Press-forming Molded Pulp from Repulped Liquid Packaging Board: Role of Heat Input, Pressing Force, and Defect Formation

Abstract

Laboratory sheets were prepared from repulped liquid packaging board (LPB) for press-forming experiments and tensile tests to study convertibility and mechanical properties of molded pulp material developed from the repulped LPB. Maximum forming depth was utilized as a convertibility indicator, and defect formation in press-formed molded pulp samples was observed with a visual analysis. Female mold temperature and pressing force were altered among press-forming parameters. The results showed that the laboratory sheets had a limited convertibility. The fragile structure of the laboratory sheets was connected to negative effects from the presence of plastic particles in the material. Increased heat input and decreased pressing force improved the convertibility, and the defect formation during the press-forming was aggravated by flattening of the material in flange and bottom regions of the samples. The use of repulped LPB as the raw material in the manufacturing of molded pulp by press-forming was found viable, and the presented solution offers an ecological alternative to conventional recycling of LPB.