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Heat After floating in the first buoyancy test, the conglomerate of small plastic pieces consists of low density polyethylene (LDPE), high density polyethylene (HDPE), and polypropylene (PP). The mixture is heated to above 450°F in a heated holding container. The extreme heat causes the HDPE to convert to LDPE. This is because hydrogen atoms escape from the HDPE, adding "space" to the plastic at the molecular level. This empty space causes it to become the less dense LDPE. The mixture now consists solely of LDPE and PP. |