Inferring hydrogen bonding in extracted microcrystalline cellulose from coffee cups and their impact on tensile properties of poly(methyl methacrylate)/poly(urethane): Study of potential application through durability

. Disposable coffee paper cups (DCPCs) represent an important post-consumer by-product that requires recycling methods due to t he difficulty of separating cellulose fibers from polymeric lining . In this work, microcrystalline cellulose (MCC) was successfully extracted from DCPCs through environmentally friendly pretreatments, followed by acid hydrolysis with sulfuric acid and citric acid for 30, 60, and 90 min, to obtain CCS and CCC particles, respectively. The influence of hydrolysis conditions on polymorphism, crystallinity, hydrogen bonding, morphology, and reinforcing capability in poly(methyl methacrylate)/castor-oil-based poly(urethane) (PMMA/PU) interpenetrating polymer networks (IPNs) is investigated. Structural analyses revealed high cellulose II content (up to 93.8%) and crystallinity values ranging from 52 to 95%, depending on the hydrolysis route. Analyses confirmed ribbon-like fibrillar morphologies with nanometric equivalent hydrodynamic diameters ranging from 58 to 80 nm. Hydrogen bond analysis demonstrated that citric acid promoted intermolecular interactions, whereas sulfuric acid generated combined intra/intermolecular interactions. The incorporation of 0.1 wt.% compared to 0.5 wt.% significantly improved the tensile properties of PMMA/PU IPNs, achieving tensile strengths up to 5.08 MPa and enhanced Young´s modulus compared with unfilled systems. The accelerated weathering test demonstrated that MCC polymorphism and crystallinity strongly influenced durability and mechanical retention. The results demonstrate that waste-derived MCC from DCPCs can act as an effective, sustainable reinforcement for PMMA/PU IPNs, which are unsuitable for outdoor applications but intended for indoor panelboard applications.