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Extrusion 6-2023


Extrusion 6-2023


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7 Solutions to Common Plastic Recycling Operation Problems: A Stable Production Guide

7 Solutions to Common Plastic Recycling Operation Problems: A Stable Production Guide


Different characteristics of each type of plastic might cause plastic recycling operations be challenging time to time. In most cases, many common problems can be solved with minimum effort when you have user-friendly and flexible plastic recycling machines. Here we have listed the possible solutions to 7 common plastic recycling operation problems.

Plastic recycling machine material feeding system CMYK
Polystar feeding system of a plastic recycling machine

1. Material Feeding instability

Feeding waste materials into plastic recycling machines must be stable to achieve maximum productivity while preventing machine downtime. Excess feeding or insufficient feeding often results in poor production efficiency.

Solution: Automatic material feeding systems with a belt conveyor, screw conveyor, or nip roller feeders that work synchronously with the plastic pelletizer can provide stable material feeding. These POLYSTAR feeding systems pause or run based on the load of the pelletizer, resulting in maximum feeding efficiency.  

 2. Contamination of the plastic material

Food residue, dirt, oil, and other impurities as well as mixing different types of plastics can contaminate the recycled pellets and cause a decrease in quality and reusability of them. Contamination also makes the recycling process less efficient, producing more waste while raising costs.

Solution:The easiest solution is to ensure that the waste plastics are clean and sorted to their types before they are fed into the recycling machines. Dirty post-consumer plastic waste must be washed and dried before the recycling process.

3. Blockages and hopper bridging

Material blockage generally causes by improperly prepared materials or poor maintenance of the machine components. In the hopper-feeding recycling machines, the material might cause bridging because of interlocking each other or due to the moisture (for tiny particles).

Solution: Proper preparation based on type, shape, and condition of the waste material for your recycling machine, and using auto-feeding systems can solve many material blockage problems. Periodic maintenance on the machine components, regularly changing filter meshes, and unclogging the die head are also easy and common preventions. Using force feeders for hopper-feeding recycling machines can help prevent material bridging.

4. Overheating

Overheating the plastic waste in the integrated pre-conditioning equipment (such as the cutter compactor and shredder) or overcooking the plastic melt in the extruder often causes the degradation of the recycled pellets. This reduces their reusability and weakens the quality of final plastic products. 

Solution: Setting the right temperature on the particular sections of the recycling machines based on the materials, calibrating heating and cooling elements efficiently, and using reliable components which do not cause temperature imbalance can significantly prevent material overheating problems. Prevention of material blockages also reduces local clogging and overheating problems. 

5. Sticky plastic pellets

There might be several reasons that makes recycled pellets stick to each other. Higher extruder temperature, poor pellet cooling, and material characteristics are the most common reasons.

Solution: Setting the right extruder temperature parameters based on your material, and ensuring the cooling water temperature (air temperature on air-cooled recycling machines) is at a suitable level can solve most of the sticky plastic pellets problem. Using a centrifuge dryer can also prevent pellets stick to each other while also further drying them. Using a chiller, especially for hot climates is also suggested.

 6. Hollow plastic pellets

Hollow plastic pellets are not preferred 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 circulation speed can be the common reasons for hollow plastic pellets.

Solution: Vacuum degassing system options based on the condition of the material is an effective solution to remove gas from the materials which causes hollow pellets. Adjusting the right and stable temperature on particular zones of the recycling extruder and die head provides smooth plasticization, and prevents quick temperature changes. Adjusting the right cooling water temperature and speed (not too cold and not too fast) also prevents recycled pellets form a hollow shape.

 7. Non-uniform pellets or chunks

Uniformity in the final recycled pellet shape and size is one of the most important points determining the quality of recycled plastic. Many factors including instability in feeding, material flow, and especially poor pellet cutting system are the common reasons for non-uniform pellets output. Pelletizing inefficiency is the most common reason for plastic chunk creation.

 Solution:Stabilizing material feeding, ensuring smooth melt flow with the right temperature adjustment, preventing clogging, and using an auto speed and pressure-controlled pellet cutting system will solve most of the non-uniform pellet output problems.

Such as the POLYSTAR water ring pelletizer automatically adjusts pellet cutting speed based on the speed of the melt coming out from the die head. The system also ensures the pelletizing knives are always positioned on the die head synchronously with the die head pressure.

These result in cutting uniform size and shaped pellets all the time. Dull pelletizing knives or their disposition might cause plastic chunk creation, replacing the knives with original spare parts and maintaining the right position can solve this problem.

 How to choose a stable plastic recycling machine?

While investing in a plastic recycling machine, recyclers and plastic producers are suggested to consider the machine's performance, user-friendliness, and ease of maintenance all together. A stable plastic recycling machine must work in harmony with its all sections and equipment. Moreover, responsive after sales service with quick spare parts support provides a big advantage and help you stay competitive in the market in the long run. This is one of the important keys to our customers’ fast ROI.


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