May be in our lives, there are many people in contact with plastic products, but careful people will find that it will be sticky for a long time plastic products, especially some plastic products film, although often used these plastic products film, But many people still do not understand how the viscosity of plastic products film is caused.

Plastic products film under a certain temperature and pressure, after a period of time between the layers sometimes occur mutual adhesion, found that the roll resistance is large, indicating that the roll film occurs adhesion; When the curing temperature is too high in the curing chamber, the film is also prone to adhesion, and it must be rolled back to normal use. These phenomena show that the film of plastic products has viscosity, in fact, this viscosity is caused by the thermal movement of the chain segment.

Causes of viscosity of plastic products film

If the ambient temperature is above the Tg of the polymer, the single bond on the molecular chain segment of the plastic products film material will rotate freely, and the conformation of the molecular chain will change. Because the distance between the layers of the rolled film is very close, and under a certain shrinkage tension (pressure), this thermal movement of the chain segment will even cause the apology of the chain segment, and the chain segment in a certain layer of the film will migrate to the depression on the surface of the plastic product film in the adjacent layer, resulting in adhesion.

If the polymer plastic product film is amorphous, then this adhesion will be more obvious; For amorphous polymers, the lower the Tg, the more likely it is to appear adhesion. If the polymer is highly crystalline, because most of the molecular chain segments are confined to the lattice, can not achieve thermal motion, so the adhesion phenomenon is less.

adhesion phenomenon is not only related to the aggregate state composition and Tg of the material, but also related to the surface smoothness of the film of plastic products. For example, for the surface of a smooth film of plastic products, the layers of the roll film are in close contact with each other and there is almost no gap, and the local vacuum formed during separation will also cause adhesion.

Application of adhesive film of plastic products

The cling film widely used on the market at present is an example of the use of adhesive film of plastic products. In the past, PVC is often used as plastic wrap. PVC has low crystallization capacity and is a typical amorphous polymer. After adding 40% ~ 50% plasticizer, its Tg is reduced to -30¡æ, so the film of plastic products is very soft and has great viscosity. It is very suitable for use as a film of fresh plastic products. However, plasticizer DOP is more harmful to the human body, so PVC plastic cling film has been eliminated, replaced by PE plastic cling film.

LDPE has a low Tg and is suitable for use as a plastic wrap, but PE has a certain degree of crystallinity, so the use effect is not as good as PVC. However, if we can effectively organize the crystallization of PE, we can prepare plastic cling film with good adhesion.