Cure behavior of resins formulated with petroleum phenol replaced by 25 and 50 wt% of softwood
bark-derived pyrolysis oils, using various formaldehyde to phenolics molar ratios and alkalinity
content, was characterized by Differential Scanning Calorimetry (DSC). Kinetic parameters were
obtained by the Borchart-Daniels method and the model-free (Vyazovkin) method. Resins containing
up to 50% by wt of pyrolysis oils had slower cure kinetics and lower extent of condensation reaction
compared to a neat laboratory made phenol-formaldehyde resin. However, very similar kinetic curing
behavior to the standard resins was found for resols having 25% by wt of the petroleum phenol
replaced by the pyrolysis oils. Thermogravimetric analysis (TG) of cured pyrolysis oil-PF resins has
been done under nitrogen and air environments at a constant heating rate. Thermal behavior of resins
containing pyrolysis oils differed depending on the nature of the purge gas used in TG. Increasing the
amount of pyrolysis oils decreased the thermal resistance of the experimental resins.
Wood adhesives derived from softwood bark pyrolysis
oils (PO) and isocyanates (pMDI) have been developed
for particleboards with a non-conventional blending system.
The PO produced by the vacuum pyrolysis Pyrocycling™ process was used to replace between 30 and
40% by weight of the pMDI in a 4% adhesive-containing
particleboard. Results showed that mechanical properties
(IB, MOE and MOR) and thickness swelling of homogeneous
boards exceeded the minimum requirements
set by ANSI A208.1-1993 and ASTM 1037-96a standards.
The study showed that pyrolysis oils can be mixed
at ratios as high as 40% with pMDI and give acceptable
interior grade particleboard properties. It was also shown
that PO reduces panel to metal adhesion by 86%, in
comparison to the control.
Phenol-formaldehyde (PF) resols were prepared with different proportions of phenol replaced with
softwood bark pyrolysis oils under varying formaldehyde to phenolics molar ratios and sodium
hydroxide contents. Propylene carbonate (PC) was added to these adhesives to improve the cure of
resins. The cure behavior was characterized by differential scanning calorimetry (DSC). Cure kinetics
and amount of cure of the experimental resin were improved by adding PC to the resins. Low amounts
of PC were used (less than 1.5% of PC on a resin solid basis) to avoid premature gelling of the
adhesives. Results obtained by DSC suggested that PC catalyzed the resin cure reaction and also
participated in resin cross-linking reactions. Low percentages of PC, 0.5 and 1% on a resin solid basis,
were added to the experimental resins for bonding strandboards. These addition levels did not
significantly improve mechanical properties of strandboards. It is concluded that a PC addition level
of more than 1% by wt (on a resin solid basis) should be used to modify the mechanical properties of
panels bonded with pyrolysis oil-PF resins.