The stretched film material usually has a high viscosity after melting. During the processing, when the molten polymer passes through a narrow slit, a gate, etc., the polymer melt must be rubbed against the surface of the processing machine. Friction reduces melt flow, while severe friction can roughen the surface of the stretched film, lacking luster or flowing. For this reason, stretch film manufacturers need to add additives to improve lubricity, reduce friction and reduce interfacial adhesion.

        In addition to improving fluidity, the lubricant can also function as a melt accelerator, anti-blocking and antistatic agent, and a slip agent.
The role of the external lubricant is mainly to improve the friction between the polymer melt and the hot metal surface of the processing equipment. It has poor compatibility with the polymer and is easy to migrate from the inside of the melt, so it can be in the intersection of the plastic melt and the metal. The interface forms a thin layer of lubrication. The internal lubricant has good compatibility with the polymer, and it acts to reduce the cohesive force between the polymer molecules inside the polymer, thereby improving the internal friction heat generation and melt flowability of the plastic melt.

        In fact, each type of lubricant has the effect of achieving a certain requirement. It is always combined with internal and external lubrication, but it is more prominent in one aspect. The same lubricant will exhibit different lubrication effects in different polymers or under different processing conditions. For example, under high temperature and high pressure, the internal lubricant will be extruded to become an external lubricant.

       In the production of stretched film, we will encounter some adhesion phenomena. For example, in the production of stretched film, the two films are not easy to separate, which brings difficulties to automatic high speed packaging. To overcome this, a small amount of surface lubricity-enhancing aid may be added to the resin to increase external lubricity, commonly referred to as an anti-blocking agent or slip agent. Generally, in the molecular structure of a lubricant, there are long-chain non-polar groups and polar groups, and their compatibility in different polymers is different, thereby showing different internal and external lubrication effects.

        At the time of extrusion molding, the fluidity is improved, the adhesion of the polymer material to the cylinder and the mold is improved, and the retentate is prevented and reduced. It also improves the appearance and gloss of the stretched film. The amount of lubricant is generally from 0.5% to 1%.

Stretch film wholesale
        When using a lubricant for the stretch film, pay attention to:
        1. The flow properties of the polymer have met the needs of the molding process, and the effect of external lubrication is mainly considered to ensure internal and external balance;
        2. Whether the external lubrication is effective or not, whether it can form a complete liquid stretch film on the plastic surface layer at the molding temperature, so the melting point of the external lubricant should be close to the molding temperature, but the difference is 10 °C~ 30 ° C can form a complete stretch film;
        3, the surface gravity is small, the viscosity is small, the expansion at the interface is good, and the interface layer is easy to form;
        4, its own heat resistance and chemical stability is excellent, does not decompose, does not volatilize during processing; does not corrode equipment, does not pollute stretch film, no toxicity.
Use characteristics of different types of lubricants:
        Natural paraffin wax is used for external lubrication. It can be used as a lubricant and release agent for various plastics. The general dosage is 0.2~1phr, but its compatibility, thermal stability and dispersibility are not very good. The dosage should not be too large. The internal lubricant is used in combination; while the white oil is mostly used as the internal lubricant of PVC and PS, the lubricating performance is good and the thermal stability is also good, and the general dosage is 0.5 phr. They are all drug-free and can be used for food packaging. There is also a microcrystalline paraffin: it is also used as a lubricant in plastic processing. The dosage is 1~2Phr, and the thermal stability and lubricity are better than ordinary paraffin. Low molecular weight polymers are also widely used as lubricants, such as polyethylene wax, low molecular weight polypropylene, which have good internal and external lubricity and are non-toxic. Polyethylene wax is suitable for extrusion and calendering of PVC and other materials. The dosage is generally 0.1~1phr, which can improve the processing efficiency, prevent the stretching film from sticking, improve the dispersibility of filler or pigment, and the compatibility and transparency are not very good.