Polymers and Soccer Balls

One of the things that I don't understand about soccer/football/futbol [*] is never ending changes in the design of the ball. You can read a little bit about the construction at Compound Interest, which briefly discusses some of the polymers used (urethane for the skin, butyl rubber for the bladder...). Every time there is a World Cup, out comes a new ball design. The 2014 World Cup had the Bazuca, which was used because nobody liked the knuckle ball characteristics of the Jabulani which was used in the 2010 World Cup. Before that, there was the Teamgeist and the Fevernova.

It's not just the World Cup that switches things up. The Euro Cup for instance, used the Tango 12 back in 2012 and this year is using the Beau Jeu.

Just the fact that these ball have names has me shaking my head. Can you imagine a baseball having a name and its design being changed every few years? Or an (American) football with a name? Part of the beauty of those sports is that the designs are so constant. Unless partially deflated, a football is a football is a football. Why would such an well established game as this need to keep changing the ball? (Obviously Adidas is making some money off of all this, but it can't be that much.)

The differences in these balls are not just the color, but the actual construction. The number of pieces in the skin and their joints are always in play and that translates into different aerodynamics, such as how the player can bend the ball when it is kicked. That means that every few years or so, or maybe even just between different competitions, the players have to adjust to a different ball.

Since FIFA is fine with such adjustments, why not start adjusting other things. Let's make the goal a couple of meters taller in all international competitions (that way guys wide open with the ball in front of the net with a sterling chance to score will have a harder time sailing it clear over the top). Don't worry - the keepers will adjust.



[*] Other things I don't understand include:

• Why can't the players do a better job of drawing a foul? You can see better acting at a 6th grade school play. Surely there must be some actors who are soccer fans that would be thrilled to help coach that skill
• Why don't they have retractable/removable flags in the corners? There are no other obstructions anywhere on the field except in the corners. I think we could devise a simple solution.
• Hooliganism

Previous Years

June 16, 2015 - When does the "chemistry" disappear in a polymerization?

June 16, 2011 - UV Abosrption and Sun Protection Factors

June 16, 2009 - A sign of economic turnaround?

The Mysteries of Ice Skating

That the physics of ice skating are still is not fully understood is not surprising. Making measurements on a small area that has dynamic pressure conditions wedged between the ice and the steel blade is extremely challenging. We know that ice is inherently not slippery, and that only because of the pressure of the blades somehow "melting" the ice or otherwise creating a liquid-like surface that skating happens at all. Long ago as an undergrad, I was taught that the pressure of the blade alone is enough to alter the melting point of the ice. This change can be calculated via the Clausius-Clapyeron equation but a quick back-of-the-envelope estimation shows that an enormous amount of pressure is needed. This was handwaved away by the instructor stating that skates are hollow ground (i.e., they are concave down as you look to the length of them) to increase the pressure.

Imagine my shock a few years later when I took up speedskating and found out those blades are flat ground. That right, the skates that are the fastest are the ones with the largest contact area. So much for Misters Clausius and Clapyeron (and my instructor).

New research offers a potential new explanation of ice skating. It's currently pay-per-view so I haven't read it (it will likely become downloadable in the near future as are most of the PI's papers, but I wonder if the article will really get at the dilemma that I mentioned above: the role of contact area.

Hollow ground skates are used for sports where turning tight corners is necessary, so have a "biting" edge is essential. In speedskating, having a friction free glide is essential to maintaining speed. But are there points where either approach becomes too extreme? Can skates with an extremely small contact area (an atomically thin edge?) have any value or would the performance degrade? And for speedskates, would a larger surface area aid or hinder performance? Is there a limit on either end?

I've puzzled on these questions over the years, but the greatest mystery to me is this: is there any value in creating a hybrid skate? One that is hollow ground on one or more portions and flat ground elsewhere. Maybe hollow on the front and back for turning on the toes or heels, but flat ground in the middle for maintaining speed. Even without understanding the physics of ice skating, I would love to see someone try such hybrids as I think it could provide in some very unusual results.

Previous Years

January 12, 1015 - Kinetics, Thermodynamics and Polymer Phase Transitions

January 13, 2014 - Still Proposing Changes to the Resin Identification Codes

January 13, 2010 - Race Horses and Rheology

January 13, 2009 - Walking Polymers

A Frisbee (Murder) Mystery

Fellow (retired) blogger Eric F. Brown brought to my attention an article about Frisbees, in particular, the Frisbees used playing Ultimate Frisbee. It become apparent pretty quickly in the article that the participants of the sport take it extremely seriously.

To me, a Frisbee is a Frisbee. I grew up with the Wham-O brand, but probably because there weren't any other brands to choose from. That has changed, and worse yet (for Wham-O), they are no longer the top dog. Or even the number 2 dog. And apparently, Wham-O is to blame for their own problems, and it's all because of the additives that they chose use. White Frisbees were traditionally made white by the addition of titanium dioxide. TiO₂ is a great white pigment as it has great hiding power and you can add lots of it without it showing signs of yellowing (unlike, say calcium carbonate). But it is expensive and so people are always looking for alternatives.

And Wham-O found an alternative set of additives:

I'm not sure what type of analysis this is other than poorly done. This shows the titanium dioxide as just titanium (What type of instrumental analysis can't detect oxygen?) So while it's tempting to assume that the other metals are probably oxides as well, the aluminum is more likely to be aluminum hydroxide, a common white pigment. I can't believe that silicone was ever added (as opposed to silicon, and probably the oxide at that). The zinc could be either the oxide or the sulfide (more on this in a minute). I can't see that iron oxides would ever be used (that bloody red color is not too appealing in most applications). And what's this "other" category? (Seriously, who did this analysis? Whoever paid for it got taken good.)

Regardless, the new additive package was not accepted by the players:

"At the time, Titanium Dioxide was getting pretty scarce. So the [Wham-O] people in Mexico, when they were molding the discs, they put in some Aluminum Oxide and other fillers, instead of straight [Titanium Dioxide]. I don�t know how much you know about polymer chemistry, but the other additives were aggressive and they actually caused some degradation of the plastic and loss of performance."

Plastic degradation? Now that get's interesting. Which brings us back to the zinc. We don't know what form the zinc was in - elemental (probably not), sulfide (a white pigment, but not the greatest and it is somewhat pricey) or the oxide (another white pigment). Zinc oxide is my guess, as it is photocatalytic under mildly acidic conditions (pH ~5.5) which would lead to the degradation state. Going from 8 % zinc to 10% zinc isn't going to make that big an impact - but that's assuming that the zinc was the oxide in both formulations. What if the initial formulation was zinc sulfide while in the new formulation it was zinc oxide? This analysis can't tell the difference, so it's entirely possible and it fits the limited data.

Sadly, based on this poor analysis, we'll never know but that is my guess: the TiO₂ gets the blame, while the ZnO skates free for the killing of the Wham-O Frisbee business. It's a miscarriage of justice.

Previous Years

November 5, 2012 - Job Titles and Business Cards

November 5, 2010 - Flow-Induced Crystallization

November 5, 2009 - Public to Private and Back Again

November 5, 2007 - Negative Intrinsic Viscosity and Positive Intrinsic Viscosity

March Madness: Brought to you by Plastic

The United States right now is going through "March Madness", the time of year when the annual college basketball tournament takes place. 64 teams are placed in a single-elimination bracket and over 3 weeks, the national champion is decided. But that is not "the Madness". Instead, "the Madness" comes from all the betting pools that are formed in the workplace or with friends. You get a empty sheet with the pairings and have to pick the winner of all 63 games before the first whistle is blown (more on that in a minute) for the first game. If you pick the Drooling Nazg�ls from Big State U to win it all and they are eliminated in the 1st round by the Biting Gnats of Tiny Town University, well, better luck next year since your bracket is blown. Correctly picking brackets is rather difficult, and basketball junkies who put a lot of thought into the matter are often made to look foolish by a spouse who picks their teams based on the mascots or the teams jersey colors.

The New York Times yesterday had an article about a tiny piece of plastic that plays a tremendous role in the tournament - the whistles used by the referees. I always figured that the whistle were metal and a had a little ball (called a pea) inside. Wrong and wrong. They are plastic and pealess. Being pealess means that the pea can't get stuck to an interior wall due to saliva or dirt building up (or the official blowing too hard!). Being pealess also means that the internal geometry is pretty complicated and molding it from plastic is a necessity. Here's a look at the one of the drawings from the US patent covering the whistle (# 5,816,186)

The two parts need to fit together to form the main chamber. Could you make this from metal? Probably. Is it worth it? Hardly.

The article revealed an interesting twist about the whistles used in this basketball tournament. They are not entirely plastic. (Gasp!)

"Each whistle hangs on a lanyard. And just below the whistle is a clip that holds a black wire with a tiny microphone. The wire is wrapped around the lanyard, tucked inside the collar of the official�s striped shirt, and plugs into a box clipped to the belt.

It is the Precision Time System, invented in the 1990s by the former N.B.A. referee Mike Costabile. Each time the referee blows the whistle, the game clock, if it is running, stops. To start the clock, the referee reaches to the box on the belt and pushes a button.

It is choreography that few fans notice. But eliminating the reaction time of a clock operator on the sideline � who pushes a button after hearing the whistle � saves at least 30 seconds of action in a 40-minute college game, tests showed."

I'm not so sure that that extra 30 seconds is worth it to me. After all, it would have changed the outcome of the SMU/UCLA game in a way that would have significantly favored my bracket selections. Well, better luck next year.

Previous Years

March 12, 2013 - Lubricating liquids

March 12, 2012 - The Mixed Up World Views of Paracelsus