Plasma Vs Dyneema

Plasma™ was the first fibre rope used to replace steel wire ropes on 4 x 4 winches in Australia and overseas. This small but nonetheless important revolution had its genesis in a small Western Australian company called Jeyco.

Jeyco specialises in the supply of high quality marine mooring and towing equipment and had already established the bone-fides of Plasma™ rope in the extremely harsh world of maritime towage. Plasma™ ropes had been used to protect the large and expensive polyester towlines used by the various tug operators around Australia. Plasma™ had proven to be an extremely hardy and robust rope, able to withstand the harsh rigours of the marine towage environment and overcome the massive abrasion damage which previously limited the towline to a lifetime of reduced efficiency.

By using Plasma™ Rope as a sacrificial tail on the end of the towrope the Plasma™ would be passed up to the larger vessel under tow and it would be the Plasma™ that would pass through the fairlead in the ship’s hull to be connected to the bollards on deck. These fairleads are typically in very poor condition with corrosion and damage from wire ropes, they would normally destroy a towrope in a short period of time. Since the introduction of these Plasma™ tails towline life has increased 3-4 times previous benchmarks. The Plasma™ itself has lasted up to 4-5 times longer than the previous rope in this application.

Having established that Plasma™ rope was a very tough rope Jeyco embarked on a mission to replace steel wire ropes in many applications where Plasma™ could either improve efficiency or safety. One of the first areas they looked at was winching applications as these tend to be highly abrasive to ropes and dangerous to humans.

During this time Jeyco had worked with the manufacturer, Puget Sound Ropes of Seattle to fully understand the properties of this new “wonder rope” as it was starting to be called by various people who had used the product. At this time and during subsequent testing Jeyco realised that the rope stored very little kinetic energy and as it was of a low density (light weight) there was little or no snap back or re-coil when the rope broke under tension. This made the rope very safe to use, and coupled with the high abrasion resistance and a higher than wire rope breaking strain it was also a very desirable combination of properties for a rope in winching situations.

OK I hear you saying, you have heard all of this before. I have taken you down this path to get to where we are now, that is accepting this rope for what it is…bloody brilliant, (to steal a line from JK Rowling). What I would like to show now is just why Plasma™ is so good at what it does.

One of the reasons for wanting to continue the education process about Plasma™ is so that people are armed with all of the information. We live in a competitive world and there will undoubtedly be imitators, some good, some not so good. So, just why is Plasma™ so good? And is it better than the other ropes on the market? To answer this question we need to look in detail at the rope in terms of the raw materials that go on to make up the various ropes and the methods of manufacture of those ropes.

For the types of applications we are discussing here, namely winching for 4x4 vehicles no fibre type other than HMPE or LCP should considered and there are very good reasons for that statement. OK, here we go again with techno-babble, what the hell is HMPE and LCP you say.

Well perhaps I should start by giving a very short history of fibre rope. ;

The first recorded fibre ropes appeared about 5-6000 years ago in Egypt and the Middle East, these were typically made from Papyrus or other similar vegetable fibre. Rope continued to be made from vegetable fibres such as Manila, Sisal and Hemp for many thousands of years. These ropes were made in two basic constructions, 3 strand and 4 strand with some larger ropes being cable laid by laying three 3 strand Right Hand Layed ropes into a large Left Hand Layed rope that acted as a core.

In 1930 the first synthetic fibre Nylon was invented, since then there have been some half a million combinations of fibre type and construction developed for a myriad of uses. The most common fibres used in rope manufacture are Polypropylene (Pp), Polyethylene (Pe), nylon (Pa), Polyester (Pes), aramid (Kevlar* Twaron* Technora*) HMPE (High Molecular Weight PolyEthylene) , Liquid Crystal Polymers (LCP) and blends of these fibres.

Now why are HMPE and LCP fibres the only ones that should be used for 4x4 winching? Pp and Pe ropes are simply not strong enough and would require ropes of around 18-24mm diameter to replace the 8mm steel wire ropes typically used on most 4x4 winches. Nylon and polyester stretch too much such that the recoil would injure or kill anyone with in range of the rope. Aramid fibres whilst having the strength, suffer enormously from abrasion and bending fatigue, so much so that they would be considered extremely risky in this sort of application.

HMPE ropes on the other hand demonstrate the right amount of strength so that they can replace steel wire rope on a size for size basis, and offer almost no recoil. They also have very good abrasion resistance and excellent bending fatigue resistance, some superior to wire rope in fact. Now the trick here is that there are two types of HMPE fibre, one is the raw material for Plasma™ and it is called Spectra*. The other is a product called Dyneema*.
(LCP fibre ropes are excellent for a number of applications including 4x4 winching, however they are around 40% more expensive than Plasma so we have not considered them in this article).

While these two HMPE products are virtually identical in many ways and have almost identical strength values, they can however perform somewhat differently in use, depending upon the application. Both fibre types have two grades, Spectra* 900 and Spectra* 1000 compares to Dyneema* SK-60 and SK-75. It is worth mentioning at this point that Plasma is not simply a high grade of Spectra, it is a fibre that has undergone Puget Sound Rope’s patented re-crystallisation process.

This process basically sees the fibre drawn down to increase tensile strength in a manner similar to that used in the steel industry to increase strength. Without going into too much detail it basically works like this; multiple filaments of Spectra 900 are twisted into a yarn and super heated then drawn through a series of baths to produce the finished high strength fibre. This process refines the molecular structure such that almost 98% of the molecules are parallel to each other thereby increasing strength substantially. This is the fibre at the heart of Plasma rope’s strength, and this is where things get really interesting.

To compete on a strength basis with Plasma many of the ropes made from Dyneema have to in some way, enhance their strength, but as the Re-Crystallisation process is patented to Puget Sound Ropes these rope makers have to use other methods to increase the base strength of their ropes. One of the most popular methods is to make a complete rope then subject it to high heat and load to basically stretch the rope in an effort to draw the fibres. This process does indeed increase rope strength, but at a cost as it is actually fatiguing the ropes. Flex fatigue figures for Plasma are far superior to those of ropes made in this manner.

There is one other large difference that exists between the two fibre types and it translates across the grades as well. This big difference is in the size of the filaments (the diameter), a filament of Spectra is about ten times the cross sectional area of a filament of Dyneema. Now this adds up to better abrasion resistance, both internal and external. You all know about external abrasion damage and how it can destroy a rope, but internal abrasion damage is just as important. Perhaps it is important to realise that a rope is the most complex machine of all time, every part is a moving part so therefore moves against another moving part. As you can imagine the abrasion going on inside the rope is always there and is one of the major forms of rope deterioration.

All of that extra material in the Spectra filament increases the surface bearing area thereby reducing inter-filament pressures with an attendant reduction in internal abrasion damage. Test results from yarn on yarn abrasion tests* show that Spectra based fibres can have up to 287% longer life than Dyneema fibres. Recent studies^ into the behaviour and life of ropes used in marine towage applications indicate that Dyneema ropes suffer from strength degradation at a much faster than Plasma ropes. Certainly when compared to tested results of Plasma ropes in similar applications, Plasma outperforms Dyneema.

The same can of course be said for the external fibres of the rope body, the increase in surface area reduces the effect of abrasion and therefore increases rope life. The larger size just makes them a bit tougher, and for the sort of work done by a 4x4 winch, toughness is a paramount quality.

During the course of a research program into the life of ropes in towage operations in the US, it was discovered that ropes made from Dyneema can suffer from drum compression damage, that is damage caused to the rope while it is stored on the winch drum. This is basically a fatigue mechanism that sees the rope strength degrade over time from being stored on a winch drum. This would appear to diminish the effectiveness of these types of ropes in 4x4 winching applications. Compression testing results indicate that Plasma would have a 30% longer life in these sorts of applications.

One other thing to be aware of is the method of determining rope strength. Most ropes made from Dyneema adopt the European or ISO standards method which quotes the theoretical breaking strain of a rope in the un-spliced condition, whereas all Plasma ropes breaking strengths quoted are for completed ropes fully spliced. A splice can reduce the strength of a rope by 10%.

We hope we have been able to give you all a better understanding of these high tech synthetic ropes and more importantly the reasons why you should choose one over the other.