Wet Specimen Macro Stickies Measurement Method, 1999 Recycling Symposium Proceedings

Roy Rosenberger

Verity IA LLC

Mahendra Doshi

Doshi & Associates

William Moore

Fox Valley Technical College

A new measurement technique has been developed to measure the concentration of thermoplastic contaminants in the recovered fiber process stream. Plastics, pressure sensitive adhesives, hot melts, and waxes are all classed as stickies and are also thermoplastic. In this method, handsheets and filter papers with screened stickies produced from process samples are dried at under controlled conditions. The time and temperatures are such that that the thermoplastic contaminants melt and flow into the interstices of the surrounding and contacting fiber matrix. When the specimens are re-wet the water acts as a stain on the fibers having no waxy or plastic coating, turning the white filter paper translucent and the brown fibers a dark brown. The areas wet-out by the wax components remain white or light brown and contrast with the surrounding translucent or dark brown wet fibers. An image analysis system able to adjust for varying background intensities measures the white and light brown areas. Thus, no inks, dyes, special coated paper, or powder are needed to enhance the contrast between thermoplastic contaminants and the ackground. In addition to describing the method, the paper reports on the measurement repeatability using brown fiber waxy contaminants.