History of the Golf Ball
Gowf, as the Scots called the game, originated in Eastern Scotland in the 1500s, although precursors of golf existed in Belgium and the Netherlands as early as 1257. Despite the fact that King James II,III, and IV of Scotland each banned the game to encourage skill in archery instead, the sport surged in popularity among royalty and nobles once the ban was lifted—King James IV even purchased his own set of golf equipment (Mallon and Jerris 2011). At this time, players would play with balls and clubs fashioned out of wood. In the 1600s, the game was improved by the introduction of a “featherie,” a small leather ball stuffed with feathers. The seams on the ball provided needed turbulence to make the ball fly farther than the simple wooden balls. Making a featherie was a time-consuming and expensive process, since an experienced golf ball maker could only produce four in a day (Seltzer 2008). These featheries thus restricted the game to an elite group that could afford the expensive balls. The expense of the game, however, caused the next breakthrough in golf balls – a university student at St. Andrews began experimenting to make a cheaper ball, since he could not afford to buy his own featherie. He used some tree sap called gutta percha, molding it into a ball and then baking it (Seltzer 2008). Thus the next revolution in golf was launched; “gutties,” which could be mass-produced, became the dominant ball (Goodman 1974). The modern ball came into existence when American Coburn Haskell began using the polymer rubber to create a new ball by coating a rubber-wound ball core with a gutta-percha covering and dimpled the outside surface. (A polymer is a molecule that has repeated smaller subunits joined into a large molecular chain.) Shortly thereafter, players began to break dozens of records with the new ball (Mallon and Jerris 2011). Since then, many modern golf balls have been developed through extensive research in a quest to find the best polymer with superb properties to create the best ball.
The Modern Ball: Properties
The modern ball, of which there are many varieties, vastly outperforms previous golf balls because it offers more desirable qualities than the older golf balls: good “feel,” resilience, high abrasion resistance, high coefficient of restitution, and good release from the mold during the manufacturing process. A good golf ball must “feel” soft to the golfer, but must be resilient enough to rebound to its original shape and hardness after the momentary deformation that necessarily results after being struck repeatedly with a force that can equal 10,000 N (Penner 2003). The ball covering must not get small cracks upon the recurring impacts, because then performance is decreased not only because the cracks affect the way the air moves around the ball, but the tiny cracks may also provide an opening for moisture to get inside the ball. The “feel” is thought to be attributed primarily to the ball’s flexural and tensile moduli (a material’s tendency to bend and the stiffness of an elastic material; Morken and Talkowski 2011).Golfers want balls with high abrasion resistance, balls that take a long time to wear down from repeated hits from the club and skittering on grass and sand. A coefficient of restitution (COR) is the ratio of the velocity of the ball relative to the club before impact over the velocity after impact (Penner 2003). A COR of 1.00 would be a perfectly elastic collision, meaning that a ball’s maximum possible initial speed is limited only by what the golfer can put into his swing. Finally, there is the side of the manufacturers to consider; do the polymers in a ball release easily from a mold? If not, not only is it inefficient and causes a decrease in productivity for manufacturers, but it can result in damage to the ball itself (Shimosaka et al. 1998). These golf ball qualities differ not only from ball to ball, but within the components of a golf ball itself.
Golf balls are made up of two parts: a cover and a core. The core typically takes up a vast majority of the volume of the ball, often exceeding 80% (Morken and Talkowski 2011). Variations in the number of layers in golf balls form the three main types of balls: traditional wound, two-piece, and multilayer golf balls (Figure 2; Gorss 2005).
The Modern Ball: Polymers
The first wound ball had three layers made by winding a small, hard core with elastic, rubber thread stretched many times its length and then coating it with a layer of gutta-percha. It was also the first modern ball, although it did not take long for manufacturers to replace the more rigid gutta-percha with rubber. Figure 1 shows rubber (A) and gutta-percha (B). Both are polyisoprene, but rubber is cis and gutta-percha is trans (Goodman 1974, Yikmis and Steinbüchel 2002). This slight difference causes rubber to be more elastic because its more kinked structure makes for a larger molecular spring, unlike the more brittle gutta-percha.
In a search to find something simpler and better (and cheaper to produce), manufacturers went to the two-piece ball, after discovering that a one piece ball simply could not bring all of the desired properties to a golf ball – a composite had to be made to obtain the optimum qualities. One polymer simply could not have both great durability and a high COR (Cochran 2010). Those qualities are more or less mutually exclusive in one polymer. But by focusing on a cover with high durability, but a core with a high COR, a simpler, better ball was born that now holds about 75% of the market: the two-piece, solid-core ball (Cochran 2010).
The most recent in golf ball innovation shows that multi-layer balls produce drastically better results than any ball previously developed. These balls, which cost $40-50 per dozen, ushered in a revolution of distance in golf (Gorss 2005, McKay et al. 2008). Elements such as titanium may be found in the outer layer of these balls, to ensure near-perfect transmission of energy from the club to the ball, providing great distance (Giffen et al. 2002). The cores of these balls vary greatly, being compressed air, metal, or even honey.
The keys to the modern golf ball are the different polymers used in the ball. By slightly varying the length of the chain or the number or type of atoms in each subunit, everything from Styrofoam to Kevlar can be created. Different polymers bring different strengths to the golf balls as well: while middle layers may be compressible and elastic, the cover may be hard and resilient, and a core may be rigid to maintain form.
One of the most common polymers in use is balata, a resin from the latex of a tree native to South America. Balata can create a cover for golf balls that is softer than most, providing a high spin rate and precision when the club grips the ball (Giffen et al. 2002). This provides the desired “feel” that golfers want in their balls. Indeed, even though balls covered in balata are cut easily if they are mis-hit and they have a short lifetime, the “feel” produced by balata is what researchers seek to imitate in new polymers (Nesbitt 1984, Sullivan et al. 1990).
One solution to creating the “feel” of balata, but also doing away with its lack of durability, is to combine it with another polymer such as the commonly used polybutadiene (Proudfit 1994). An added advantage to combining balata with other polymers is that the cost of production goes down. Polybutadiene, a synthetic rubber, is a thermally linked elastomer (heating causes the elastic-like polymer chains to link together). Since polybutadiene has such a high wear resistance, it can be found in car tires, as well as golf balls. In this way, a golf ball may be endowed with a soft “feel,” but also have great durability. Polybutadiene may also be used in golf ball cores. A combination of two different polybutadienes has been shown to increase the distance of a golf ball by 1 ft. when compared to just a single type of polybutadiene, thus earning the polymer combination a patent (Gendreau and Cadorniga 1990).
Finally, ionomers (polymers with some subunits that carry an electric charge) are also common polymers found in golf balls. Ionomers are a harder resin, providing great durability, wear and tear resistance, and a substantial amount of resilience in golf ball covers (Egashira and Takehana 2010, Morken and Talkowski 2011). These covers are almost cut-proof, although their durability comes at the cost of having a hard “feel.” Additionally, ionomer resins offer an excellent barrier to moisture seeping into the ball.
With so much research and high-tech know-how going into golf balls to make them go farther than ever before, what else remains for scientists to develop in golf? Besides the ever-present search for the perfect blend of polymers for optimal durability and “feel,” the effect of water adsorption into golf balls has come to the forefront. Over time and use, the COR decreases as weight increases, whether the ball has actually been in water or is only in a humid environment, thus decreasing the distance a ball can fly (Sullivan et al. 1998). Even if the ball has been in the water for only a week, the ball’s distance capability is decreased by 6 yards (Performance Indicator 2012). In order to combat this problem, some researchers are striving to develop balls that possess a moisture barrier at the core or an ability to change color if their integrity has been compromised (Sullivan et al. 1998, Performance indicator 2012). Either way, the difficulty lies in developing a coating that will not alter the properties of the other polymers in the ball. As long as there are golfers in search of the perfect ball to better their game, researchers will be there with them.
By: Jessica Egan, University of Utah
Jessica Egan began her love of chemistry under her mom’s direction with homeschool experiments in middle school and then up into high school through her high school chemistry teacher. She pursued a chemistry and art double major at Hillsdale College and decided to continue her chemical education by attending graduate school at the U. She has recently graduated with a M.S. from the U in Analytical Chemistry and is looking for a career in industry.
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Articles by Jessica Egan.