TY - JOUR
T1 - Longitudinal and concurrent dimensional changes of cellulose aggregate fibrils during sorption stages
AU - Lee, Jung Myoung
AU - Pawlak, Joel J.
AU - Heitmann, John A.
PY - 2010/5
Y1 - 2010/5
N2 - Atomic force microscopy (AFM) studies of the dimensional changes of cellulose microfibril materials, called cellulose aggregate fibrils (approx. 100 μm × 3 μm × 300 nm), exposed to two distinct relative humidities of 80% and 23% for 24 h and then suddenly subjected to 50% RH and 23 °C show that the fibrils are responsive to the surrounding environments in a nonspecific fashion. AFM images (10 μm × 10 μm) of the individual straight cellulose aggregate fibrils were taken as a function of elapsed time during both desorption and adsorption of moisture. The longitudinal distance between discrete natural defects observed on the cellulose aggregate fibrils as well as the width, cross-sectional area, and height of the cellulose aggregate fibril were measured from the AFM images. The length of the cellulose aggregate fibrils was found to have reduced after exposure to either high or low relative humidity, and then placement in ambient conditions. Over time in ambient conditions, the cellulose aggregate fibrils progressively relaxed to their original length during both desorption and adsorption of moisture. However, the relaxation rate during adsorption was faster than that during desorption. The possible explanations for this phenomenon are discussed including the sample preparation method, volume conservation, entropy elasticity, and free volume theory. The changes in the width, height, and cross-sectional area are also discussed.
AB - Atomic force microscopy (AFM) studies of the dimensional changes of cellulose microfibril materials, called cellulose aggregate fibrils (approx. 100 μm × 3 μm × 300 nm), exposed to two distinct relative humidities of 80% and 23% for 24 h and then suddenly subjected to 50% RH and 23 °C show that the fibrils are responsive to the surrounding environments in a nonspecific fashion. AFM images (10 μm × 10 μm) of the individual straight cellulose aggregate fibrils were taken as a function of elapsed time during both desorption and adsorption of moisture. The longitudinal distance between discrete natural defects observed on the cellulose aggregate fibrils as well as the width, cross-sectional area, and height of the cellulose aggregate fibril were measured from the AFM images. The length of the cellulose aggregate fibrils was found to have reduced after exposure to either high or low relative humidity, and then placement in ambient conditions. Over time in ambient conditions, the cellulose aggregate fibrils progressively relaxed to their original length during both desorption and adsorption of moisture. However, the relaxation rate during adsorption was faster than that during desorption. The possible explanations for this phenomenon are discussed including the sample preparation method, volume conservation, entropy elasticity, and free volume theory. The changes in the width, height, and cross-sectional area are also discussed.
KW - Atomic force microscopy
KW - Cellulose aggregate fibrils
KW - Dimensional changes
KW - Humidity
KW - Hygro-expansivity
KW - Longitudinal contraction
KW - Relaxation
UR - http://www.scopus.com/inward/record.url?scp=77950860697&partnerID=8YFLogxK
U2 - 10.1016/j.matchar.2010.02.007
DO - 10.1016/j.matchar.2010.02.007
M3 - Article
AN - SCOPUS:77950860697
SN - 1044-5803
VL - 61
SP - 507
EP - 517
JO - Materials Characterization
JF - Materials Characterization
IS - 5
ER -