Effect of Gamma Irradiation on Polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic polymer of tetrafluoroethylene. A sample of this material was left in intimate contact with a 1 microcurie radioisotope source of Cesium (Cs-137) for 2 weeks.
Control sample showing intact edges and opacity with minimal granularity
Irradiated sample shows unraveling of edges.
Gamma irradiation frees fluorine and depolymerizes (more accurately photoinduced polymer degradation: photolysis / photodisassociation) the PTFE into granules.
The gamma ray energies emitted by the radioisotope equal 661keV.
Control sample showing smooth, homogeneous surface and edges.
A raw lump of calcium carbide is a grey, slightly metallic looking object. It smells like ozone, stale air from and old tire plus sulfur. Ozone is the smell of electricity in air: the smell of slot cars and toy electric trains.
These combinations of weird smells add up to something familiar, but I couldn't remember what-until I looked at the chemical reaction notation. Then I had a "Proust Moment", only with lime and not lemon cookies. I just had this memory of the smell and seeing my fingers caked with acidic sludge. More on that later.
As you can see in the video, it will not catch fire when a flame is held to it. Once I add water with a syringe it produces Acetylene gas which does ignite. Acetylene burns so well it's used in welding torches!
Calcium carbide is CaC2, written on my sample as CaCa.
Water is H2O.
CaC2 + 2H2O = C2H2 + CA(OH)2
C2H2 is Acetylene, the gas shown burning in the video.
CA(OH)2 is a grey, sludge that smells a bit like... Plaster of Paris!
Back as an undergrad I took a sculpting class. After carving a huge limestone rock I polished it with wet sandpaper and water. The result was this same stinky sludge called slaked lime. Plaster of Paris uses gypsum, while fancier lime plaster uses slaked lime. They smell pretty similar, though lime plaster will burn your skin (as I found out while sanding my sculpture). I remember my fingers burning and that smell of slaked lime, just like Proust was inspired to write 2000 pages after he smelled a lemon Madeline cookie.
Meow-that's funny. I have a Proust Memory Moment every time I smell ferns...of people yelling at me to not kill ferns. I don't listen though.
Strangely enough, I was texturing my hallway ceiling and BOOM there was that smell again! Turns out that the stuff I was glopping on had carbide in its ingredient list.
Placing a lump of calcium carbide into a container and dripping water into it is how old miner's helmets worked (but never do this: read below). A pipe/nozzle system allowed the acetylene gas to rise out of the water and lime sludge: this way the flame doesn't sputter like in the video.
However: miner's helmets are precision instruments with small valves. You may think, "what of he put the lid on that container with the water and calcium carbide and then poked a little hole in the top and lit it?"NEVER, EVER do that!!! I guarantee that it will instantly explode, sending pieces of the container shredding through the room!
Acetylene welding torches often pop while people are using them. It's scary and can blow through your weld-but that flame is out in the open. Contain acetylene (even just a bit, like a bowl with turned inward edges) and you get a bomb with shrapnel! People put acetylene in paper cups laying sideways and ignite them: loud bang, perforated eardrums and wads of paper embedded in your eyeball. It will be the loudest (and last) thing you'll ever hear.
Just laying a piece of paper over the container is enough to make the acetylene explode instead of burn.
If you fill a container with acetylene past 29psi it can explode all by itself-no flame needed! To be able to put acetylene into welding tanks they have to dissolve it into acetone. That lets it get up to 250psi, so it will squirt out of the tank/hose/nozzle while welding-instead of just exploding the tank.
Acetylene in contact with brass or copper forms even more dangerously explosive compounds!
Acetylene is the scariest, most unstable thing I've ever been around...and that's coming from someone who's experimented with neutron radiation.
Leave it alone.
So, besides antique mining helmet lights and ceiling plaster what is calcium carbide and the acetylene it produces good for? Something insanely high tech: thiol vinylation reactions which bind molecules of things like fluorescent markers to biomolecular material being studied. I love fluorescent and phosphorescent stuff!
Kind of like: the glow in the dark fluorescent stuff "clicks" onto the cancer cells. This is called "click chemistry". Thiol bind with acetylene using these methods. Click chemistry focuses (somewhat) on creating reactions that mimic nature, are modular (click together) and are one pot reaction: tons of glassware and tubes and stuff looks cool, but scientists would rather through a bunch of stuff in a bucket and get to work, not spend time synthesising things with a gillion steps.
Another cool thing the carbide and water reaction is good for? Polymers! Search around and you'll find my older posts about polymer. See: everything comes full circle over and over again for me.
In my continuing assault on Isaac Newton I will demonstrate how boring old Newtonian fluids (like water) are less fun than non-Newtonian ones. First, we need to get our hands on a non-Newtonian fluid.
To make a non-Newtonian fluid we can just mix laundry spray starch and white glue. This will make a shear-thickening non-Newtonian fluid. Under stress it thickens and hardens (increases viscosity), once the stress passes it turns into a runny liquid. Put it in a cup and its like white glue you can stir with your finger. Poke your finger into the cup forcefully and it will harden into a single blob and you can pull it out of the cup!
Here's how quickly it is to make, it's actually easier without the gloves-they're too slippery to get a good gauge on the mix:
Here's my non-Newtonian fluid in action. Slap it and it hardens enough to let me peel it up off the plate. Wait a second and it'll drizzle down as a liquid:
There are many variations of non-Newtonian fluids besides shear-thickening ones.
Ketchup is a shear-thinning non-Newtonian fluid, which is why people smack (shear) the ketchup bottle to get it to thin and flow out faster. Xanthum gum is added to ketchup for just this effect.
If you put this spray starch and white glue mixture in a ketchup bottle the only way to keep it from pouring out would be to keep smacking the bottle! If you wanted it to thin and flow faster your just leave it alone for a few seconds. If you slap it hard enough it will instantly harden and break into two pieces, only to flow back together of left alone for a few seconds.
It seems pretty weird, but I've dealt with having a non-Newtonian fluid and the problems that it can cause:
I play a variety of bowed instruments. Rosin is used on the bow to let it grab the strings of the violin, cello or as in the photo above a double bass viol. The rosin looks and feels like a cube of yellowish glass:
This is the harder rosin I've used for years, but recently I started playing the huge upright double-bass which required me buying newer, softer rosin. It's in the red canister next to the violin. The softer rosin seemed like regular rosin: hard, produces a white powder when rubbed with the bow and will shatter into a zillion pieces if hit with a hammer; however you leave the canister on its side after a few days the seemingly glass-like rosin will ooze out. Leave it as a blob on a shelf and it will slowly pancake out: spreading and flattening, and eventually oozing off the edge.
Now, some people will tell you that regular old glass is a fluid that oozes over time, but they're wrong. Glass is a solid, although it isn't a crystallized solid so it's an amorphous solid. Crystals are rigid lattices of ordered molecules. Fluids and gases are unlatticed unordered molecules. Glass is unlatticed, unordered yet rigidly bound. Glass is a solid.
Most rosin for instruments is a solid, so solid on fact that it sometimes crystalizes. However bass rosin is much softer relative to regular rosin-although if you found a piece on the sidewalk you'd probably assume it was a chunk of old, broken glass.
Common myths: old glass windows are thicker at the bottom because the glass oozed down. Wrong: the spun old glass and cut it, the outside edge was always thicker and it was installed thick edge lower. A glass shelf will bend in the center over time so it's an oozing liquid. Wrong: it bends for the same reason wood shelves bend, it was too thin and/or too overloaded or gravity just got the best of it.
Polymers are repeating molecular units. They tend to create semi-crystalline structures and glasses. It tends to make things "plasticy" and in fact it gives the name for polystyrene is polymer of styrene (styrene being obtained from benzine).
What else has a crystalline structure? The starch spray in our non-Newtonian fluid. It has a semi-crystalline structure, that helps bind the glue into big molecules that are a polymer. Starch itself is considered a polymer. Adding a little borax powder* to the mix would make it a stronger polymer--strong enough that it would stop being a thinning/thickening liquid and become a rubber-like blob that you could throw and bounce off the walls. If you add an enzyme it will break the polymer up into smaller units (monomers) which changes its properties. Stringing together units of silicon yields a semi-liquid silicon polymer, which we call Silly Putty!
*Borax powder is sodium borate a natural compound of the element boron, which is what you want to get in the laundry aisle. Boric acid is hydrogen borate is an acidic form of borax that is either a natural compound or manmade using the element boron with sulfuric or hydrochloric acid; as such it is acidic. Borax crystals are usually crystallized boric acid. They are sort of not the same. Kind of like ice is frozen water and good for putting in soda, ice dipped in acid is not quite the same.
Boron is B
Boric Acid is H3BO3
Borax is (NA2B4O7)(10H2O)
When dry boric acid crystals are added to water it grabs electrons and becomes weakly acidic. This weak acid is used in eye washes and hygiene products to combat yeast.
You'll also remember boron in its elemental form has awesome properties when used to lace blocks of paraffin wax during out experiments with slowing down radioactive neutron particles in my previous post "My Radioactive Dime".
Where else is boron/borax used? Taxidermy!
This is part of my Game fowl Collection: photo-books by Hiro; my bird Alouicious (named after the teddybear from Brideshead Revisited); and copies of Feathered Warrior (a catalogue where you can buy fighting spikes and the live-fertilized eggs of *past* fighting champions).
Alouicious is actually from an organic market in Rochester Hills - not a fighting bird (so if you were upset when you thought he died in a cockfight, but relieved he was just normal food-then you're a hypocrite, unless you're vegan). LOL.
Here's a pic of my room-mate Boris the Book Boar visiting Melvindale Public Library during a charity event. He came all the way from the Black Forest in Germany!
As you can see, boron is very useful! But enough of boron for now, it's time to get back to starchy polymers...
Boron has an incomplete set of electrons (in a compound) and seeks them out to bond with. This gives boron (not boric acid) many uses in the adhesives industry, including mixtures involving our good old friend starch! I see this all the time (I'm a librarian) in bookbinding pastes. One great glue for paper (used to make cardboard poster tubes) made from a water soluble synthetic polymer is polyvinyl alcohol (PVA) with boric acid added to it.
Usually polyvinyl alcohol (PVA) has a formula of (CH2CHOH)n), but this particular chunk of PVA is actually:
(-(CH2CHOH)n-(CH2CHOOCCH3)m-)
PVA is sorta weird in that it's not made up of chained monomers, it's polyvinyl acetate that is polymerized, and then the acetate is converted to alcohol! It's very bouncy:
PVA is (CH2CHOH)n or it is -(CH2CHOH)n-(CH2CHOOCCH3)m-
Glucose is C6H12O6
Starch is C6H10O5
As a side note: the specific gravity of this PVA ball is 1.24 according to the MSDS (Material Safety Data Sheet) provided by the manufacturer, Chang Chun Petrochemical. It sinks in water, but if you tip the bowl it's in it only slowly rolls to the lower side.
Here's a weird enzyme vs polymer test: chew a saltine cracker. Your saliva will break up the polymers and the crackers will get sweeter and sweeter as you keep chewing (and not swallowing) and adding more crackers. The monomer of starch is glucose. Glucose is a simple sugar. Simple sugar is sweet. It's the enzymes in your saliva (not the acids) that do this.
As a polymer, starch tastes like bread or potatoes. Break it up into its glucose sugar monomers and it's sweet! Glucose attracts water around it. Starch just attracts other starch around it. Glucose grabbing water can cause swelling and other problems-especially in the bloodstream of humans. It also causes plants (which store sugar/energy in the form of glucose) to need more water to make the glucose happy. The result is thirsty plants.
Many plants have wised up and stored their glucose in the form of longer chains of starch: the plants aren't so thirsty and the starch isn't bothered by whatever water is in the plant (too much water can mess with the glucose storage). Glucose in plants and animals calls for a balancing act with the amount of water, starch doesn't really care so much.
So...I guess have to find someone besides Newton to blame for the constant barrage of cantaloupes "oozing" off the glass table? Cantaloupe polymerization via face rubbing? I don't want to be taxidermied. Meow.
