Polyethylene (PE)
DATE：2022/4/9 8:46:33 / READ： / SOURCE：This station
Polyethylene (PE)
PE can also be made into pre foamed particles and then molded to obtain high foaming molded products, which is similar to PS. In addition, it also carries out two-step molding and application through other technological processes, the foaming multiple can reach 30 times, and the thickness of formed foaming plate can reach 100mm. The two-step molding foaming of PE is introduced below.(the 1 phase and the S phase are made of expandable polyethylene beads first, then pre foaming, then placed in the locking mold with small holes, and then foaming into the desired shape of the foamed plastics in the steam. The bulk density of the products is about 0.05 g/cm, thus eliminating the two processing steps of the general polyvinyl moulded sheet, and eliminating the generation of the corner waste.
Generally speaking, the processing and molding of expandable polyethylene beads is not as easy as that of expandable polystyrene beads because it requires higher temperature. Breathable membrane production line www.handern.com com
(i) In the manufacture of expandable polyethylene beads, organic peroxide is put into a pressure kettle containing surfactant aqueous solution as a crosslinking agent to dissolve or disperse it into particles. Add inorganic salt that is insoluble in water as dispersant, then add polyethylene particles to suspend them in the aqueous phase, heat the autoclave to 100 ℃, and the crosslinking agent can be impregnated into polyethylene resin. Further heating at high temperature will lead to crosslinking of polyethylene. Add foaming agent into the water suspension of crosslinked polyethylene haolazi (crosslinking degree is about 10% 70%), and then heat it to 130 ℃ to impregnate the foaming agent into polyethylene particles. After cooling, take out the resin puller from the swab: filter, wash and dry to obtain expandable particles. These particles can be put into use with foaming agent. The main raw materials used are as follows: high pressure steam or other ways to heat and foam into pre foamed particles, and then impregnate the breathable membrane production line in the pressure kettle www.handern.com com
① Surfactant. The surfactant solution can be used to dissolve organic peroxide and produce a uniform fine particle state, which is a necessary condition for producing uniform and fine foamed plastics. Otherwise, the crosslinking degree of each polyethylene particle may be inconsistent, the cell of expandable particles will be uneven, and the foaming ability will be weakened. The selection of surfactant shall not significantly hinder the crosslinking reaction and the suspension stability of polyethylene particles. One or both surfactants can be used. Such as non-ionic surfactant polyoxyethylene octyl phenol ether, anionic surfactant sodium dodecylbenzene sulfonate, other amphoteric surfactants and cationic surfactants can be used. Its dosage is generally 5 ~ 50 ℃ of organic peroxide. In addition, organic peroxides can also be dissolved in lower alcohols such as methanol, and then used together with the above surfactants.
② Dispersant. The dispersant is not only used to prevent the resin particles from melting, adhering and caking when the temperature exceeds the melting point of polyethylene, so that the particles are in a stable suspension state, but also makes the crosslinking reaction more rapid through high temperature. Dispersants are inorganic metal salts, such as calcium phosphate and zinc phosphate in phosphoric acid compounds; Aluminum hydroxide in oxyhydrogen compounds; Oxides and phosphorus water compounds. The use amount of dispersant varies with the type of inorganic metal salt, processing temperature, resin category, surfactant category and dosage. Generally, the use amount is less than 1% of the weight of the resin. Breathable membrane production line www.handern.com com
③ Foaming agent. Physical foaming agents such as dichloroethane, chlorobutane, isoprene, methane, etc. can be used, such as dichloroethane, chlorobutane, isoprene, etc. These foaming agents are fluorine foaming agents in gaseous state under normal conditions. In actual use, one foaming agent can be used, or more than two foaming agents can be used at the same time. Its type and dosage depend on the category of resin, crosslinking degree and quality requirements of products. Generally, it is used
④ Crosslinking agent. The crosslinking agent can be diisopropyl peroxide and 2,5-dimethyl-2.5-di TERT, with the amount of 1% ~ 20%.
Butyl hexane peroxide, etc. the dosage is generally 3% of the weight of the resin.
⑤ Polyethylene resin. Polyethylene resin can be pre foamed with LDPE, MDPE and HDPE, cross-linked polyethylene with pre containing agent with particle size of agglomerating beads. It is best to use hot air, water vapor, infrared ray, high service telephone and hot gas that does not melt bubble substances at 100-300 ℃. The initial pre foaming cell rate (multi foaming ratio) obtained is 5-30 times. Put the expandable particles into the pressure tag, and then maintain a certain pressure, temperature and time. The temperature change is maintained at the contact pressure of the expandable particles, and the pressure can completely crush the expandable particles. The curlable particles can be held in the wheat gas of foaming agent gas, regaining gas and more like emotional gas of dioxide. The sequence can be carried out once or repeated several times, depending on the requirements for the final foam washing plastic and the type of haoethylene. Breathable membrane production line www.handern.com com
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