Investigation of mechanisms and approaches for improving hydrophobicity of molded pulp biocomposites produced from apple pomace

Cellulose fiber based molded pulp packaging is a sustainable solution to the persistent plastic crisis. This study utilized apple pomace (AP) as a renewable source of fibers and cardboard fibers (CF) as reinforcement material to create molded pulp biocomposites (boards) at AP:CF ratio of 2:1 in 3% solid pulp. For improving water resistance of pomace board, two approaches were employed: 1) incorporating rhubarb pomace (RP), chitosan, and glycerol into pulp formulation, and 2) applying heat resistant, superhydrophobic coatings on the board surface. In addition, composition, water retention value, and morphology of pomace, cardboard and newspaper fibers were evaluated for understanding their interactions and effect on water retention of fiber pulp and quality of derived boards. Response surface methodology was used to optimize pulp formulations based on high water resistance and low board deformation after drying. The optimum pulp formulation consisted of 26.9% w/w of RP, 0.039% w/v of glycerol, and 15.7% of w/w chitosan in the 3% solid pulp. The superhydrophobic coating further enhanced the water resistance of the board. The developed pomace boards were compostable in soil. This study brought new insights for using pomace as alternative fiber to produce water resistant and compostable packaging for various applications.