CHARACTERIZATION OF A CARDBOARD RECYCLING FACILITY'S PLASTIC WASTE FOR BENEFICIAL USE

Tova Sardot, The University of Montana

Abstract

An issue with old cardboard container (OCC) recycling is the generation of a plastic waste that currently either gets land-filled or burned. A Wandel screen, a common process unit, generates 35% of overall rejects that contain 75% of the facility's total plastic output. Plastic-rich Wandel wastes have not been well characterized. This study evaluated the plastic waste stream for engineering new, second-life products. Wandel wastes were composed typically of hot melt adhesives (37%), polypropylene (32%), polyethylene (17%), and polystyrene (9%). Proportions varied 10% or less in each polymer category. The plastic waste was compounded, milled and injection molded into test specimens. Differential scanning calorimetry (DSC) analysis showed that the polymers exist generally in separate phases. Thermal gravimetric analysis (TGA) determined that the onset degradation (405°C) of the mixed stream is an average of its components. In tensile tests, the mixed plastic waste stream performed comparably to its starting materials (tape, hot melt glue, thin film, etc.) with a modulus of 9.6 MPa, ultimate strength of 8.7 MPa, and toughness of 52.6 J. After initial characterization, the material was compounded with wood flour (WF), cement, ash and maleated polyethylene (MAPE). WF and MAPE increased the tensile modulus by 65%, ash and cement increased moduli by 49% and 39%. All additives decreased error in breakage indicating an increase in internal compatibilization. MAPE decreased crystallinity and compatibilized both mixed polymers and additives. Samples were characterized by DSC and TGA. Additives decreased phase separation. TGA analysis showed wood flour, ash, cement and MAPE thermally stabilized the plastics. These improvements make this mixed plastic waste more attractive for reuse.