Phenol in phenol formaldehyde (PF) resin has been partly substituted with lignin extracted
from sugarcane bagasse. In order to optimize the lignin-based resin for applications in coating and composite materials, thermal and rheological tests were performed with different
wt% of lignin substitution into PF resins. Differential scanning calorimetry scans showed a
small exothermic peak and a large endothermic peak, typical of resins. The Tg
of the resins
was seen between 125 and 150◦
C and this transition was clearly evident when the lignin content was increased from 10 to 40 wt%. Increasing the lignin content in the PF resin increases
the rate of cure and the heat of reaction. Water absorption tests show that the lignin-PF resin
films are effective water-barrier coatings for cardboard substrates. It is speculated that the
interaction between the substrate and the lignin-PF resin has resulted in a negative surface
charge which would have contributed to the reduction in the contact angle.