This blog post examines how synthetic fibers overcome the limitations of their artificial sheen and achieve an elegant, deep luster akin to natural fibers through micro-crater processing, focusing on fiber surface structure and the principles of light reflection.
As consumer tastes increasingly gravitate toward luxury, synthetic fibers must now possess properties similar to or even superior to natural fibers to remain competitive in the market. Amid this trend, various processing methods have been developed to differentiate synthetic fibers, one of which is the microcrater fiber introduced here.
Polyester remains the most widely used synthetic fiber due to its affordability and ease of care. However, polyester suffers from the disadvantage of having an overly strong sheen compared to silk, which detracts from its luxurious appearance. While silk, a natural fiber, also possesses sheen, its lustre is soft and elegant due to the structural characteristics inherent to the fiber itself. Consumers naturally prefer garments that convey this luxurious impression.
While using silk fabric with its luxurious sheen to make clothing would be ideal, silk is expensive and has limited supply. Consequently, manufacturers sought to apply processing to polyester, which is relatively easier to mass-produce, to achieve an elegant sheen similar to silk.
The surface of synthetic fibers is inherently very smooth, so they exhibit a different type of sheen compared to natural fibers. This occurs because light rays entering a smooth surface undergo specular reflection. The human eye perceives color and form by receiving light reflected from objects via the optic nerve; the greater the amount of light reflected from an object’s surface and reaching the eye, the stronger and more dazzling the perceived sheen.
Therefore, creating fine irregularities on the fiber surface reduces specular reflection occurring on the surface. As a result, the amount of light entering the human eye decreases, yielding a soft, deep luster. In other words, the originally strong gloss inherent to polyester is transformed into a quality closer to the elegant sheen of silk by imparting irregularities to the fiber surface.
The process by which humans perceive an object’s color is based on the same principle. This is because color is recognized through the process of light reflected from the object being transmitted via the optic nerve. Synthetic fibers like polyester have a limitation: even when dyed, they struggle to achieve the subdued color tones or deep hues seen in natural fibers. However, by forming numerous microscopic holes on the polyester surface, the previously explained light reflection principle enables the realization of subdued and deep colors.
To understand the cause of this phenomenon, refer to the following graph. Since polyester fibers treated with alkali reduction processing have properties similar to micro-crater fibers, examining how the dyeability of alkali-treated polyester fibers differs from untreated polyester fibers allows us to infer how micro-crater fibers’ dyeability changes relative to conventional polyester fibers.
The longer polyester undergoes reduction processing, the more its fabric moisture absorption improves. This occurs because the reduction process generates hydrophilic functional groups on the fiber surface that readily bind with water, or because numerous microscopic pores form on the fiber surface, increasing the area available for water adsorption. Since dyes also function in a hydrated state, improved moisture absorption directly enhances the fiber’s ability to adsorb dye. In other words, the greater the degree of sizing, the deeper the color tone the fabric can achieve during dyeing.
To produce such fibers with superior dyeability, silica (SiO₂) particles of a fine size, specifically 0.1 micrometers or smaller, are blended into the spinning solution before spinning. After spinning, an alkaline treatment dissolves and removes the silica, forming numerous microscopic grooves on the fiber surface. This principle is analogous to sprinkling ceramic fragments onto cement that is not yet fully dry; when the ceramic is removed, the imprints of the fragments remain on the cement surface. Fibers manufactured in this manner are called microcrater fibers.
According to data from the Korean Intellectual Property Office, this process was first patented in 1995 by Kolon Corporation under the invention title “Polyester Fiber and Its Manufacturing Method.” Subsequently, similar patents were registered: SK Chemicals Co., Ltd.’s “Method for Manufacturing Rayon/Deep-Dyed Polyester Composite Yarn” in 2002, and Hyosung Corporation’s “Modified Polyester Polymer and Its Manufacturing Method, Polyester Fiber Manufactured from the Polymer, and Manufacturing Method of the Fiber” in 2004. The fact that similar technologies continue to be registered even now, since micro-crater fiber was first patented in Korea in 1995, demonstrates that this is a practical and useful technology widely utilized in the actual Korean textile industry.
Micro-crater fibers are recognized as high-value-added fibers due to their dry yet soft handfeel and their ability to achieve both deep and bright color tones. These characteristics demonstrate synthetic fibers’ potential to overcome the limitations of natural fibers and sustain their use in the high-end fiber market, clearly revealing the industrial significance and technological value of micro-crater fibers.
