High Strength Ropes

Chapter 1: What are High Strength Ropes?

Rope is a collection of strands, fibers, piles and yarns joined together to form a strong and a large structure. These strands or fibers are either twisted or braided with one another to give high tensile strength to the rope. The higher the tensile strength, the stronger a rope is. High strength ropes are also used in lifting and dragging purposes. Ropes were used by mankind since prehistoric times for different purposes such as tugging, hunting, climbing, securing things, fastening, and carrying things. In ancient times, natural fibers were used to construct ropes. In the 1950s, synthetic fibers started to be used in rope making. There are two types of high strength rope. These are natural and synthetic rope.

Natural Ropes

Natural ropes are made from natural products that are environmentally friendly and do not cause any harm to the environment from the byproducts of the rope making process. Some natural fibers are cotton, hemp, sisal, or other naturally found fibers. If the manufacturer chooses to blend natural with synthetic fibers in rope making, this will result in a stronger and more durable rope. Natural fiber rope is very strong when used, but can be damaged easily if exposed to water, mildew, molds, or UV light. The natural rope is not affected by high exposure of heat and can only be burnt if there are actual flames present. Natural fiber rope is affected by water exposure and cannot go back to its original shape and size if it shrinks. This can affect its use in certain fields, whereas natural rope is good for fastening objects because of its non slippery properties.

Synthetic Fiber Ropes

Synthetic fiber rope is made from synthetic or manmade materials such as nylon, polyester, polypropylene and multiple other synthetic materials. Synthetic ropes are stronger and last longer than that of natural fiber. Their average life span is about 30% more than that of natural fiber rope. Wet environments can’t cause damage to these ropes. Another beneficial aspect is that they are not prone to damage from mildews, UV light, or mold, making them useful in an open atmosphere. Synthetic ropes do not perform well when exposed to heat because it will melt these ropes. They are not environmentally safe because of harmful by-products emitted in the atmosphere during the production process. But they are strong and can be used easily for lifting or towing purposes.

Construction of High Strength Ropes

High strength ropes come in different types of construction depending on the style of twists or braids of the rope. These are categorized and named on the basis of their construction. Each of the rope style is discussed below:

Single Braid Rope

This rope is commonly called a solid braid and it is made by braiding the rope rather than twisting it. It is very strong because the braids are interlocked with each other to give a firm look and strength. It is a good choice for heavy pressure or weight of an object to be pulled or lifted. These are mostly used in pulleys or blocks due to durability because of their braided construction. Single braid rope is different sizes ranging from 8-12 strands per rope to even 8 plaited ropes.

Plaited Rope

This rope is also called a square braid and it is coarser in touch than other twisted ropes. There are about four sets of different strands that are present. These strands are twisted and wound around each other to form a braid type structure. These types of ropes are very flexible and strong, and can be easily knotted. One problem that arises in these ropes is that they are all twisted around the core and hence all strands are exposed to the environment. This makes them prone to damage easily.

Twisted Rope

Twisted rope, commonly known as laid rope, is the best one if there is a need to splice the rope. These ropes are made by coiling or twisting the strands together in the same direction. Three of the strands in these are coiled in opposite directions to each other to form a braid type structure to make it possible for a stronger grip. These ropes are generally less flexible and have a high chance of kinking if mishandled. These kinds of ropes are used in dock lines or for towing purposes.

Double Braided Rope

Double braided rope is the best choice if strength and resistance are needed. This rope is made by coiling double braided strands on a double braided core. The double braided core and strands will give extra stability and flexibility to these ropes. Due to abrasion resistance, they are the best choice for marine environments but not a manufacturing site. Double braided ropes are very tough and don’t kink easily.

Hollow Ropes

Hollow ropes are empty or hollow from the inside and can be spliced easily. It is a lightweight synthetic rope that can be used for ski towing and anchor lines because these are water resistant.

Diamond- Braid Rope

Diamond braid ropes are made by braiding the strands of fiber around the inner core carefully, tightly, and securely to ensure that the structure is firm and rigid.

These diamond braided ropes are more expensive than the other kinds of ropes because of its neatly and tightly woven structure, which gives a good look and durable structure to these ropes. These ropes are durable, round, firm, and can work well under stressful conditions. Diamond braided ropes can be easily spliced making them good to work with other kinds of ropes.

Chapter 2: Types of Material Used

There are many different types of materials used in manufacturing high strength ropes with some of the popular ones discussed here. These are:

• Aramid
• HMPE
• VECTRAN
• PBO
• Polyester
• Polypropylene
• Nylon
• PEEK
• Polyethylene

These are the types of material that are generally used in manufacturing high strength ropes. These materials are further categorized into different types, which will be discussed here in this chapter.

Aramid Fiber

Aramid, also known as poly(para-phenylene terephthalamide), is a high strength fiber with a very low stretch in it and is resistant to high temperatures and creep. It is one of the first and best performance fibers that are used in rope manufacturing. Examples of it are Technora, Twaron, and Kevlar. This material has poor abrasion and UV resistance. It is best to wrap it in any other material such as polyester. However, meta aramids (Normex and Teijinconex) have high resistance to heat and abrasion, but the para linked aramids are stronger than meta aramids.

HMPE Material

HMPE, also known as high modulus polyethylene, is a stronger material than aramids and it was an exotic material that was used tremendously in high strength ropes manufacturing. These are lighter than aramids with a density of 0.97 with common examples of this material as Dyneema and Spectra.

Nylon or Polyamide

Nylon is a synthetic material also known as polyamide. This material is a bit stronger when it is in dry form compared to polyester. But when nylon gets wet, it is weakened by 10%. The abrasion and UV resistance of nylon are good but its stretch is best. It is stretchable up to 30% and thus it is best for pressure bearing situations. The relative density of nylon is 114, and its melting point is 220°C.

PBO or Zylon

Zylon is the market name for PBO. PBO is also called poly (p-phenylene-2, 6-benzobisoxazole)and is a new product introduced in the rope industry. It is a very strong material with low stretch and high resistance to high temperatures. Like aramids it needs to be protected from UV light and abrasions.

PEEK

PEEK, also known as polyetheretherketone, is a polymer that belongs to the ketone family. The ketone family exhibits excellent dimensional and thermal stability along with high resistance to harsh chemical and abrasion conditions. The Zyex PEEK fiber is very well known for its ability to withstand high temperatures, chemicals, and heat.

Polyester in Rope

Polyester is the best synthetic material ever used in the rope industry. It is highly resistant to water, UV, and abrasions. These properties make this material a good choice for covering other materials’ braids to give them durability and resistance. The polyester material has a density of 1.38, a melting point of 260° C, and a breaking extension of 12%.

Polyethylene Material

Polyethylene is similar to polypropylene in many properties except UV resistance which is a bit better than polypropylene. Polyethylene has a relative density of 0.97 and its melting point is 165° C.

Polypropylene Material

Polypropylene has floating properties because of its low density of 0.91. It is a light weight material and can float easily on water. Polypropylene bears a moderate UV and abrasive resistance. Its extension break is just like polyester though it is weaker than polyester. Polypropylene is also highly resistant to chemicals and has a melting point of 170°C.

VECTRAN Material

VECTRAN, also called aromatic liquid crystal polyester, is also a material of high strength. It is also a low stretch material like that of aramids and a resistance to heat.

Types of Fibers

Different types of ropes are made from these stated high strength fibers, which are used in many fields. Common examples of high strength fiber products are Kevlar, Twaron, Technora, Dyneema, Spectra, Polyester, and Nylon. These types will be discussed here.

Aramid Fibers (Kevlar, Technora, Twaron)

Due to their strength, stiffness, hardness, and thermal stability, aramid fibers are the best option for many purposes. It is best to use for these characteristics, but the Kevlar rope is known for its low shock resistance property. If kevlar ropes are subjected to shocks, they can be easily damaged.

Chemical Structure of Kevlar (Aramids)

The chemical structure of Kevlar shows that it is a polar molecule and its long crystal structure contributes a lot in its strength. However, as Kevlar is a polar molecule, it can attract many chemical substances to bond with it, such as epoxy and water. These bonds are helpful in some circumstances but sometimes bonds with water can harm this rope by wetting it easily.

Physical Properties of Kevlar

Kevlar fibers are inter-chained, and its high capacity to bond with other molecules gives aramids a unique combination of properties. The physical properties of Kevlar are:

• High resistance to cut makes it suitable to use as protective clothing.
• They have a high chemical resistance though chlorine can affect Kevlar.
• Aramids have a high tensile strength i.e. 2920 MPa.
• Kevlar is flame resistant and hence is self extinguishing.
• The critical temperature of aramids is 400° F and decomposes at 800°F.
• Low temperatures cannot affect aramids because of the low thermal shrinkage property.
• The specific gravity of Kevlar is 1.44
• High stiffness
• Kevlar can absorb moisture easily.
• Subjected to UV radiations.
• Electrical conductivity is not a feature of Kevlar.
• Kevlar can be easily damaged by shock loads.
• It has a low elongation break i.e. 1.5-4.5 %.
• Kevlar exhibits excellent dimensional stability.

Chemical Properties of Kevlar

• Kevlar ropes are resistant to organic solvents.
• Degrades quickly in strong acids and bases.
• Chlorine can damage Kevlar rope quickly and should not be used as bleach for this rope.
• Oxy clean is a safe option but never use hydrogen peroxide as bleach.

Aramid Rope Uses

Kevlar ropes are chemical resistant and lower in weight, so these are the best option to replace steel cables. But they can be degraded in the sun so a protective covering is necessary for these ropes. The core is made of aramid rope and the outer layer is of some UV resistant material such as polyester. Kevlar ropes are widely used in boating. For climbing purposes, these ropes are not considered reliable because of their inability towards shock loads. They can break easily without giving any warning signs and can be dangerous for climbing or other loaded activities. Kevlar ropes can replace steel in winches, the suspension bridge in Scotland and guy wires in hydro tower Kevlar ropes are used. They are highly resistant to heat therefore in many applications asbestos is being replaced by these aramid ropes.

Aramid Advantages

• Aramids have high strength, toughness and rigidity.
• They have an excellent resistance to heat, burning or thermal degradation.
• They are non conductive but can conduct electricity when wet.
• Aramids are chemically stable ropes but cannot stand strong acids or bases.
• Kevlar ropes are low stretch.
• They are difficult to cut.

Disadvantages of Aramids

• Aramids cannot float in water.
• They are polar molecules and thus they attract water towards them.
• Quite expensive material.
• Kevlar ropes can be easily damaged by shock loads and do not give warnings before and can break down easily after 1000th use.
• Properties of compression are quite poor for these ropes.
• Technora and Kevlar ropes require special attachment sites to maintain strength.
• Knots in these ropes can damage them.

High Modulus Polyethylene (HMPE) Dyneema, Spectra

High modulus polyethylene is also called high performance polyethylene (HPPE) and in the sailing and boating industry as Spectra and Dyneema.

Chemical Structure of HMPE

The chemical structure of HMPE has long molecular chains with no groups attached to the molecule. This structure gives no space to other molecules attached to its site for any chemical attack. Its long molecular chain is very strong and can be stretched easily. HMPE doesn’t attract water molecules, any chemical or any microorganisms so they do not get wet or even stick to hands. Gel spinning is the process for manufacturing Dyneema and Spectra.

Physical Properties of HMPE

High modulus polyethylene is a great fiber because of its unique chemical structure and hence it depicts different characteristics or properties to it. These are:

• HMPE does not attract water so it is hydrophobic and repels water.
• Dyneema and Spectra have stronger ropes and do not weaken when they are wet.
• HMPE feels too slippery to handle.
• It is a self lubricating rope fiber.
• Its melting point is about 144 to 152° C.
• HPPE can easily float on water due to its low density of 0.95.
• Under continuous load polyethylene creeps quickly.
• It is very strong, as strong as hardened steel.
• Low coefficient of friction is a property of HMPE and it is as slippery as Teflon.
• Polyethylene is very resistant to abrasions and UV radiations.
• It has low elasticity and cannot be stretched much.

Chemical Properties of HMPE

• HMPE chemical structure shows long chains of molecules and it does not contain any chemical group attached to it therefore they are not chemically active.
• It repels water, but certain oxidizing agents can attack these molecules.

Uses of HMPE

HMPE is a strong fiber with a low weight which helps it to float on water. It has good abrasion, chemical, and UV resistance. HMPE is used in high performance sails and rigging in yachting. High performance polyethylene is also used in body armour clothing, vehicles, cut resistant gloves, climbing equipment, fishing lines, paragliding equipment, spear lines for spear guns and bow strings, parachute’s suspension lines, and many more activities. Spectra is also sometimes used in towing and winching. Due to being able to float, it is the best to use for marine towing.

Advantages of UHMWPE

• They are high strength and low weight
• UV and abrasion resistant
• Light enough to float on water
• HMPE are low conductors of electricity
• They are smooth and slippery, as self lubricating material.
• Vibration damping and a low stretch
• They are chemically inactive but sometimes strong oxidizing agents can react to them.
• Transparent to radar is also a property of HMPE.

Disadvantages of UHMWPE

• It has a lower melting point of 144 to 152° C
• Needs a lower boiling point of less than 80° C
• It can creep easily due to consistent shock load.
• It is so slippery in nature and cannot bear knots.
• Low friction can distort and twist the rope layers.
• It is 4-5 times more expensive than polyester.
• HMPE is so slippery in nature, making it difficult to cut smoothly.

Nomex Fiber

Like Kevlar, Nomex is an aromatic polyamide. The Meta-Aramids molecular position is different to Para-Aramids in their linkage. The chemical bonding of Nomex is zigzag in composition, making it lower in tensile strength and rigidity. Nomex is an elongated fiber and is used best in making yarns.

Physical Properties of Nomex Fiber

• Nomex is a flame resistant fiber.
• UV resistance of Nomex is exceptional.
• It is heat and abrasion resistant.
• Breaking tenacity of Nomex is 5.0g/d.
• Specific gravity of Nomex is 1.38.

Chemical Properties of Nomex

• Nomex has a good resistance to acids and alkalis.
• It also exhibits excellent resistance to organic solvents.
• But strength loss drops in acid like hydro-sulphuric acid.
• It has good resistance to alkalis at room temperature but degrades quickly at a high temperature.

Uses of Nomex

Nomex fiber is really well known to be used in protective gears of firefighters, pilot crews, in industries for saving from flames and electricity. Cement and asphalt factories use filter media made of Nomex. Protective gears from Nomex can save from flames, electric currents and many other hazards.

Advantages of Nomex

• Highly resistant to UV, heat and abrasions.
• It is a strong and durable material.
• High resistance to acids and alkalis.
• Low shrinkage properties
• Helps in yielding good protective clothing.
• Nomex is a soft and lightweight material.

Disadvantages of Nomex

• It is resistant to acids and alkalis at room temperature but degrades at high temperatures.
• It is an expensive material.
• Its strength drops in strong acids.

Nylon Fiber

Nylon is a synthetic fiber also known as polyamide. It can be molded, spun, and machined. Nylon ropes are widely used in many fields and applications. The physical and chemical properties are given below.

Physical Properties of Nylon

• Nylon is strong and durable
• It has excellent abrasion resistance.
• Nylon can be stretched a lot before breaking down making it an excellent shock absorber.
• Nylon has a specific gravity of 1.13. Nylon does not float.
• Nylon melts at high temperatures rather than burning. If it burns it will emit cyanide.
• Nylon has a good strength to weight ratio.
• Infrared light can pass through nylon, meaning it is transparent to infrared light.
• Nylon has a maximum temperature of 99° C and a minimum temperature of -70°C.
• Melting point of nylon is 420°C, with a tensile strength of 5800 psi
• Nylon has a good UV resistance.
• In dry form nylon is an electrical insulator but its properties change when it is wet.

Chemical Properties of Nylon

• Nylon is a good resistant to oils, alcohols and formaldehyde.
• Nylon has poor resistance to phenols, alkalis, iodine, chlorine and acids
• Nylon cannot be degraded easily because of its great resistance to insects, animals, fungi and rot.
• Nylon cannot burn but if it burns it will emit cyanide, which is a highly poisonous gas.

Advantages of Nylon

• Nylon is strong and abrasion resistant.
• It does not melt easily thus showing high heat resistance.
• Nylon can be made from lustrous, semi lustrous and dull material.
• It can be dyed and can be found in many colors.
• Polyamides are good at UV resistance.
• It is a quite inexpensive material.
• It is resistant to solvents, acids and bases.
• Nylon is highly elastic and can be stretched up to 40%.
• It is made soft and feels pleasant to handle.

Disadvantages of Nylon

• Nylon does not float and sinks in water.
• If it burns, nylon will emit a highly poisonous gas called cyanide.
• It is too stretchy and is not suitable for places where dimensional stability is needed.
• Nylon loses strength when it is wet and repeated cycles can cause it to emit internal heat at a higher pace which resultantly degrades its performance.

Uses of Nylon

Nylon is used in dock lines as it can be dyed in any color so fishermen dye it and place it on their docks to make it more aesthetically beautiful. Nylon nano filament has been used in fishing lines for many years. Anchor lines for most yachts are made of nylon. Paracord is a nylon string that is suspended with a parachute.

Polyester Fiber

Terylene, Dacron or Trevira are the commercial names of polyester fiber. Polyester fibers are used in boat lines and sailing because of the durability, flexibility and reasonable prices. Polyester fibers are very thin with a diameter of 0.023mm dia. They are white in color. Generally it is difficult to distinguish between nylon and polyester.

Physical Properties of Polyester

• Polyester does not float and has a specific gravity of 1.38.
• Polyester fiber is strong, durable and rigid.
• Polyester is non stretchy material and has a low creep under load.
• Polyester is good at retaining its strength when it is wet.
• Melting point of polyester is 240° C.
• UV resistance of polyester is better and only loses by 10% if used for outdoor purposes. Therefore, it is considered best for outdoor use.
• It exhibits excellent abrasion resistance.
• Polyester is a non- conductor of electricity.

Chemical Properties of Polyester

• Polyester fiber exhibits a good resistance to strong acids and alkalis at room temperature, but if the temperature is increased then resistance will be decreased.
• Polyester fibers are good in showing resistance to petroleum based solvents such as bleach. If soaked in bleach for a while it will deteriorate.

Advantages of Polyester

• Polyester is widely available and a well priced fiber.
• A good resistance to UV radiations making it an excellent choice for outdoor applications.
• Exhibit good chemical resistance but only at room temperature.
• Polyester is typically a hard, rigid and strongest fiber in the market.
• Polyester’s strength doesn’t wear off when it gets wet.
• Low stretch and can bear loads

Disadvantages of Polyester

• Polyester is not designed to float on water.
• Polyester is low stretch and rigid, which makes it unable to work in blocks
• If there is a jerking factor in loads then it is not a good choice. It can be used as protective layering instead.

Application of Polyester

Polyester is the best synthetic fiber that is used for several applications where other fibers fail because of its good UV and abrasion resistance and also its stiffness. It is widely used in making sheets, sailing boats, and ropes that are used for mooring or winch lines. At high temperatures other fibers melt but polyester has a high melting point so this can be used easily in such circumstances. They act as good shock absorbers and also on blocks and capstans where low creep is necessary. Polyester is also used in protective layering of many other fibers such as aramids. These can be used for longer times in an outdoor environment without the fear of wearing off.

Zylon Fiber (Meta- Aramid)

Zylon is the best synthetic fiber in the market nowadays with a high tensile strength and rigidity. The tensile strength of zylon is 1.6 times higher than that of Kevlar. Zylon can be found everywhere from tennis racquets to construction projects.

Physical Properties of Zylon

• Zylon is rigid and strongest synthetic fiber of all.
• Tensile strength of zylon is 1.6 times higher than that of Kevlar.
• Zylon has a high flame and heat resistance.
• Chemical bonding of zylon gives maximum strength to this fiber.
• This material can be modified into any form and any product.
• Zylon is found in a variety of media such as filament, chopped fiber, spun yarns and many more.
• Zylon fiber can be recycled and reused over time.

Chemical Properties of Zylon

• Zylon has an excellent strength to weight ratio.
• Zylon chemical properties are even better than that of carbons and aramids.
• It has outstanding dimensional stability which means it cannot creep easily.
• It has a very good resistance to many organic solvents.

Uses of Zylon

Zylon is widely used in making protective clothing because of its heat resistant properties. It is also used in the protective coating of certain wires and also found in cement for reinforcement purposes. Zylon is also found in the sports industry present in bike tires, tennis racquets, snowboards, yacht ropes and many more. Zylon is also used in cable cover material for welding machines.

Advantages of Zylon

• Highly rigid and stronger material.
• High tensile strength 1.6 times more than Kevlar.
• Highly resistant to heat and organic solvents.
• It cannot creep easily due to its strong dimensional stability.
• It can be reused and recycled by the respinning method.
• It is considered as the world strongest material that is made synthetically.

Disadvantages of Zylon

• Zylon is highly sensitive to light and its tensile strength can be decreased upon exposure to light.
• It is a highly expensive material to manufacture.

Conclusion

• High strength ropes are used in making the best kind of ropes in the market.
• Ropes are constructed in many shapes such as braided, plaited, hollow and many more.
• Different types of material are used in rope making such as aramids, polypropylene, polyethylene, PBO, polyester, etc.
• All the fibers have different and specific qualities which distinguish them from each other.
• Zylon is the best fiber for rope manufacturing.