How much do you know about foaming agents? What should I pay attention to when purchasing foaming agents?
What is a foaming agent?
The so-called foaming agent is a substance that makes a target substance pore. It can be divided into three major categories: chemical foaming agent, physical foaming agent and surfactant. Chemical foaming agents are those which release carbon dioxide and nitrogen gas after being decomposed by heating and form fine pores in the polymer composition; physical foaming agents are foam pores which are changed by the physical form of a certain substance. , which is formed by the expansion of compressed gas, the volatilization of liquid or the dissolution of solid; the foaming agent has high surface activity, can effectively reduce the surface tension of the liquid, and surrounds the air in the double electron layer on the surface of the liquid film. , forming a bubble, and then consisting of a single bubble.
The role of blowing agent
1. A foaming agent is a special polyurethane product in which a polyurethane prepolymer, a foaming agent, a catalyst and the like are filled in a pressure resistant aerosol can.
2. When the material is ejected from the aerosol can, the foamed polyurethane material will rapidly expand and solidify with air or the moisture in the contacted matrix to form a foam.
3. The foam after curing has many effects such as caulking, bonding, sealing, heat insulation and sound absorption. It is an environmentally-friendly, energy-saving and easy-to-use building material, which can be applied to sealing and sealing, filling and filling, fixing and bonding. , thermal insulation, especially suitable for sealing and sealing between plastic steel or aluminum alloy doors and windows and walls.
How to choose a foaming agent?
Commonly used foaming agents are divided into physical foaming agents and chemical foaming agents. A typical physical blowing agent is nitrogen. Using a physical blowing agent, the blowing agent can be injected into the plastic melt by means of a physical blowing agent injection device mounted on the machine.
1. Selection requirements for physical foaming agents
(1) Non-toxic and odorless.
(2) Non-corrosive.
(3) High density.
(4) Non-flammable.
(5) Even local solubility has no effect on the properties of the thermoplastic.
(6) The evaporation rate is fast.
(7) It is thermally stable and has no chemical reaction in the gaseous state.
(8) In the gaseous state, the diffusion rate in the thermoplastic is lower than in the air.
(9) At room temperature, the vapor pressure is low (easy to use).
The chemical blowing agent generally used is composed of azodicarbonamide or other compounds in an amount of 0.3% to 0.7% (mass fraction). The chemical blowing agent powder can be added to the plastic in advance by granulation, or it can be mixed into the plastic before injection molding, or directly mixed into the thermoplastic by a metering device on the machine.
2. Selection requirements for chemical foaming agents
(1) The decomposition is non-toxic and narrow.
(2) The decomposition speed is fast and controllable.
(3) The decomposition product has no candle effect.
(4) It has storage stability.
(5) There is no flaw in the foaming agent and residue.
(6) The residue is colorless and odorless.
(7) Do not release heat during decomposition.
(8) The residue is compatible with the polymer.
(9) Decomposition of residual products has no effect on the properties of the molding material.
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