This research addresses re-use of recycled paper mill sludge (RPS), a waste by-product of recycled paper manufacturing. The growth of the paper recycling industry over the past 15 years has led to ecological benefits; however it is estimated that over 9 million tonnes of sludge by-product are produced each year in North America, with limited use in beneficial applications.;Recycled paper mill sludges that represent a significant segment of the recycling industry were used in this work. Sludges were prepared using a novel kinetic de-watering system that dried and fiberized the material. The unique constitution of the dry sludge overcame constraints of failed utilization attempts of the past. Comprehensive physical and chemical characterization elucidated differences in the sludges based on generating process and raw furnish. Differences in organic content, fibre length, inorganic content and fibre chemistry were found to be strongly influenced by the recycling processes. Fibre contained in recycled newsprint manufacturing sludge had characteristics similar to TMP/mechanical fibre, while the fibre contained in recycled tissue manufacturing sludge were more similar to chemically prepared fibre.;Investigation into using the sludge as filler/reinforcing fibre in thermoplastic composites was carried out, as was an investigation into recovering a fibrous fraction for re-use in paper. The viability of using the recovered fibre portion in paper making is limited by its lack of bondability. This is caused by cell wall hornification and lack of bonding surface area resulting from the absence of fibrils. Sludge was incorporated successfully into thermoplastic composites displaying strength properties superior to the polymer matrix material. Flexural strengths were 50% higher, flexural moduli were over 100% higher and tensile moduli were 25--100% higher. Fibrous morphology, non-polar extractives, high volume packing and high intrinsic fibre strength contributed to ease of processability and superior performance. This application warrants further investigation based on economic viability and ecological benefits.
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