TPE and TPU wire and cable materials Performance comparison and application
Low smoke | Halogen-free | Flame retardant
Thermoplastic elastomers are now favored by many Wire And Cable factories for their advantages of high elasticity, flexibility, and smooth feel. As PVC materials are restricted in many occasions, thermoplastic elasticity has been vigorously promoted.
In the past 15 years, more and more flame retardant development of thermoplastic elastomers in China. Flame retardant thermoplastic elastomers, especially TPE and TPU, have been widely used in consumer product data lines, new energy charging pile sheathed lines and insulated lines, and in-vehicle high-voltage lines.
However, there are still many objective problems in the research on flame retardant of thermoplastic elastomers. For example, friends often ask what are the differences between TPE and TPU. This article mainly briefly discusses the characteristics, performance comparison and application of thermoplastic elastomers TPE and TPU wire and cable materials.
01 Application of TPE in the field of wire and cable
TPE refers to a thermoplastic elastomer with SEBS as the matrix resin. SEBS is a block copolymer composed of styrene (S)-ethylene (E)/butene (B)-styrene (S).
The double bonds in SEBS, that is, SBS, are saturated by hydrogenation, so SEBS has good weather resistance, heat resistance, compression deformation resistance and excellent mechanical properties.
(1) SEBS products have excellent electrical insulation performance, non-toxic, weather-resistant and aging resistance, good flexibility and high strength, and have a wide temperature range. They are excellent materials for making outer covers and insulation tapes of wires and cables. They are mainly used in mobile smart terminals and home appliances and other fields.
At present, it has become a general trend to replace PVC in the field of low-voltage wires (such as headphone cables, charger cables, USB cables, audio/video cables, computer cables, etc.).
(2) Because consumer electronic products have the characteristics of fast updates and short service life, with the advent of the era of consumption upgrading, SEBS-related products have huge room for development in this industry.
With the increasing demands on cable fire resistance and environmental protection performance at home and abroad, people's consumption level continues to improve, the trend of high-performance flame retardant SEBS products to replaCe Cable substrates such as PVC and CPE is becoming increasingly apparent in the future, and the future application prospects are broad. At present, there is a great market demand for SEBS flame retardant modification and high-performance development.
Special function TPE material: With the application and development of new technologies of TPE materials, the current special function TPE material mainly includes conductive TPE, antistatic TPE, TPE insulating material, irradiated crosslinked XLTPO, high resilience TPE, high flame retardant TPE, etc.
02 Application of TPU in the field of wire and cable
TPU thermoplastic polyurethane elastomer, which is a linear block copolymer produced by the reaction of diisocyanate and macromolecular polyol, chain extender/crosslinker and a small amount of additives. One is mainly polyurethane material, and the other is mainly polyether type.
It is usually a block polymer, and the PU obtained by reacting a long-chain polyol with isocyanate is used as a soft segment, and the PU obtained by reacting a short-chain diol with isocyanate is used as a hard segment.
The applications of TPU elastomers in wires and cables are mainly in the following fields:
·Automobile wiring harness: Anti-lock system (ABS) wiring harness, odometer cable, automobile communication cable, charging pile flame retardant sheath cable, etc.;
·Geographic exploration cables: oilfield\ocean\land exploration cables, seismic wave detection cables, etc.;
·Consumer electronic wires: headphone cable, (flame retardant) Data Cable for mobile phone charging, audio cable, USB cable, computer accessories cable, etc.;
·Energy and industrial cables: computer CNC cables, wind power cables, mining cables, power energy cables;
·Wire communication cable: fiber optic cable sheathed wire, required flame retardant;
·Medical equipment cables: electrocardiogram cable, blood oxygen detection cable, electrode lead cable, massager cable.
03 Comparison of performance of TPE and TPU wire and cable materials
(1) TPU has better strength than TPE, tensile strength and elongation rate: The tensile strength of TPU is 2 to 3 times that of natural rubber and synthetic rubber, and the TPU has good bending resistance; good wear resistance, Taber wear value is 0.35-0.5mg, which is the smallest among plastics, so it has good skin breaking resistance.
(2) TPE and TPU feel and soft performance: TPE can adjust hardness and flexibility from a wide range of 0 degrees to 99A, while the hardness range of TPU is 60~95A, and it still maintains elasticity when hardness is above 85A. This is a characteristic that other elastomers do not have, so TPU has high load support capabilities and good suction and discharge effect; the feel of the two is quite different in different hardness ranges, and it adapts to different occasions according to requirements; TPE has a large elastic loss in high hardness occasions.
(3) Polyether TPU and TPE have good water resistance, but polyester TPU has poor water resistance; TPU has better oil resistance than TPE.
(4) The UV resistance of polyester TPU is relatively poor and is prone to yellowing. Because the benzene ring of the polyurethane hard segment and the aromatic curing agent are conjugated with the carboxylic acid ester, an oxidation and rearrangement occur, forming a quinone structure with chromogenic groups, thereby creating an unsaturated bond in the polymer segment; under the action of ultraviolet rays, energy "free radicals" are provided for the color change reaction, which provides enough energy to destroy the chemical bonds of most polymers, trigger an automatic oxidation reaction, and cause aging and degradation.
The yellowing performance of polyether TPU is better than that of polyester TPU. It can improve the anti-UV capability after modification, ensuring that it does not turn yellow within 1 to 2 years. The anti-UV of TPE is generally better than that of TPU, so the color-resistant TPE is much better than that of TPU.
To sum up, polyether TPU has the advantages of hydrolysis resistance, mildew resistance, high resilience and low temperature performance. Polyester TPUs have the advantages of high tensile strength, flexibility, wear resistance, solvent resistance, oxidation resistance and high temperature resistance.
04 Processing and forming of TPE and TPU wire and cable materials and cost comparison
Comparison of TPE and TPU wire and cable material processing and forming:
(1) TPU is very easy to absorb water. It needs to be dried at 100℃*3~4H before processing, while TPE is dried at 70~80℃*2H;
(2) TPU requirements for extruders. Single-screw three-stage extruders with L/D ratio between 20-30 and compression ratio between 2-4 are suitable for TPU processing; the gap between screws and material pipes is about 0.1-0.2mm. The optimal screw design should avoid intense friction and overheating, causing material to decompose and crack, thereby reducing the mechanical properties of the product.
The speed of the screw depends on the diameter of the screw. Since the TPU is sensitive to frying and cutting, too high speed can easily lead to TPU cracking. If it is too low, it will also lead to cracking due to the long residence time. Generally, the screw speed is set in the range of 25-60rpm, while TPE requires a relatively loose extruder.
(3) Before starting the TPU, make sure that the screw, machine head and screw cylinder are cleaned without dead corners. All preparations are completed, such as semi-finished product preparation, printing and debugging, etc. The final step is to really open the finished product before pulling the hopper to release the material to the screw. In the initial stage of starting the machine, try to minimize the residence time of the rubber on the screw. After the material is discharged, the machine will be quickly started within 5 minutes. This critical period must be handled well in the beginning. Pay attention to the order, and you will have twice the result with half the effort.
(4) TPE is not sensitive to shearing, and will not easily decompose if it stays for a long time. It is relatively more convenient to process.
Comparison of processing costs of TPE and TPU wire and cable materials:
(1) The cost of TPE material and polyester TPU are not much different. Polyester TPU is slightly higher, but the cost of polyether TPU is relatively high.
(2) The three have the lowest TPE density, followed by polyether TPU density, and the largest polyester TPU density, and the lowest cost of using TPE.
By comparing the basic properties of TPE and TPU materials and the material processing technology, both have their own advantages and disadvantages. However, from the analysis of the domestic TPU and TPE industry chains, the TPE raw material market channel is more stable and convenient, while most of the TPU production raw materials rely on imports, and the domestic production process is relatively backward, so product stability is difficult to ensure. The raw material characteristics of each manufacturer are quite differentiated. Our elastomer peers need to understand enough to facilitate application and modification development.
Through in-depth exploration of the internal structure of the material, real-time monitoring of performance changes and continuous identification of stability, the compatibility and endurance of wires under harsh sea areas are demonstrated. Looking forward to the future, the continuous improvement of the material and structure of submarine transmission lines will inevitably lay a more solid foundation for the mining and application of marine resources.
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