The main factors affecting the self-adhesiveness of the stretched film

The self-adhesiveness of the stretched film is mainly affected by the following factors:
(1) Additives in base resin The base resin such as LLDPE, mLLDPE, LDPE, or EVA used for the production of a stretched film, if it contains an additive such as a slip agent, a lubricant, or a surfactant, causes the adhesion of the film to be remarkably lowered.
(2) Density of resin  The lower the resin density of the stretched film, the better the softness and adhesion of the film. Some types of resins of mLLDPE and ULDPE have a density of less than 0.923 g/cm2. In the production, these ultra-low density polyethylene resins are blended, and even if no tackifier is added, it has good self-adhesiveness.
(3) Process conditions for molding When the stretched film is produced by the extrusion casting film method, since the melt is quenched after leaving the die, the film is only added with a small amount of tackifier, and a good self-cating property can be obtained.
When the stretched film is produced by the extrusion blown film method, the bubble cooling rate is slow, and even if the same formulation is used, the self-adhesiveness of the film is not as good as that of the extrusion cast film. Therefore, a larger amount of tackifier is required, however, the temperature of the wind-cooling wind also affects the self-adhesiveness of the stretched film. It can be seen from Fig. 5-10 that the lower the temperature of the cooling air, the better the cooling of the bubble, and the shearing force of the film is correspondingly improved. Moreover, the viscosity of the stretched film increases as the storage time increases.
When a stretched film is produced by an extrusion blown film method, the transverse blow ratio of the film also affects the tackiness of the stretched film. For films of the same thickness, the greater the blow ratio, the better the self-adhesiveness.
(4) Cling additive In the production of stretched film, adding an appropriate amount of tackifier can improve the self-adhesiveness of the film. Moreover, the self-adhesiveness of the film increases as the amount of tackifier added increases.
Tackifiers include ethylene-vinyl acetate copolymer (EVA), ultra low density polyethylene (ULDPE), and atactic polypropylene (APP). Polyisobutylene (PIB) and glycerol monooleate. PIB is the most commonly used and most effective tackifier.