doPPCan we use the same granulation equipment to make PE material again
The answer iscanYes, but certain technical conditions need to be met. If operated improperly, it not only affects product quality, but may also cause damage to equipment.
01The technological differences between the two
Although PP and PE are both polyolefin materials, there are significant differences in their key physical properties:
Different melting points: PP has a melting point of about 170-220 ℃, PE (with...)
LDPEFor example, it is about 180-230 ℃.
Different melt flowability: PP has a relatively low melt index and high melt viscosity; PE melt is thinner and has stronger fluidity.
Differences in thermal stability: PP is more sensitive to temperature and is prone to thermal oxidation degradation over prolonged periods of high temperature, resulting in yellowing of color and decreased performance.
Therefore, when sharing equipment, it is necessary to make process adjustments based on the above differences.
PP sheet material
PE sheet material
To make a machine universal, you must do these three things well
01Adopting customized universal screws
Customize a "PP/PE universal screw" - take the middle value of compression ratio and aspect ratio, and leave wider adaptability in the design. In this way, during daily production, it is only necessary to adjust the temperature and control the speed, which can effectively balance both aspects
raw materialUsers should clearly indicate the type of raw materials and switching frequency when purchasing equipment, so that manufacturers can provide the most suitable screw solution.
02When replacing materials, the screw must be cleaned
PP and PE are incompatible. If the residual material is not completely discharged before being added to the new material, it will cause the particles after mixing to exhibit layering, flower formation, and other phenomena. It can only be used as a low-grade filling material. It is recommended to use specialized cleaning materials or low-grade LDPE (such as LLDPE or recycled film materials) for screw washing before material replacement to ensure that there are no residues in the barrel and mold head.
03Partition adjustment of heating temperature
After material replacement, the temperature in each area must be reset according to the melting point of the new material:
Switching from PE to PP: Temperature in each zone increases by 15-20 ℃;
Switching from PP to PE: The temperature in each area is reduced by about 15 ℃, and the remaining material in the mold head is first emptied before cooling down and entering normal production.
Special note:⚠️ It is strictly prohibited to mix PP and PE for feeding. The two are incompatible, and when mixed together and granulated, they produce "flower materials" with a sharp decline in physical properties, which can only be sold as low-end fillers.
03. Equipment selection suggestions
✅ For users with low material replacement frequency (no more than 2-3 times per month) and mass production, a granulator equipped with customized universal screws can fully meet the needs of alternating production of PP and PE.
✅ For users who frequently rotate production and have a large daily output, it is recommended to use dedicated extension machines. Although the initial equipment investment increases, it can save cleaning time and reduce waste rate, resulting in lower long-term comprehensive costs.
