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In modern industry and daily life, PVC-coated fabrics are widely used in tents, truck tarpaulins, inflatable products, luggage, outdoor furniture, and many other fields. As one of the key technologies for producing high-performance PVC-coated fabrics, the thermal lamination process is both precise and fascinating.
First, let's briefly understand what "thermal lamination" is. This is a process for producing PVC-coated fabric. Its core is to evenly apply PVC paste resin (a liquid or paste-like PVC raw material) to a base fabric (such as polyester or nylon) through methods such as knife coating. The resin is then placed in a high-temperature oven through a process of "gelation" and "melt plasticization." Finally, the PVC layer and base fabric are firmly bonded together, forming a single piece. The term "thermal lamination" stems from the crucial role played by high temperatures in this bonding process.
The entire thermal lamination production line is a continuous, automated assembly line, and each step is crucial, determining the quality of the final product.
The first step in production is to treat the base fabric. The base fabric roll is placed on the unwinding device, smoothly unrolled, and fed into the production line. To enhance adhesion between the PVC coating and the base fabric, some base fabrics require corona treatment or a thin pre-coat of adhesive. This step significantly improves subsequent lamination and prevents delamination.
This is a critical production stage that directly determines the product's performance, feel, and appearance. In a large mixing tank, the PVC paste resin, as the main ingredient, is mixed with various additives according to a precise formula.
Plasticizers are the most important additives, acting like a "lubricant" that penetrates the PVC molecular chains, making it soft and flexible. The amount added directly controls the product's softness and hardness.
Stabilizers prevent PVC from decomposing and yellowing during subsequent high-temperature processing, ensuring stable product performance and long-lasting color. Pigments and colorants impart a rich, vibrant color to the product. Other additives, such as flame retardants, mildew inhibitors, and UV stabilizers, are used to meet customers' specific functional requirements.
The prepared PVC paste is transported via pipes to the coating head. This is the core molding step. The most common coating method is knife coating. The substrate passes under a large steel scraper, creating a precise gap between the scraper and the substrate. The PVC paste is evenly "scraped" onto the surface of the substrate. The height and angle of the scraper gap, as well as the speed of the substrate, determine the thickness and uniformity of the coating. This step requires extreme precision; any fluctuation will result in uneven thickness of the product.
The coated wet material immediately enters a multi-section, high-temperature oven. This is where the name "hot lamination" comes from, and this is where the magic happens.
Gelation: In the front section of the oven (where the temperature is relatively low, such as 140-160°C), the plasticizer begins to fully penetrate and swell the PVC resin particles. The paste gradually loses its fluidity and becomes a gel-like solid. At this point, the coating is initially set.
Fusion: As the fabric continues to advance, it enters the high-temperature zone at the rear of the oven (where temperatures can reach 180-200°C). The PVC resin particles completely dissolve and melt in the plasticizer, forming a homogeneous, continuous, and dense film layer that firmly bonds to the base fabric fibers. This process fully unleashes the various properties of the PVC material.
Embossing: The material, still hot and softened, exits the oven and immediately passes over a pair of embossing steel rollers. These rollers are engraved with a designed pattern (such as plain, orange peel, or leather). Under pressure, the corresponding pattern is embossed onto the surface of the material. This not only enhances aesthetics but also improves the feel, hides scraper marks, and increases surface friction.
Cooling: The hot, embossed material must be rapidly cooled to set its shape. It passes over a large cooling roller (with circulating cold water inside), where the temperature drops dramatically, completely solidifying the PVC layer and permanently fixing the pattern. Winding: Finally, the fully cooled, formed PVC-coated fabric passes through an automatic web-correcting device and is neatly rolled into a large roll for easy transportation and subsequent slitting and manufacturing.
The production of thermal lamination for PVC-coated fabric is a complex process that integrates chemical formulations, precision machinery, and automated control. From the preparation of the base fabric and the careful mixing of the PVC paste, to precise doctoring, high-temperature gel plasticization, and finally embossing and cooling, every step is meticulously crafted to create this composite material with excellent performance and a wide range of applications.
