How Plastic Bottles are Recycled into Polyester

There's a whole lot of labor involved in recycling.

And it looks like it's largely done by hand in nations with lower worker payments and laxer labor laws than the US.

But then again, what else are we going to do with all our old water bottles?

Hydraulic Press | Prince Rupert Drops | Remake | Safe Tails

When it comes to hydraulic press YouTube channels, I'm more of a Hydraulic Press Channel guy than I am a PressTube guy. I'm particularly fond of the destruction of a hockey puck and of the vicious clay creatures that are stopped from wanton murder at the end of each video.

But I am willing to watch the derivative PressTube when they come up with something creative to destroy. In today's video, the PressTube folks destroy a Prince Rupert drop...or two...or ten. And, in the process, they also make some pretty big dents in a chunk of lead.

AISI/SAE Steel - numbering system

I spend a decent amount of my summer talking to industry folks. Sometimes they're materials engineers, sometimes metallurgists, sometimes polymer engineers, forgers, welders, failure engineers.

No matter what they're titles, they're typically far more knowledgeable about industrial materials than I am. They throw around all sorts of acronyms that I have to take note of and look up later.

Sometimes I save reference materials here just so I can look them up later.

Today's reference material is about the AISI (American Iron and Steel Institute) / SAE (Society of Automotive Engineers) steel numbering system. See, the wikipedia article - while thorough - is a little too thorough for me.

Instead, I like the simplicity of the Engineering Toolbox's reference chart...

10XX	Carbon steels	Plain carbon, Mn 1.00% max
11XX		Resulfurized free machining
12XX		Resulfurized / rephosphorized free machining
15XX		Plain carbon, Mn 1.00-1.65%
13XX	Manganese steel	Mn 1.75%
23XX	Nickel steels	Ni 3.50%
25XX		Ni 5.00%
31XX	Nickel-chromium steels	Ni 1.25%, Cr 0.65-0.80%
32XX		Ni 1.75%, Cr 1.07%
33XX		Ni 3.50%, Cr 1.50-1.57%
34XX		Ni 3.00%, Cr 0.77%
40XX	Molybdenum steels	Mo 0.20-0.25%
44XX		Mo 0.40-0.52%
41XX	Chromium-molybdenum steels	Cr 0.50-0.95%, Mo 0.12-0.30%
43XX	Nickel-chromium-molybdenum steels	Ni 1.82%, Cr 0.50-0.80%, Mo 0.25%
47XX		Ni 1.05%, Cr 0.45%, Mo 0.20-0.35%
46XX	Nickel-molybdenum steels	Ni 0.85-1.82%, Mo 0.20-0.25%
48XX		Ni 3.50%, Mo 0.25%
50XX	Chromium steels	Cr 0.27-0.65%
51XX		Cr 0.80-1.05%
50XXX		Cr 0.50%, C 1.00% min
51XXX		Cr 1.02%, C 1.00% min
52XXX		Cr 1.45%, C 1.00% min
61XX	Chromium-vanadium steels	Cr 0.60-0.95%, V 0.10-0.15%
72XX	Tungsten-chromium steels	W 1.75%, Cr 0.75%
81XX	Nickel-chromium-molybdenum steels	Ni .30%, Cr 0.40%, Mo 0.12%
86XX		Ni .55%, Cr 0.50%, Mo 0.20%
87XX		Ni .55%, Cr 0.50%, Mo 0.25%
88XX		Ni .55%, Cr 0.50%, Mo 0.35%
92XX	Silicon-manganese steels	Si 1.40-2.00%, Mn 0.65-0.85%, Cr 0-0.65%
93XX	Nickel-chromium-molybdenum steels	Ni 3.25%, Cr 1.20%, Mo 0.12%
94XX		Ni 0.45%, Cr 0.40%, Mo 0.12%
97XX		Ni 0.55%, Cr 0.20%, Mo 0.20%
98XX		Ni 1.00%, Cr 0.80%, Mo 0.25%

...with its couple of examples:

Example AISI/SAE No. 1020

• the first digit indicates that this is plain carbon steel.
• the second digit indicates there are no alloying elements
• the last two digits indicates that the steel contains approximately 0.20 percent carbon
   

Example AISI/SAE No. 4340

• the first two digits indicates a Nickel-Chromium-Molybdenum alloy steel
• the last two digits indicates carbon content roughly 0.4 percent

Ikea plans mushroom-based packaging as eco-friendly replacement for polystyrene

Styrofoam cases?

Air-filled bags?

Starch 'peanuts'?

Mushrooms?

Well, not exactly mushrooms...more like something called mycelium which is certainly mushroom-adjacent. It's certainly a fungus-based product.

And apparently if you grow it just right, let it grow into the right shape, bake it to make sure the final product doesn't grow mushrooms in the process of shipping, you can use mycelium - as produced by a company called Ecovative - to protect your widgets during shipping.

And Ikea ships a whole lot of stuff across the oceans. They're not quite ready to ship entirely in fungus-based packaging, but they're looking into it.

Sand Castle Holds Up A Car! - Mechanically Stabilized Earth

I wouldn't want to build my house on a sand castle foundation, admittedly. In fact, I posted something about the dangers of that before

Reinforced sand, on the other hand, looks like it might be something a little different. Just adding in some fabric - or screening - between layers of packed sand makes for a far stronger product. It's almost like it's a composite.

(It is a composite, by the way, gaining new-found strength from the combination of strengths of the materials comprising the composite.)

Mitch Anthamatten Explains a Shape-Memory Cycle Involving Strain Induced Crystallization

Wait, a shape memory polymer?

There's a bunch of good connections here to what we teach in our material science course.

• The polymer switches from being largely amorphous to largely crystalline on addition of strain.
• The addition of heat energy then causes the polymer to shift back to amorphism.
• The phase change happens around body temperature, like the stints we talk about.
• We have a solid-state phase change.
• At 0:55, the professor says the energy is 'enough to melt those crystals.' I'm way less knowledgeable and more a neophyte about all this than he is, but that sounds wrong to me. I don't think of a crystalline solid changing to an amorphous solid as 'melting.'

All that in less than two minutes time...

That's better than watching the Kentucky Derby.

Condensation Polymerisation | Chemistry for All | The Fuse School

Great animation for condensation polymerization here, folks.

The standard color codings are used - black=carbon, red=oxygen, blue=nitrogen, white=hydrogen. The animations are simplified to focus on the functional groups. And they show the by-products clearly and cleanly.

I do wish they would have suggested that the by-product could be something other than water (like in our preferred nylon demonstration from summer camp), but I'll happily take a great visual of the by-product first.

And we get applications of a couple of condensation polymers.

Overall, a winning, quick video.