Effect of Unsaturation on Thermoplastic Lignocellulosic Fatty Acid Ester Properties

ABSTRACT

Fatty acid esters of lignocellulose are emerging as potential sustainable bio‐based alternatives to fossil plastics. However, most studies focus on cellulose and saturated fatty acids; those made using lignocellulose or unsaturated acids are receiving considerably less attention. This study explores pine sawdust and microcrystalline cellulose (MCC) after modification with 3 commonly available unsaturated acids: oleic (octadecenoic, C18:1), linoleic (octadecadienoic, C18:2), and sorbic (2,4‐hexadienoic, C6:2) acids. The six resulting bioplastics are extensively characterized using FTIR, XRD, and solid‐state ¹³ C NMR for the chemical structure and crystallinity, TGA, DSC, and TMA for the thermal properties, SEM and water contact angles (WCAs) for surface analysis and tensile testing for the mechanical properties. There are only small differences between the oleate and linoleate esters, which have properties similar to previously described cellulose stearate (decaoctanoate) esters, as well as tensile strengths or elongation at break values comparable to some forms of conventional fossil plastics and bioplastics. The sorbate esters, however, have inferior properties. This study demonstrates that thermoplastic materials can be derived from unsaturated fatty acids, which are readily obtained from plants and either sawdust or cellulose.