Efforts in increasing the yield in NCC extraction have important
impact on final cost. Bondeson et al. (2006), investigated optimizing
the hydrolysis conditions by an experimental factorial design
matrix and demonstrated that NCC is obtained with a yield of
30% (based on initial weight) with sulphuric acid 63.5% (w/w) for
2 h. More recently Hamad and Hu (2010), carried out a systematic
investigation of the structure–process–yield interrelations in the
NCC extraction from a commercial softwood Kraft pulp. NCC with
high crystallinity (>80%) was obtained using 64% sulphuric acid,
with yields between 21 and 38%. The highest yield was obtained
using a temperature of 65 ◦C when shortening the reaction time
down to 5 min.