride has excellent physical and chemical properties. As the main product of balanced chlorine in the chlor-alkali industry, it has rich sources of raw materials and consumes less non-renewable resources. With the application of new technologies and new technologies for the synthesis and processing of polyvinyl chloride, its production and processing costs have been greatly reduced. Now polyvinyl chloride resin has become a synthetic polymer with high output, low price, wide application field and good development prospects. variety. In recent years, PVC coated fabrics have developed rapidly, and new products such as PVC whole-core flame-retardant conveyor belts, PVC light conveyor belts, high-end waterproof fabrics, advertising fabrics, etc. have appeared, with bright colors and excellent mechanical properties .
At present, a common problem of PVC-coated fabrics is that the tear strength is too low, and some tear strength losses are as high as more than 50%. This study uses PVC paste resin as raw material, and by adjusting the coating agent composition and process conditions, studies the factors affecting the tear strength of PVC-coated fabrics and explores methods to improve its strength. 1. Experiment 1. Raw materials: P-440 polyvinyl chloride paste resin (PVC); dioctyl phthalate (DOP); dioctyl adipate (DOA); chlorinated paraffin (PCL) (chlorine content 40 %); dibasic lead stearate; antimony trioxide; heavy calcium (particle size 3 ~ 5 μm); polyester warp knitted fabric. 2. The fabric coating process is carried out on the MATHISLIF coating testing machine with knife-roller scraping. The coating process conditions are: baking temperature 155°C; baking time 1, 1.5, 2 minutes. 3. PVC coated fabric performance test ①. Determination of the tear strength of the coated fabric. Use the YG-026 fabric strength meter to measure the tear strength of the coated fabric. The test results are shown in the attached table.
②. Coated Fabric Flexible test coated fabric is made into 5×20 (cm) sample strips. Place the sample flat on the edge of a horizontal tabletop and push it out of the tabletop along the length of the sample at a uniform speed. With the front end of the sample facing toward The length of the bent part of the sample when it is bent downward to be perpendicular to the tabletop indicates the flexibility of the coated fabric. The test results are shown in the attached table. 2. Results and Discussion Adding plasticizers to polymers can reduce the forces between polymer macromolecules and provide space for movement of macromolecule segments. Therefore, plasticizers are a lubricant that reduce the frictional resistance within the movement of macromolecules [2 ]. Polyvinyl chloride macromolecules are polar macromolecules. The large number of polar groups on the molecular chain makes the force between macromolecules larger, making it difficult for the macromolecule chain to move. The entry of plasticizer molecules into the molecular chains of polyvinyl chloride can reduce the frictional resistance within the movement of macromolecules, making the relative movement between macromolecular chains easier on a microscopic level, and making the chain-breaking movement of plasticized polyvinyl chloride relevant on a macroscopic level. The properties have undergone major changes, such as flexibility and high-temperature fluidity significantly increasing.
In the experiment, we selected dioctyl phthalate (DOP), dioctyl adipate (DOA) and chlorinated paraffin (PCL) to form the plasticizing system. Dioctyl phthalate (DOP) and dioctyl adipate (DOA) are the main plasticizers, and chlorinated paraffin (PCL) is the auxiliary plasticizer. Dioctyl phthalate not only has excellent compatibility with polyvinyl chloride (Huggins parameter χ1=-0.03), but also has good compatibility with polyethylene terephthalate (polyester). Capacity. The structure of dioctyl phthalate is very close to the macromolecular unit structure of polyethylene terephthalate. Therefore, the polyvinyl chloride paste resin plasticized by dioctyl phthalate not only has better high-temperature fluidity, but is also easier to diffuse into the polyester fabric. Although the structure of the auxiliary plasticizer chlorinated paraffin (PCL) is similar to that of polyvinyl chloride, due to its higher molecular weight, the plasticizing efficiency of polyvinyl chloride (the amount of plasticizer added to change the quantitative physical and mechanical properties) is: 220, which is much lower than the plasticizing efficiency of dioctyl phthalate (100) . In a plasticizing system composed of dioctyl phthalate, dioctyl adipate and chlorinated paraffin, when the plasticizer content in the resin is fixed, as the content of the auxiliary plasticizer chlorinated paraffin increases, the mixing increases. The plasticizing efficiency of the plasticizer is reduced , and the high-temperature fluidity of the resin and the diffusion rate of the resin into the polyester fabric will also be reduced.
The experimental data in the table shows that as the total plasticizer content in the resin increases or the chlorinated paraffin content of the auxiliary plasticizer (plasticizer content is fixed) decreases, the tear strength of the coated fabric decreases significantly. We believe that This is caused by the diffusion of the coating agent between yarns and between fibers within yarns. When the uncoated fabric is torn, the fibers and yarns will be easier to be concentrated by elongation and movement under the action of external force. This will cause multiple yarns to resist damage from the external force at the same time when the fabric is torn, so the uncoated fabric is torn. The fabric exhibits high tear strength. After the fabric is coated, the resin that diffuses into the fabric limits the movement and deformation of the yarns and fibers. This makes it difficult for the fibers and yarns to move and concentrate under the action of external forces when the coated fabric is torn, and its ability to resist damage caused by tearing force is reduced. As the total plasticizer content in the resin increases or the chlorinated paraffin content of the auxiliary plasticizer decreases (the plasticizer content is fixed), the plasticizing efficiency of the plasticizer will be improved, and the high-temperature fluidity of the coating agent will be improved and transferred to the fabric. The diffusion capacity within the fabric increases, the amount of resin diffused into the fabric increases, the fixation effect on yarns and fibers increases, and the tear strength of the coated fabric further decreases. The bending length of the coated fabric in the table can indicate the flexibility of the coated fabric, and a long bending length indicatesCoated fabrics are less flexible.
Although there is no obvious regularity in the bending length of the coated fabric (this may be due to the dispersed weight gain of the coated fabric), the general trend is that as the total plasticizer content in the resin increases or the auxiliary plasticizer chlorine increases, As the paraffin wax content (with a fixed plasticizer content) decreases, the flexibility of the coated fabric decreases. According to the polymer plasticization theory, as the plasticizer content in the polymer increases, the flexibility of the polymer will also increase. The flexibility of the coated fabric does not increase with the increase of plasticizer or main plasticizer content. We believe that this is also due to the fixation effect of the resin that diffuses into the fabric on the yarn and fiber. As the content of plasticizer or main plasticizer increases, although the flexibility of the polymer outside the yarn increases, the penetration of resin into the interior of the yarn during processing will also increase, increasing the bonding between fibers within the yarn. force, which reduces the flexibility of the yarn. The result is a reduced flexibility of the coated fabric. The effect of baking time on the tear strength and bending length of coated fabrics can also prove that the amount of resin diffusion into the fabric is a factor affecting the tear strength of coated fabrics. Fabrics using No. 3, 6, and 7 formula coating agents have better fluidity and can complete diffusion into the fabric in a shorter time. Therefore, the baking time has a significant impact on the tear strength and bending length of the coated fabric. The impact is smaller. Fabrics coated with formula coating agents No. 1 and 4 have poor high-temperature fluidity, and the amount of resin diffusion into the fabric is greatly affected by the baking time. As the baking time increases, the diffusion of the resin into the fabric decreases. The diffusion amount increases greatly, and the fixation effect on yarns and fibers increases, so the tear strength of the coated fabric decreases more.
3. Conclusion 1. The main reason for the decrease in tear strength of coated fabrics is the influence of the coating agent on the movement and deformation of yarns and fibers after diffusing into the fabric. 2. Reducing the plasticizer content in the resin or the main plasticizer content in the plasticizer can reduce the high-temperature fluidity and diffusion speed of the coating resin into the fabric, reduce the diffusion amount of the coating resin into the fabric, and reduce the coating resistance. Loss of tear strength of ply fabric. 3. Baking time has a certain impact on the tear strength of coated fabrics. IzthoY3W1
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