Taking the most widely used polypropylene tape casting film (CPP) as an example, CPP is a kind of non-stretching and non-directional flat extruded film produced by melt tape quenching. Compared with blown film, it has the advantages of fast production speed, high output, good transparency, gloss and uniformity of film thickness. At the same time, because of the flat extrusion film, the follow-up processes such as printing, compounding and so on are very convenient, so it is widely used in the packaging of textiles, flowers, food and daily necessities.

CPP production has two ways: single layer casting and multi-layer co-extrusion casting. Monolayer thin films mainly require materials with good heat sealing performance and flexibility at low temperature. Multilayer co-extrusion casting film can be generally divided into three layers: heat seal layer, support layer and corona layer. The material selection is wider than that of single layer film. The material that meets the requirements of each layer can be selected separately, and the film can be endowed with different functions and uses. Thermal sealing layer should be processed by thermal sealing, requiring low melting point, good hot melting property, wide heat sealing temperature and easy sealing; supporting layer plays a supporting role in the film, increasing the stiffness of the film; corona layer should be printed or metallized, requiring moderate surface tension, and strict restrictions on the addition of additives.

The casting methods of other materials such as LDPE, LLDPE, mLLDPE and PA are similar.