Recycling existing plastic materials conserves energy and reduces greenhouse gases. But reusing plastics requires processing the materials and often mixing them with new plastic to make new products.
Pelletizing involves converting raw polymers or scrap plastics into uniform pellets suitable for manufacturing. You melt down the material and extrude it through a die, then cut it with pelletizer blades.
High-quality blades minimize dust and help cut uniform pellets consistently. You get more usable material to sell or manufacture products.
Despite the benefits, we currently recycle less than 10% of the plastic used globally. This is in part because plastic is chemically complex and can be hard to process.
Pelletizing transforms raw polymers or scrap plastics into standard pellets that are easier to melt, mold, and transport. The process involves:
There are multiple ways to pelletize plastics, but all require fine control of the polymer extrusion and cutting processes for better uniformity. Consistently sized pellets are easier to transport and store. Manufacturing is also more efficient as uniform pellets melt at consistent rates and can be fed into machines without stoppage.
The choice of pelletizing system impacts overall capacity and quality. The most common systems are strand pelletizing and die-face pelletizing.
This is a form of cold pelletizing, in which the plastic strands cool completely before being cut into pellets. After exiting the extruder, the strands are placed in a water basin to cool down. In an automated strand machine, the strands move onto a slide and are sprayed with water to cool.
Once the strands are cool and dry, they're fed into a machine that uses strand pelletizer blades to slice the extruded polymer down into uniform pellets.
Strand pelletizer machines tend to be simpler and easier to operate than die-face equipment. You may choose this method if you’re working with a small production line.
In hot pelletizing, the molten polymer is cut into pellets before it's completely cooled. Die-face underwater pelletizing uses pelletizing blades to cut the pellets in a water chamber as they cool.
Underwater cutting reduces the need to handle hot strands and move them to another machine after cooling off. Instead, the machine feeds the melted plastic through holes in a die plate into a water bath, where it is cut by a pelletizer blade at the face of the die. Because the pellets are underwater, they solidify rapidly. This method keeps strands from sticking or moving around the blade, making the pellets more uniform.
Depending on the polymer and system design, die-face and underwater pelletizing can support higher throughput and greater automation than strand systems. In many applications, underwater pelletizing can reduce fines and dust compared with conventional strand pelletizing. However, underwater systems require process-water handling, temperature control, and drying equipment, which can increase capital and operating complexity.
Whichever system you choose, you need high-quality pelletizer blades. A sharp blade designed for pelletizing gives better pellet uniformity every time. You get the most out of industrial blades when you customize them for your pelletizing system.
In a die face system, your blades face high temperatures and fast production speeds. You need tough, durable industrial pelletizer blades optimized to your specific processes and machines.
In pelletizing, certain resins and additives can contribute to buildup on blades or nearby cutting components if process conditions are not well controlled. Some plastics are also abrasive, which makes your blades wear out faster. Regular blade wear affects pellet uniformity. Dull or damaged blades don’t make clean cuts, which causes “tails” or clumped pellets if the blade doesn’t cut all the way through the polymer mix. These defects can increase off-spec material, screening losses, and downstream quality problems.
By working with an industrial knife company with experience in plastics recycling, you get optimized blades that extend blade life. This reduces machinery downtime, since you’re not replacing them as often.
When choosing pelletizer blades, don’t try to substitute with products optimized for granulating. While these processes are both common in plastics recycling, they’re not the same. Granulators are used in regrind processing, breaking scrapped plastic into smaller pieces for recycling. Granulator blades are made for high-speed impacts to cut tough, abrasive plastic scrap and sheets.
Pelletizers are used in manufacturing plastics as well as later in the recycling process. Rather than regrinding plastics for reprocessing, they cut strands of a melted polymer mixture. These blades must make precise cuts and may have to endure high temperatures in die-face pelletizing.
You need a custom blade manufacturer experienced with the different equipment needs of granulators vs. pelletizers to craft long-lasting, durable pelletizer blades.
Because pelletizer blades wear out quickly, you may be tempted to replace them with less expensive blades to keep costs down. But installing blades that aren’t specifically crafted for this task can be more costly over time, as you have to replace them more often.
A blade with the wrong metallurgy or wear profile can increase cutting resistance, accelerate wear, and reduce pellet consistency.
Choosing blades engineered for pelletizing and properly maintaining them saves you from this unnecessary downtime. Be sure to check your machine regularly:
Hyde offers blade maintenance services to keep your pelletizer running longer. We have 150 years of experience customizing industrial pelletizer blades. Because we are based in the US, we can also quickly refurbish or replace your rotor to get you back on track as soon as possible.
Contact us today to find out more.