Research at the Dept. of Mechanical Engineeering at the University of Washington in Seattle has applied CO2 impregnation to microlayer coex films, creating a soft cushioning material like fine bubble wrap. University researcher John Lu presented his work on flexible films for the first time at the SPE ANTEC meeting last month in Milwaukee. In films, the gas doesn’t create micro-bubbles in polymer layers. Instead, it forms relatively large air pockets of delamination between layers. Lu starts with 29-layer film made of alternating layers of cyclic olefin copolymer (COC) and LDPE with surface layers of EMA. He impregnates the film with CO2 under pressure for 10 min, then heats it to 175 F to expand the gas. This creates a thicker film with only 5% to 10% of the density of the original film, but it is still clear and relatively smooth. The voids are oval and measure roughly 0.5 to 1 mm, with hundreds of them per square inch. The 29-layer film was made by BBS Corp., Spartanburg, S.C., using a stack of its patented modular disc dies. MicroGreen Polymers Inc. in Seattle is separately commercializing foamed rigid packaging with a similar CO2 impregnation approach, also developed at the University of Washington. U. Wash.: (206) 543-7504 • E-mail email@example.com BBS: (864) 579-3058 • E-mail: firstname.lastname@example.org
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