Wuhan Handern Foaming Agent
日期：2020/11/27 9:21:45 / 閱讀： / 來源：本站
Wuhan Handern Foaming AgentBlowing agent is a kind of material that can make plastic in a liquid or plastic state within a certain viscosity range form a microporous structure. They can be solid liquid into gas. According to the way the pores are generated in the foaming process, it can be divided into physical foaming agents and chemical foaming agents. www.www.dressup9x.com Hollow Profile Sheet Equipment
1. Physical foaming agent
The foaming process relies on changes in its physical state to achieve the purpose of foaming. Such substances include: ①Compressed gases: such as N2, CO2, etc., when the pressure is reduced, the gas expands to create pores in the plastic ②Volatile liquids: such as low boiling point aliphatic hydrocarbons, halogenated aliphatic hydrocarbons and low boiling point alcohols, ethers, Ketones and aromatic hydrocarbons, etc., they are heated and vaporized to produce pores in the plastic; ③ Soluble solids: such as water-soluble inorganic salts, water-soluble polymers and starch, etc., leave voids when they are washed away from the plastic. www.www.dressup9x.com Hollow Hollow Profile Sheet Equipment
1 The selection points of physical blowing agent
An ideal physical blowing agent must meet the following requirements.
(1) Tasteless, non-toxic, non-flammable, non-corrosive; colorless or light-colored;
(2) Do not damage the physical and chemical properties of plastics;
(3) The vapor must be thermally stable and chemically friendly;
(4) It must have a low vapor pressure at room temperature;
(5) It has a faster evaporation rate, that is, lower specific heat capacity and latent heat of evaporation;
(6) Small molecular weight and high relative density;
(7) The diffusion rate through the polymer membrane into the air during gasification should be slow;
(8) The source is sufficient and easy to obtain, and the product is inexpensive.
The boiling point of volatile liquids should generally be below 110°C.
2 Commonly used physical foaming agents
Physical blowing agents are mainly aliphatic hydrocarbons, substituted aliphatic hydrocarbons and aliphatic alcohols, ethers, and ketones. A mixture of aliphatic hydrocarbons containing various isomers of C5 to C7 separated from low petroleum fractions is called petroleum ether in industry. Because of its low toxicity, low price, but flammability, it is mainly used for styrene foam plastic. Halogenated aliphatic hydrocarbons are non-combustible and have good foaming properties, but are toxic. Among them, chlorinated aliphatic hydrocarbons are commonly used in PVC, PS, PUR; and fluorinated aliphatic hydrocarbons are often used in PS, CA, and PE because they are close to the requirements of ideal foaming agents. , PP, PVC, PUR, EP, UF, PF and other plastic foaming. www.www.dressup9x.com Hollow Hollow Profile Sheet Equipment
2. Chemical foaming agent
Plastic foaming is the by-product gas of molecular chain extension or cross-linking when the polymer itself is plasticized by heat, or by the chemical foaming agent (heat-sensitive inorganic or organic compound) added to the plastic due to heat at a certain temperature. Decompose to produce one or more gases, thereby promoting plastic foaming. The former is such as polyurethane, and the latter is the content to be discussed in this section.
1. Key points for choosing chemical blowing agent
An ideal chemical blowing agent should have the following requirements:
(1) The temperature of the gas produced by decomposition must be within a certain narrow temperature range;
(2) The gas release should be appropriately fast, and the gas generation rate should be controlled;
(3) The released gas should be non-corrosive, N2 is the best, CO2 is also possible, NO2 is not good because of corrosiveness;
(4) It should be easy to disperse in plastic, and the one that is miscible is better
(5) Low price, stable storage and non-toxic;
(6) The decomposition residue should be free of bad smell, colorless, non-toxic, non-polluting, and should not affect the physical and chemical stability of the plastic;
(7) There should not be a lot of heat during decomposition, which will not affect the melting rate and solidification of the plastic;
(8) It should have the same effect when it is closed and formed, that is, its decomposition rate should not be affected by pressure;
(9) The decomposition residue should be compatible with the plastic, that is, no blooming of the residue will occur. www.www.dressup9x.com Hollow Hollow Profile Sheet Equipment