Dyneema®
Brief History Of DSM High Performance Fibres.
DSM commercially produces the strongest fibre in the world, Dyneema®.
The basic theory about how a superstrong polyethylene fibre should look was already available in the thirties. It took almost half a century to produce the high performance polyethylene fibre (HPPE).
In 1979 DSM invented and patented this fibre and the gel spinning process to produce it.
Dyneema® fibres have been in commercial production since 1990 at their plant at Heerlen, the Netherlands. The production of Dyneema® fibres demands relatively little energy and uses no aggressive chemicals.
The product can easily be recycled so environmental pollution from product and process is minimal.
In the USA DSM has granted a manufacturers license to Honeywell.
The basic theory about how to produce a superstrong fibre from a polymer such as polyethylene is easy to understand.
Polyethylene with an ultra high molecular weight (UHMWPE) is used as the starting material. In normal polyethylene the molecules are not orientated and are easily torn apart.
In the gel spinning process the molecules are dissolved in a solvent and spun through a spinneret.
In the solution the molecules that form clusters in the solid state become disentangled and remain in that state after the solution is cooled to give filaments. As the fibre is drawn, a very high level of macromolecular orientation is attained resulting in a fibre with a very high tenacity and modulus. Called Dyneema®, this fibre is now available in different grades.
It is characterized by a parallel orientation greater than 95% and a high level of crystallinity, up to 85%. This gives Dyneema® its unique properties.
Commercial Production:
In the meantime, research and development continue at DSM.
Since the start of commercial production, the performance of the Dyneema® fibre has been improved considerably. New grades have been introduced and others will follow.
Gel spinning of HPPE fibres is a process that hinges on mechanical and physical parameters, not on chemistry. This makes it relatively easy to produce a wide range of fibre grades. From the start, quality control has been a major item for DSM High Performance Fibres and quality acreditation was soon obtained.
A large number of applications and products using Dyneema® have been developed. Technical support is considered to be essential in the introduction and marketing of this high performance fibre. Accordingly, a well-equipped laboratory, called Technicum, is available to support textile-processing and rope-making customers. It also develops protective and anti-ballistic products.
High Strength, High Modulus, Low Weight:
Dyneema® fibres have a unique combination of properties. The density is slightly less than one, so the fibre floats on water. But the tenacity is the highest in the world and can be up to 15 times that of a good quality steel! The modulus is very high and is second only to that of special carbon fibres grades. Elongation at break is as low for Dyneema® fibres as for other high performance fibres, but due to the high tenacity the energy to break is high.
The strength of a fibre can be expressed as the free breaking length. The free breaking length is the theoretical length of a fibre, yarn or rope which breaks under its own weight, when freely hanging. This free breaking length is product related and is independent of the thickness of the fibre or the rope. Dyneema® would in theory reach to a satellite's orbit.
High Energy Absorption:
Dyneema® fibres can absorb extremely high amounts of energy. This property is utilized in products for ballistic protection. But this makes the fibre equally suited for products such as cut-resistant gloves, motor helmets and to improve the impact strength of laminated boat hulls. In these applications not only the high tenacity is used but also the high energy absorption.
Durability:
Dyneema® fibres are produced from polyethylene and do not contain any aromatic rings nor any amide, hydroxylic or other chemical groups that are susceptible to attack by aggressive agents. The result is a highly crystalline fibre with excellent resistance to water, moisture, most chemicals, UV light and micro-organisms. Unlike some other anti-ballistic fibres, Dyneema® fibres do not swell or hydrolyse in water, sea water or moisture.
The high molecular weight polyethylene used to produce the Dyneema® fibre, is also well-known as an engineering plastic.
As an engineering plastic, it is especially used for its superior wear and abrasion resistance.
So it is not surprising that Dyneema® fibres, too, have good abrasion resistance. Carbon fibres and glass fibres have a high modulus and a brittle breaking mode, but Dyneema® fibres demonstrate that this is not an obvious combination. Dyneema® fibres have a high modulus but still are flexible, with long flex life.
Thermal Properties:
Dyneema® has a melting point between 144 and 152 º C depending on the test method used.
The tenacity and modulus decrease at higher temperatures but increase at sub-zero temperatures. There is no brittle point found as low as minus 150ºC, so the fibre can be used between this temperature and the 80 to 100ºC. Brief exposure to much higher temperatures will not cause any serious loss of properties.
Absorption Of Ballistic Energy:
Most important in ballistic protection is the level and the mechanism of energy absorption at ballistic speeds. The specific modulus of and the sonic velocity in the fibre determine the anti-ballistic potential whilst wearing comfort is achieved because of the very light weight and flexibility of the sheet material.
Dyneema® UD In Police Vests:
A special sheet called Dyneema® UD is best at stopping bullets. Dyneema® UD is a unidirectional construction in which the yarns are not woven but lie parallel to each other. Using Dyneema® UD the minimum weight is needed for protection at different levels, the body armour is flexible and gives good wearing comfort. Dyneema® UD is not affected by water or sunlight and needs no special protection.
Another important consideration is the blunt trauma effect. Due to the high sonic velocity within the fibre, the impact energy is dissipated very rapidly over a large area. This makes for the low blunt trauma, the indentation on the inside surface side of the vest.
Armoured Cars:
Police cars can be readily armoured using Dyneema® protective armour panels.
Armour panels are most commonly used for protection against 9mm bullets, the threat mostly encountered by police forces.
Dyneema® panels weigh only 6.5kg/m². Thus, they can be installed in car doors without changing the hinges or the door itself. At the end of the service life of the car, the armour panel can be removed and re-used. The original door panel can be mounted back again.
Dyneema® light weight armour can also be used for protection against heavier ammunition. The thermoplastic armour is easy to form, is not affected by light or moisture and can be processed using standard equipment. For common FMJ (full metal jacket) ammunition such as 7.62 NATO Ball and 5.56 Ball, no steel or ceramic strike face is needed.
Military Helmets:
Military helmets are normally designed to protect against fragments.
Several helmet designs using the Dyneema® fibre in different forms and in different matrix systems have been tested using 1.1.gram (17 grain) FSPs (fragment simulating projectiles). Best results are obtained using thermoplastic resin as the matrix system. Service life of this type of helmet promises to be long and wearing comfort is very good due to its low weight.
The effects of sunlight and moisture are negligible, as with all other Dyneema® products.
Hard Plate Inserts Against Rifle:
Hard armour plates an be used to upgrade soft body armour.
A unique feature of the full-Dyneema® inserts is that they protect against all common rifle bullets without a heavy steel or ceramic strike face.
Continued Expansion:
DSM High Performance Fibres built a third production line. This raised production capacity for Dyneema® fibre by another 500 tons per year. The new facility came on stream in 1997 and boosted production capacity to 1500 tons. The third production line used the innovated gel spinning technology, the same technology as used in the second line that came on stream in 1996.
The innovated technology makes it possible to produce Dyneema® fibres having a strength of approximately 4 N/tex. This is 30% stronger than the present Dyneema® fibres and almost twice the strength of standard-grade aramid fibres.
A forth fibre production plant opened in 2001 in Heerlen and a fith fibre production plant in the USA.
Latest Process Technology:
DSM Dyneema® remain at the forefront of research, development and application of UHMWPE fibres.
Since the introduction of the Dyneema® fibre DSM High Performance Fibres has achieved essential innovations in the patented gel spinning process for the superstrong polyethylene fibre. These innovations led to steady improvement in the strength of the Dyneema® fibre.
This was initially achieved by optimising the process parameters without affecting the stability of the process.
The first Dyneema® fibre grades of the new quality are Dyneema® SK75 and Dyneema® SK77. Dyneema® SK75 is used in ropes and cordage and in ballistic protection. Dyneema® SK77 will be the top in anti-ballistic fibres and have a tenacity of about 4.0 N/tex (45 g/den).
Dyneema's® position as the strongest fibre in the world is clearly reinforced with these new fibre grades.
