Process principle of polypropylene staple fiber:

Definition and application of polypropylene staple fiber

The polymer is heated and fused into a spinning melt of a certain viscosity, which is continuously and evenly squeezed to the spinneret by a spinning pump, and then pressed into fine filaments flowing through the spinneret holes, and then cooled and solidified in air or water, and then produced by drawing.

Polypropylene staple fiber process:

Polypropylene staple fiber, direct spinning and slice spinning.

Direct spinning is the process of direct transfer of polymeric melt to spinning.

Slice spinning requires the polymer solution to be transported to spinning after the preparation process such as casting and cutting.

Polypropylene staple fiber technology mainly includes:

Preparation of spinning melt; The melt is pressed out through the holes in the spinneret -- forming a melt flow; The melt flows, elongates, tapers, cools and solidifies. Oiling and winding of solid wire.

The main characteristics of polypropylene staple fiber:

Fast winding speed, no need for solvent and precipitating agent, simple equipment, short process time. Using this method, fiber polymers can be prepared with melting point lower than decomposition temperature and can be melted to form heat stable melt. Such as polyester, polypropylene, nylon, etc.

The polypropylene staple fiber is a univariate system which only involves the heat transfer between the polymer melt filament and the cooling medium. The spinning system composition did not change, wet and dry spinning system was binary system (polymer + solvent) and ternary system (polymer + solvent + precipitator).

During spinning, the polymer melt is precipitated from the fine pores of the spinneret at a constant flow rate. Between the spinneret and the winding device, the filaments are stretched to the desired fineness and cooled sufficiently to set. The diameter of the spinneret is generally 0.1-0.4mm, and the diameter of the wound wire is only 20-30μm. After melting out of the spinneret hole, the diameter of the silk needs to be reduced ten times, and the silk needs to be stretched one hundred times, so the winding speed is one hundred times higher than the extrusion speed.

Because the polymer melt filament has strong tensile resistance after curing, the speed of polypropylene staple fiber is very fast. In industry, melt spinning is wound at a rate of several hundred to several thousand meters per minute. Cooling and curing of steel wire is usually done in the air under the spinneret. To enhance cooling, a airflow of temperature and humidity is blown vertically or parallel to the wire behind the spinneret. Stretching can change the internal structure of the fibril, improve the breaking strength and wear resistance, and reduce the elongation of the product. Thermal setting can regulate the intermolecular forces in the spinning process of polymer, improve the stability of the fiber and other physical mechanical properties, dyeing properties. Crimp improves the working performance of synthetic fibers (wool and cotton fibers are crimp) and overcomes the disadvantage of uneven, flat surfaces. False twist is an improvement on the fabric pattern to ferment it and increase elasticity.