29 rankings of plastic properties, recycling and processing

Plastic properties:

density

The ratio of the mass of a plastic to its volume is called density. Common units are g/cm3 or l/m3. Sometimes the ratio of the mass of plastic at 20 ° C to the mass of the same volume of water at 4 ° C is called the relative density of plastic, or specific gravity.

Tensile strength and elongation at break

The plastic sample is stretched at a certain speed, and the maximum tension required when the sample is broken is called the breaking force. At this time, the tensile breaking force on the cross-sectional area of ​​the sample is called the tensile strength. The percentage (%) of the increase in length of the sample when it is broken is called elongation at break, which is called elongation.

The melt flow rate

MFR, also known as melt index MI. The number of grams of molten plastic extruded from a certain cavity every 10 minutes at a certain temperature and pressure. The unit is g/10min.

Oxygen Index

The minimum oxygen concentration required to maintain the flaming combustion of the plastic is expressed in terms of the volume percent concentration of oxygen, the symbol OI or LOI. The higher the oxygen index, the harder it is to burn plastic. Plastics with an oxygen index of less than 21 are flammable materials. Flash point, ignition point and spontaneous ignition point

The temperature at which the plastic is thermally decomposed to generate a flash of flammable gas in contact with an open flame is called a flashing temperature, which is simply referred to as a flash point. The temperature at which a plastic is thermally decomposed to generate a flammable gas and can be ignited by a fire is called a fire temperature, which is simply referred to as a ignition point or a fire point. Make the plastic spontaneously ignite

The burning temperature is called the auto-ignition temperature, referred to as the auto-ignition point. The burning point of plastic is higher than the flash point and the self-ignition point is higher.

Flame retardancy

Plastics are difficult to burn or have the property of retarding or preventing the spread of flame.

Heat deformation resistance

The plastic has the resistance to deformation under the action of high temperature and pressure.

cold resistance

The ability of plastics to maintain the desired mechanical and physical properties at low temperatures is known as cold resistance.

Heat aging resistance

During the processing and use of plastics, the deterioration of plastic properties due to heat is called heat aging. The ability to resist heat aging is called heat aging.

Weather resistance

Plastics are used under atmospheric conditions, and are subjected to harsh natural conditions such as sun, rain, wind, and air pollution. The deterioration of plastic properties is called atmospheric aging.

Volume resistivity

Under the action of an electric field, the volume of a 1 m3 cube of plastic relative to the volume between the two faces is the resistance generated by the leakage current. Common symbol ρ, the unit is Ω. m. In the past, Ω.cm was commonly used as the unit of volume resistivity, and the conversion relationship was 1 Ω. m=100 Ω·cm. Volume resistivity

The higher the insulation, the better.

Environmental stress crack resistance

Some crystalline plastics, due to the presence of internal stresses during processing and exposure to chemicals during use, cause cracking during storage and use, known as environmental stress cracking. The ability to withstand environmental cracking is called environmental stress cracking and can be bent with grooves on the surface.

The sample was placed in the surfactant to measure the number of samples that cracked within a specified time and the proportion of the sample.

Plastic recycling:

Primary return plastic pellet

Refers to the raw materials used are non-landing scraps, also known as undercuts, and some are spouts, rubber heads, etc., the quality is better, not used, the remaining small edges in the process of processing new materials Corner, or recycled plastic pellets that are not of good quality. Use these

The recycled plastic granules processed by the wool material have good transparency, and the quality of the recycled plastic granules can be compared with the new materials, so it is called a first-grade plastic granule or a special-grade plastic granule.

Secondary return plastic pellet

It means that the raw materials have been used once. (Except for high-pressure recycled plastic pellets, most of the imported high-pressure plastic pellets are imported. If the imported large parts are industrial films, they are not exposed to the wind and the sun, so the quality is also very Well, processed recycled plastic particles transparency

Good) At this time, it should be judged according to the brightness of the plastic particles returned and whether the surface is rough.

Three-stage return plastic pellet

Refers to the raw materials that have been used twice or more. The processed plastic pellets are not very good in terms of elasticity and toughness and can only be used for injection molding. The first and second return plastic pellets can be used for blown film, wire drawing and the like.

Spout

Refers to the flow paths, corners and scraps generated by the unqualified products produced during the production of injection molded products.

Machine head

Refers to the leakage material or transition material in the production process of the extruded product and the cleaning material when the injection molding machine is empty.

Sub-material

Plastic raw materials that are unqualified in the synthesis process due to the replacement of grades or varieties.

Submerged material

Refers to materials with a specific gravity greater than 1 g/cm3. This is specifically referred to as a mineral-filled plastic material (polyolefin-based filling).

Floating material

Refers to materials with a specific gravity of less than 1 g / cm3. This refers specifically to plastic materials (polyolefins) that do not contain mineral fillers.

Dead material

A material that is not plasticized after heating. Generally refers to crosslinked thermoplastics. Some places are also called "raw materials."

Bubble material

A pellet of plastic made by a plastic pelletizer. Plastic processing

Weld marks, water marks, lines, and lines

In the process of injection molding, when the two streams meet, the traces caused by the incomplete fusion of the world surface.

Shrinkage, shrinkage

When the plastic parts are cooled and solidified in the cavity, the plastic parts are recessed due to uneven wall thickness, insufficient injection pressure, insufficient cooling time, and the like.

White, white, white, white, high

The plastic part is partially subjected to external pressure, causing some molecular structures to be rearranged or broken, causing partial whitening of the surface of the plastic part.

Surface protrusion, top height, convex height, high height

The plastic part is partially raised due to the out-of-mold or the ejector pin and the top plate acting on the surface of the plastic part.

Warpage, deformation

Partial or overall deformation of the plastic part caused by internal stress.

Color does not match, color difference, color depth, light color, poor gloss

The color and gloss of the plastic parts do not match the standard board.

Poor assembly, tight test, loose test, tight buckle, loose buckle, no noise

Among the components that cooperate with each other, there are problems of large size and small size, which causes problems such as tightness, looseness, and noise during trial assembly. Such problems are collectively referred to as poor assembly.