In this study, we investigated the feasibility of applying bentonite to the papermaking wet end
to retain raw starch in paper sheets. The results indicated that an increased starch dosage reduced
the first-pass retention (FPR), while a polymer and starch showed an interaction and was helpful
for increasing the FPR. However, the interaction of starch and bentonite, and the triple interaction
among polymer, starch, and bentonite were detrimental to the FPR. The interaction of a polymer
and bentonite hampered the decrease in the white water chemical oxygen demand. The main effect
of the polymer and bentonite application was to improve static drainage. On average, the ringcrush
strength of the resulting paper increased 31%, with a maximum gain of 53%. With respect
to the main effects, increasing starch and bentonite dosages were both helpful for the ring-crush
strength; conversely, the polymer tended to decrease the ring-crush strength. As for interactions,
all were detrimental to gains in the ring-crush strength. On average, the burst index increased 25%,
and the maximum gain was 61%. For the main effects, an increase in the starch dosage enhanced
the burst index, while polymer and bentonite combination reduced the burst index. All interactions
were found to detract from increasing the burst index.