The 138 is a long-standing OTECH proprietary technology that has been re-imagined into the emerging wind-power cable application.
The wind turbine industry showcases the performance characteristics better than any other application of The 138.
Electricity generated by wind turbines travels down large cables from the nacelle, though the tower, and into an underground cable providing a consistent flow of renewable energy during high and low temperatures, all thanks to OTECH’s innovative team of compounders.
Through formulary excellence OTECH has been able to stretch the performance temperature range from 105 °C to -40 °C to cold impact.
Today there are several variations of The 138 tailored to meet specific extreme harsh environments and high performance customer needs.
OTECH continues to dominate the wire market in areas where wire manufacturers need one compound which can reach extreme opposite properties, and still be affordable.
OTECH has a wide product line of, and custom development capability for, flame and smoke suppressed wire & cable compounds to meet the entire flame-retardant hierarchy of wire constructions. OTECH’s compounds satisfy all the requirements across the entire hierarchy of wire constructions, from vw1 to tray cable to plenum compounds.
-55°C Brittle Point
Specialized compounds allow wire and cable to perform in the environment that it is designed for. The compounds must meet the electrical, thermal, chemical, UV and durability requirements to last where they will be used.
In the 1880’s a natural latex was used to insulate cables. If the insulation was not kept wet, it would fail to insulate the conductors. In the 1890’s, impregnated paper was used as insulation on cables that carried voltages as high as 10kV.By the 1930s, PVC was being experimented with in Germany to insulate cables. By the end of WWII, there were several varieties of synthetic rubbers available for this purpose. In the 1950’s PVC was commercially viable and replaced rubber cables in many areas, especially domestic wiring. In the 1980’s, PVC alternatives such as low smoke zero halogen compounds were developed due to a number of public fires demonstrated the dangers of toxic gasses that were released during the combustion of the PVC.
A balance must be maintained between thermal resistance, electrical insulation, mechanical strength, chemical and UV resistance while also considering cost. Compliance with regulatory agencies such as Underwriters Laboratories or the Canadian Standards Association must also be considered if required for the application.
PVC compound is commonly used in domestic wiring applications in homes. PVC is also used for insulation for low and medium voltage applications. It can be used in control and instrumentation systems, mining and ship wiring. It is also widely used in the telecommunication industry to protect the conductors from moisture, heat and other environmental factors. PVC compounds are also used for automotive wiring, consumer electronics and marine applications where resistance to salt water is crucial. PVC is generally the most economic option for (a wide variety of ) wire and cable (applications).
XLPE offers resistance to environmental stress cracking, ozone, solvents and soldering. They have high thermal stability and mechanical strength making it suitable for long distance transmission and applications in harsh environments. XLPE is generally less flexible than thermoset rubber and may have higher dielectric losses.
Thermoset rubbers have greater flexibility and resilience which makes them suitable for dynamic environments. They have excellent low temperature resistance and chemical resistance. They also feature good mechanical impact resistance and resistance to moisture. They may not be as mechanically strong as XLPE compounds.
TPE compounds combine the properties of plastic and rubber offering a balance of flexibility, durability and performance in various environments. They offer a wide range of temperature performance able to withstand environments from -35C to 100C. TPEs (specifically TPU) provide excellent abrasion resistance. There are halogen free options available using TPE compounds.
Halogenated compounds, such as PVC, can off-gas carcinogenic materials such as dioxins and phthalates when exposed to heat and flame. The smoke from halogenated materials is also corrosive. This can cause damage to equipment in the area of a fire. This is also a risk to be considered when attempting to recycle halogenated materials. Halogen free compounds began to be developed in the 1990’s to eliminate these risks. Halogen free compounds use polymers such as silicone rubber, polyurethane, polyethylene, polypropylene and EPDM.
When selecting a compound for an application several factors need to be considered. Will the finished cable be exposed to high or low temperatures in the environment where it will be installed? Will it be installed in a dynamic environment where it is part of a system of moving parts? Will the cable be exposed to sunlight? Will the cable be exposed to chemicals such as oils and lubricants? What voltage load will the cable be expected to carry? What are the regulatory requirements for the cable?
Plasticizer plays a major role in determining the performance characteristics of the compound. The quantity of plasticizer used determines the hardness of the compound. The type of plasticizer selected will determine the compound’s resistance to heat, cold, and chemical attack. Certain plasticizers are disallowed by certain regulatory agencies and must not be selected for compounds that need to meet these regulatory requirements.
Flame retardants prevent or slow down the spread of fire by inhibiting ignition and flame propagation. This extends the time available for safe evacuation during a fire. They are generally produced from heavy metals. Some examples are, antimony trioxide, aluminium hydroxide, magnesium hydroxide and tetrabromophthalate based plasticizers. As with plasticizers, care must be taken when selecting a flame retardant as some are disallowed by various regulatory agencies.
Stabilizers are crucial, especially in PVC compounds. They prevent polymer degradation caused by exposure to heat during processing and in end use applications. Stabilizers also protect against discoloration caused by exposure to heat. A few examples of heat stabilizers include calcium zinc and barium zinc. Lead stabilizers are no longer used due to environmental and health concerns. UV stabilizers are used to protect polymers from degradation caused by exposure to ultraviolet radiation. Compounds that aren’t protected against UV radiation can become brittle causing a loss of mechanical properties. Discoloration can also occur.
Conductive wire and cable jacketing and insulation compound is formulated using a conductive carbon black filler. These are used in cables where anti-static properties are needed to mitigate the risk of electronic components being destroyed by overvoltage due to electrostatic charging. These compounds are also used to shield cables from electromagnetic interference (EMI). A cable in proximity to a strong electromagnetic field gets exposed to unwanted currents and experiences surges in voltage resulting in electrical “noise”.
Dielectric strength refers to the maximum voltage an insulating material can withstand before dielectric breakdown occurs. This value is manipulated in the compound through use of fillers with a plated structure such as calcined clay. Increasing the level of this filler increases the dielectric strength of the insulating compound.
The mechanical properties of wire and cable include: Tensile strength and elongation. These refer to the maximum force a wire or cable can withstand before breaking under tension and how far they are capable of stretching before breaking. These properties are primarily influenced by material hardness and the molecular weight of the resin that is used. Another important property is a cable’s ability to remain flexible in low temperature environments. Plasticizer selection is crucial to pass the cold bend test that is associated with this property.
Wire and cable fire safety regulations are crucial for minimizing fire risks. They primarily deal with the insulation and jacketing materials that are used on wire and cable. These materials must be flame retardant and produce a minimal amount of smoke in a fire. Specific tests are carried out by UL to determine that cables meet regulations. A few of the more common tests are the vertical wire flame test (VW-1) and the vertical tray flame test (FT-4), UL 1666 Riser and Ul’s 910 Steiner Tunnel plenum flame test.
UL will carry out accelerated oven aging tests to ensure that a compound complies with heat resistance requirements. OTECH offers compounds that range from 60-105C in temperature rating. Thermal stability and plasticizer selection play important roles in passing this accelerated aging test. UL also carries out cold bend testing which involves conditioning a cable at a specified low temperature (-40C is one example) for a specified time. The cable is then wrapped around a mandrel to ensure that the jacketing and insulation will not crack if installed in a cold location. Cold impact testing can also be performed to ensure that a cable will not crack when a specified amount of weight is dropped on it after being conditioned in a low temperature freezer.
In addition to the cold bend and cold impact testing mentioned above, UL also tests for UV resistance. Cable specimens are conditioned in a xenon arc UV chamber for 300 or 720 hours depending on the rating of the cable. After conditioning, tensile strength and elongation are tested. The conditioned samples must have 80% of the values of unconditioned control samples. A similar test is performed by conditioning samples in IRM 902 oil at elevated temperatures. Again, tensile strength and elongation data is compared to that of unconditioned samples.
NSF and CSA conduct annual audits where production records are examined and samples are submitted by OTECH for compliance testing in their laboratories.
UL conducts quarterly audits where OTECH submits samples for elemental analysis which is compared to a standard that UL has on file to ensure that the formulation contains all of the proper additives at the correct addition levels.
Wire and cable extrusion is the process of extruding coating over a conductor or conductors. The process involves conveying pelletized compound through a heated screw and barrel. At the end of the barrel the melted material is extruded through a die onto the conductor. Different dies are used depending on the desired dimensions of the wire or cable. The cable then runs through a bath of water which cools the material. After this, the cable is printed with the necessary markings. Finally it is wound onto a reel.
Electrical components are injection molded. This process involves feeding pelletized compound into a hopper where they are fed into the barrel of the injection molding machine. The molten compound is then pushed to the front of the screw and is ready for injection. The mold is closed and the molten material is forced through a nozzle into a mold cavity. Pressure is used during injection to make sure the mold cavity is completely filled. After cooling in the mold, the finished part is then ejected.
The biggest key to processing successfully is choosing the proper process parameters. The design of the screw used in the extruder must be appropriate for the polymer you intend to process. The correct screen pack configuration must be selected. Too much screening can cause shear to build up in the screw which will cause the material to burn. Too little screening can allow contaminants to pass through and cause surface defects on the jacket. It is also critical to select the proper temperature parameters. Too high a temperature will result in burnt material and voids in the finished jacket from gasses getting trapped in the extruder. These voids will negatively impact the mechanical properties of the finished cable. Too low a temperature will result in a finished surface which is not smooth.
OTECH is able to provide customers with processing recommendations for every compound we produce. We are also available for onsite technical service visits to assist with processing the material.
Copper and aluminium are highly recyclable. Thermoplastic waste is able to be ground up and re-introduced into the product stream at a low percentage. Recycling rates can be greatly improved by ensuring that scrap types are properly sorted.
A continuing trend in the wire and cable industry is the shift to low smoke, zero halogen materials. Growing regulatory compliance standards are pushing industries to adopt LSZH compounds that ensure safety and environmental sustainability.
Specimens must be cut periodically from the cable for the lab to test. These tests include measurement with calipers to ensure that the dimensions of the cable are within tolerances. Tensile strength and elongation need to be measured to ensure the cable will meet UL standards. VW-1 testing is relatively uncomplicated and may be performed to ensure cables meet UL flame specifications. Once process conditions have been established, they must be followed to ensure consistency.
Researchers are working to enhance the flexibility, mechanical strength and temperature resistance of LSZH compounds to make them suitable for a wider range of applications. Innovations in polymer chemistry and additive technologies are driving the development of new LSZH compounds with superior performance characteristics.
There are an increasing amount of bio based resins and plasticizers available for use in the production of wire and cable compounds. Some examples are: Polyethylene produced from sugar cane ethanol, plasticizers derived from natural oils such as soybean oil. Other available feedstocks include: sunflower oil, canola oil, corn and algae.
OTECH produces a variety of conductive PVC compounds suitable for use in the wire and cable industry. The surface resistivity of these compounds can range from 10^1 – 10^7 making them ideal for semi-conductive or ESD applications.
Industry 4.0 has not been widely embraced by the wire and cable industry outside of Germany. It is more challenging to integrate Industry 4.0 in a linear manufacturing process where customization is a vital aspect of the business. Manufacturers are reluctant to make the large up front investment when they feel satisfied with their profitability they achieve using Industry 2.5. It can be difficult to accept the expense of using robotics when one human can service five machines where a robot can only service one. These short-sighted philosophies may not be a viable approach as the market develops.
With the restrictions on exportation of Antimony to the United States by China, alternative flame retardant solutions must be found. OTECH has partnered with our suppliers to develop flame retardant, antimony free compounds for use in the wire and cable industry.
4744 E. Oaknoll Road
Rolling Prairie, IN 46371
Phone: 219-778-8001
Fax: 219-778-8007
