What is the Manufacturing Process of plastic bag

Plastic bags, an everyday convenience in modern life, are produced through a well-defined manufacturing process that combines raw materials, technology, and skilled labor. From the initial stages of raw material preparation to the final packaging and shipping, each step plays a crucial role in creating the final product. Here, we will explore the comprehensive manufacturing process of plastic bags in detail.

Raw material preparation

Polymer selection: According to the purpose and performance requirements of the plastic packaging bag, select suitable polymers as the main raw materials, such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), etc. These polymers usually exist in granular form.

Additive mixing: In order to improve the performance of plastics, some additives such as plasticizers, stabilizers, colorants, antistatic agents, etc. are also added. These additives are fully mixed with polymer particles in a high-speed mixer in a certain proportion.

Extrusion blow molding

Heating extrusion: Add the mixed raw materials to the hopper of the extruder, and the raw materials are conveyed forward and heated and melted by the rotation of the screw of the extruder. Under the action of high temperature and high pressure, the molten plastic forms a uniform melt.

Blow molding: The extruded melt is extruded into a tube through the die head, and then compressed air is immediately introduced into the tube, so that the tube blank expands under the action of air pressure and adheres to the inner wall of the mold to form the desired plastic bag shape, such as flat bags, vest bags, etc.

Printing

Surface treatment: In order to improve the adhesion of printing ink on the surface of plastic bags, the plastic bags after blow molding need to be surface treated, such as corona treatment, which uses corona discharge to polarize the surface of plastic bags, increase surface energy, and improve the adhesion of ink.
Printing operation: Print the designed pattern and text on the plastic bag by gravure printing, flexographic printing or screen printing. Gravure printing has the advantages of bright colors, rich layers, and high printing accuracy. It is one of the commonly used printing methods for plastic packaging bags. Generally, we will use a printing machine to complete

Bag making

Cutting: Cut the printed plastic film according to the required size to obtain a single plastic bag blank. Cutting can be done by hot cutting or cold cutting. Hot cutting has a fast cutting speed and a neat cut, but some melted edges may be produced; cold cutting has a smoother cut, but the cutting speed is relatively slow.
Edge sealing: Seal the cut plastic bag blank to form a sealed packaging bag. Edge sealing usually adopts heat sealing, which melts the edges of plastic bags and bonds them together by heating. The heat sealing temperature, pressure, time and other parameters need to be adjusted according to the material and thickness of the plastic bag to ensure the firmness and sealing of the edges. This task is usually completed by bag making machine, which is simple to operate and efficient, and is an ideal equipment for bag making.

Quality Inspection

Appearance inspection: Check the appearance of the produced plastic packaging bags to see if there are printing defects, scratches, bubbles, deformation and other problems. Screen and remove defective packaging bags.

Physical property test: Test the physical properties of plastic packaging bags, such as tensile strength, tear strength, heat sealing strength, moisture permeability, air permeability, etc., to ensure that their performance meets relevant standards and customer requirements.

Packaging and storage

Packaging: Pack the qualified plastic packaging bags according to a certain quantity, usually in cartons or plastic films for easy transportation and storage.

Storage: Store the packaged plastic packaging bags in a dry, ventilated and cool warehouse, avoid direct sunlight and humid environment to prevent aging, deterioration or damage of the packaging bags.

Overall, the plastic bag manufacturing process is a mature and highly automated industry. However, it is important to note that the specific steps and techniques used may vary depending on the type and size of plastic bag produced, as well as the equipment and technology available to the manufacturer. In addition, we are committed to using environmentally friendly practices and materials to reduce the impact of plastic bags on the environment.