Physical Properties Of Spunbond Non Woven

During the production of spunbond non woven, various factors may affect the physical properties of the product. Analyzing the relationship between these factors and product performance is helpful to correctly control the process conditions and obtain products with good quality and wide applicability.

1. Melt index and molecular weight distribution of spunbond non woven polypropylene chips

The main quality indicators of polypropylene chips are molecular weight, molecular weight distribution, isotacticity, melt index and ash content. The molecular weight of PP chips used for spinning is between 100,000 and 250,000, but it has been proved that the rheological properties of the melt are the best when the molecular weight of polypropylene is about 120,000, and the maximum allowable spinning speed is also high. . The melt index is a parameter that reflects the rheological properties of the melt. The melt index of polypropylene chips for spunbond is usually between 10 and 50. If the melt index is larger in spinning, the viscosity of the melt will decrease, the rheology will be better, and the drafting resistance will decrease. Under the same drafting conditions, the drafting multiple will increase. When the orientation degree of macromolecules increases, the breaking strength of the spunbond non-woven fabric increases, and the fineness of the filaments decreases, and the fabric appears soft to the touch. Under the same process, the higher the melt index of polypropylene, the smaller the fineness and the greater the breaking strength.

The molecular weight distribution is often measured by the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polymer, which is called the molecular weight distribution value. The smaller the molecular weight distribution value, the more stable the rheological properties of the melt and the more stable the spinning process, which is beneficial to increase the spinning speed, and has lower melt elasticity and extensional viscosity, which can reduce the spinning stress. It makes PP easier to stretch and thin, and finer denier fibers can be obtained, and the uniformity of the web is better, with good hand feel and uniformity.

2. Spinning temperature of spunbond non woven fabric

The setting of the spinning temperature depends on the melt index of the raw material and the requirements for the physical properties of the product. The higher the melt index of the raw material, the higher the spinning temperature, and vice versa. The spinning temperature is directly related to the melt viscosity, and the temperature is low. The viscosity of the melt is high, spinning is difficult, and it is easy to produce broken filaments, stiff filaments or thick filaments, which affects the quality of the product. The lower the spinning temperature of the spunbond non-woven fabric, the higher the elongational viscosity of the melt, the greater the tensile resistance, and the more difficult it is to stretch the thread. be higher.

3. Cooling and forming conditions of spunbond non woven fabric

During the forming process, the cooling rate of the strands has a great influence on the physical properties of the spunbond nonwoven. After the molten polypropylene comes out of the spinneret, if it can be cooled quickly and uniformly, the crystallization rate is slow and the crystallinity is low. Relatively large, the orientation of the molecular chain is better, which can further improve the crystallinity, improve the strength of the fiber, and reduce its elongation, which is manifested in that the breaking strength is large and the elongation is low; if it is cooled slowly, the obtained The fiber is a stable monoclinic crystal structure, which is not conducive to the drafting of the fiber, which is manifested in that the breaking strength is small and the elongation is large. The cooling distance is generally selected between 50 and 60 cm.

The seemingly simple production process of spunbond non woven fabric is actually the result of the long-term efforts of many technicians and workers. A little negligence in processing and manufacturing will bring a bad experience to the product. I hope our industrial technology will become more and more developed.