Plastics have leakage current flowing through them under the action of electric field. The resistance when leakage current passes through plastic is called volume resistance. Resistance through 1cm3 of plastic That is the volume resistivity pv, the unit is ohm meters, The unit symbol is 0.m. The higher the volume resistivity, the The better the insulation performance

When the voltage applied to the plastic reaches a certain limit , the plastic loses its insulating properties and is broken down, the moment of breakdown The applied voltage value is called the breakdown voltage of the plastic, The ratio of breakdown voltage to plastic thickness is called breakdown field strength E, unit symbol is kV/mm

It is an indicator of the polarity of plastic. between The smaller the electrical constant e, the plastic will The smaller the polarization intensity, the smaller the dielectric loss.

The amount of energy consumed in plastic under the action of an alternating electric field is called Dielectric loss. It is often calculated as the tangent value tg of the dielectric loss angle. express. The smaller the dielectric loss angle tangent tg is, the smaller the dielectric loss is. The smaller the plastic, the better its electrical insulation properties. Used under high frequency and high pressure When used, it is required that the tg value of the plastic is not greater than a few thousandths or a few thousandths ; For low voltage and general insulation, the tg value of plastic is no more than a few percent.

Under high voltage conditions, due to insulating surface discharge and cause corona, when its When attacking an insulator, due to Ion impact, electron attack attacks, ozone attacks and The effect of external heat leads to The polymer cleaves, causing it to Electrical insulation properties and physics Mechanical properties deteriorate. Plastic resists corona effects while maintaining its performance The ability is called electricity resistance halo

Static application of plastic specimens on a material tensile testing machine A tensile load is applied and stretched at a certain speed until the specimen breaks. At this time, the tensile force borne by the unit section of the sample is called the plastic The tensile strength of the material; the percentage increase in length when the sample is broken is called the elongation of the plastic

At a certain temperature (usually 20°C), The mass of a plastic sample per unit volume, weighed is the density of plastic

During the processing and use of plastics, due to changes in The phenomenon of deterioration of plastic properties caused by heat is called thermal Ageing. The ability of plastics to resist thermal aging is called heat resistance Aging properties. Using accelerated thermal aging at high temperatures Chemical testing to determine plastic properties (mechanical properties or electrical Performance) retention rate after aging to measure the plastic's Heat aging resistance

By testing plastic samples under high temperature conditions of 200°C . Start decomposition reaction time to determine the heat of the sample Stable performance. Suitable for PVC insulation materials and PVC sheathing Determination of set material

Plastics can still protect themselves under heated conditions Maintaining good physical and mechanical properties High temperature is the heat resistance of the plastic Deformation performance. Usually waiting in plastic When heating up quickly, use it under a certain load The temperature when its deformation reaches the specified value To represent

Plastics are used under atmospheric conditions and exposed to sunlight , rain, wind, air pollution and other severe Due to the natural conditions, the performance of plastics deteriorates Atmospheric Aging Plastics Resist Atmospheric Aging The ability of plastics to weather resistance

When plastic comes into contact with mineral oil or various solvents, it resists oil or solvent ability is called the oil resistance or solvent resistance of plastics agent performance. The sample can be immersed in oil or solvent and After a certain period of time at a certain temperature, measure its oil absorption or solubility. The absorption rate, volume change rate or tensile strength, elongation of the agent elongation retention

Plastic resists water or moisture when immersed or humid The ability of gases to penetrate, known as the water resistance or moisture resistance of plastics . When plastic absorbs water or moisture, it will cause insulation resistance and breakdown fields. The strength decreases, the dielectric loss increases, and the appearance, weight, and There are changes in mechanical properties and so on. Therefore, plastics are required to have good water resistance and moisture resistance. For plastics used in wires and cables, the main consideration is that in immersion After water or moisture absorption, it should be ensured that the electrical insulation performance of the plastic meets the usage requirements. The water absorption capacity of plastics can be measured as water absorption per unit area, water absorption rate or water absorption. Expressed by weight. The moisture permeability of plastics is expressed in terms of moisture permeability coefficient and vapor permeability.

Some crystalline plastics, due to the existence of internal stress during processing and Contact with chemicals during use may cause cracking during storage and use. It's called environmental stress cracking. The ability of plastics to resist environmental stress cracking is called Environmental stress cracking resistance. Plastic bending specimens with grooved surfaces available , put it into surfactant, and observe the samples that crack within the specified time. Measured by quantity and proportion

.For thermoplastic plastics, under certain temperature and load, the melt will flow through every 10 minutes. Weight passing the standard port. Expressed by M1, the unit is g/min. ordinary feelings Under the circumstances. The larger the melt index, the better the extrusion fluidity and the lower the required extrusion temperature.

·The ability of plastics to maintain certain physical and mechanical properties at low temperatures is called the cold resistance of plastics. It is often expressed by the following cold-resistant temperatures. Low temperature embrittlement temperature: It is the temperature at which 50% of the samples are damaged when the plastic is subjected to a specific impact load at low temperature. Low-temperature folding temperature: It is the temperature at which the plastic sample is about to break but does not break when it is bent at 180°. Low-temperature impact compression temperature: It is the temperature at which a plastic sample is impacted and compressed by a punch with a certain energy and speed at low temperature, so that the rupture rate reaches 50%.

Basic features

Main performance

type

Type: low density polyethylene, medium density polyethylene, high density polyethylene

characteristic

type Peroxide cross-linking Silane cross-linking Radiation cross-linking UV cross-linking

characteristic: High heat resistance Resistant to environmental aging

Plastic cables and equipment cables are mainly insulated with solid

Solid insulation, foam insulation and skinned foam insulation for plastic communication cables

The thicker the insulation layer, the higher the withstand voltage.

General standards stipulate that the minimum thickness of insulation shall not be less than 90% of the nominal value

Inner sheath

Outer sheath

Inner lining layer: prevents being crushed by the armor layer and resists external corrosion.

Armor layer: prevents mechanical damage and chemical corrosion during laying

Outer sheath: protects the armor layer from mechanical damage and corrosion