TY - JOUR
T1 - Impact of molecular weight of kraft lignin on adhesive performance of lignin-based phenol-formaldehyde resins
AU - Solt, Pia
AU - Jääskeläinen, Anna Stiina
AU - Lingenfelter, Peter
AU - Konnerth, Johannes
AU - Van Herwijnen, Hendrikus W.G.
PY - 2019
Y1 - 2019
N2 - This study describes the influence of improved lignin homogeneity on the adhesive properties of lignin-based phenolic resins. Softwood kraft lignin was separated by applying an ethanol-based solvent fractionation to obtain three lignin fractions with a narrow molar mass distribution (smallest [Mw 1,590 g/mol] to largest [9,570 g/mol]). Lignin-phenol-formaldehyde (LPF) adhesives were prepared by 50 percent (by weight) substitution of phenol with an adjusted formaldehyde-to-phenol molar ratio. For investigating the storage stability of the resin, viscosity was monitored, curing behavior was determined by differential scanning calorimetry (DSC), and development of the bonding strength was analyzed via tensile shear strength as a function of press time. An acceleration of the condensation process for LPFs with higher molecular mass was observed. DSC signal indicated that LPFs need a slightly higher temperature for a complete curing than the phenol-formaldehyde reference resin. Furthermore, it was found that the tensile shear strength decreases with the use of fractionated kraft lignin in phenolic adhesives. No significant difference in reactivity was found for the resins making up the different lignin fractions.
AB - This study describes the influence of improved lignin homogeneity on the adhesive properties of lignin-based phenolic resins. Softwood kraft lignin was separated by applying an ethanol-based solvent fractionation to obtain three lignin fractions with a narrow molar mass distribution (smallest [Mw 1,590 g/mol] to largest [9,570 g/mol]). Lignin-phenol-formaldehyde (LPF) adhesives were prepared by 50 percent (by weight) substitution of phenol with an adjusted formaldehyde-to-phenol molar ratio. For investigating the storage stability of the resin, viscosity was monitored, curing behavior was determined by differential scanning calorimetry (DSC), and development of the bonding strength was analyzed via tensile shear strength as a function of press time. An acceleration of the condensation process for LPFs with higher molecular mass was observed. DSC signal indicated that LPFs need a slightly higher temperature for a complete curing than the phenol-formaldehyde reference resin. Furthermore, it was found that the tensile shear strength decreases with the use of fractionated kraft lignin in phenolic adhesives. No significant difference in reactivity was found for the resins making up the different lignin fractions.
UR - http://www.scopus.com/inward/record.url?scp=85067969863&partnerID=8YFLogxK
U2 - 10.13073/FPJ-D-17-00079
DO - 10.13073/FPJ-D-17-00079
M3 - Article
AN - SCOPUS:85067969863
SN - 0015-7473
VL - 68
SP - 365
EP - 371
JO - Forest Products Journal
JF - Forest Products Journal
IS - 4
ER -