After being affected by external factors, the internal molecular structure of synthetic fibers will change, causing the shape of the fibers to bend and the length to decrease, which is known as fiber shrinkage phenomenon. In the papermaking industry, fiber shrinkage is an important indicator of fibers.
The influence of fiber shrinkage on papermaking is mainly reflected in the dimensional stability of paper and the quality control of paper.
Fiber shrinkage rate is the effect of moisture in the air on paper, that is, the change in relative humidity, which causes the size of the paper to shrink or elongate. When paper is soaked in water or excessively dried, it can also undergo size changes. The property of expansion and contraction due to changes in humidity or moisture is called dimensional stability. Therefore, fiber shrinkage directly affects the dimensional stability of paper and is one of the important indicators for measuring paper quality.
The influencing factors of fiber shrinkage rate include the content of pentose and cellulose in pulp, paper machine conditions such as wire speed ratio, proportion of fiber lateral arrangement, tension control of paper in the drying section, and adjustment of drying cylinder temperature curve. Maintaining an appropriate ratio of pulp to mesh, increasing the proportion of fibers arranged horizontally, correctly controlling the tension of the paper in the drying section, adjusting the temperature curve of the dryer, and other measures can effectively reduce the shrinkage rate of the paper. In addition, the condition of mechanical equipment also has an impact on the expansion and contraction rate of papermaking paper, such as the paper sheet being tightly attached to the surface of the dryer, which can reduce lateral shrinkage.
The morphological characteristics of fibers, such as the length, thickness, flexibility, fineness, and paper density of polyester fibers, also affect the shrinkage rate of paper. The fiber length is closely related to the comprehensive strength of paper. Long fibers can provide a larger bonding area and better stress distribution, resulting in a stronger fiber network. However, when the fiber length increases to a certain extent, the pulp suspension is prone to agglomeration, which has a negative effect on the uniformity of the paper and even reduces its strength. Fiber thickness has a significant impact on the characteristics of paper, especially printing performance, and is related to the tear resistance of the paper sheet. Fiber strength refers to the intrinsic strength of a single fiber, which is related to the thickness of the cell wall and the angle of the microfibers in the cell wall, with the latter having a greater impact. The fiber strength decreases with the increase of microfiber angle, indicating that the strength of a single fiber cannot determine the strength of the paper sheet. At the same time, it indicates that the strength of the paper sheet depends on multiple factors, including the bonding strength between fibers, fiber length, and the inherent strength of the fibers themselves.
In summary, the shrinkage rate of polyester fibers is a parameter that needs to be closely monitored during the papermaking process, as it directly affects the quality and dimensional stability of the paper. By optimizing the papermaking process conditions and fiber properties, fiber shrinkage can be effectively controlled and reduced, thereby improving the quality and performance of paper.
The low shrinkage polyester fibers we produce have a shrinkage rate of less than 2% and are evenly and easily dispersed in pulp solutions, which can improve the dimensional stability of paper and increase its flexibility.