2022.06.02
Expandable polystyrene (EPS), also known as expandable polystyrene, is a polystyrene resin with a small relative density (1.05g/cm3), low thermal conductivity, and low water absorption. It has the advantages of high efficiency, low impact resistance, heat insulation, sound insulation, moisture resistance, vibration resistance, good dielectric properties, etc. . With the rapid development of the global economy, the consumption of Styrofoam is also increasing.
This kind of waste polystyrene foam material is small in size, light in weight, anti-aging and not easy to corrode. It is a major problem in garbage disposal. In recent years, the recycling of foamed polystyrene has become one of the focuses of the industry. .
Preparation process:
There are two ways to prepare EPS particles:
1. One-step dipping process (or called one-step method). First add styrene monomer, foaming agent, dispersing agent, water, foaming agent (usually pentane and butane) and other auxiliary agents into the reaction kettle, and polymerize to obtain resin particles containing foaming agent, then wash, Centrifugal separation and drying to obtain polystyrene particles with good foaming properties;
2. Two-step impregnation process, referred to as two-step method, is to polymerize styrene monomer into polystyrene beads of a certain particle size in a reaction kettle, classify and sieve, and then add water, emulsifier and foaming agent. And other additives, heated and impregnated in a reaction kettle to form an expandable polystyrene bead product. The process has the advantages of simple process, less investment, better energy-saving effect than the two-step method, and good energy-saving effect. In foreign countries, the production process of expandable polystyrene mainly adopts the suspension method.
Molding:
There are also two main molding methods for EPS:
1. Extrusion route, that is, direct hot extrusion after foaming of EPS particles, which is often used to manufacture sheets and films;
2. Molding route: First, pre-expand the EPS particles by 30~50 times with 100 ℃ air (or water vapor), then let them mature for 24 hours, and then put the mature particles into aluminum or cast In the mold, after being heated by air (or water vapor) at 115~120°C, the surfaces of the particles fuse with each other while the material expands to form a foam part, and the heat energy causes the particles to fuse with each other to form a foam part.
EPS products are generally safe and non-toxic, but the raw materials are in different states during processing, and there are certain risks. Respiratory and skin can be irritated by polystyrene powder. Stored EPS pellets release pentane vapor, a gas that burns very easily and forms an explosive mixture with air. When heated, polystyrene polymers release styrene monomer, which is a dangerous substance.
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