LLDPE Production Process and viscosity control

LLDPE Production Process and viscosity control

Stretch film is a packaging material used with a winding machine or by hand. It is used to pack an object for more convenient transportation. Early LLDPE stretch films were mainly blown films, developed from single layer to two and three layers. With social and economic development, LDPE stretch film has become a mainstream packaging material in the market.
Melt temperature during stretch film production
The melt temperature is typically controlled at 250 -280 , and the temperature of the casting cooling roll is controlled at 20 -30 . The winding tension must be low, generally less than 10kg, to facilitate outflow of the viscous agent and at the same time reduce stress on the finished film. These are its production process conditions.
Viscosity control
Good viscosity ensures that different packaging film layers will stick together and thus firmly hold goods. There are mainly two methods to gain viscosity: One is to add PIB or its parent material in the polymer; the other is to mix in VLDPE. PIB is a semi-transparent viscous liquid, and to directly add it, special or modified equipment is needed. Generally, the PIB parent material is used; the outflow of PIB generally takes three days. Viscosity is also affected by temperature: high temperature leads to high viscosity, and low temperature leads to low viscosity, meaning that after stretching, the viscosity will be greatly reduced. Thus finished film should be stored in a certain temperature range (recommended storage temperature is 15 -25 ). Compared to the above method, blending VLDPE will result in a lower viscosity, but there are no special requirements for equipment, and the viscosity is relatively stable, and not subject to time control (but is also affected by temperature). A decent viscosity is acheived when the temperature is above 30 , but lower when the temperature is lower than 15 , and in this case, the required viscosity can be achieved by adjusting the amount of LLDPE in the sticky layer. This method is generally used in three-layer coextrusion.