Marlex is a trademark name for solid HGX-030-01 polypropylene. This chemical is a type of plastic that is used in a variety of things from Hula Hoops to plastic bottles. Marlex is made using ethylene and propylene with a catalyst of chromium oxide. It was first created in the 1950s by workers at the Phillips Petroleum Company – now the Chevron Phillips Chemical Company. What sets Marlex plastic apart from other plastics is the density it can achieve from relatively little pressure. Most other plastics take thousands of pounds of pressure to squeeze them into soft shapes. Marlex plastic only takes a few hundred pounds of pressure to squeeze it into a rigid shape.