That makes sense, if I don't rip open a bag on the first try it'll just stretch and never open

Stretch it in one direction, then grab in the middle of the stretched area and pull sideways, and it pops open like nothing.

Cool, need to try that!

Now I wonder if that is how these "magic cut" wasabi and ginger sachets work.

it varies a lot with polymers, and it's a different effect. steel is entirely crystalline; ldpe is mostly amorphous. a big part of what's happening in the strain hardening of ldpe, aside from making it uniaxially oriented, is that it's crystallizing; the crystalline domains become larger, greatly reducing the amorphous volume fraction. (there are also other ways of achieving this effect, such as annealing, which you will notice softens steel rather than hardening it.) ldpe's strength isn't determined by crystal dislocation density in the same way as steel's, and of course steel doesn't have polymer chains to align

This is exactly what dyneema is only with hdpe.

no, dyneema is not hdpe; it's uhmwpe, and it isn't just strain-hardened, it's gelspun

Assuming these terms are all correctly spelled, this has to be the shortest sentence I've understood the least of on HN.

Guess I've got some googling to do.

UHMW = ultra high molecular weight. Each molecule is literally heavy because they have a lot of atoms.

PE = polyethylene. The most popular plastic on this planet.

HDPE = high-density polyethylene. One of the most common plastics. Milk jugs, glue bottles, etc.

Stick some UHMW tape on anything that needs to slide easier. Its surface is quite slippery

HDPE is also what Nalgenes and the like are made of (or used to be anyway), and is very popular for storing chemicals as well. It is very nearly completely inert.

you cunninghammed me: nalgenes are polycarbonate, which is a lot less inert

all the polyethylenes are relatively inert, because polyethylenes are in some sense just heavy paraffins. paraffin is germanized latin for 'relatively inert'

And you have Cunninghammed me :-)

Some Nalgene's are polycarbonate, like those commonly drunk from. But not all, some are HDPE[0,1,2].

Some are Polypropylene co-polymer[3] but those are more for specialist things I guess.

[0] https://ultralightoutdoorgear.co.uk/ultralite-1-litre-wide-m... [1] https://www.cotswoldoutdoor.com/p/nalgene-hdpe-125ml-wide-mo... [2] https://www.elitemountainsupplies.co.uk/camping-trekking-c4/... [3] https://www.thelabwarehouse.com/products/bottle-nalgene-ppco...

oh, thanks! i only knew the pc ones

The clear Nalgenes are polycarbonate, but the opaque ones (sold as "Ultralite Bottle" on their website) are made of HDPE

they are! sorry to be telegraphic

I stand corrected! Thanks for the headsup <3s