Page 72 - Plastic News November 2023

REPORT

ment (such as the cutter compactor temperature (air temperature on air- Uniformity in the final recycled pellet
and shredder) or overcooking the cooled recycling machines) is at a suit- shape and size is one of the most im-
plastic melt in the extruder often able level can solve most of the sticky portant points determining the quality
causes the degradation of the recy- plastic pellets problem. Using a cen- of recycled plastic. Many factors in-
cled pellets. This reduces their reus- trifuge dryer can also prevent pellets cluding instability in feeding, material
ability and weakens the quality of final stick to each other while also further flow, and especially poor pellet cutting
plastic products. drying them. Using a chiller, especially system are the common reasons for
Solution: for hot climates is also suggested. non-uniform pellets output. Pelletiz-
6. Hollow plastic pellets ing inefficiency is the most common
Hollow plastic pellets are not pre-
ferred for plastic production. They
often cause inefficient production and
poor final product quality because of
their low density, reduced strength,
inconsistent size, and shape. Poor
degassing, poor plasticization, the
temperature, and cooling water cir-
Setting the right temperature on the culation speed can be the common
particular sections of the recycling reasons for hollow plastic pellets.
machines based on the materials, cali- Solution:
brating heating and cooling elements
efficiently, and using reliable compo- reason for plastic chunk creation.
nents which do not cause tempera- Solution:
ture imbalance can significantly pre- Stabilizing material feeding, ensur-
vent material overheating problems. ing smooth melt flow with the right
Prevention of material blockages also temperature adjustment, prevent-
reduces local clogging and overheat- ing clogging, and using an auto speed
ing problems. and pressure-controlled pellet cutting
5. Sticky plastic pellets system will solve most of the non-uni-
There might be several reasons that form pellet output problems.
makes recycled pellets stick to each Such as the POLYSTAR water ring
other. Higher extruder temperature, pelletizer automatically adjusts pel-
poor pellet cooling, and material char- Vacuum degassing system options let cutting speed based on the speed
acteristics are the most common rea- based on the condition of the mate- of the melt coming out from the die
sons. rial is an effective solution to remove head. The system also ensures the
Solution: gas from the materials which causes pelletizing knives are always posi-
hollow pellets. Adjusting the right tioned on the die head synchronously
and stable temperature on particular with the die head pressure.
zones of the recycling extruder and These result in cutting uniform size
die head provides smooth plasticiza- and shaped pellets all the time. Dull
tion, and prevents quick temperature pelletizing knives or their disposition
changes. Adjusting the right cooling might cause plastic chunk creation,
water temperature and speed (not replacing the knives with original
too cold and not too fast) also pre- spare parts and maintaining the right
vents recycled pellets form a hollow position can solve this problem.
shape.
Setting the right extruder tempera- How to choose a stable plastic recy-
ture parameters based on your ma- 7. Non-uniform pellets or cling machine?
terial, and ensuring the cooling water chunks

72 PLASTICS NEWSASTICS NEWS November 2023
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