In the production process of PP non-woven fabric, various factors may affect the physical properties of the product. Analyzing the relationship between these factors and product performance helps to correctly control process conditions and obtain high-quality and widely applicable PP non-woven fabric products. Below, Chengxin’s non-woven fabric editor will briefly analyze the main influencing factors on the physical properties of PP non-woven fabrics, and share with everyone:
1. Melt index and molecular weight distribution of PP non-woven fabric polypropylene chips
The main quality indicators of polypropylene chips are molecular weight, molecular weight distribution, regularity, melt index, and ash content. PP chips used for spinning have a molecular weight between 100000 and 250000, but practice has shown that the rheological properties of the melt are best when the molecular weight of polypropylene is around 120000, and its maximum allowable spinning speed is also high. The melt index is a parameter that reflects the rheological properties of the melt, and the melt index of polypropylene chips used for spunbond is usually between 10 and 50. During the spinning process, the filament only receives one airflow draft, and the draft ratio of the filament is limited by the rheological properties of the melt.
The larger the molecular weight, i.e. the smaller the melt index, the poorer its rheological properties. The smaller the draft ratio obtained by the filament, the larger the fiber size of the filament obtained under the same amount of melt ejected from the spinneret, resulting in a hard hand feel for PP non-woven fabric. If the melt index is high, the viscosity of the melt decreases, the rheological properties are good, and the resistance to stretching decreases. Under the same stretching conditions, the multiple of stretching increases. As the orientation of macromolecules increases, the breaking strength of PP non-woven fabric will increase, and the fiber size of the filament will decrease, resulting in a soft texture of the fabric. Under the same process, the higher the melt index of polypropylene, the smaller its fiber size, and the greater its fracture 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 a polymer, known as the molecular weight distribution value. The smaller the molecular weight distribution value, the more stable the rheological properties of its melt, and the more stable the spinning process, which is conducive to improving the spinning speed. It also has lower melt elasticity and tensile viscosity, which can reduce spinning stress, make PP easier to stretch and fine, and obtain finer denier fibers. Moreover, the uniformity of the web formation is good, with good hand feel and uniformity.
2. PP non-woven fabric spinning temperature
The setting of 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 corresponding spinning temperature, and vice versa. The spinning temperature is directly related to the viscosity of the melt, and the temperature is low. The viscosity of the melt is high, making spinning difficult and prone to producing broken, stiff or coarse fibers, which affects the quality of the product. Therefore, in order to reduce the viscosity of the melt and improve its rheological properties, the method of raising the temperature is generally adopted. The spinning temperature has a significant impact on the structure and properties of fibers. The lower the spinning temperature, the higher the tensile viscosity of the melt, the greater the tensile resistance, and the more difficult it is to stretch the filament to obtain the same fiber size
Post time: Mar-16-2024