Linear Correlation between True Density and Crystallinity of Regenerated and Mercerized Celluloses

Regenerated and mercerized celluloses are widely used in our daily life and industries. Examples include clothes, medical supplies, and separation membranes. In such applications, the true density is an important derived physical quantity for refining the structural designs of regenerated and mercerized celluloses. Here, we report the true density–crystallinity correlation of regenerated and mercerized celluloses. Seven samples were prepared through either dissolution–regeneration or mercerization, and the true density of each sample was measured by helium gas pycnometry. The crystallinity was evaluated by solid-state 13C nuclear magnetic resonance spectroscopy based on the ratio of the carbon atoms in the crystallite core to those at crystallite surfaces and in the surrounding amorphous matrix. We found that the true density of regenerated and mercerized celluloses is directly proportional to crystallinity, irrespective of the preparation process. Additionally, the molecular packing density at the crystallite surfaces was found to be similar to that in the amorphous matrix.