Frequently Asked Questions
Find answers to the most frequently asked purging compound questions for comparing, purchasing and implementing EASYPURGE products.
Are chemical purges safe for the machinery?
Absolutely. Different products use different chemical formulas, but they are safe for use with plastic processing equipment.
Indeed, Easypurge APC incorporates an additive which neutralizes hydrochloric acid (a product of degradation common in chlorinated PVC and other polymers) which is harmful to machinery.
EASYPURGE APC components listed by the FDA as “additives used for indirect food contact “or “GRAS“ and are identified on the TSCA and REACH inventory list.
Why should we intersperse purging material with virgin material?
Easypurge APC acts by chemically breaking flow lines and emulsifying pigments and impurities while vastly increasing the MFI. Virgin material (which has a lower MFI) is needed to expel the whole mixture from the system. In the end, the virgin material finishes the job.
What types of products are available in the market?
Basically, there are two main groups: physical and chemical.
Physical purging compounds depend on fluidity differences or on mineral or glass fibre filters and the presence of a surfactant/lubricant to displace the polymer. These products are wide-ranging because a specific product must be used depending on the polymer or the temperatures you are working at.
Chemical purging compounds are based on active molecules to break the polymer chains into smaller segments, increasing the MFI and facilitating the other additives that emulsify the impurities. Then they are expelled along with the purging material.
Chemical purging compounds are available as pellets or as an emulsion. The former consists of additives plus a vehicle. The vehicle is normally a polymer and therefore must be specific to the polymer that you are using.
The prepared emulsions are made up of only active ingredients. Here the mixture with the polymer is done in the screw itself therefore only one type is sufficient for a wide range of thermoplastics. It is worth mentioning that some brands use amide compounds that produce unpleasant and irritating gases.
Is it more economical chemical purge?
Definitely, it is more effective, and you are not paying for the vehicle.
Easypurge APC is more efficient and up to 3 times cheaper than the main purges available on the market.
Why just one product for all thermoplastics?
Easypurge APC is 100% additive ingredients. The thermoplastic vehicle is added in the screw, so you are only buying the active ingredients. How much purging compound is needed?
How much purging compound is needed?
Easypurge APC recommends a dose of 20 g / Kg screw capacity and to repeat the operation if this is insufficient.
What happens if I increase the dosage?
Generally, a dose between 20 and 40 g / kg of screw capacity should work well. Depending on the configuration of the worm gear, as this strongly affects the MFI, the material could “slip” if too strong a dose is used.
Are chemical purges safe for the operator?
If they are used according to the precautions on the safety sheet they are, some chemical purges produce annoying gases but Easypurge APC does not have this problem. We also count with automatisation called Easypurge APS. Learn more.
How can we tell if a purge compound will work in our situation?
If you require more than 45 minutes to change from a dark to a light colour or to change the material a good purging compound can help improve your productivity.
If you lose time and material during start-up due to spots, gels or scratches you should probably be using a purging compound during the shutdown.
If you must frequently disassemble the machinery for manual cleaning of degraded material, the implementation of a preventive maintenance program based on a high-performance purging compound may make this a thing of the past.
Can I use recycled material?
It is not recommended because when adding the emulsion, a plug can be formed in the screw.
What kind of purging compound should I use?
The type of compound obviously depends on how complicated the change or cleaning is and the final cost.
If you work with engineering plastics, with hot runners or processes that use complex machines, you must select a high-performance purging product.
Usually, chemical purges are 3x less expensive and work where other compounds don’t, for example, extrusion blow moulding or hot runners.
What is the procedure when I have to change to a polymer that works at a different temperature?
Use a polymer that supports both temperatures such as HDPE and use the temperature of the original material that was in production.
After cleaning the system raise or lower the temperature to the temperature of the new material, then you can proceed with the new polymer.
Could I use a different polymer for cleaning?
Yes, if for example, you are working with an expensive polymer, this can be replaced during the cleaning process with any polymer that has a similar MFI or less and that can work in the same temperature range or higher. Once the system is clean you can switch back to your regular material.
Is it normal for gas to be produced?
Yes, chemical purges generate gases during the reaction process. Sometimes, depending on the equipment, they could produce small explosions that are perfectly normal and will not affect the machinery at all. However, the operator should wear safety goggles and gloves.
If you don’t find the answer you’re looking for here, please contact a Purging Process Expert at EASYPURGE.
Automatic Purging System
Easypurge APS is a dosing system, developed to solve in a simple, and economical way colour and/or material changes on machines that process large volumes. Sectors such as blow moulding, film, preform injection or injection of large pieces benefit greatly.