Colored Polymer Frames - Weaker than Black?

[Cowboybebop]

I heard a rumor that firearm frames in FDE, OD, etc are weaker than the standard black frame due to less carbon black in the mixture to absorb UV energy.


Is there any truth to this?

 

[Aim1]

I heard a rumor that firearm frames in FDE, OD, etc are weaker than the standard black frame due to less carbon black in the mixture to absorb UV energy.


Is there any truth to this?

I thought I read that it was an issue with Magpul mags and they had to find the right mixture to make colored mags just as good as black ones.

 

[bassjam]

There probably is a minor difference, but it's also a very small difference.

My background is in plastics, I've working in injection molding and blow molding for 12 years now. Plastic in it's natural state is a milky translucent white (think milk jugs). That will be your strongest polymer, so even adding black weakens it somewhat. But like I said, it's a small difference.

The chart in the link shows various mechanical properties of natural, red, and yellow with the same polymer. Don't take these as gospel truth, as changeling the polymer or specific masterbatch will give different results, but you can see how the properties can vary some by color.

https://www.polyplastics.com/en/product/safety/coloring/

 

[bassjam]

Also, it has little to do with UV rays, which are damaging to plastics. It has more do do with the chemical bonds that the pigment interrupts by being there.

 

[bannockburn]

bassjam

Thanks for the link. Interesting stuff that I never knew about colored polymers.

 

[Blkhrt13]

Does this mean I should give up on the purple and sparkly Pavona?

 

[fpgt72]

There probably is a minor difference, but it's also a very small difference.

My background is in plastics, I've working in injection molding and blow molding for 12 years now. Plastic in it's natural state is a milky translucent white (think milk jugs). That will be your strongest polymer, so even adding black weakens it somewhat. But like I said, it's a small difference.

The chart in the link shows various mechanical properties of natural, red, and yellow with the same polymer. Don't take these as gospel truth, as changeling the polymer or specific masterbatch will give different results, but you can see how the properties can vary some by color.

https://www.polyplastics.com/en/product/safety/coloring/

Pretty cool....I love sites like this that have people that actually work in the area that have real know how on just how stuff works.

 

[scaatylobo]

I heard a rumor that firearm frames in FDE, OD, etc are weaker than the standard black frame due to less carbon black in the mixture to absorb UV energy.


Is there any truth to this?

Article by Jim Tarr who states that its a loud YES,IF the color material is put into the mix of polymer.

I see it as a yes,for sure.

But I doubt that is a problem for any but military who require REALLY strong frames.

 

[Chemistry Guy]

"Strength" isn't just based on a single characteristic. The fiber-polymer composites that firearm frames are made of are evaluated on a whole bunch of characteristics, including mechanical traits such as toughness, tensile and compressive strength, and rigidity, but also on more subtle characteristics such as resistance to solvents, heat, freezing, sunlight, and "wear" characteristics related to rubbing against different surfaces. There will always be trade-offs, as no single substance is the best in all categories.

I did some analytical work for some engineers who were designing polymer composite medical devices used to screw broken bones together, and you would not believe how much testing and evaluation goes into this type of material. These guys worked for a small startup, so I am guessing the big firearm manufacturers like Glock and Ruger have whole teams of engineers optimizing their polymer options.

 

[ironworkerwill]

CNN just reported that black polymer is the most dangerous. Added notes was that pink and purple was just as strong just a little different.

 

[Cowboybebop]

Interestingly enough, the military FN SCAR rifle is usually in FDE and the new XM17 Sig handgun just selected by the army is also in FDE. Maybe the issue is more academic than anything else.

 

[Tirod]

Aside from color, the design engineer also increased the thickness where needed and can add metal reinforcement to the frame for major structural enhancements. The P320/M17 has a drop out trigger guard assembly with slide rails, Glocks are molded in.

Color of polymer has very little do to with the final moldings overall strength, as the compound polymer is actually fiberglass reinforced - not polymer only. They are proprietary FRN, same basic stuff as cheap lockback knife handles. How much fiberglass and its diameter and length have more to do with it, it's proportion in the mix with nylon is a more important characteristic. There are also different types of nylon to choose from. This gives the injection molding team a "palette" of resins and reinforcements to select to get the proper strength characteristics.

The polymer AR15 lower molding discussions here and elsewhere brought out a lot of this in the recent past. Color is about the least important when given all the factors. One issue is that black absorbs a lot of solar radiation which can affect the weapons temperature, at elevated numbers characteristics change. I'd rather have a lighter color with cooler handling than a gun soaking up the suns rays all day. Black has it's disadvantages and some are significant.

 

[jmorris]

My background is in plastics, I've working in injection molding and blow molding for 12 years now. Plastic in it's natural state is a milky translucent white (think milk jugs). That will be your strongest polymer, so even adding black weakens it somewhat.

The topic created a question for me you may know, what is it that makes PVC ultraviolet resistant and why does it seem UVR PVC is usually not white?

 

[bassjam]

The topic created a question for me you may know, what is it that makes PVC ultraviolet resistant and why does it seem UVR PVC is usually not white?

I have very little experience with PVC, I work in food grade plastics and the industry has been moving away from PVC for a while now.

I do know that PVC can be harmed by UV light over time still, and I'd have to guess that UVR PVC is a different color because the additives added to make it more UV resistant probably change the base color. Most plastics are a milky clear color by themselves, I'd guess the solid white of common plumbing white PVC pipe is deliberately done to make identification easy, or it's due to the impact modifiers or other additives that are added to the base resin.

 

[Hanzo581]

Was this rumor started by a company offering only black polymer perhaps?

 

[hdwhit]

cowboybebop wrote:
...due to less carbon black in the mixture to absorb UV energy...

As bassjam noted, different colorants take different places in the mixture and so should be expected to have different impacts on the mechanical properties of the material.

But, this positioning of the colorant in the mixture has nothing to do with absorption of UV energy. Ultra-violet degradation of polymers is a result of UV radiation disrupting the structure of the underlying polymer chains, not the structure of the colorant. So, it could be that some colorants other than black actually strengthen - rather than weaken - the polymer when compared to black.

 

[hdwhit]

bassjam wrote:
I work in food grade plastics...

Ah! So you're an Oriented PolyPropylene (OPP) expert?

 

[bassjam]

Haha, not an expert by a long shot, but I do work with OPP a decent amount. And straight PP. And PET, PETG, PETE, as well as PE and some of it's variants (HDPE, LDPE, LLDPE). Mechanical Engineer by schooling, Packaging Engineer by trade.