The present study was conducted to modify kaolin clay by coating cationic starches, maize and tapioca, aimed at effective incorporation into recycled pulp fibers. The modification process was examined by using zeta potential, filler size, filler retention, and scanning electron micrograph (SEM) observations. In addition, paper sheets (65 ± 5 g/m2 basis weight) filled with unmodified kaolin or kaolin–starch filler followed by an internal sizing were fabricated and analyzed. Based on the results of zeta potential, the charge reversal of kaolin–starch particles substantiated the coating of kaolin fillers by cationic starches. Additionally, the kaolin–starch filler revealed a higher tendency to form clusters 3.5–7.5 times larger than the unmodified kaolin filler. Consistently, SEM images showed well–distributed kaolin–starch fillers, aggregated together and jointed to the fibers. Consequently, the paper filled with kaolin–starch fillers exhibited higher brightness and mechanical strengths indices compared to the unfilled papers, as well as the papers filled with unmodified kaolin. Interestingly, the results of water resistance and dynamic contact angle (DCA) indicated stable hydrophobic performance of kaolin–starch filled papers.
