The effects of combination of CPAM/NCC and CS/NCC on
improvement of pulp strength properties were investigated, and
the results are shown in Fig. 6. When the NCC was used
together with CPAM and CS, the strength properties were further
improved, better than they were used individually. The
reason maybe attributed to two aspects. Firstly, more NCC could
be retained due to the retention property of CPAM and CS.
Secondly, the CPAM and CS themselves could be used in the
papermaking to improve the strength properties. The amounts of
CS and CPAM adsorbed on the fiber surfaces could be increased
due to the NCC addition, which could also increase the pulp
strength properties. For the CPAM/NCC system, the breaking
length kept increasing at the entire range of NCC addition in
this test, and increased by 15.7% at addition of 2.5% NCC, while
the tear index reached the maximum (2.50 mN m2/g, 13.1%) at a
very low addition of 0.02%. The CS/NCC system showed higher
improvement of strength properties than the case in CPAM/NCC
system. The breaking length increased by 20% at an addition of
0.02%, and the tear index increased by 21% at an addition of
0.1%.