Hydrophobization of cellulose oxalate using oleic acid in a catalyst-free esterification suitable for preparing reinforcement in polymeric composites.

It is common practice to use cellulose as reinforcement and fatty acid as compatibilizer in the preparation of polymeric composites. However, the used catalysts (e.g., pyridine) are usually toxic and should be avoided. In this study, a new type of microcellulose - cellulose oxalate (COX) was chosen as reinforcement to be reacted with oleic acid to prepare hydrophobic fillers in a catalyst-free esterification for different times. For comparison, microcrystalline cellulose (MCC) was also selected. The success of esterification of COX and oleic acid was confirmed but little esterification occurred when MCC was used. After reacting COX with oleic acid for 18 and 48 h, the products showed stable water contact angles of about 130°. Composites of polypropylene with COX or MCC were prepared. Tensile tests showed that for a given reaction time, the COX-based composites exhibited higher values of both Young's modulus and tensile strength than those of MCC-based composites.