A plant oil-based eco-friendly approach for paper coatings and their packaging applications

Abstract

The use of plant oil-coated paper could provide a greener approach to develop packaging materials in contrast to reliance on synthetic polymer-coated paper such as that coated by nylon, polystyrene (PS), polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene (PP), epoxy (commonly known as plastic), including plastic−paper hybrid materials. As described herein, we have successfully demonstrated the use of acrylated epoxidized soybean oil (AESO) for paper coating applications. It was found that the AESO-coated paper exhibited excellent oil and water resistance as reflected by kit rating (12/12) and Cobb 1800 (~2 g/m2) analysis. The coating steps include doctor-blade casting of AESO and 2 wt% of photoinitiator (2-hydroxy-2-methylpropiophenone) onto paper substrates followed by UV curing that yields highly crosslinked polymeric coating on the surface of paper. Fourier-transform infrared (FTIR) data confirms the crosslinking of AESO monomers, where the CC stretching frequency (~1638 and 809 cm−1) disappears after UV treatment. Mechanical property measurements show retention of >80 % in tensile index in the coated sample as compared to the uncoated paper. Further analysis such as ring crush test, bending stiffness, and internal tearing resistance measurements demonstrate that AESO-coated paper offers a significant improvement over the uncoated paper in terms of mechanical stability. Thermogravimetric analysis indicates that the crosslinked AESO-matrix is stable even at an elevated temperature (~340 °C), which demonstrates the stability of this polymeric material on paper substrates, thus increasing its utility in food packaging by mitigating the risk of the coating material leaching into food at high temperatures.