Enhancing the barrier performance of paper derived from Broussonetia papyrifera L. fibers through a spray coating process

Paper derived from Broussonetia papyrifera L. fibers is a promising sustainable substrate for packaging applications; however, its inherently poor oxygen and water vapor barrier properties limit its practical use. Herein, a spray-coating approach was employed to fabricate multilayer coatings on paper using biodegradable bioplastics for enhanced barrier performance. The multilayer architecture comprised a paper substrate derived from Broussonetia papyrifera L. fibers, a cellulose nanofibril (CNF) interlayer, and outer coatings of poly(propylene carbonate) (PPC), polyhydroxyalkanoates (PHAs), and their blends. The CNF interlayer suppressed coating penetration into the porous paper structure and improved coating uniformity, enabling the formation of continuous multilayer coatings with improved surface integrity. Compared with uncoated paper, all coated systems exhibited enhanced mechanical properties, as well as improved oxygen and water vapor barrier performance. Differences in bioplastic composition influenced coating morphology and thermal behavior, while the blend systems provided balanced barrier functionality. These results demonstrate that the developed multilayer coating strategy provides an effective and practical approach for enhancing the functional performance of cellulose-based paper materials. Importantly, this work establishes a foundational pathway for the production of bioplastic-coated paper, highlighting its strong potential for commercialization through the integration of bioplastics with paper-based substrates. However, a complete transition from conventional organic solvent–based systems to environmentally benign, non-toxic solvent systems remains an important objective for future development.