Some terms for plastic raw materials are as follows:
1, melting point and freezing point
The temperature at which a substance is at equilibrium under its vapor pressure is called the melting point or freezing point. This is due to the regular arrangement of atoms or ions in the solid due to temperature rise, thermal motion becoming messy and activated, forming a phenomenon of irregularly arranged liquids, and the opposite process is solidification. The temperature at which a liquid becomes a solid is often referred to as a freezing point or a freezing point, and differs from the melting point in that heat is released rather than absorbed. In fact, the melting point and freezing point of the substance are the same.
2. Density and relative density
Density refers to the mass contained in a unit volume of a substance, in short, the mass to volume ratio, in units of megagrams per square meter (Mg/m3) or kilograms per square meter (kg/m3) or grams per centimeter. 3 (g/cm3). Relative density, also known as density, refers to the ratio of the density of a substance to the density of a reference substance under their respective specified conditions, or the mass of a volume of material at t1 and the equivalent volume of reference material at t2. The ratio of mass at temperature. A commonly used reference material is distilled water and is represented by Dt1/t2 or t1/t2 as a dimensionless amount.
3, the melting point range
Refers to the temperature range from the start of melting of the material to the full melting as determined by capillary method.
4, crystallization point
Refers to the phase transition temperature of a liquid that changes from a liquid to a solid during cooling.
5, pour point
One of the indicators that indicate the nature of liquid petroleum products. Refers to the temperature at which the sample is cooled under standard conditions to the point at which it begins to stop flowing, that is, the lowest temperature at which the sample can be poured while cooling.
6, boiling point
The temperature at which a liquid is heated to boil and become a gas. Or the temperature at which the liquid and its vapor are in equilibrium. In general, the lower the boiling point, the greater the volatility.
7, boiling range
In the standard state (1013.25hPa, 0 ° C), the distillate volume within the temperature range specified by the product standard.
8, sublimation
A solid (crystalline) substance is directly converted into a gaseous state without passing through a liquid state. Such as ice, iodine, sulfur, naphthalene, camphor, mercury chloride, etc. can be sublimated at different temperatures.
9, evaporation rate
Evaporation refers to the phenomenon of gasification that occurs on the surface of a liquid. The evaporation rate, also known as the evaporation rate, is generally judged by the boiling point of the solvent. The fundamental factor determining the evaporation rate is the vapor pressure of the solvent at this temperature, followed by the molecular weight of the solvent.
10, vapor pressure
The vapor pressure is an abbreviation for saturated vapor pressure. At a certain temperature, the liquid and its vapor are in equilibrium, and the equilibrium pressure at this time changes only due to the nature of the liquid and the temperature, which is called the saturated vapor pressure of the liquid at that temperature.
11, azeotrope
The constant boiling point mixture formed by two (or several) liquids is called an azeotropic mixture, and refers to a mixed solution in which the composition of the gas phase and the liquid phase are in the same state under equilibrium. The corresponding temperature is called the azeotropic temperature or the azeotrope.
12, refractive index
The refractive index is a physical quantity that represents the ratio of the speed of light in two different (isotropic) media. The speed of light varies from medium to medium. When light enters another transparent medium of different density from a transparent medium, it changes in the direction of its progress because it changes in speed, so it is called refraction.
The sinusoidal ratio of the sine to the angle of refraction of the angle of incidence of the light, or the ratio of the velocity of the light as it passes through the vacuum and through the medium, is the refractive index. The refractive index n generally indicated is the value of light entering any medium from air. The refractive index usually referred to is sodium yellow light (D line), measured at tC, so it is represented by ntD, and if measured at 20 ° C, it is n20D.
13, flash point
The flash point, also known as the flash point, is one of the indicators of the nature of flammable liquids. It refers to the lowest temperature at which a mixture of vapor pressure and air heated by a flammable liquid onto the surface of the liquid is in contact with the flame. Flashing is usually a light blue spark that flashes off and cannot continue to burn. Flash fire is often a precursor to a fire. The flash point is measured by an open cup method and a closed cup method. Generally, the former is used for measuring a high flash point liquid, and the latter is used for measuring a low flash point liquid.
14, the ignition point
The ignition point, also known as the fire point, is one of the indicators of the nature of the flammable liquid. It refers to the lowest temperature at which the vapor and air mixture heated to the surface of the flammable liquid contacts the flame and immediately ignites and continues to burn. The flammable liquid has a burning point higher than the flash point of 1 to 5 °C. The lower the flash point, the smaller the difference between the flash point and the flash point.
15, spontaneous ignition point
The lowest temperature at which a flammable substance can cause a fire without contact with an open flame is called an autoignition point. The lower the self-ignition point, the greater the risk of fire. The spontaneous ignition point of the same substance varies with pressure, concentration, heat dissipation and other test methods.
16, the explosion limit
When a combustible gas, a flammable liquid vapor or a flammable solid dust is mixed with air or oxygen to a certain concentration range under a certain temperature and pressure, an explosion may occur when a fire source is encountered. This certain concentration range is called the explosion limit or the combustion limit. If the composition of the mixture is not within this certain range, the energy supply will be large and will not catch fire.
Vapor or dust is mixed with air and reaches a certain concentration range. The lowest concentration at which a fire source will burn or explode is called the lower explosion limit; the highest concentration is called the upper explosion limit. The explosion limit is usually expressed as a percentage by volume of vapor in the mixture, ie % (vol); dust is expressed in mg/m3 concentration. If the concentration is below the lower explosion limit, the open flame will not explode or burn because the air accounts for a large proportion of the flammable vapor and dust concentration.
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