The raw material of plastic is synthetic resin, which is extracted and synthesized from petroleum, natural gas or coal cracking. Oil, natural gas, etc. are decomposed into low-molecular organic compounds (such as ethylene, propylene, styrene, ethylene, vinyl alcohol, etc.), and the low-molecular compounds are polymerized into high-molecular organic compounds under certain conditions, and then plasticizers, Lubricants, fillers, etc., can be made into various plastic raw materials. Generally, resins are processed into granules for ease of use. They are usually molded into devices with certain shapes under heating and pressure conditions.
Physical properties of plastics. There are many kinds of physical properties of plastics, the following are only a few that need to be understood for learning toning technology:
1. Relative density: Relative density is the ratio of the weight of the sample to the weight of the same volume of water at a certain temperature, and is an important method to identify raw materials.
2. Water absorption rate: The plastic raw material is made into a sample of specified size, immersed in distilled water with a temperature of (25±2) ℃, and the ratio of the amount of water absorbed by the sample to the raw material after 24 hours. The size of the water absorption determines whether the plastic raw material needs to be baked and the length of the baking time.
3. Molding temperature: The molding temperature refers to the melting temperature of the resin raw material
4. Decomposition temperature: The decomposition temperature refers to the temperature at which the macromolecular chain of the plastic breaks when heated, and is also one of the indicators for identifying the heat resistance of the plastic. When the melting temperature exceeds the decomposition temperature, most of the raw materials will turn yellow, even charred and black, and the strength of the product will be greatly reduced.
Post time: Jun-13-2022