Direct Adhesive Measurements
between Wood Biopolymer
Model Surfaces
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Abstract
For the first time the dry adhesion was measured for
an all-wood
biopolymer system using Johnson–Kendall–Roberts (JKR)
contact mechanics. The polydimethylsiloxane hemisphere was successfully
surface-modified with a Cellulose I model surface using layer-by-layer
assembly of nanofibrillated cellulose and polyethyleneimine. Flat
surfaces of cellulose were equally prepared on silicon dioxide substrates,
and model surfaces of glucomannan and lignin were prepared on silicon
dioxide using spin-coating. The measured work of adhesion on loading
and the adhesion hysteresis was found to be very similar between cellulose
and all three wood polymers, suggesting that the interaction between
these biopolymers do not differ greatly. Surface energy calculations
from contact angle measurements indicated similar dispersive surface
energy components for the model surfaces. The dispersive component
was dominating the surface energy for all surfaces. The JKR work of
adhesion was lower than that calculated from contact angle measurements,
which partially can be ascribed to surface roughness of the model
surfaces and overestimation of the surface energies from contact angle
determinations