Inventory of the four major properties of plastics: physical, mechanical, aging and thermal properties

Inventory of the four major properties of plastics: physical, mechanical, aging and thermal properties

01

physical properties

1. air permeability

Air permeability is expressed by air flow rate and air permeability coefficient. Air permeability refers to the volume of gas permeated by a plastic film of a certain thickness in an area of 1 square meter under 0.1MPa pressure in 24 hours. The air permeability coefficient is the amount of gas permeating the plastic film per unit area and unit thickness per unit time and unit pressure.

2. moisture permeability

Moisture permeability is expressed by moisture permeability and moisture permeability coefficient. Moisture permeability is the mass (g) of water vapor permeated by 1 square meter of film within 24 hours under the condition of constant vapor pressure difference on both sides of the film and film thickness. The moisture permeability coefficient is the amount of water vapor permeating the film per unit area and thickness per unit time and under unit pressure difference.

3. water permeability

The determination of water permeability is to directly observe the water permeability of the test sample with the naked eye after a certain period of time under the action of a certain water pressure.

4. water absorption

Water absorption refers to the amount of water absorbed by a sample of a specified size immersed in distilled water at a certain temperature after a certain period of time.

5. Relative Density and Density

At a certain temperature, the ratio of the mass of the sample to the mass of the same volume of water is called the relative density. The mass of a unit volume of a substance at a specified temperature is called density, and the unit is kg/m3, g/m3 or g/mL.

6. Refractive index

The ratio of the sine of any angle of incidence to the sine of the angle of refraction when light enters the second medium from the first medium (except direct incidence).

7. Transmittance

The transparency of plastics can be expressed by light transmittance or haze.

Light transmittance refers to the percentage of luminous flux passing through a transparent or translucent body to its incident luminous flux. The light transmittance is used to characterize the transparency of the material, and the measuring instrument used is a total light transmittance measuring instrument, such as a domestic integrating sphere A-4 photometer.

Haze refers to the cloudy or cloudy appearance caused by light scattering inside or on the surface of transparent or translucent plastics, expressed as a percentage of forward scattered luminous flux to transmitted luminous flux.

8. luster

Gloss refers to the ability of the surface of an object to reflect light, expressed as a percentage (gloss) of the amount of light reflected by the sample in the direction of regular reflection relative to the amount of light reflected by the standard surface.

9. Molding shrinkage = molding shrinkage x 100%

02

mechanical properties

1. tensile properties

Tensile strength, elongation at break, tensile elastic modulus, Poisson's ratio, strain, tensile stress-strain curve

2. Impact performance

(1) Izod beam impact strength Izod beam impact test is to use the cantilever beam impact testing machine. Under the specified standard test conditions, an impact load is applied to the sample clamped by the vertical cantilever to rupture the sample. The unit of sample is The work consumed by the width is a way to characterize the toughness of a material.

(2) Charpy impact strength The Charpy impact test is to use a Charpy impact testing machine to apply an impact force to the sample placed horizontally and supported at both ends under the specified standard test conditions to rupture the sample and A method of characterizing the toughness of a material by the work consumed per unit cross-sectional area of the sample.

3. compression performance

Including compressive stress, compressive strain, compressive deformation, compressive load-deformation curve, compressive yield stress, compressive bias yield stress, compressive strength, slenderness ratio, compressive modulus

4. Bending properties

The bending performance of engineering plastics is one of the important properties to measure plastics under bending load, which is divided into deflection, bending stress and bending strength

5. shear performance

(1) Interlaminar shear strength The relative sliding between adjacent layers of fiber reinforced plastics along the direction of parallel layers is called interlaminar shear, and the resistance to shear stress generated by interlaminar shear is called interlaminar shear strength .

(2) Stamping shear strength The shearing that occurs when shear stress is applied to laminated materials in the vertical lamination direction is called stamping shear, and the ability to resist the shear stress generated by stamping shear is called stamping shear strength . For plastic sheets reinforced with glass fiber fabrics, this strength is also called broken grain shear strength, and for plastics reinforced with chopped glass fibers, it is called shear strength.

(3) The shear strength of rigid microporous plastics is the shear force per unit shear area when the rigid microporous plastics are damaged under shearing action, which is called the shear strength.

6. hardness

Hardness refers to the plastic's ability to resist indentation, scratching or rebound by other materials or objects. Hardness is a conditional quantitative reflection that characterizes the degree of softness and hardness of materials. It is not a purely definite physical quantity, but a comprehensive performance parameter composed of mechanical properties such as plasticity, elasticity and toughness of materials. The hardness of engineering plastics is not only related to the characteristics of the material itself, but also depends to a large extent on the test conditions and measurement methods.

7. Tear resistance

Tear resistance of plastics is a measure of how well soft or thin film plastics resist tearing forces. Methods for measuring the tear resistance of plastics include the Elmendorf tear method, the trouser tear method, and the flexible foam plastic tear method.

8. Fatigue performance

Fatigue performance refers to the process of local structural changes and internal defect development caused by materials subjected to alternating cyclic stress or strain, which reduces the mechanical properties of materials and eventually leads to cracks or complete fractures.

03

thermal performance

1. load heat deflection temperature

Load heat deflection temperature refers to the temperature at which the bending deformation of a rectangular plastic sample of a certain size reaches a specified value under the action of a static bending load of a three-point simply supported beam when it is immersed in a heat-conducting medium that heats up at a constant rate.

2. Vicat softening point

Vicat softening point refers to the temperature at which a flat thimble with a specified load and a cross-sectional area of 1mm2 is placed on the sample under the condition of constant temperature rise. Kind of Vicat softening point.

3. Martin heat resistance temperature

The Martin heat resistance temperature refers to the temperature at which the sample is bent and deformed in a constant temperature rising environment under a certain bending moment, and the sample reaches the specified deformation.

4. Melt mass flow rate and melt volume flow rate

Melt mass flow rate (MFR) and melt volume flow rate (MVR) refer to the mass or volume of a thermoplastic material passing through a specified standard die every 10 minutes at a certain temperature and pressure. It used to be called melt index, commonly known as melt index, also known as melt flow index. The melt mass flow rate is expressed in g/10min, and the melt volume flow rate is expressed in cm3/10min.

5. glass transition temperature

The process of amorphous or semi-crystalline or non-crystalline polymers from viscous fluid state or high elastic state to glass state or reverse transition is called glass transition, and the temperature at the approximate midpoint of the narrow temperature range in which glass transition occurs is called It is the glass transition temperature, usually expressed in Tg.

04

Aging performance

Aging refers to the phenomenon that the performance of plastics deteriorates over time due to external factors such as light, heat, oxygen, water, organisms, and stress during use, storage, and processing. It mainly includes the following parts:

1. Weather aging is a phenomenon in which the performance of plastics deteriorates over time when they are exposed to the outdoors.

2. Artificial climate aging The phenomenon that the performance of plastics deteriorates over time when exposed to artificially simulated climate conditions.

3. Hot air aging The phenomenon that the performance of a plastic sample deteriorates over time under conditions such as a given temperature and wind speed.

4. Damp heat aging The phenomenon that the performance of plastic samples deteriorates with time under given temperature and humidity conditions.

5. Ozone aging The phenomenon that the performance of plastic samples deteriorates with time under the action of ozone.

6. Mold resistance Plastic resistance to mold.