In this case study we look at the effectiveness of Barrel Blitz Universal when changing the material in a 160T BMB machine from Black Acetal (aka Black POM or Black Polyoxymethylene) to Clear Polycarbonate.
Black POM to Clear Polycarbonate

Donatella Isopi, our Italian Export Assistant took the reins on another Aquapurge tough-in-theory-successful-in-practice assignment. POM can be a difficult material to purge because it decomposes releasing formaldehyde gas when heated for a length of time so the purge needs to be quick. And when you start to use the next material you need to make sure there is no more POM in the barrel, otherwise it could be risky.

Previously our clients had taken a rather long-winded purge journey which wasn’t always 100% successful:

The first purge used 7Kg of 30% Glass Fibre Polypropylene at POM temperatures, then it takes 15 minutes for the machine to increase from POMtemperatures to Polycarbonate temperatures, the second purge used 5kg of 30% Glass Fibre Filled Polypropylene at Polycarbonate temperatures, then it could take 20 minutes of rejected parts before the first perfect product arrived.

In addition this procedure required removal of the nozzle and the material left inside cleaned manually. With Barrel Blitz Universal it’s a whole other story as Donatella explains:


“At POM temperature we purged using just 2.7kg of BBU. You can see from the photos that we removed the Black POM in the first purge, during the 2nd purge the carbon was removed, not just the POM

and the nozzle was completely clean too…
Black POM to Clear Polycarbonate

I was generous with the BBU to get pure white and probably could have achieved the same results using just 1.9 kg, but as this was the first time I wanted to be sure. Despite this the entire process only took 9 minutes. Next time they will probably only need to use 1.6 kg”

Our clients were impressed that after the BBU purge there were only 5 shots with milky mouldings (but black spec free, naturally!) before they were completely clear.

Milky mouldings are a common problem when changing from Polypropylene to Polycarbonate but as BBU is self-emptying it keeps the number of milky mouldings to a minimum.

Our clients had no idea if the purge would work so were delighted about the quantity of purging agent used and the time taken. However, they still needed convincing so Donatella carried out a second trial on a different machine.


Their 50T Demag machine was producing black specs and orange blemishes because they regularly switch between polycarbonate medical products and polypropylene or ABS gardening products, this had resulted in ongoing black spec and colour contamination problems.

In fact the day before our case study took place they had tried to remove orange PC/PET using 10 kg of Glass Fibre PP. When they started with natural TPUthey had problems with carbon and colour (as you can see in the photo below) so were interested to see how BBU fared.

Donatella judged the quantity of BBU perfectly and purged the 50T Demag using only 900g and it took just 20 minutes from starting the purge to producing good quality products.

The first products were perfect as you can see from this before and after image.
With their previous procedure they also needed to purge during the run and this could be very time-consuming. With BBU they only needed to purge once to allow them to complete an entire run.

Donatella left the client with more BBU (and in a happy disposition!) enabling them to carry out further trials.


If you would like to find out how Aquapurge products, including Barrel Blitz Universal could assist your POM, Polypropylene and Polycarbonate manufacturing processes please get in touch.

Barrel Blitz Universal can be used in any type of injection moulding machinery. In this case study it was a 160T BMB machine and 50T Demag enabling the manufacturer to switch easily between different colour material and produce black spec-free products saving time, money and material.

If you are not sure about the benefits we are only a phone or an email away.