From Textile Waste to Packaging Board: Pilot-Scale Evaluation of Denim Fibers in Recycled OCC Furnish—Part II (Continuous Production on a Laboratory Fourdrinier Paper Machine)

Abstract

Growing consumer demand for plastic-free packaging and tightening environmental regulations are driving the paper industry toward alternative, recycled fibre sources. Post-consumer textile waste, particularly 100% cotton denim, represents an underused fibre resource. This study evaluated the use of jeans denim fibres (JDF) as a partial replacement for old corrugated container (OCC) fibre in recycled board production on a 12-inch (304 mm) laboratory Fourdrinier Paper Machine (LFPM) at SUNY-ESF. Denim pieces were disintegrated in a Sprout Bauer laboratory refiner, screened through a 150 µm screen plate (87.5% usable fibre yield), and refined in a Valley beater to 450 mL CSF. OCC was pulped and refined to 440 mL CSF in a conical Jordan refiner. Board with a target basis weight of 162 g/m² was produced at OCC/JDF ratios of 100:0, 90:10, 80:20, 70:30, and 60:40 without wet-end chemicals. It was tested for structural, mechanical, surface, and optical properties according to TAPPI standards. Increasing JDF content reduced basis weight by 22% and caliper by 25%, whereas air resistance increased by 41%, indicating a denser sheet. Zero-span strength increased by up to 38% and tensile index by up to 24% (MD), confirming the high intrinsic strength of the denim fibres. Short span compression index peaked at 10–20% JDF. In contrast, elongation and tensile energy absorption decreased by up to 56% and 64%, respectively, at only 10% JDF and did not recover. Burst index declined by up to 32%. Together, these results describe a stronger but more brittle sheet. Optical properties improved consistently: brightness increased by 37%, CIE whiteness improved by 55%, and red and yellow tints decreased, with most gains reached by 20–30% JDF. Overall, a 10–20% JDF substitution offers the most balanced combination of compression strength, surface smoothness, and appearance. However, the early loss in toughness may limit higher JDF use in impact-sensitive applications unless offset by refining or additive strategies.