Dimensional Stability. Introduction. Wood fibers swell under the influence of water. Thus, the dimensions and shape of paper or board change with change in moisture content.
Wood fibers swell under the influence of water.
Thus, the dimensions and shape of paper or board change with change in moisture content.
Poor dimensional stability causes many problems including misregister in multicolor printing, curl, cockling, wavy edges and asymmetric shrinkage in fusers of laser printers and copiers and during drying of ink on press.
We consider the control of moisture content and relate moisture change to dimensional changes.
RH=Pw / Pws
or as bound water
where b is the hygroexpansivity and Dmc is the change in moisture content.
The corresponding expression for the cross direction is available for hydrogen bonding with water.
bLf and bTf are the longitudinal and transverse hygroexpansion coefficients of fiber,
f2j describes the transfer of stress from direction j (j=1 for MD and 2 for CD) in the network to the transverse direction of a single fiber.