Plastic pelletizing machine

Plastic woven bags are primarily made from polypropylene and high-density polyethylene. Their auxiliary additives typically include modifiers, lubricants, and color masterbatches. With the widespread use of plastic woven bags, the volume of discarded bags has been steadily increasing. Recycling and reusing these waste plastics not only helps reduce environmental pollution but also ensures the efficient utilization of resources. High-density polyethylene–woven fabric offers superior手感, softness, and low‑temperature resistance, while polypropylene is abundant and cost‑effective; therefore, polypropylene is commonly used as the primary material for woven products. At present, an effective and practical recycling technology involves regranulation: the recycled pellets are then reused in the production of new woven items. Although their physical properties and quality fall short of virgin materials, proper selection can still enable compliance with specified standards.

If the flat yarn produced from recycled material lacks luster, a small amount of lubricant can be added to the formulation to improve its appearance. When selecting polypropylene (PP) recycled material, follow the “look‑bite‑burn‑draw” method: first examine the surface—material with a waxy feel, a dark sheen, and no bubbles is preferable; second, gently bite a pellet with your teeth—harder pellets indicate PP recycled material, while those that resist biting are high‑quality PP; softer pellets suggest PE‑based recycled material; third, ignite a pellet in a flame—if it self‑sustains after removal from the flame, with a blue base and yellow tip, producing copious black smoke and molten drippings accompanied by a petroleum odor, it is PP recycled material; finally, if the molten material can be continuously drawn into fine filaments, with short filament ends and a wax‑like burning smell, it is likely PE recycled material. The primary equipment for manufacturing plastic flat yarn is an extrusion molding machine.

After drying, the raw material should be maintained at 18–25°C, while the molding temperature of the recycled material is controlled at 150–200°C. During extrusion, the molten polymer in the plastic pelletizing machine must be filtered as it passes through the three-way manifold under pressure. The primary purposes of filtration are threefold: first, to remove impurities from the melt; second, to ensure stable flow; and third, to produce a denser, more compact final product. Currently, most filters employed are high‑elastic steel mesh screens with a mesh count of 60. Typically, the number of filter layers should be between 15 and 30—depending on operational experience—since too few layers can lead to unstable flow and insufficient density, whereas too many layers may create excessive resistance and cause the manifold to rupture. Following filtration, the molten polymer should be cooled after exiting the die, usually by water cooling. The cooling temperature is best maintained within the range of 30–35°C. Cooling serves three key purposes: first, to solidify the melt and set its shape; second, to prevent high‑temperature oxidation; and third, to inhibit crystallization, thereby providing the necessary conditions for subsequent thermal stretching. After extrusion, the molten film produced by the plastic pelletizing machine is cut using an appropriate knife gap, selected according to the type of flat filament being manufactured. During cutting, care should be taken to ensure uniformity across the entire width of the film. Only after thermal stretching can the cut film yield flat filaments with enhanced tensile strength; however, to minimize shrinkage during subsequent weaving, the filaments should also undergo a thermal setting process.