Scrap plastic as Blasting Media worth more than copper

Ten pounds plastic blasting media made from scrap plastics at $39.99. is worth more than copper.

Plastic Surface Blasting Media — 10 Lbs. | Blasting Media| Northern Tool + Equipment

I'm guessing that's different grades of random chunks of plastic? Would be interesting to see how many of those buckets they actually sell, that would tell wither it's worth more then copper.

Originally Posted by alloy2

I have been doing some research on water soluble abrasives, my thoughts on this are once the precious metals for example gold or silver has been worn away from the substrate the used abrasive along with the precious metals could be dissolved in water the metals could be filtered out in a filter.

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50 lb Sodium Bicarbonate Blasting Media from Princess Auto our Canadian equivalent to Harbour Freight is only $59.99

I read this and put it together with your comments on the keyboard Mylar with silver discussion on another thread. Without doing any testing my imagination brings me to what I believe are similar conclusions.

Using mechanical means to separate the silver from the mylar can end up with the silver being transferred to other unwanted surfaces. Using a water soluble material delivered by water pressure seems to be a possible great answer. Of course I am certain other parts of the process have to be adjusted.

Rather than chopping the mylar into small bits it could be left whole and each sheet blasted quickly(perhaps).

I am interested in how you might envision a process to remove perhaps solder traces so components could be easily removed and processed separately.

One of the main benefits I imagine in using water/media blasting is the control of fumes into the air.

Thanks for a great subject. Mike

Originally Posted by alloy2

Guys that do automotive restoration would love to purchase plastic basting media in bulk, Most other blasting media is to aggressive on the sheet metal, plastic is perfect..

No the media is not random in size. The screen size ( holes ) used in the hammer mill would depict the maximum sizing of the material being discharged then passed through a cyclone to remove dust before passing over a set of screens to fine tune the final classification.

I'd have to agree - we use to pass around different ideas of abrasives in shop. Thanks for sharing.

[QUOTE=miked;262346]I read this and put it together with your comments on the keyboard Mylar with silver discussion on another thread. Without doing any testing my imagination brings me to what I believe are similar conclusions.

Originally Posted by alloy2

Precious metals refinery’s use abrasives on some of their processes, on old gold china that has gold guiding you will see that some of he gold has worn away just from being handled by humans. Silver plated cutlery often badly worn, the more expensive silverware usually plated over with rhodium.

Soon we'll have newattitude blasting gold guiding from chinaware

Using mechanical means to separate the silver from the mylar can end up with the silver being transferred to other unwanted surfaces. Using a water soluble material delivered by water pressure seems to be a possible great answer. Of course I am certain other parts of the process have to be adjusted.

Originally Posted by alloy2

No this is no so, the conductive silver Ink has a binder agent to assure the ink will bond with the substrate when it's applied wet, once dried the binder is of no further use. Ink removed from mylars will stay in it's new powder form. Static electricity may cause the powder to migrate to unwanted places, water will discharge the static.

Rather than chopping the mylar into small bits it could be left whole and each sheet blasted quickly(perhaps).

Originally Posted by alloy2

Chopping or shredding the mylars highly recommended, I would tumble the pulp with out an abrasive dry with out water during the initial process. Your tumbler barrel should be totally enclosed, once the process has been completed this is when you may want to dampen the pulp with water to keep the silver dust under control. Also this would rinse off any residue silver free from the pulp.

It may even be possible that mylar plastic floats in water then you could skim the plastic off leaving your silver to settle on the bottom of your tub.

I am interested in how you might envision a process to remove perhaps solder traces so components could be easily removed and processed separately.

Originally Posted by alloy2

A sandblasting cabinet to remove components from boards would be work, just change or overlay a screen on the bottom rack of your blasting cabinet that would only allow the blasting media to pass through. If there was any gold plating on the boards its coming off with the solder.

Modern solder used on electronics is about 95% tin, your recovered tin has scrap value. To maximize profit I would sell my tin scrap on ebay to be used as bullet or sinker casting material..

On a side note tin solder is the death of modern day electronic devices, tin whiskers grow on the circuits causing shorts. Already there are many multi million dollar satellites in orbit rendered useless because of tin whiskers.

NASA on tin whiskers, some good info, NASA Goddard Tin Whisker Homepage

Originally Posted by alloy2

Another NASA Whisker Failures

Commercial Satellite Failures
Military Failures
Medical Failures
Industrial/Power
Computers
Anecdotes

Catch the read on Industrial power where tin whiskers caused a nuclear power plant problems.

One of the main benefits I imagine in using water/media blasting is the control of fumes into the air.

Originally Posted by alloy2

No fumes produced with blasting only dust so yes a closed environment or a combination thereof using water or cyclone.

Thanks for a great subject. Mike

Those of you that disassemble computers and servers should be wearing some sort of breathing protection, dissembling electronics inside the apartment or house could put your family at risk.

It's a well known fact that server cabinets and the rooms they occupy are full of tin and zinc whiskers.

These whiskers are light enough to become airborne particles that may enter your lungs casing respiratory problems.

Zinc whiskers in server room.Photo Gallery: ZINC Whiskers on Raised Floor Structures

The whiskers below are ZINC WHISKERS. They were found growing on the zinc-coated steel underside of raised floor tiles. In these examples the floor tiles were part of a computer room in which zinc whisker debris was shed from the floor tiles especially during maintenance activities within the data center . The conductive whisker debris was distributed around the room via the air cooling system. Ultimately, some whisker debris was drawn inside of the electronic systems (e.g., servers, routers, disk arrays) operating in the data center resulting in catastrophic and/or intermittent short circuit failures.

Originally Posted by miked

I am interested in how you might envision a process to remove perhaps solder traces so components could be easily removed and processed separately.

Mike when my $500.00 Garmin GPS became intermittent then finally quitting altogether I blamed tin whiskers, apparently I may have been wrong. I lived in rural Manitoba with winters well below freezing, leaving the Garmin inside my truck at all times.

Allotropic transformation

At 13.2 degrees Celsius (about 56 degrees Fahrenheit) and below, pure tin transforms from the silvery, ductile metallic allotrope of β-form white tin to brittle, nonmetallic, α-form grey tin. The transformation is slow to initiate due to a high activation energy but the presence of germanium (or crystal structures of similar form and size) or very low temperatures ~-30 degrees Celsius aids the initiation. There is also a volume increase associated with the phase change. Eventually the α-form decomposes into powder, hence the name tin pest.^[3]
The decomposition will catalyze itself, which is why the reaction speeds up once it starts; the mere presence of tin pest leads to more tin pest. Tin objects at low temperatures will simply disintegrate.


Tin metal when exposed to low temperatures breaks down, the procedure is called Tin Pest, I suspect the Garmin circuits had lead free solder mostly composed of tin which I have come to learn breaks down in the cold. Below are some historical events involving tin.

It looks to be any board soldered with tin will break down when cold, so freezing your boards maybe to easiest method of removing components. Just do not use the home freezer that you store your food in, plenty of old beat up freezers out there that still work.

Possible historical examples

Scott expedition to Antarctica

In 1910 British polar explorer Robert Scott hoped to be the first to reach the South Pole, but was beaten by Norwegian explorer Roald Amundsen. On foot, the expedition trudged through the frozen deserts of the Antarctic, making for caches of food and kerosene deposited on the way in. In early 1912, at the first cache, there was no kerosene; the cans - soldered with tin - were empty. The cause of the empty tins could have been related to tin pest, and some observers blame poor quality soldering, although tin cans over eighty years old have been discovered in Antarctic buildings with the soldering in good condition.

Napoleon's buttons http://everything.explained.today/Tin_pest/

The story is often told of Napoleon's men freezing in the bitter Russian winter, their clothes falling apart as tin pest ate the buttons. Whether failing buttons were indeed a contributing factor in the failure of the invasion remains disputed; critics of the theory point out that the tin used would have been quite impure and thus more tolerant of low temperatures. Laboratory tests provide evidence that the time required for unalloyed tin to develop significant tin pest damage at lowered temperatures is about 18 months, which is more than twice the length of Napoleon's Russian campaign.^[4]
Modern tin pest since adoption of RoHS

With the adoption of the Restriction of Hazardous Substances Directive (RoHS) regulations in Europe and California banning most uses of lead, and similar regulations elsewhere, the problem of tin pest has returned, since some manufacturers now use pure tin, but previously used tin/lead alloys. For example, the leads of some electrical and electronic components are plated with pure tin. In cold environments, this can change to α-modification grey tin, which is not electrically conductive, and fall off the leads. After reheating, it changes back to β-modification white tin, which is electrically conductive, and can cause electrical short circuits and failure of equipment. Such problems can be intermittent as the powdered particles of tin move around. Tin pest can be avoided by alloying with small amounts of electropositive metals or semimetals soluble in tin's solid phase e.g. antimony or bismuth, which prevent the decomposition. Silver, indium, and lead have also been used, but lead is not soluble in tin's solid phase.


The time laps video 1 sec = 1 hour.