Cellulose is a natural hydrophilic polymer used in many applications such as packaging, filtering etc. Furthermore, cellulose is used as a support for different rapid tests using liquids of different polarity. Despite its hydrophilic nature apolar liquid penetration in cellulose is possible via capillary phenomena since under a broad range of conditions the contact angle between cellulose and apolar liquids is <90o.
This work investigates the effect of ambient conditions and namely the effect of humidity and temperature on the penetration of an apolar liquid in a cellulose fiber porous matrix. For these tests a cellulose fiber porous medium of nominal pore size in the range of 20-25μm and refined sunflower oil were used. During the capillary penetration experiment the porous medium was used dry and in other cases it was equilibrated with water and oil vapors at different temperatures. Furthermore, measurements were performed after fully wetting and subsequently partially drying the porous medium. Depending on the conditions applied the oil penetration rate either increased or decreased respective to the penetration rate of the dry cellulose matrix. It is suggested that the changes in oil penetration rate are due to the changes in the oil-porous medium contact angle and to the partial blocking of pores with water.
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