Identifying Plastic Materials in Airsoft Guns

Discussion in 'Gun Building, Modifications & Repairs' started by wetpee, Oct 23, 2020.

  1. wetpee

    wetpee Member

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    Unsure if this is the proper category for this post, but it feels relevant as it is a more technical topic.
    I was wondering if anyone could shed more light on how to test plastics at home with common household items in an attempt to identify and/or categorize them.
    I have watched this video a couple times:

    It provides a great starting point for this topic, but still lacks some clarity and completeness.

    I have recently opened up a a teammate's RIF to find this piston cracked at the back after one month of use.
    Piston_MTX_IN0405_1_lg.jpg https://www.evike.com/products/31699/
    I will discuss the failure more in my "Tech Log" thread as there were a few things going on that I feel could have contributed to this, including either bad design of the piston, and/or a deformity, but also some custom modifications and other aftermarket parts. I am very certain it is not polycarbonate, but there is some added texturing to the body that appears to somewhat mimic the appearance of polycarbonate.

    Point of failure:
    IMG_20201021_154240_01.jpg IMG_20201021_154219_01.jpg
    In the second image you can see to the left of the tooth rack there appears to be some missing material. I am unsure if this was part of the damage or if this is a deformity.
    The plastic is very difficult to break or deform with a single pair of pliers.
    Deformation and breakage testing:
    Screenshot_20201023-133915_Video Player.jpg IMG_20201021_175419_02.jpg IMG_20201021_175419_01.jpg
    Flame/Melt test:
    20201023_140910.jpg
    Held a small blue flame easily and did not char. Just kind of deformed and holds its new shape well after cooling off. Produced a good bit of smoke after blowing out the flame.
    Smell was a bit difficult to pick up on. Very faint. Possibly like burnt electronics as Maekiii describes polyacetal in the above YouTube video.
    I believe this to be polyacetal. Thoughts?
     
    Last edited: Oct 23, 2020
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  2. Guges Mk3

    Guges Mk3 Well-Known Member Supporting Member Lifetime Supporter

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    That is a horrendous design. The entire load of the piston on 2-3mm of polymer with a 90 degree joint. Design "fail" majorly.

    That is a PC piston...not PolyA

    Issue...number one. Matrix rebrand product. As exemplified by the long defunct bad design. A piston hasn't been made like that for Airsoft AEG's in over 14 years. Another example of Fleecing the newbs with Matrix products.
     
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  3. wetpee

    wetpee Member

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    Agreed.
    That seems a bit contrary to Maekiii's video. The polycarbonate pistons just fall apart and have a very noticeable crystalline structure. This Matrix piston was very difficult to deform and break apart with the pliers, and came apart in large pieces. The dude was studying plastics engineering at the time, check it out. I brought this up with my dad who has a chemical engineering degree and he thought perhaps polycarbonate + ABS blend. I'm pretty certain at the very least the Matrix piston is not nylon. Seemed similar to the green Madbull PolyA piston Maekiii experiments with in that video around 12:20. His mad bull piston was much more brittle/weaker than this Matrix piston, though.
     
  4. aotsukisho

    aotsukisho Well-Known Member

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    My guess is nylon.

    POM is very hard, very stiff, and does not deform under stress. It also has a low coefficient of friction, and does not react well to fire (no smoke, not self-extinguishing - also releases formaldehyde). It is also notoriously hard to glue. I've also only seen POM pistons in either white or black. It tends to resist chemicals and solvents well apart from some specific ones like chlorine.

    upload_2020-10-23_9-56-3.png
    upload_2020-10-23_9-57-47.png
    Retro Arms piston failure from PME, due to its stiffness probably the crack is gigantic

    POM can be injection molded so that might explain the surface texture, but again majority of the POM pistons I see are smooth or CNC finished. The surface sheen and destructive plastic deformation patterns match a softer material like nylon.

    True polycarbonate pistons are a very bad idea which continues to puzzle me why VFC is held in such high regard when they make such bad decisions
    [​IMG]
    Any degree of transparency tends to mean polycarbonate (think acrylic/plexiglas), and while it is stiff it is also brittle. A 400fps gun is capable of shattering or punching through 1/4" plexiglas sheet, I know because I've done so.

    Both nylon and POM are used in electronics but I think that smell more closely matches nylon. Burning electronics usually means epoxy resin, fiberglass, and plastic wire insulation/jackets which tend to be polyvinyl chloride (PVC), polyethylene, or polypropylene...and less commonly, polyurethane and nylon.

    ABS burning is very noticeable with a large weird-looking flame due to how it boils before combusting.
     
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  5. wetpee

    wetpee Member

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    I'm really leaning towards POM on this one. It was extremely tough to deform or break with a set of pliers and not soft at all. I cut my hand trying to break it and I'm not clumsy with my hands.
    Also very slick where it was not textured. So although it was injection molded, I believe that is almost universally cheaper than machining and its a cheap matrix piston. It certainly did not combust like ABS. That's nuts. Do you know the material of that white piston?

    @aotsukisho Side note: what are your opinions on the retro arms pistons?
     
  6. aotsukisho

    aotsukisho Well-Known Member

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    It's a Retro Arms POM piston, which is why I don't think yours is made of the same material as it failed in different ways. The photos of the parts in your hand show plastic deformation, which POM does not really do

    Other than the fact that it broke, I liked it a lot. Very good dimensional conformity as it is CNC'd rather than injection molded (no post-mold distortion due to heat cycle) but it is heavier than nylon like SHS despite there being 8t and 9t rack models intended for DSGs.
     
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