Foam surfaces roughened with pockmarks left by gas bubbles are usually considered a cosmetic fl aw.

Foam surfaces roughened with pockmarks left by gas bubbles are usually considered a cosmetic fl aw. But some fi lms need a rough surface for anti-slip properties An unusual approach to roughening the surface of polyolefi n fi lms uses a foaming agent dissolved in one of three layers of a coex blown fi lm. As the melt leaves the die, gas bubbles form in that layer. As the bubble begins to blow up, weak areas in the foamed layer stretch and crack, allowing gas to escape. This creates a mesh-like surface when the bubble is fully expanded. The film division of Huhtamaki in Forscheim, Germany, developed the technology (U.S. patent application #19 953 707.0, June 2005) and commercialized it four years ago for anti-slip wrap for large items and anti-slip sheets for pallets to keep heavy loads from slipping during shipping. It's also used for anti-slip surface film on selfadhesive roofi ng membranes. Unlike typical granulated bitumen roofi ng membranes, the foamed film withstands high ambient temperatures and creates no loose surface particles. Tel: +49 (9191) 81-448 /-249 . www.huhtamaki.com