You have many choices when purchasing purging compounds for your plastics processing company. While it may seem logical to choose a purging compound with the cheapest cost per round, doing so comes with many drawbacks.A very low cost per round often indicates a subpar product, which may take longer to clean your machines, lead to higher scrap rates and often requires more material to accomplish the job. Not to mention, inferior products may not eliminate the contamination in the first place, regardless of the quantity used. When you add up these factors, the result is a higher cost per purge compared to a high-quality purging compound.
Low-quality purging compounds typically aren’t created based on extensive research and development, using the latest materials technologies. Additionally, companies that sell low-quality purging compounds do not provide adequate technical support or knowledgeable sales reps.
When selecting a purging compound, it’s important to understand what separates a high-quality purging compound from a low-quality alternative.
Here are five critical elements to look for in a purging compound:
1. Formulated To Clean Injection Molding Machines And Extruders
Sometimes, companies try to group regrind, virgin resin, laundry detergent and homemade concoctions in with purging compounds. It’s important to understand that these products are not purging compounds and shouldn’t be confused with engineered commercial purging compounds.
A high-quality purging compound is a plastic resin compound specifically formulated to clean all primary plastic machinery – injection molding machines, blow molding machines and extruders – when changing color or resin. It can also be used to clear color or carbon contamination from machines and downstream tooling such as extrusion dies and hot runners.
2. Material Affinity For The Products
Subpar purging compounds may not be formulated with material affinity in mind. You should only use purging compounds compatible with the material you’re purging. This ensures complete purges, leaves less residue behind and eliminates contamination buildup in your machines.
3. Low Residue Characteristics
A high-quality purging compound should leave behind little residue to make for quick and efficient purging. If you’re experiencing repeated issues with residue in your machines, use a grade designed for residue-sensitive applications or low-temperature resins. These grades are formulated for lower residue and can be used in conjunction with other purging grades, as a chaser, whenever you’re trying to reduce purging compound residue.
4. Different Product Grades Available
Purging compounds are not one-size-fits-all, and the purging compound you use depends on your specific process.
A high-quality purging compound should offer product grade choices for different types of resins including commodity, engineering, and super-engineering materials such as PPS, PEI, PEEK and LCP. Subpar purging compounds often have limited grade choices and may lack glass-filled or high-heat grade alternatives.
5. Thermally Stable For Sealing
Sealing the screw and barrel with an appropriate, thermally stable purging compound is critical during machine shutdowns. This ensures that your purging compound displaces heat-sensitive resin left over from your last production run.
Sealing the screw and barrel is typically done upon shutting down for the weekend or before extended holidays, and it prevents oxygen from entering the barrel. When your screw and barrel are not sealed properly, the presence of oxygen causes and heat create an environment that leads to degradation and carbonization. Residual polymer degradation can delay machine startup and create unnecessary material waste.
When choosing a purging compound, don’t sacrifice quality for cost. Ultimately, a high-quality product will boost efficiency, reduce downtime and result in higher profitability for your business.
Learn how the right purging compounds and procedures impact your process efficiency.
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