What is a Purging Compound?

A purging compound is a plastic resin compound designed to clean all primary plastic machinery (injection molding machines, blow molding machines, extruders) when changing color, resin or simply to remove black specks or contaminations.

Why buy a purging compound?

A plastic processor needs to buy a purging compound to reduce the machine down time or improve the quality of their products.

Machine Down Time

Changing color in an IMM or in a Blow Molding Machine is very difficult if a purging compound is not used. Companies that do not use a purging compound when they need to change color usually use regrinded plastic. If they operate this way, they are not cleaning the machine. They are simply pushing out the color of the barrel. It will appear that the molded part seems clean when production is initiated. In the event that machine is stopped for any reason, the previous color will re-appear when the production begins again. To clean a 500-ton machine in this manner, it may take 45 minutes to 2 hours depending on the color and type of plastic resin. Sometimes, demounting the nozzle and the screw may be required to hand clean and thus requires additional time.

Ultra Purge is simple to use. Load only the content of the barrel of Ultra Purge and run the machine to remove the previous color and resin. In a 500-ton machine, it will take only 10 – 15 minutes. Ultra Purge is very easy to remove from the machine – it only takes 3 shots to completely remove it, which means it will save time and improve production quality.

If the machine is very dirty or if they use special additives (flame retardant), they may need to use more product than the content of the barrel.

The benefit in using a purging compound is enormous. Companies can change color easily and without demounting any equipment in less time, thus obtaining maximum results.

All these problems are intensified in blow molding machines with accumulators. The accumulators are difficult to clean because there are “dead spots” inside. Changing color in a blow-molding machine with a 5-liter accumulator from black to clear PP may take 8 hours without using a purging compound. Using Ultra Purge CE-E grade, specifically designed for blow molding machines, usually takes only 30-40 minutes. This is dependant on the condition of the equipment. Older machines generally take longer to clean.

Improving Quality

Using a purging compound will help the processors to remove all plastic resin and all contamination from the barrels and screws. This is important to improve the quality of the molded parts. The processors can have peace of mind knowing that the equipment is perfectly clean and that no other contaminants will appear in the future production. Keeping the machine clean is very important so that we can avoid the old resin from combining with the new resin during the production process.

Another common problem is black specks, especially with PC, PET, PMMA, etc…. If changing color is not required, using Ultra Purge will easily help eliminate black specks. Black specks are big problem for PET preform producers and also for injection molders specializing in medical production.

How Ultra Purge Works

There are a lot of purging compound out on the market and they work through different mechanisms. Some of them are physical purging compounds, which are very abrasive and not so efficient. They do not dissolve the color - they only scrub the insides of the equipment. Be abrasive for a purging compound is not a good thing and if use often will ruin the equipment inside.

Ultra Purge is a chemical purging compound and performs through a chemical reaction when melted. With different grades it can clean all thermoplastic resin. Ultra Purge expands when heated and active ingredients will dissolve all color and eject it from the machine. Equipment will not be damaged, as Ultra Purge contains no abrasives or solvents. It will also leave a protective film inside that will make harder for the color to stick on the walls of the machine. Ultra Purge is completely safe to use - some Ultra Purge grades have the EU’s Food Contact Certificate, which means the molded product can be in contact with food without releasing any harmful agents/substances.

The other chemical purging compounds are not as efficient as Ultra Purge and usually the processors need bigger quantity to get the same results they can get with Ultra Purge.

These chemical and physical purging compound are also difficult to remove - a problem that does not occur with Ultra Purge.


One of our injection molders had a lot of problems in changing color in 4-cavity hot runner mold. He was running a 500 –ton machine producing plastic cups. By using Ultra Purge, he was able to change color and clean the hot runners in only 20 minutes - using only a few pounds of Ultra Purge. He was using a competitor’s purging compound before he discovered Ultra Purge. With Ultra Purge, he only needed to use one-third of the original amount he used with the competitor’s product. The competitor product was always a chemical purging compound. He was also able to clean the hot-runners- which was impossible to clean with the other compound. He was extremely surprised when Ultra Purge removed colors that he ran 4 colors prior. In the molded part you could see all 4 colors he ran before.

A company who produce glass lent had good results in using Ultra Purge. Their main problem was the black specks. They were running PC and PMMA. With a small amount of purging compound they remove all the black specks and they were able to run again the production after the third molded part after the purging. They had a lot of problem before using another purging compound because it was efficient with the black specks but very difficult to be removed from the machine and they had to mold a lot of parts before the production was good.

One of our blow molders had a lot of problem in changing color from a red to a clear PP. He uses to purge the machine with natural PP for 5 hours. After he tested Ultra Purge he was able to change color in only 30 minutes saving 4.30 hours of down time and a lot of resin too. Also the quality was improved because right now they do not have any problem in the event they have to stop the production. Before using Ultra Purge when they stopped the production they always had some stripe from the previous color.

We have a lot of PET preform producer that solve a lot of their problems with Ultra Purge PET. The machine they run are very expensive and the preform produced are a very inexpensive. Their down time costs a lot of money and it difficult for them to change color rapidly. They have also a lot of problem with black specks. I would say that all of them use a purging compound but they found out that Ultra Purge is the most cost-effective one. They also feel secure in using Ultra Purge because it is completely safe also when molded. The problem they had with the other purging compounds was that they were difficult to be removed from the machine. After a long time the machine was running the production some white speck from the purging compound was still in the preforms. The main problem was that the quality department didn’t feel safe selling the preform with a contamination that could be also dangerous, as most of the preform are sold to the food industry.