Not that we shouldn't try to make better helmets. But this article does a good job explaining the limits of polyurethane.
The problem is ultimately one of physics. All helmets work under the same principle. The force striking one’s head--acceleration mixed with mass--can’t actually be prevented. Physics says that energy has to go somewhere, right? What good helmets do is lengthen the duration of the impact itself (in the hundredths of a second range), reverberating energy through various structures and materials, to smooth a hit from a sharp, high-g strike to a relatively smooth curve of deceleration. Consider landing on a concrete floor or a pile of pillows. Which impact takes longer and which impact hurts more?
“I think that it’s true that football helmets are 85% as good as they’re ever going to get,” Dr. Timothy Gay, University of Nebraska physics professor, writer, and industry helmet consultant tells me. “The optimal football helmet won’t be much better than the helmet you can buy right now because there are just physics restraints on the kind of padding you can use. We have a pretty good micro, nanotechnological understanding of how materials work. And basically, there are limits on what padding materials can do for a given thickness.”
Then of course, you have the "let's remove the facemasks" crowd. In theory, this would change the way players tackle, because a high percentage of BROKEN FACES would ensue.
Which would be like trying to bring down average speeds on the highway by OUTLAWING SEAT BELTS, so that way most people would drive a LITTLE slower thinking "holy shit, I don't have a seatbelt, maybe I should slow down."
Yeah, it'll kill a lot more people, but eventually it would bring down speeds.
The only real "solution" to helmet-to-helmet hits in the NFL, is to even further legislate against what are "armless tackles."
It won't sit well with the public, but it's the only way to prevent using that polyurethane warhead as a weapon.