Why are there fine lines on some tpu coated webbing?

TPU coated webbing is widely used in many industries due to its superior performance, such as waterproofing, abrasion resistance, and flexibility, making it an ideal choice for various products. However, some users may notice fine lines, known as drag marks, on the surface of the coated webbing. This phenomenon is not uncommon and can be attributed to two main factors: an uneven mold surface and the moisture content in TPU raw materials.

The mold plays a crucial role in the production process of coated webbing. The quality of the mold directly affects the appearance and surface quality of the product. When the mold surface is uneven or has defects, it can cause drag marks on the coated webbing during extrusion.

Over time, molds can wear down due to friction, pressure, or other factors. This wear can lead to small pits or scratches on the mold surface, resulting in drag marks during production. If the mold is not precisely processed or has minor defects from the beginning, these flaws will transfer to the surface of the coated webbing during production.

To ensure the smoothness of the mold surface, regular maintenance and polishing are necessary to eliminate any potential flaws and unevenness. Besides, using high-precision equipment and processes during mold manufacturing can significantly reduce surface defects, ensuring the surface quality of the coated webbing.

Apart from mold issues, the moisture content in TPU raw materials is another significant factor leading to the appearance of fine lines on coated webbing. TPU (thermoplastic polyurethane) is a material prone to absorbing moisture from the air. If TPU raw materials are not thoroughly dried before production, moisture can cause several problems during processing.

TPU materials have a certain level of hygroscopicity, meaning they can absorb moisture from their surroundings. If this moisture is not completely removed before production, it can cause various issues during extrusion and molding.

When moisture-laden TPU raw materials are processed at high temperatures, the moisture evaporates quickly, forming bubbles. These bubbles can cause irregular depressions or drag marks on the surface of the coated webbing. As bubbles pass through the cooling water tank, the water vapor inside them condenses, forming fine lines. These lines typically spread across the surface of the coated webbing, affecting its appearance and quality.

Then how to address moisture issues in TPU raw materials?

Before production, TPU raw materials must be thoroughly dried to remove any absorbed moisture. Typically, TPU raw materials need to be dried in a drying oven for several hours to ensure their moisture content is minimized. During production, specialized drying equipment, such as dehumidifying dryers, can further reduce the moisture content in the raw materials, preventing the formation of bubbles.

The appearance of fine lines or drag marks on coated webbing is mainly due to an uneven mold surface and moisture content in TPU raw materials. Ensuring strict control over each stage of the production process is crucial for producing high-quality TPU coated webbing.