In the production of polypropylene yarn, the breakage rate is a key factor affecting production efficiency and product quality. Reducing the breakage rate requires a multi-dimensional, systematic solution involving raw material selection, process optimization, equipment maintenance, operational procedures, and environmental control.
Raw material quality is the foundation of polypropylene yarn production. The grade of polypropylene resin must be precisely matched to production requirements. Different grades have significantly different melt flow rates, molecular weight distributions, and other characteristics. Inappropriate selection can lead to decreased fiber spinnability. For example, resins with excessively high melt flow rates are prone to forming low molecular weight fractions during stretching, resulting in insufficient fiber strength and increasing the risk of breakage. Simultaneously, impurities, moisture, and low-molecular-weight substances in the raw materials must be strictly controlled. Impurities can clog the spinneret, moisture vaporizes at high temperatures leading to fiber breakage, and low-molecular-weight substances affect the fiber's crystalline structure, reducing its mechanical properties. Therefore, raw materials must undergo rigorous inspection before entering the factory, rejecting unqualified batches, and pre-treated before production, such as by drying and filtering, to ensure raw material purity.
Optimizing spinning process parameters is the core step in reducing the breakage rate. Spinning temperature needs to be precisely set according to the characteristics of polypropylene resin. Too low a temperature will result in poor melt flow and easy clogging of the spinneret; too high a temperature may cause resin degradation, producing low-molecular-weight substances and affecting fiber quality. Matching the stretching temperature and speed is equally crucial. Too low a stretching temperature results in insufficient fiber crystallinity and low strength; too high a stretching speed leads to stress concentration within the fiber, easily causing fuzzing and breakage. Generally, the stretching temperature of polypropylene staple fibers is controlled within a suitable range, and the stretching speed is adjusted according to fiber specifications. For filament production, the stretching speed needs further optimization to balance fiber strength and elongation. Furthermore, the heat setting process is essential for improving fiber dimensional stability and crystallinity. Reasonable settings of heat setting temperature and time can reduce fiber shrinkage and deformation in subsequent processes, lowering the probability of breakage.
The condition of the equipment directly affects the production stability of polypropylene yarn. The spinneret in the spinning equipment needs to be cleaned and replaced regularly to prevent clogging or deformation that could lead to uneven fiber thickness. Wear on drafting components such as rollers and spindles can cause tension fluctuations; worn parts need to be inspected and replaced regularly to ensure the smoothness of the drafting process. The design of the winding mechanism must consider yarn tension control to avoid yarn breakage due to excessively tight or loose winding. For example, in the production of a doubling machine, controlling the yarn storage is crucial; too much or too little yarn storage can cause abnormal air ring shape, increasing the risk of yarn breakage. The yarn storage must be controlled within a reasonable range by adjusting components such as the bullet head and counterweight shims. Furthermore, the transmission components of the equipment, such as bearings and gears, require regular lubrication and maintenance to reduce yarn breakage caused by mechanical jamming.
Following operational procedures is an important guarantee for reducing the breakage rate. Operators must strictly follow the cleaning schedule to clean the equipment, especially key areas such as carding and drafting, to prevent the accumulation of short fibers and fly waste that can cause yarn defects. During splicing operations, the quality of the splice must be ensured to avoid subsequent yarn breakage due to improper splicing. During routine inspections, close attention must be paid to the condition of the cotton web, yarn channels, and air ring shape, and any problems must be addressed promptly. For example, if problems such as holes or torn edges in the cotton web are not addressed in time, they will lead to defective yarn breakage in subsequent processes, requiring immediate machine shutdown and rectification. In addition, operators need to receive regular training to improve their quality awareness and operational skills, reducing yarn breakage caused by human factors.
Environmental control is equally crucial for polypropylene yarn production. Fluctuations in workshop temperature and humidity affect fiber strength and static electricity, thus impacting breakage rates. Suitable temperature and humidity enhance fiber strength, reduce static electricity and entanglement, and improve spinning efficiency. For example, excessively high temperatures in the spinning process can cause roller and apron entanglement, increasing breakage; excessively low temperatures can lead to increased fly waste and fiber static electricity, affecting yarn quality. Therefore, a reasonable temperature and humidity range must be set according to the process characteristics and precisely controlled through an air conditioning system. Furthermore, workshop cleanliness is also essential. Dust, fly waste, and other impurities adhering to the yarn path can cause yarn defects and breakage; regular cleaning and maintaining a clean environment are necessary.
