Abstract:
This research investigated the possibility of substituting coir fiber lignin in
synthesis of bio-based phenolic resol resins. Coir fiber was subjected to
alkaline soda process from which the lignin was recovered. The optimum
conditions were found to be at 100 oC with coir/water (1:8 w/w) and at
pH=11 where the lignin yield attained ca. 26% with a purity of ca. 83%. By
simultaneously reacting with phenol followed by formaldehyde in a
condensation polymerization catalyzed by sodium hydroxide the coir fiber
lignin has been subjected to hydroxymethylation reaction for the
introduction of hydroxyl groups into its structure, to enhance the reactivity.
For more complete exploitation of coir fiber lignin in the partial
replacement of petroleum based phenol, a series of phenol-lignin formaldehyde resins was prepared. Here polyblended bio-based resol resins
were synthesized by varying the coir lignin (w/w) % ratio in the 0-50 range.
Structural analysis of the resulting resins was determined by Fourier
transform infrared spectroscopy (FTIR), ultraviolet – visible (UV-vis)
absorption measurements and gel time measurement. A dramatic decreasing
effect of the gel time in the copolymer system was observed with gradual
increment of the (w/w) % lignin. By analyzing the FTIR and UV-vis
spectroscopic data, the optimum conditions to achieve lignin
hydroxymethylation could be deduced. The obtained analytical results
proved the powerful potential of coir fiber lignin as a natural polyphenol.
