Hemp as Bio Fiber Material for Board Paper Applications: Laboratory Evaluation of Handsheets

Abstract

Hemp (Cannabis sativa L.) is one of the oldest fibre crops used in papermaking, predating wood pulp by centuries, and its renewed legal status under the 2014 and 2018 U.S. Farm Bills has revived interest in it as a sustainable papermaking fibre. This study evaluates Hemp fibre as a partial or full replacement for Old Corrugated Container (OCC) recycled fibre in handsheet manufacturing. Hemp stems from Cornell University were processed using two laboratory refining methods - a Kumagai Riki Kogyo Co. (KRK) pressurised refiner and a Sprout Bauer Laboratory Refiner (SBLR) - followed by screening, beating to a common 450 mL Canadian Standard Freeness, and handsheet formation at a target basis weight of 70 g/m². Blends ranging from 100% OCC to 100% Hemp, in 10% increments, were tested for mechanical, structural, and optical properties in accordance with TAPPI standard methods. The results show that the two refining routes yield markedly different fibre characteristics: KRK-refined Hemp produces denser, less porous sheets with a higher tensile index, whereas SBLR-refined Hemp yields more open, porous sheets with superior burst, tear, and zero-span tensile strength. Blending Hemp into OCC substantially improves tensile index and brightness even at low Hemp content, with an apparent optimal reinforcement window around 20–40% Hemp; beyond roughly 50–60% Hemp, tensile index, elongation, and tensile energy absorption drop sharply and then plateau. Opacity remained near 100% across all blends, brightness increased steadily with Hemp content, and CIE whiteness showed a non-monotonic dip at intermediate ratios. These findings indicate that Hemp is a viable supplementary fibre for recycled paperboard, with the pulping route selected according to target end-use properties, pending further pilot-scale validation.