A Question of Plastic

[Mukaukau Nuva]

As I'm sure that many of you know, prior to 2003, Bionicle masks were made of solid, ABS plastic. Starting in 2003 (after a brief stint with bulky Nuva masks), masks began to be made out of a softer, flakier plastic that was used until the line ended (probably because 2001 masks were prone to shattering under pressure; this is also probably why the Nuva masks were so over-sized, to strengthen them). The new masks were made of the same plastic that many weapons were made out of (other parts like Metru shins and feet were also made of the material).

I have a question for those more in the know: is this plastic a flavour of ABS (a diluted formula, etc.) or an entirely different type of plastic altogether? I'm mainly wondering about how they're expected to age; assuming they aren't damaged, are they expected to last as long as ABS parts under proper storage, or should extra precautions be taken? I haven't found much info looking around, but perhaps I'm looking in the wrong place...

[Master Inika]

I never realized before just now that the Mata masks were much harder than the Metru masks. That's why they make such a distinctive sound when they touch each other or the floor...

[Xboxtravis]

I honestly have been curious as to what plastic it is for a while. The Metru plastic I think was actually first used on the Avhokii and Kraahkan in 2003, then adopted in bulk with the Metru on through the Glatorian. Its interesting that 2015 with the reboot saw a return to a harder plastic. I assume it is safe to say the following:

2001-2004: ABS Masks (Mata & Nuva style masks)
2003-2010: Softer Plastic
2015-2016: Hard plastic 

My guess is the 2003-2010 soft plastic is Polyethylene, they have sort of the same feel to them as the Lego plants being softer than other Lego pieces, if not there is at least one other plastic Lego uses which might be the source of the 2003-2010 soft masks. Maybe its some sort of Styrene variant? My guess for the 2015 masks is Polycarbonate (PC). ABS cannot be transparent, and G2 had a heavy focus on blended masks with transparent and solid colors in the same piece. As such I feel confident that PC is the likely source of most G2 masks (and likely used in a few G1 masks too like the Trans-Neon Green Miru, the various Kaukau's etc). There is a good resource on plastic types in this thread here: https://bricks.stackexchange.com/questions/191/what-kind-of-plastic-are-lego-bricks-made-of

[Mukaukau Nuva]

I did not know about that transparent part before now, thanks! (now I know why these pieces were so hard to take apart from one another).

That makes me all the more curious as to what exactly the trans glittery Avohkii and trans great Rau are made out of; presumably something slightly different from their dull gold and Metru counterparts respectively.

[The Master of Energy]

On 5/22/2020 at 2:22 PM, Mukaukau Nuva said:

probably because 2001 masks were prone to shattering under pressure

This has actually happened? How did you find out about it?

[Mukaukau Nuva]

Judging by images like these, it's happened at least twice. 

Mainly caused by stepping on the mask. Masks like the original Hau have a lot of plastic on the sides so stepping on the mask from the front or sides will create a stress mark that may or may not begin to crack.

Due to the materials these masks are made of, the plastic could splinter off with jagged edges. It may not have happened a whole lot, but ideally it shouldn't happen at all (given stepping on LEGO is practically cliche). The newer style ones could still be damaged by stepping on them, of course, but they would just bend, not shatter, so the person playing with them shouldn't get hurt.