Polystyrene PS
DATE：2022/4/7 8:58:50 / READ： / SOURCE：This station
Polystyrene PS
The two step molding process of PS foam can be divided into two stages: the first is the preparation of EPS, that is, the pre foaming of PS granules, the second is the molding foaming molding, and the high foaming molding products are obtained. EPS can be divided into two stages: the first stage is the preparation of EPS foam particles and the first stage is the preparation of EPS beads. Expandable PS is the raw material for manufacturing EPS, and expandable PS cannot be equal to EPS. PS high hair foam molded products formed by this method have bubble particle bonding traces on the surface. Those with a unit weight of 0.015 ~ 0.020g/cm can be used as packaging materials, and those with a unit weight of 0.02 ~ 0.05g/cm can be used as waterproof and thermal insulation materials; The unit weight of 0.03 ~ 0.10g/m can be used as the core material of lifebuoy and buoy. The physical properties such as impact strength are not as good as the PS one-step molding process of emulsion polymerization. four hundred and fifteen(1) The permeability and storage of the manufacturing agent of soluble B beads is an important problem. Low boiling point hydrocarbons or commercial compounds such as petroleum ether, butane, pentane and isopentane are added to suspension polymerized polystyrene beads as foaming agents. this
If it is stored in the beads, it is expandable polystyrene beads. Under the condition of heating and pressure, the swallow fraction permeates into the polystyrene beads to make them swell. Casting film production line www.handern.com com
The preservation of foaming agent for expandable polystyrene beads is the key problem to be solved in the storage of bead products. Because the expandable polystyrene beads are stored at low temperature for more than one week to one month, the foaming agent in the beads diffuses in the molecular structure and molecular gap, becoming a much smaller and tighter foaming core. Once heated, the foamed core will vaporized and the beads will also expand to form foam plastics. In the storage process, the foaming agent is still diffusing to the outside of the beads, reducing the foaming agent in the beads. The longer the storage time, the less the foaming agent content in the beads. When the foaming agent is reduced to less than 5%, it is not possible to make foamed plastics with light weight. Therefore, the sealing package and the temperature of paper storage after the production of polystyrene beads are serious problems. Casting film production line www.handern.com com
According to the different ways of adding foaming agent, the manufacturing methods of expandable polystyrene beads can be divided into three steps: one-step method, one-and-a-half step method and two-step method. One step is to add styrene, initiator and foaming agent into the reaction pot at the same time, and polymerize in one step to obtain expandable polystyrene beads containing foaming agent. The expandable polystyrene prepared by one-step method has uniform and fine bubbles and good elasticity. Because the foaming agent is added in one step during polymerization, the operation process is simplified. However, when adding foaming agent during polymerization, the foaming agent will inhibit polymerization, so the molecular weight of this polymer is low, generally 40000 ~ 50000. After the reaction, some powdery objects are generated and need to be treated. One step and a half method is to polymerize the monomer styrene to form elastic beads, and then add foaming agent to continue the polymerization until the end. The expandable polystyrene beads thus obtained are basically the same as those of the one-step method, but because the foaming agent is added in the middle of the reaction, the polymerization inhibition is reduced, the operation cycle is shortened, and the molecular weight of the polymer is higher than that of the one-step method. The two-step rule is to polymerize styrene into polystyrene beads, and then screen the obtained polystyrene beads in order to divide the polystyrene beads into different fractions. Add foaming agent into the polystyrene beads of the same fraction and reheat to make the foaming agent penetrate into the beads. After cooling, it becomes expandable polystyrene beads. Obviously, the two-step operation process is the most, and the penetration of foaming agent also takes a long time, but its advantage is that the quality of polymer is improved, and the molecular weight can reach 50000 ~ 60000. The particle control degree is divided into different grades through band selection, which is helpful to improve the quality of products. The production process of expandable polystyrene beads taking the two-step method as an example is shown in Figure 8-9, in which the foaming agent is sent to the high-level metering tank 3 from the storage tank 1 through the re pump 2, and then into the reactor 9. The dispersant is dissolved in the dissolving pot 4 and sent to the reactor 9 through the centrifugal pump 5. Polystyrene beads are fed from hopper 7, sent to cyclone feeder 8 by blower 6, and then added to reactor 9. After the reaction, the expandable polystyrene beads are put into the movable washing car 10 from the bottom of the reactor 9, washed and stored at low temperature, and then sent from the feeding hopper 12 to the dryer 14 by the feeding blower 11, and then bagged by the charging Jane 15 after being dried by the drying blower 13. Casting film production line www.handern.com com
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