Low density polyethylene is also called high pressure polyethylene, often abbreviated as LDPE. Milky white, odorless, odorless, non-toxic, matte wax-like particles, it is the lightest variety among polyethylene resins. Low-density polyethylene can be divided into high-pressure method and low-pressure method according to the polymerization method. According to the type of reactor, it can be divided into a kettle method and a tube method. Ethylene is used as the raw material and sent to the reactor. The polymerization reaction is carried out under high pressure compression under the action of the initiator. After the unreacted ethylene is removed from the reactor through the separator, it is melt-extruded and pelletized, dried, and mixed Close and send for packing.
The characteristics of low density polyethylene are as follows:
(1) The film is slightly milky transparent and soft. Its strength is lower than HDPE, and its impact strength is higher than HDPE.
(2) Resistant to cold, low temperature and high temperature. Thicker films can withstand sterilization by hot water immersion at 90 ° C.
(3) Good moisture resistance, stable chemical properties, insoluble in general solvents.
(4) It has large air permeability, so the storage period of its contents should not be too long when it is used as packaging for easily oxidized food.
(5) The oil resistance is poor, and the product can be swollen slowly. When packing greasy foods, it will make the food taste halal after long storage.
(6) UV rays and heat will age for a long time, affecting its physical properties and dielectric properties.
(7) The melting point is 110 ~ 115 ℃, and the processing temperature is 150 ~ 210 ℃. If it is in an inert gas, the temperature can reach 300 ℃ and it is still stable. But the melt and oxygen contact easily degrade.
Low-density polyethylene applications: suitable for seasonings, cakes, sugar, candied fruits, biscuits, milk powder, tea, fish floss and other food packaging. Packaging of pharmaceutical products such as tablets and powders, and packaging of fiber products such as shirts, clothing, knitted cotton products and chemical fiber products. Packaging of daily necessities such as washing powder, detergent and cosmetics. Due to the poor mechanical properties of single-layer PE film, it is usually used as the inner layer of a composite packaging bag, that is, the heat-sealing substrate of a multilayer composite film.