The Chemistry of Tennis Racquets

Introduction

YouTube Video



Tennis is one of the most elegant and athletic sports that there is.  The game that we know and love today has been evolving since the early 1800’s. The rules regarding the racquets that are allowed in today’s professional field were not established until 1981.  Prior to this set of rules everything from a gloved hand to a wooden bat was used in place of the racquet.  Every aspect of tennis, from the court surface to the shoes on a player’s feet affects the way a match is played.  A tennis racquet makes each player unique.  In fact, most professional players have racquets made to their own personal specifications.  As a tennis player myself, I can attest to the importance of a well-made racquet that matches my style of play.  I chose to explore the chemistry of a tennis racquet because I was interested to learn how the the different parts of a racquet affect the level of play on the court.  My greatest passion in life is the game of tennis.  If it was up to me, I would eat, sleep and breathe the game of tennis.  Tennis continues to keep me active, fit and happy!

Composition of ...

  • Titanium (frame)

    • Element (Ti) atomic number: 22

    • 2x stronger than aluminum (cheap racquets made of aluminum)

  • Carbon Fiber (frame)

    • The precursor is formed by 90% polyacrylonitrile and 10% rayon or petroleum pitch.

      • organic polymers (long strings of molecules held together by carbon atoms)

        • polyacrylonitrile: (C3H3N)n = Empirical Formula

        • rayon imitates the feel of nylon

          • naturally occurring fiber; made of wood pulp or cotton.

        • general petroleum formula:  CnH2n+2  (varies)

          • petroleum = 93-97% carbon, 10-14% hydrogen, 0.1-2% nitrogen, 1-1.5% oxygen and .5-.6% sulphur

  • Rubber (grip)

    • derived from petroleum or natural gas

    • an elastomer (elastic polymer)

    • Chemical formula = C5H8

  • Neoprene (grip)

    • maintain flexibility over wide temperature range/ good durability

    • has chlorine and carbon

    • obtained by the chlorination of Butadiene (C4H6) and Isoprene (CsH8)

  • Kevlar (strings)

    • very strong material

    • chemical formula = C14H10N2O2

      • Carbon, Hydrogen, Nitrogen, Oxygen

      • a polymer


Main Chemicals, Compounds, Components

  • Carbon Fiber (precursor empirical formula:  (C3H3N)n)

           (carbon fiber: pure carbon; graphitic structure)

    • Carbon Fibers are microscopic fibers that can be woven into larger sheets or combined with other materials and metals to make composites.  Carbon fiber is valuable because of its high strength and lightweight.  Because of its small size, carbon fiber offers strength to very small objects as well as being able to strengthen larger objects when it is woven into large sheets.  Carbon fiber also has a high temperature tolerance.  These traits make carbon fiber a very desirable material for motorsports, aerospace, military equipment as well as competition sports such as tennis and golf.  The making of carbon fiber is a fairly extensive process.  It is made from a polymer precursor of polyacrylonitrile (90%) and either rayon or a petroleum pitch (the remaining 10%).  The plastic is cut into strips that are heated to extreme temperatures without the presence of oxygen to prevent burning.  The heating process expels all of the other molecules so that what remains on the inside is pure carbon.  Then the carbon molecules naturally align themselves parallel to the axis of the fiber which gives the material its incredible strength.  However, the fiber remains brittle due to the weak london dispersion forces (the weakest molecular force) between parallel atoms in the hexagonal graphitic carbon structure.

  • Natural Gut   (structure explained below)

    • Natural gut refers to the serous membrane that comes out of a cow’s gut.  This membrane is two layers of epithelial cell groups that are connected by a thin layer of connective tissue.  The purpose of this membrane is to prevent organs within the gut from rubbing against each other, which creates friction and heat that eventually causes the organs to adhere to each other (a.k.a. very bad).  Inside of this membrane there is a protein known as collagen.  Collagen is the most abundant protein in the body.  Its job is to hold everything together and is found in almost every part of the body.  Collagen’s triple helix molecular structure makes the protein extremely strong and allows it to withstand the compressing and stretching of the intestine.  The strength and elasticity of the natural gut makes it compatible to the traits desired for tennis racquet strings.  In 1875 Pierre Babolat manufactured the first set of natural gut tennis strings and they became popular among professionals almost immediately afterwards.  Natural gut still produces the highest quality of strings.  The strings retain their tension for much longer than any other material which lessens the number of times that a racquet needs to be restrung.  The natural gut’s elasticity allows the strings to be strung at high tensions without stiffening.  This prevents vibrations from reaching the player’s arm and decreases the likelihood of tennis elbow.  This trait also allows for ball-pocketing, which grants the player more control.  The value of well-performing strings in shown by some of the great players who use them: Novak Djokovic, Roger Federer, Bob and Mike Bryan, and Ana Ivanovic.


Chemistry's Role

Carbon Fiber (Racquet Frame)

Although Carbon fiber is one of the most abundant elements on the planet, making carbon fiber is an extensive process that involves many chemical reactions.  The process begins with the precursor polyacrylonitrile (C3H3N)n .  The precursor is made of Acrylonitrile (C3H3N) and Methyl Acrylate (CH2CHCO2CH3) which are both monomers.  The monomers are mixed together in powder form and then mechanically agitated (stirred) in water.  The agitation causes the powder to coagulate and it creates the polymer polyacrylonitrile.  Once the polymer (which is also the precursor) is created, it is heated to molten temperature and shot through a get into a chemical bath. (unfortunately, the specific chemicals used are considered proprietary)  The chemical causes the plastic to form into a long fiber.  Then it is stretched to allow the molecules to align themselves parallel to the axis of the fiber which gives the fiber its strength.  Next the fibers are heated (390 - 590°F) in the air.  The polymer attracts oxygen from the air and the molecular structure is redesigned into a more thermally stable ladder structure.  Next the fibers are carbonized.  The fibers move through a series of ovens that have no oxygen present and as the heat increases (1,839 - 5,500°F) the fiber expels the hydrogen and nitrogen out.  What is left are chains of pure carbon that link, twist and fold together, giving the carbon fiber its strength.  Now the fibers need to be immersed into carbon dioxide, air or ozone in order to coat the outside of the fiber with oxygen so that it bonds more easily with other materials.  Finally several thousand fibers are twisted together to make a yarn and then sized with a glue-like material that will prevent damage to the fibers when they are packaged.


Natural Gut:  (Strings)

Surprisingly, there is not very much chemistry involved in the process of making natural gut strings.  The strings are made from a membrane that comes out of a cow’s gut, called the serous membrane.  When the membrane has been removed from the cow, it is cut into strips.  Those strips are then slowly and gently washed in order to remove impurities without damaging.  Sometimes the membrane is bleached during the washing process.  Bleach whitens by destroying a group of atoms, called chromophores, that let of a specific wavelength that humans see as color.   Then the strips of membrane are dried over several days in an environmentally controlled room that ensures consistency.  When the strips are dry, they can be dyed a different color, if desired.  Dye works by attacking chromophores with a group of atoms called auxochromes.  The auxochromes attach themselves to the chromophores and alter the wavelength that the chromophores give off so that humans perceive a different color.  Next the strips are bound together while tension is being applied.  However, when the strings are formed, the edges are rough and need to be smoothed.  Once the strings are polished, they are tested to make sure that they meet the required specifications and then they are packaged and sent around the world to be sold.


Background Research

  1. Why is the tennis racquet important?

    1. The tennis racquet is very closely fitted to the type of player who holds it.  A power player who hits the ball hard is going to play with a different type of racquet than a player who is seeking more technical play.

    2. The racquet has a lot to do with the type of ball that a player hits.  The racquet will affect the type and degree of spin, the power of the ball, and how much control the player has.

  2. What are the different parts of a tennis racquet?

    1. The Head:

      1. The head strongly influences the power of the racquet.  A large head will offer more power, but less control.  A small head will offer more control, but less power.  Head sizes range from approximately 80 sq. inches to 115 sq. inches.

      2. A large head has a larger “sweet spot” (a.k.a. the ideal place for the ball to hit the racquet for the most power and best bounce) and a smaller head has a smaller sweet spot.

      3. Balance: A head-heavy racquet will have more power, less control.  A head-light racquet will have more control and less power.

      4. Stiffer frames are used on lighter racquets (which typically have larger heads) in order to counteract how light they are (so it doesn’t break).

      5. The larger the head the longer the racquet becomes. (from the butt of the racquet to the tip of the head)

      6. The frame of the head can have lead bearings that are inside plastic chambers in order to prevent vibrations from reaching the player's arm that might cause tennis elbow.

    2. The Beam:

      1. The beam of the racquet changes (mostly size and material) depending on the size/purpose of the racquet.

      2. A racquet with a large head will most likely have a lighter frame with a larger beam in order to allow the strings more freedom to move when the ball bounces against them (the strings are woven through the beam/frame).

      3. A racquet with a small head will most likely have a heavier frame and a smaller beam to keep the strings from moving/stretching too much when the ball bounces against them (allows for better control).

    3. The Strings:

      1. Strings come in a variety of materials, thicknesses (gauges) and colors.

      2. Strings impact spin, control, power and vibrations.

        1. Vibration is how much a racquet vibrates when striking the ball.

          1. dampers and some of the materials used in the frame of the racquet help to absorb vibration and keep it from reaching the hand, arm and shoulder of the player.

      3. Strings can be strung at different tensions (tightness) for different effects.

        1. tight strings have less bounce while looser strings have more of a bounce.  The best string tension for different racquets is based mostly on the material and size of the racquet head.

    4. The Bumper Guard:

      1. The bumper guard is a protective plastic covering over the top of the head that prevents scratches, cracks and breaks to the frame that are caused by hitting the tip of the racquet on the court when hitting ground strokes.

    5. The Grommets:

      1. The grommets are inserted in the holes of the frame that the strings are woven through to prevent the strings from being cut by the sharp edge where the racquet frame was cut to allow it to be strung.

    6. The Handle:

      1. The circumference of the handle ranges from 4 to 4 ⅝ inches

        1. It is important that the circumference of the racquet fits the size of your hand in order to decrease the risk of injury and increase the level of performance.

      2. Some racquet models have an “extended version” which is a racquet with an extended handle to allow the player to reach further.

    7. The Grip:

      1. The grip is a thin wrap that covers the handle of a racquet to provide comfort and friction between your hand and the racquet.  The grip also ensures that the butt of the racquet stays firmly secured to the handle.

      2. There are different types of grips:

        1. Some grips are thick with padding that makes the handle more comfortable in the hand of the player.

  1. Over-grips (which go over another grip) are sticky in order to keep the racquet from sliding in the player’s hand.

    1. The Butt:

      1. The butt is a cap on the end of the handle that provides a larger surface for your hand so that it sets comfortably on the bottom of the racquet.

  1. The Evolution of Tennis:

    1. The tools used prior to 1500:

      1. bare hands

      2. gloved hands

      3. hands wrapped in rope

      4. wooden bat

    2. The progression of the tennis racquet:

      1. 1965 - all racquets were made of wood

      2. 1965 - first steel racquet

      3. 1968 - first aluminum racquet (originally mocked by professionals)

      4. 1970 - Howard Head introduces the first aluminum racquet with an       oversized head

      5. 1980 - large racquets became standard

      6. 1991 - rules were set that banned spaghetti string racquets    

    3. The first official book of tennis rules:

      1. Published by Major Walter Clopton Wingfield of north Wales in 1873.

Resources

https://sites.google.com/a/isd77.k12.mn.us/crappy-chem/

Introduction to how chemistry relates to tennis

Racquet materials and the benefits of the materials used today

Most common racquet materials

https://trishalee34.wordpress.com/2013/11/19/the-chemistry-of-tennis-2/

Basics information on the materials, chemicals and elements that are used in a tennis raquet, ball, court, string and grip

Titanium, graphite, carbon fiber and sometimes tungsten are used in the more expensive racquets

Less expensive racquets are made of Aluminum and Carbon Fiber

https://www.youtube.com/watch?v=sgV2DMstyPo

Video about Wilson engineers and how they design and make their racquets

The racquet frame is mainly carbon fiber (range of average to expensive), fiberglass, kevlar, basalt fibers

http://www.tennisexpress.com/info/wilson-blx-racquet-tennis-technology.cfm

How basalt fibers are inserted into the BLX Wilson racquet and why

superior to other materials

other information is listed under “basalt fibers”

http://www.madehow.com/Volume-3/Tennis-Racket.html

Information on the history of tennis and general facts about the game

All information from this site is listed under “Background Research”

https://www.youtube.com/watch?v=JMBqPbLrZMA

Video that looks at Head designs and how they make their racquets.

https://www.youtube.com/watch?v=DUkAxvZq__I

What grips are made of

the over grip is made of rubber (some textured, some smooth)

the replacement grip is two parts: a rubber underlayer and a cotton fiber cushion over the top.

http://www.livestrong.com/article/276131-materials-used-make-tennis-racket/

Good information on grip, string and racquet materials as well as information about the game in general.

http://www.tenniscompanion.org/parts-of-a-tennis-racquet/

Information on how different parts of a racquet affect the play of the game and how to choose the right one for yourself.

information is listed under “Background Research”

http://www.tennisnuts.com/shop/tennis/tennis-rackets/racket-guides/how-to-choose-a-tennis-racket.html

The differences between a power racquet, control racquet and power-control racquet.

http://zoltek.com/carbonfiber/how-is-it-made/

The process of making carbon fiber.

https://en.wikipedia.org/wiki/Polyacrylonitrile

Information is listed under “The Composition of Tennis Racquets”

http://www.chm.bris.ac.uk/webprojects2002/edwards/chemistry.htm

Information is listed under “The Composition of Tennis Racquets”

https://en.wikipedia.org/wiki/Carbon_fibers

Information on carbon fibers

http://www.tennis.com/gear/2013/02/question-day-revisiting-spaghetti-racquet/46306/#.Vog-2ELt7sA

Explains what “spaghetti stringing” is and how it is different from a racquet that is strung the standard way

https://en.wikipedia.org/wiki/Strings_(tennis)

Information on the different materials used to make strings

http://www.tennis-warehouse.com/LC/Naturalgut.html

Explains what natural gut is and how it is used

Information listed under “Main Chemicals, Components and Compounds”

http://www.compositesworld.com/articles/the-making-of-carbon-fiber

Information on how Carbon fibers are made

All information listed under “Chemistry’s Role”

http://www.enzymestuff.com/digestion.htm

The enzymes that work inside our guts and what they do

All Information listed under “Chemistry’s Role”

http://www.chemistryexplained.com/Ar-Bo/Bleaches.html

The chemistry behind bleach

Information under “Chemistry’s Role”

http://www.chemistryexplained.com/Di-Fa/Dyes.html

The chemistry behind dyes

Information under “Chemistry’s Role”

http://www.madehow.com/Volume-4/Carbon-Fiber.html

Basic information about making carbon fiber

http://web.mit.edu/3.082/www/team2_f01/chemistry.html

The molecular structure of carbon fiber precursor and how it changes as it becomes carbon fiber



About the Author
Stephanie Beal is a junior at Billings Senior High School who spends her free time (when the weather allows) playing tennis.  Stephanie’s love for tennis started when she was nine years old.  She also enjoys playing and going on walks with her great dane, Moose.  Stephanie plans on going to college and pursuing some form of design.

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