Silicone material is one of the important and indispensable materials in automobile manufacturing, which can not only optimize the process of automobile production and manufacturing, but also improve the performance and safety of the car, and has been widely used in a variety of automobile parts, such as airbag coatings, powertrain seals, gaskets, hoses, windshield liners, automobile engine seals, ignition wires and coils sheaths, automobile turbocharger tubes, cooling tubes, and automobile components.Sealing and protection of automotive components, high-voltage cable and wiring harness sealing, and so on.
Today, we mainly introduce the silicone rubber material in the silicone in the new energy vehicle cable applications.
一、What is silicone rubber?
Silicone rubber is an organosilicon elastomer material, which, unlike polymers from petroleum-based sources, originates from silicate ores in the earth's crust.Silicone rubber is widely used in digital electronics, home appliance parts, mother and baby products, food contact, medical equipment, automotive parts, power transmission, wire and cable and other fields.Through specific formula design, silicone rubber shows its special advantages in the field of new energy automobile wires and cables.
Silicone rubber is rubber whose main chain consists of alternating silicon and oxygen atoms, with two organic groups usually attached to the silicon atom.Ordinary silicone rubber is mainly composed of silicone-oxygen chain links containing methyl and a small amount of vinyl. The introduction of phenyl can improve the high and low temperature resistance of silicone rubber, while the introduction of trifluoropropyl and cyano can improve the temperature and oil resistance of silicone rubber.
Depending on the curing method and the viscosity of the base polymer, silicone rubber can be divided into the following categories in addition to hot and cold curing:
Solid Silicone Rubber (HTV), Liquid Silicone Rubber (LSR), Two-component Room Temperature Vulcanized Silicone Rubber (RTV-2), One-component Room Temperature Vulcanized Silicone Rubber (RTV-1), Silicone Gel, and so on.
Silicone rubber has good resistance to low temperatures, generally can still work at -55 ℃, after the introduction of phenyl up to -73 ℃.
Silicone rubber's heat resistance is also outstanding, in 180 ℃ can work for a long time, slightly higher than 200 ℃ can also withstand a few weeks or longer still have the elasticity, instantaneous resistance to temperatures above 300 ℃.
Silicone rubber is breathable and has the highest oxygen transmission rate of any synthetic polymer.
二、Why silicone rubber is used in new energy vehicle cables?
With the increasing global energy constraints and the worsening environmental degradation, energy saving and emission reduction have made new energy vehicles become the direction of the global automobile industry. New energy vehicles include Hybrid Electric Vehicles (HEVs), Pure Electric Vehicles (BEVs), Fuel Cell Vehicles (FCEVs), Hydrogen Engine Vehicles, and Gas Vehicles, Alcohol Ether Vehicles, and so on.
Hybrid and pure electric vehicles relative to traditional fuel vehicles, increase a lot of high-voltage accessories, such as power batteries, high-voltage distribution boxes, drive motors, motor controllers, etc., which also puts forward new requirements for automotive cables.As these cables are arranged in the front cabin engine and chassis area, high temperature, space is narrow, the need for cable soft, small turning radius, high and low temperature performance; secondly, the road conditions are complex, the cable wear resistance must be good and high mechanical strength; in addition to the speed of the car at times high and sometimes low, especially fully loaded climbing and other harsh conditions, the instantaneous high-current requirements of the cable line has a short-time overload capacity.
In summary, the new energy vehicle cable must have: good electrical insulation properties; thermal stability, weather resistance; corrosion resistance, oil hydrophobicity, flame retardant properties; superior mechanical properties, a high degree of flexibility and high tear resistance and so on.
Currently automotive power cable insulation materials are cross-linked polyolefin, thermoplastic elastomer.One of the cross-linked polyolefin materials heat-resistant up to 150 ℃, but the material cable is relatively hard, in the narrow space of the body of the car is inconvenient to install, and the need for irradiation cross-linking, process complexity, is not suitable for large cross-section cable.The thermoplastic elastomer material heat-resistant not more than 125 ℃, used for power cable temperature level is low, and thermoplastic elastomer material cable long-term use will have the risk of cracking.
Silicone rubber has high and low temperature resistance, ozone resistance, weather resistance, and excellent electrical insulation; silicone rubber line with high current carrying capacity, saving conductor cross-section, can cope with the requirements of long-time full-load operation; can be added through the flame retardant to achieve the requirements of fire-resistant performance; has a high degree of softness, easy to install in a limited space; high tear resistance silicone rubber, trouser tearing up to 25N/mm. Therefore, the silicone rubber material can be used in the comprehensive cross-linkedPolyolefin, thermoplastic elastomer materials to make up for their shortcomings at the same time, and silicone rubber can reduce the weight of the car and carbon dioxide emissions, is suitable for automotive power cables of high quality choice.
New energy vehicle cable and ordinary automobile cable there are certain differences：
一、The environment in which it is used has changed
1、High voltage and high current (on-board)
It can reach 600/300A, while the battery voltage of traditional fuel vehicles is generally 12V, and the corresponding conductor voltage resistance level is less than 60V.
2、Large wire diameter, high number of cables (on-board)
High-voltage battery inverter/transformer/low-voltage battery/air conditioning compressor/electric heating/power distribution unit... Numerous power-using structures are connected using cables, resulting in a huge number of cables to be laid out in a limited space.
3、Exposed space (non-vehicular)
The cable of the charging gun part is exposed to space for a long time, and its weather resistance, abrasion resistance, bending resistance and tear resistance have strict requirements.
二、In-vehicle high-voltage wiring harnesses are characterized by high voltage/current and large number of conductors of large diameters, and the design of the harnesses is faced with the challenges of wiring, safety, shielding, weight and cost.
New energy cable selection and requirements
Because of the high voltage and high current in new energy vehicles and limited space, the charging pile cable is exposed to the outdoors for a long time, the special characteristics of the use of the environment on the performance of the cable material puts forward very strict requirements.New energy vehicle cables need to have high and low temperature resistance, oil and water resistance, flame retardant, tear resistance, insulation, UV aging and other properties.Commonly used materials are TPE, TPU, XLPO, NBR + PVC, neoprene rubber, silicone rubber, etc..
1、TPU for charging pile cable polyurethane jacket material
Advantages: flexible, crush-resistant, voltage-resistant, high-temperature pressure-resistant, aging-resistant, acid and alkali resistant, salt spray resistant, waterproof.Excellent high tension, high tensile strength, strong and aging resistance properties, environmentally friendly material.
Disadvantages: Currently, domestic processing is difficult and costly.
Working temperature: cold resistant -40 degrees; temperature resistant up to 150 degrees.
2、TPE is currently used mostly to refer to SEBS-based elastomers for charging gun cables.
Advantages: simple processing, low density, moderate price, overall cable is very soft, can meet the requirements of the existing standards.
Disadvantages: Most of them contain unsaturated bonds and have poor temperature characterization; low oil resistance, especially gasoline; poor weather resistance.
Working temperature: cold resistant -50 degrees; temperature resistant up to 120 degrees.
3、Polyvinyl chloride elastomers
Advantages: flame retardant and insulating, acid and oil resistant, easy to process and modify, cheap.
Disadvantage: There will be black smoke and HCl gas when burning.
Working temperature: cold resistant -40 degrees; temperature resistant up to 105 degrees.
4、silicone rubber
Advantages: heat, cold and weather resistant, waterproof, soft and easy to install.
Cons: Not oil resistant, poor tear resistance, more expensive.
Working temperature: cold resistant -40 degrees; temperature resistant up to 200 degrees.
5、XLPE
Advantages: higher cross-linking, better flexibility, good insulation, lightweight structure, easy to install, inexpensive.
Disadvantages: poor heat resistance, difficult to control the color difference between batches.
Working Temperature: Cold Resistant -50 degrees; Temperature Resistant up to 100 degrees.
TPV generally refers to the blended system of PP+EPDM.It is a perfect combination of plastic and rubber properties.The PP phase is a continuous phase, which provides the thermoplasticity required for the processing of TPV materials, while the EPDM rubber phase is the rubber particles after vulcanization, which provides the rubber elasticity to the material.The rubber phase is generally distributed in the form of islands or particles.The vulcanized structure of the rubber phase makes TPV materials have excellent aging resistance, acid and alkali resistance, weather resistance, high temperature resistance, oil resistance.
TPV is generally light yellow or creamy white particles, and the particles have either a strong or light odor.The difference in the relevant additives used in the co-mingling determines the difference in odor and color of the material.
durometer
TPV is generally available in a range of hardnesses from 50 to 100A.Some so-called TPVs with low hardness (below 40A) are often physically co-mingled and have not been vulcanized and cross-linked.
tensile strength
Generally between 3 to 8 MPa, the higher the hardness, the better the tensile strength of the material.
Elongation at break
Generally between 200~400%, the dispersed phase of vulcanized EPDM particles does not have high tensile properties.
oil resistance
TPV has good resistance to gasoline, and some TPVs even improve their physical properties such as tensile strength after being soaked in gasoline.
Acid and alkali resistance
TPV is immersed in 98% sulfuric acid for 24~168 hours without any major decrease in the main physical properties.
Permanent deformation
TPV has good resistance to permanent deformation.At a temperature of 23 degrees, 70 degrees test, TPV's resistance to permanent deformation between 10 ~ 30%.
degree of crosslinking
The most suitable process for TPV is extrusion molding, with relatively little injection molding.The cross-linked rubber phase reduces the fluidity of the TPV material.The higher the degree of cross-linking, the higher the performance of the TPV in addition to the processing properties.
Material Odor
Most TPVs have a large odor.The odor of the material can be reduced by starting with material selection and process control.Of course this will also bring about a rise in cost.
Tips
1.According to the relevant national standards, less than or equal to 30V voltage, the total power requirement is not greater than 100W, such as DC12V, the total current is not greater than 8A.
2.Regardless of how long the power supply distance is, it is necessary to go to the load voltage shall not be lower than the voltage range required by the power-using equipment, and it is recommended to shorten the power supply distance when the power supply over a long distance cannot reach the rated voltage of the power-using equipment.
video cable
Recommended to use SYV75 ohm series coaxial cable, SYV75-3/7:75 stands for impedance of 75 ohms, -3 stands for 5/7 refers to the insulation outer diameter.
The cable thickness transmission distance reference is as follows:
When 0m＜distance≤200m, please use SYV-75-5 (96 braid) coaxial cable.
When the distance is 200m
When the distance is 350m
SYV: Full name solid polyethylene insulated RF coaxial cable.
S - coaxial RF cable, Y - polyethylene, V - polyvinyl chloride
network cable
If divided by electrical properties, commonly used network cables mainly include Category 5, Category 6 and Category 6 Ultra.The higher the type number, the newer the version, the more advanced the technology, and the wider the bandwidth.
Unshielded Category 5/Category 6 twisted-pair cable for running 100M/1000Mbps Ethernet is recommended.
For particularly strong interference environment, such as power plants, substations, large electronic equipment, electromagnetic furnace, microwave ovens and other places you need to choose shielded network cable.If the elevator wiring, you need to choose the elevator special network cable with steel wire.
Tips
1.To achieve a gigabit network, network cables, crystal heads, switching devices, etc. need to meet the gigabit standard.
2.The transmission distance of the network cable should not exceed 100 meters, otherwise it will lead to data packet loss, intermittent video signals, or even can not be connected properly.More than 100 meters can be extended by connecting switches, and the number of switches in each section of the line should not be more than three.If the installation environment is complex, there are sources of interference, you need to use shielded cable.
fiber optics
Transmission distance is too far, need to use fiber optic transmission method
Fiber optics transmit signals in the form of light pulses and are therefore made of glass or Plexiglas.It consists of a fiber core, a cladding and a protective sheath.
Optical fibers are classified as single-mode fibers and multimode fibers.
Monitoring more single-mode fiber, with the optical converter to achieve signal transmission, the farthest transmission distance up to dozens of kilometers, and the transmission effect is stable, convenient wiring.
Other types of cables
▲RS485 cable
Recommended 2-core shielded communication cable (RVVP) or Category 3 unshielded digital communication cable (UTP)
▲Alarm Input Cable
Recommended use of twisted-pair wire, twisted-pair wire generally consists of two 22 to 26 gauge insulated copper conductors twisted around each other.
▲Alarm output cable
ZR-RVS-2*1.5 twisted pair cable is recommended.
▲audio cable
4-core shielded communication cable (RVVP) or Category 3 unshielded digital communication cable (UTP) is recommended.
▲grounding wire
The ground wire must be made of bare copper flexible wire of 25mm² or more.
Wiring Tips
▲Outdoor Wiring
Outdoor wiring can be overhead or buried way, whether overhead or buried, should use the threading pipe, easy to protect the wire, but also can make the project more beautiful.
▲Indoor Wiring
Indoor wiring can use bridge or trunking, special occasions need to use galvanized steel pipe, explosion-proof hose and so on.Ceiling, suspended parts of the wiring can be metal hose or the use of flame-retardant materials with PVC pipe casing.
▲Tips
The selection of the standard of the wire pipe and trunking can be based on the total area of the wires threaded in the wire pipe (including the outer skin), not exceeding the limit of 70% of the cross-sectional area of the inner hole of the pipe for selection.
