Most thermoplastics can be blown film production with blow molding, blow molding plastic film is to squeeze into a thin tube, then strike with compressed air to blow plastic bulge, after cooling to finalize the design of tubular membrane products, this kind of film performance between oriented film and stretch film: strength is better than stretch film, heat sealing worse than stretch film.
There are many kinds of film produced by blow molding method, such as low density polyethylene (LDPE), linear polyethylene (LLDPE), polypropylene (PP), high density polyethylene (HDPE), nylon (PA), ethylene ethylene acetate copolymer (EVA), etc. Here we briefly introduce the blow molding production process of commonly used LDPE and LLDPE films.
1. The selected raw material should be blown film grade polyethylene resin particles, containing a proper amount of smoothing agent, to ensure the opening of the film.
2 resin particle melting index (MI) can not be too large, melting index (MI) is too large, the viscosity of molten resin is too small, the processing range is narrow, processing conditions are difficult to control, resin film is poor, not easy to process into film; In addition, the melting index (MI) is too large, the relative molecular weight distribution of the polymer is too narrow, and the strength of the film is poor. Therefore, should choose melt index (MI) is small, and the relative molecular weight distribution of wide resin raw materials, so as to meet the performance requirements of the film, but also to ensure the processing characteristics of the resin. Blow molding polyethylene film is generally used in the melting index (MI) between 2 and 6g/10min polyethylene raw materials.
Blow molding film process is roughly as follows:
Hopper loading material plasticizing extrusion → blow traction → air ring cooling → herringlet splint → traction roll traction → corona treatment → film winding
Post time: Aug-15-2022