The quality of packaging film fundamentally determines the finished performance of packaging bags, so the scientific selection of film raw materials is the premise of high-standard bag making production. Manufacturers should choose blown film grade polyethylene resin particles containing a moderate amount of lubricant as the core raw material. The added lubricant can effectively improve the opening performance of the film, avoid adhesion between film layers, and facilitate subsequent bag making, cutting and heat sealing operations.

The melt index (MI) of polyethylene resin particles is a core indicator restricting film forming performance and product quality, and its value must be strictly controlled. Resin with an excessively high melt index features low molten viscosity and a narrow processing tolerance range, which greatly increases the difficulty of process parameter adjustment and operation control. Such raw materials have poor film-forming properties and are prone to processing failures during film blowing. Meanwhile, resin with excessive MI has a narrow relative molecular weight distribution, which directly leads to insufficient mechanical strength of the produced film and fails to meet the tensile and impact resistance requirements of industrial packaging bags.

In actual industrial production, low melt index resin raw materials with a wide relative molecular weight distribution are preferred. This type of material balances excellent processing adaptability and stable film performance. For conventional blow molded polyethylene films used for bag making, the applicable melt index range is uniformly controlled at 2 to 6g/10min, which can fully meet daily processing needs and finished product quality standards.

Standard Process Flow of Blown Film

The complete production process of polyethylene blown film is standardized and systematic. The standard technological sequence is as follows: feeding into the hopper, plasticization and extrusion, inflation traction, air ring cooling, herringbone clamping, traction roller conveying, corona treatment, and final film winding.

Each link in the blown film process is interlocked and mutually restricted, and process parameters are the key factors determining film quality. Unreasonable parameter settings will cause defects such as uneven film thickness, poor flatness and insufficient surface tension. Therefore, in formal blown film production, enterprises need to implement refined parameter control, standardize operating specifications for each process link, eliminate unstable production factors, ensure continuous and smooth production, and finally produce high-quality, high-precision packaging film products suitable for subsequent bag making processing.