The Chemistry of Climbing Rope

Introduction

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  • Rock climbing rope is a length of 60-80 meters of nylon rope.  Climbing rope is dynamic which means that it is able to stretch to 6-7% of its original length.  All dynamic climbing ropes have two parts: the sheath and the core.  The sheath is the outer protective layer of the rope, made of tightly woven nylon fibers.  The core of the rope the inner part of the rope making up about 70% of the ropes diameter.  The core is made up of 10-15 braided nylon strings all packed tightly into the sheath.  A standard 9.8mm dynamic rope has 11 braided nylon strings in its core.  Nylon 6,6 is used to make dynamic rope because of its strong abrasion resistance and elasticity.  The greater diameter of the rope is, the stronger that that rope will be.  Many different companies manufacture climbing rope and all must pass the standard UIAA safety tests.  

  • I chose to research climbing rope because I am an avid rock climber and rope is possibly the most important factor in remaining safe while climbing large rock faces.  My friends and I have all been saved by climbing ropes countless times.  About .2% of all climbing deaths are due to total rope failure and I was curious as to why rock climbing rope was so strong and reliable.

  • Climbing rope has affected my life by allowing me to be able to climb large rock faces outdoors safely.  Climbing outside anywhere is what I and so many climbers like me live for and climbing rope is has made it possible for climbers like myself to try and accomplish many more challenging routes without worrying about falling to our deaths.  Climbing rope has allowed me to become a better climber in the fields of endurance and concentration, because even if you do not die when you fall, it is still terrifying.

Composition of ...

A dynamic climbing rope is made of fibers from a polymer known as nylon 6,6.  The chemical formula of nylon 6,6 is C12H22O2N2.  The monomers of nylon 6,6 are hexamethylenediamine and adipic acid.  Both of these monomers are organic compounds that are held together by an amide bond.  These monomers form a long polymer chain that will eventually become large enough to be used as a fiber in the rope.  Thousands of these fibers are twisted together to form a plain nylon string.  Three of these strings are then braided together to make one of the 10-15 braided core strings.  These strings are then packed tightly together and the sheath is woven around them.  The sheath is made up of much flatter nylon strings accomplished by not twisting the the fibers together.  These flat strings are then woven tightly together to form the protective layer around the core.

Main Chemicals, Compounds, Components

The two main compounds that combine to produce nylon 6,6 are hexamethylenediamine and adipic acid.  The chemical formula of adipic acid is C6H10O4.  This acid is produced by mixing cyclohexanol [(CH2)5CHOH] and cyclohexanone [(CH2)5CO] into an oil called ketone-alcohol oil.  This oil is then oxidized with nitric acid [HNO3] to produce adipic acid.  About 60% of all adipic acid produced is used for the synthesis of nylon 6,6.  Hexamethylenediamine is the second monomer used in the production of the synthesis of nylon.  The chemical formula of hexamethylenediamine is C6H16N2.  This monomer is made by the hydrogenation of adiponitrile [(CH2)4(CN)2].  This bonds 4H2 to the adiponitrile forming hexamethylenediamine.  This amine is produced only for the synthesis of nylon 6,6.

Chemistry's Role

The two valence electrons on the nitrogen in the hexamethylenediamine are given to the carbon of the adipic acid.  The sudden negativity of the nitrogen attracts it to the carbon and the bonding of these two atoms pushes the hydrogen from the hexamethylenediamine and the hydroxide from the adipic acid out of the newly formed polymer.  The hydroxide and hydrogen molecules will combine to produce a water molecule.  The polymer is then held together by the attraction between the nitrogen and carbon.  This bond is called an amide bond.  The hexamethylene has the nitrogens and hydrogens on both sides of the molecule and the adipic acid has the carbons and the hydroxides on each side of the molecule.  This means that the amide bond will continue to form between the monomers to form the polymer chain and producing water as a byproduct.  It will keep forming a fiber for as long as there is hexamethylenediamine and adipic acid to be combined.

Background Research

The first dynamic climbing rope was developed in 1953 by Edelrid.  It is dynamic because it stretches when a climber falls and puts it under pressure.  This design of dynamic rope is called the kernmantle.  The kern is the braided nylon core and the mantle is the the protective outer sheath of the rope.  A 9.8mm diameter rope can take 5-10 completely static drops at 8kN.  This is equivalent to about 1800 pounds being dropped from about 20 feet with absolutely no movement in the anchor point of the rope.  All climbing ropes must pass these standard safety tests before they are to be distributed to climbers all over the world and are being used in all different types of rock climbing environments.


Resources

https://www.trails.com/facts_3503_what-climbing-rope-made.html

An informational site for all outdoor equipment and trails across North America

Specifications of climbing rope

Percentage of diameter of the core and the sheath, stretch percent, and what makes a rope dynamic or static

http://www.chemistryexplained.com/Ny-Pi/Nylon.html

This is a site that explains the chemistry behind different objects and products

How the nylon is bonded together and made

What type of nylon is used for climbing rope

http://www.polymerprocessing.com/polymers/PA66.html

This site gives information and specification on many different polymers

The chemical formula of nylon  

Diagram of the structure of the chain of nylon to form into fibers and eventually ropes

Other properties of nylon

Melting point, molecular weight, and density  

https://www.youtube.com/watch?v=lSAAl4HODHU

The detailed step by step production of the nylon core and nylon sheath climbing ropes at Mammut

The sheath is woven around the core strings of the rope

https://en.wikipedia.org/wiki/Nylon#Characteristics

Gives a list of detailed and extensive physical and chemical characteristics of the molecules of nylon that make up climbing rope

Other uses, durability, elongation, weaknesses

http://www.open.edu/openlearn/science-maths-technology/science/chemistry/how-nylon-made

This is a site that answers scientific questions

What monomers are involved

Adipic Acid and Hexamethylenediamine

What reaction creates nylon

Condensation polymerisation

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

The history of the kernmantle rope design

Specifications of the dynamic climbing rope  

Breaking strength and testing that it must undergo to meet quality standards of the manufacturer                               

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

Details on Hexamethylenediamine

How it is made and what other applications it has

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

Details on Adipic acid

Cyclohexanol and cyclohexanone mixture oxidized with nitric acid to produce adipic acid

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

How hydrogenation works

Combines 4 H2 with adiponitrile to create hexamethylenediamine

http://www.stephabegg.com/home/projects/accidentstats

This site gives statistics on causes of injuries and deaths related to different outdoor sports

Statistics on climbing deaths related to total gear failure

http://www2.volstate.edu/chem/2020/labs/nylon66.htm

This site provides a detailed explanation of the process of the synthesis of nylon 6,6

The structure of the two monomers and how they are bonded together to form the polymer chain


About the Author
Noah Emerick is a junior at Billings Senior High School taking all honors classes and participating in cross country in the fall.  He plans on making a career in the United States Air Force as a Combat Rescue Officer.  He is an avid rock climber and has been climbing in Needles State Park, Yosemite National Park, Ten Sleep, Wyoming, and mostly in his home town of Billings, Montana.  His life has been saved countless times by his belayer and his trusty climbing dynamic kernmantle rope.  Noah Emerick is extremely grateful for the invention of climbing rope because without it he would be extremely dead.
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