High performance PE fibers have a good strength to weight ratio with high strength and stiffness values and are commercially produced in many companies around the world. The following factors are important for obtaining high strength from PE fibers.
- The (-CH2-) building block needs to be supported by high crystallinity and orientation.
- A molecule with high flexibility should be obtained by providing minimum chain twist. The molecule should not be hard but should be crystalline.
- An attempt should be made to obtain a linear molecule with a very high molecular weight.
Manufacturers have developed a wide variety of types of PE fibers to provide various properties. PE can be withdrawn from both melt and solution. Important producers are Dutch tate Mines (DYNEEMA), Alliad – Signal Production (SPECTRA), Mitsui (TEKMİLON), Celanese and Montefiber.
Both melt or solution spinning systems are used in the production of high performance PE fibers. Although high molecular weight PE fibers can be obtained in the melt spinning system, the system is more suitable for low molecular weight PE fibers. Fibers with high modulus but relatively low strength are obtained by this process. In extraction from solution, ultra-high molecular weight PE is obtained by subjecting it to a special extraction process. With this system, both high strength and high modulus fibers are obtained.
The solution extraction system has gained more commercial success and has “shot from melt” It is called in. This system was developed by the University of Groningen and later patented by DNS.
To obtain ultra-high modulus PE fiber, ultra-drafting is required. Ultra-gravity is breaking off the coiled crystals and then forming a long chain microfibril.
PE filaments with high modulus and drawn at the same temperature have a structure called “shish kebab”. This structure is corrected by point shooting. However, a very high temperature is required for the rectification process. In addition, drawing the materials from the beginning at high temperatures (at relatively high speeds) turns the shish kebab structure into smooth fibrils.
Below are the most important factors for the commercial success of PE fibers.
- High specific strength and specific modulus with high breaking energy
- Low specific gravity
- Very good rubbing resistance
- Excellent electrical and chemical resistance
- Good UV resistance
- Low dehumidification
High performance PE fibers have high strength and low elongation.
The length of break with its own length is 280 km.
The properties of Ultra High modulus PE fiber (UHMPE) do not depend on the amount of orientation. Any deviation in the crystallization conditions leads to changes in the mechanical properties of UHMPE2. The strength of Gel-spun PE fiber reaches values such as 30 g/denier. High strength and modulus properties can be increased by electron radiation method.
In PE fibers obtained by the gel-spinning method, the strength properties can be changed by using various drafting ratios. Strength homogeneity is provided very well at drawing ratios above 30.
The strength of the melt drawn fibers depends on the defect concentration and the filament diameter. Gel-spuns behave very differently in this regard. The strength of PE fibers depends on the distribution of the irregular regions rather than the crystalline regions. The strength of ultra or high tensile high molecular weight PE fibers varies with filament diameter and propylene comonomer ratio. This structure does not conform to the Young's Modulus standard fiber behavior.
High modulus PE fibers have a chemical and crystalline structure that is resistant to various external influences. Its resistance in sea water does not cause any functional problems.
In addition to a high modulus, PE fibers have high abrasion resistance
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High performance fibers also have their limits. PE has a very low melting point and poor adhesion to various matrices. Therefore, it is difficult to use in composites. With a special surface treatment, the fiber surface can be made sticky.
Some usage areas of PE are shown below.
- boat sails
- ship ropes
- Protective clothing
- Composites (sports equipment, pressure vessels, keel and various armors)
- Concrete bracing
- fishing nets
- Medical vaccines
Lightness, high strength and low Creep are the main reasons for using PE fibers in ship sails. A good combination prevents the sails from being deformed during use. A very good ship rope is obtained if lightness, high strength, very good rubbing resistance and low moisture absorption properties are provided together.
The best market for PE fibers in the USA is ship ropes. Fishing nets are also a growing industry. Dyneema is the most common trawl net. Iceland is the largest producer of PE fishing nets in the world. PE fibers are used in boat keels by combining long strength, high hardness, lightness and good flexibility. PE also has very good impact resistance and its impact resistance properties are improved by producing composites with glass, carbon fibers.
A wide variety of helmets and helmets made of PE composites are used by mountaineers and miners. In impact strength, only E-glass can be shown as an alternative to high modulus PE fiber. Other interesting uses for PE are rocket engine blocks and pressure vessels. The burst performance factor of PE under pressure is approximately 45% higher than aramids.
PE fiber is also used in protection against cuts, stitches and ballistic impacts.
High modulus PE fibers have a much better strength than aramid and glass fibers. A bulletproof vest made of PE is 60% lighter and much more comfortable than a steel vest with the same protection value. PE fibers have also been found to be very suitable for risky jobs and sports applications. With UHMPE, products such as protective gloves, fencing clothes are made.
A protective suit made of PE fiber cannot be punctured up to a force of approx. 1000 N. With its low power factor and dielectric coefficient, PE fibers deflect signals very little and therefore have a radar shielding feature. There are also various applications in the field of geotextiles. Nets made of PE are used as anti-erosion.
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