Salvaging waste polyethylene 3

[berkshire]

I have been given the task of seeing if Router shavings from aluminum composite panels can be recycled.
The shavings consist of 75% polyethylene, 24% aluminum, 1% paint, they are removed from the router by a vacuum extraction system.
We have been dumping these shavings in the land fill because our scrap metal merchant will not take them.
Can this material be melted and filtered to remove the contaminates, and if so is it usable for low grade molding?
B.E.

 

[Demon3]

You could try burning off the PE then selling it to the scrap merchant.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[Pud]

Keep on with the landfill.

It all came from there anyway.

Polyethylene is one of the cheapest materials and hardly worth the effort. We don't even bother to recycle the sprues and runners from the parts we make from virgin polymer.


Cheers


Harry

 

[CoryPad]

Separation should be floatation-based. With a specific gravity less than 1, the polyethylene will float, while the aluminium and paint will not. After separation, you can send the aluminium to the scrap metal merchant. Polyethylene in general can be recycled (remelting post-consumer containers like milk jugs and toiletries bottles), but I don't know of a company that would take router shavings.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

Blow moulding (bottles)/extrusion (film) grades of PE are not processable by injection moulding. That is why the scrap value is nothing unless there are tonnes of it at a time.


Cheers (practical)


Harry

 

[berkshire]

Ok Guys,
So the general consensus is that it is not worth the effort.
We are currently generating about half a ton per week.
I will recommend that we keep chucking it into the landfill.
B.E.

 

[patprimmer]

At half a tonne a week it could be worthwhile.

You might need to save up a few months worth to do a decent run.

If the PE and aluminium separate easily, as stated by CoryPad the PE will float and the aluminium will sink, however if they tend to stay stuck together it certainly will not be worthwhile.

The aluminium might actually be the part that makes it worthwhile, while the PE will be a by product with some value.

If it is extrusion grade, your local manufacture of builders film might want to buy it. Other possibilities might be to sell to a local compounder, who can use extrusion grade to fortify other low molecular weight scrap or someone who moulds bar chairs for supporting concrete reinforcement rods. These are normally thick section and short flow path mouldings and mould OK in extrusion grades.

They will not want it if it contains ANY metal contamination.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

"They will not want it if it contains ANY metal contamination."

And of course, hopper magnets will be of no use.

I wonder if it would be possible to use it "as is" to make useful thick sheets by compression moulding it? The whole lot might be processable - Al filled PE anyone?


Cheers

Harry

 

[berkshire]

I was thinking that this stuff could be used for recycled plastic lumber.
I was also thinking that if I fabricated an air classifier I could get Some of the material sorted into a higher concentration of PE, and the rest into a higher concentration of metal. It would appear that if I can get enough of the PE out then the scrap metal merchant would be interested in the metal shavings.
I am trying not to get too complicated on this, and do not want to get into post processing if it can be avoided.
B.E.

 

[HDS]

pick up an issue of plastics news. There will be a couple of pages of guys in the classifieds that will want that stuff. They will probably send it to China.

 

[CalculatorDave]

If you live in California, Google "CalMAX", the California Materials Exchange.

Separating composites, in order to recycle their constituent materials, is difficult. There is a large market for post-consumer recycled polyethylene, although you won't make any money doing it.

I have seen composite materials recycled "as is" - I saw a documentary where a cotton fiber/phenolic composite was ground-up and used as brick filler. This sounds like a very low-grade form of recycling, but perhaps better than landfilling.

It might be worthwhile approaching this problem the other way around - re-designing the parts or the manufacturing process in order to MINIMIZE the composite waste that is generated in the first place.

David

 

[berkshire]

SolarDave
Thank you for the suggestion I will contact CALMAX

The process is already set to reduce the amount of waste.
Parts are sheared when possible. The primary router shavings come from vee grooving the parts to allow them to be bent to shape on site. Perimeter cutting by router is kept to a minimum.
B.E.

 

[HDS]

Pud is wrong. Keep it out of the landfill.

This week PE film regrind is going for .25-.30 us$/lb.

Don't expect to get that much for material that needs to be cleaned but someone will buy it. The last place I worked there was someone that bought the mixture of plastics that was swept up off the floor around the routers.

here is a listing of companies advertising that they buy plastic scrap. When I posted there were 50.

http://plasticsnews.com/subscriber/classifieds/subcat.html?s=Materials+Wanted

worst case is you put it into a gaylord and someone takes it off your hands instead of you paying to landfill it.

 

[patprimmer]

HDS

If it costs more than US$ 0.35/lb to separate, no one will take it, not even for nothing, unless there is a government subsidy to offset the loss.

Do you have any costings to justify bluntly declaring Pud to be wrong.

Cost of dumping to landfill has not been quantified.

The OP's location has not been disclosed and that might have a significant impact on the costs of various options.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

The op stated that the PE/Al/Paint was from composite panels - I had assumed that the PE was bonded onto the panels, not just loosely mixed...makes separation a lot more difficult.

In the UK (my location), PE is around 0.80GBP/Kg per tonne.


Cheers


Harry
(sometimes wrong, unlike my wife!)

 

[berkshire]

Pud is right The PE is very firmly bonded to the panel
and is, not, easy to separate. So at least for the time being it is going into the land fill, until I do find a person or company that can use it.
B.E.

 

[HDS]

I was referring to the statement that.

"Polyethylene is one of the cheapest materials and hardly worth the effort"

Being in the US may make a difference but since most of the material is going to China it probably doesn't.

I've never seen a plastic that wasn't considered hazardous waste that someone wouldn't take in the the last 5 years. Even if it was router chips or floor sweepings. There is even someone that takes cell cast acrylic which is a thermoset and can not be remelted. The biggest question is usually how much is there. 2 tones a month is worth it for most recyclers.

If an adhesive is used to bond the PE to the AL it maybe easier to separate if you know what disolves the adhesive. However, many PE films do not use adhesives.

 

[Pud]

There is of course, recoverable heat energy in the waste. Have you anyone near with such plant?

A large tissue mill near here is just building such a plant to recover heat from the combustible waste which would otherwise be sent to landfill...

Cheers


Harry

 

[HDS]

That is defiantly an area of active research. There are a few pilot plants that are trying to break the polymer down into raw hydrocarbons that can be burned cleanly. Most of the efforts are concentrated on tires at this stage.

 

[Demon3]

There is no need to break PE down to raw hydrocarbons to burn it. It burns cleanly just like any oil because chemically it is the same as oli just longer molecules.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell