Static build up on polymeric granules 4

[GerardoS]

Hello,
The process with which I am involved comprises feeding of polymers in granules form. This is done through feeders with feeding screws. The screw or screws transport the pellets to be fed into the extruder. The problem is that the granules stick to the outside tube of the feeder due to elestrostatic build up. The equipment seems to have a good earth, but the static is still an issue. The granules are non conductive therefore dissipating any charge built is very difficult. I wonder if there is any product that would make the surface of the granules more conductive so they do not get charged so easily or they get rid of the charge easier. I know that ionising air is an option but it is very complicated for me because of room limitation.

Thank you in advance.

Gerardo

 

[aviat]

There are antistatic agents that you can add.

http://www.specialchem4polymers.com/tc/Antistatic-Agents/index.aspx?id=

 

[unclesyd]

Here is one company we used in our production system.

http://www.exair.com/static_eliminator/stat_elim_page.htm

If you Google antistatic additives you will get nearly everyone in the business.

 

[Compositepro]

An air ionizer is needed to solve your problem. A powered ionizer will work but will cost hundreds of dollars to purchase and install. A few dollars of Ion Cord (

http://www.fibraplex.com/ioncord.asp)wrapped

around the outside of the feeder tube will also neutralize any static charge in the vicinity.

Charged, non-conductive, partcles are attracted to grounded surfaces because the charge is attracted to ground. When the particles touch ground most of the charge on the particle remains struck on the particle because it is non-conductive. Oppositely charged ions in the air will be attracted to the charge and neutralize it.

 

[GerardoS]

I wanted to thank you all for the advices. I am working on it. thank you very much.
Gerardo

 

[aspearin1]

We've had good results here using an ionizing/de-ionizing air knife on polymeric films. It's relatively cheap and hooks up to house air.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[MCDERK]

Hello GerardoS,

I am having exactly the same problem like you discribed.
What kind of solution did you find ?

It would be gread if you could help me !

 

[Carole1]

Hi, Depending upon what size the granules are, you could gas plasma treat them to cause them to "repel".My company does this for many types of elastomer/polymer small parts that are bowl fed, etc. Works quite well!

 

[BillPSU]

There was some research done on this same static problem but in seeds. The seeds would not feed properly in a planter and attempts were made to remove the static charge. A very simple solution was found putting metal objects in the supply bin and allowing them to contact the sides of the bins removed the static charge. The people doing the research actually used 1/2" nuts as the metal objects which were substantially bigger than the seeds and could not pass into the planter. Something similar would probably work in plastic pellets. You would have to make sure to stop ingestion on the metal objects into the injection screw.

 

[MCDERK]

Hi Carole,
Thanks fo your comment, do you know if there is any website which shows an example of gas plasma treatment ?
My feeling is that it will be a to expensive solution.

 

[MCDERK]

Hello BillPSU,
Your information looks indeed simular with the experience I have until now.When I use "fresh" granules from the package (plastic bag),the screw(feeder) gets contaminated. When I use granules that are put trough the screw feeder already, the granules are less sticking to the feedscrew.
The granles are round 2-3mm and long 2-3mm.The srew feeder is existing of metal parts.
Im thinking about a cheap solution to contact each graules to metal(earth), but also to have enough capacity, does somebody has any idea?

 

[Carole1]

Hi,

Gas plasma treatement solves a number of surface related problems. Please look at our web site

http://www.pvateplaamerica.com.

You can contact me with specific questions and I'll be glad to assist!

Carole Levers