The common information and history of Pe Foam
Polyethylene (PE) resin is a crystalline polymer, a linear structure, macromolecular inter-atomic forces when heated to melt is small, high elastic state of temperature range is very narrow, when the resin melt after the melt viscosity is low, so the foam decomposition gas of the foaming agent is not easy to keep in the resin, foaming process more difficult to control;if the PE crystallinity too big, crystallization speed too fast, when change from molten to crystalline state, it will release a large number of crystallization heat, plus the molten PE large heat capacity, cooling to the long time needed for solid state, is not conducive to maintain gas in the process of foaming.In addition, PE resin has a high gas penetration rate, and low density polyethylene (LDPE) is easier to penetrate gas than HDPE, and the easiest gas to penetrate is carbon dioxide (CO2).All these factors contribute to the escape of foaming gases.To overcome the above shortcomings, usually to make mutual crosslinking between the molecules become part of the mesh structure, in order to increase the resin viscosity and slow the viscosity decreases with temperature rise trend, and changing the viscoelasticity of resin and foam to adapt to the requirements.
PE foam can be divided into crosslinking and non-crosslinking.The crosslinked portion accounts for about 50% of the polyethylene foam market and is growing at a rate of 25% a year.Crosslinked PE foam is divided into two processes: radiation crosslinking and chemical crosslinking.If the external pressure is classified according to the decomposition of foaming agent, it can be divided into normal pressure foaming and pressure foaming.The development of foamed polyolefin materials has been a hot topic.Compared with PS and PU foam traditional foaming materials, PE, PP and other polyolefin foaming materials have a short history.
In 1941, a patent for the American dupont company first proposed the preparation of PE foam.Subsequently, Karen cable construction company and other companies also obtained patents to prepare PE foam.
In 1955, dupont produced a low foaming PE.
In 1958, the American chemical corporation first adopted the non-contact extrusion foaming method to realize the industrial production of high foamed PE foam. Currently, the high foaming PE in the United States is still produced by this method.
In the early 1960s, Japanese companies such as sanhe chemical, guhe electric and hydrochemical co., LTD. Successively developed and developed the high foaming PE, and began to produce high-foamed PE products in 1965.
At present, most of the manufacturers are based on the technology developed in Japan. In Europe, the production of PE foam materials has been made in Europe since the 1970s.