| 摘要 |
Low density PET foam is extruded by heating PET resin above the crystalline melt point to melt the resin, selecting a blowing agent combination, combining the blowing agent combination with the PET resin to create a mixture, cooling the mixture to a temperature of less than 538 DEG K., and extruding the foam through a die. The blowing agent combination is characterized by about 50 to less than 100 mole percent of a first blowing agent having a boiling temperature at STP of greater than 310 DEG K. The blowing agent combination is further characterized by more than 0 to about 50 mole percent of a second blowing agent having a boiling temperature at STP of less than 310 DEG K. The blowing agent combination has an equilibrium solubility vapor pressure in PET of less than 45 atm at the foaming temperature and greater than or equal to 1 atm at the glass transition temperature.
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