All the plastic properties
Specific gravity (density)
The specific gravity of the plastic is the ratio of the weight of the sample to the weight of the same volume of water at a certain temperature, the unit is g/cm3, and the liquid buoyancy method is commonly used for the determination method.
Tensile strength means that a tensile load is applied along the longitudinal axis direction of the sample at a predetermined test temperature, humidity, and tensile speed, and the maximum load at the time of failure of the sample is measured.
Bending strength refers to the strength at which the specimen is subjected to a concentrated load on two fulcrums to deform the specimen or until it breaks.
Impact strength refers to the Joule consumed per unit area when the specimen is broken by impact. For some plastics with high impact strength, the gap of the specified size is often opened in the middle of the specimen, which can reduce the need for it when it is broken. joule. (Test method: falling ball impact test, high speed tensile impact test)
Molding shrinkage refers to a molded product that is demolded after cooling in a mold, and must be shrunk, that is, the molded article is smaller than the cavity size.
Plastic hardness refers to the performance of plastic against other hard objects. Commonly used are Rockwell hardness and Shore hardness.
Creep is the characteristic that the plastic exhibits with time under the constant external force of a certain temperature and humidity. The characteristic of this deformation increases with increasing load, and decreases with the decrease of load. It has gradually recovered. Sources of creep are tensile creep, compression creep, bending creep, and the like.
The water absorption of plastic refers to the amount of water absorbed by the sample of the specified size when it is immersed in distilled water at a certain temperature (25±2) °C, after 24 hours; the size and shape of the sample are affected by the absorption of water, and the water absorption rate is expressed by weight. , often expressed in %.
Gas permeability refers to the volume (cm3) of gas permeated within 24 hours of a certain thickness of a plastic film under an atmospheric pressure, but the gas permeability and thin wax thickness, area, time, temperature , the air pressure difference and so on.
Moisture permeability refers to the transmission of water vapor to a plastic film. The basic principle and definition are the same as the gas permeability.
The ratio of the luminous flux through the object to the luminous flux incident on the object is called the transmittance; the ratio of the scattered light in the direction of the incident light to all transmitted light, called haze or turbidity. The haze is usually translucent, It has a diffuse nature to the incident light.
Coefficient of friction
The friction coefficient refers to the ratio of the frictional force to the positive pressure. A positive pressure is applied to the sample to measure the dynamic and static ratio of the rigid motion of the sample.
Abrasion refers to the mechanical destruction process in which the particles are continuously separated from the friction surface during the friction process, causing the size of the friction member to change continuously, also known as wear or abrasion.
It refers to the strength of plastic damage in an environment with static destructive force and a small amount of alternating circulation; the source of fatigue load is tensile, bending, torsion, impact and so on.
Durable strength is a function of the time at which a plastic's ability to withstand static loads for a long period of time is reduced. For example, the strength of the plastic before the load is 1000 hours, and the load may be only between 50% and 70%.
Linear expansion coefficient
The coefficient of linear expansion refers to the number of centimeters of plastic per centimeter of elongation when the temperature rises by 1 degree Celsius. The linear expansion coefficient of plastic is generally about ten times that of steel.
Specific heat refers to the amount of heat required when 1 gram of plastic is raised by 1 degree Celsius.
Thermal conductivity refers to the amount of heat that a piece of plastic per unit area and thickness can pass. The thermal conductivity of plastic is very small, only about one percent of steel, so it is a good thermal insulation material.
Glass transition temperature
The temperature at which the plastic is reduced from the melt flowable temperature to the solid state is called the glass transition temperature. At this time, the molecular segment is substantially incapable of moving, and the internal rotation of the link is also fast and fast, and only a little movement between the atoms is stretched and ordinary. The elastic deformation, so the plastic at this time will be very brittle.
When pressure is applied to a plastic at a low temperature, it breaks under a small deformation, and this temperature is the embrittlement temperature.
The decomposition temperature refers to the temperature at which the macromolecular chain breaks when the plastic is heated, and is one of the indicators for identifying the heat resistance of the plastic; when the temperature of the melt exceeds the decomposition temperature, most of the melt will have a yellowish color, and the product The intensity will be greatly reduced.
Melt Index (MFI) MI refers to the weight of the melt flowing through the orifice of the tester in a 10 minute period of the thermoplastic at a certain temperature and pressure, expressed in grams per 10 minutes.
Plastic heat resistance is a characteristic that reflects the relationship between the temperature of a plastic part and the amount of deformation. Heat resistance is more important for temperature-related plastic parts.
The flammability of plastics is expressed by the ratio of the burning rate (the burning length of the sample during the burning time) to the burning weight loss rate (the percentage of the difference between the weights before and after the burning), from the ignition time to the spontaneous combustion time and the extinguishing time. Can be used as a reference for resistance to combustion.
The voltage is quickly raised to a certain limit value and stays for a period of time. The plastic sample is broken down, and the voltage value at this time is said to be the withstand voltage that the sample can withstand.
The aging resistance of plastics refers to the destruction of chemical structure caused by external factors such as light, heat, oxygen, water, biology, stress, etc. during use, storage and processing, which leads to a decrease in the original excellent performance. phenomenon. The aging of plastics is studied to improve its stability and extend its service life.
The chemical resistance of plastics refers to whether the plastic is corroded in the chemical medium. The basis for the evaluation is usually the degree of change in weight, volume, strength, color, etc. of the plastic in the medium after a certain period of time.