Title : Biobased Novolac resins cured with DGEBA using water-insoluble fraction of wood pyrolysis bio-oil: Synthesis and characterization
Abstract:
The water-insoluble fraction of bio-oil products obtained from intermediate pyrolysis and fractional condensation of beech wood biomass were used as a phenolic source to substitute phenol for the synthesis of Novolac Resin. The replacement of formaldehyde considered an atmospheric pollutant was also studied. The ratio of phenolic fraction from bio-oil were added to partially substitute for phenol and until completely replace from 25% to 100% to synthesize bio-oil phenol acetaldehyde (BPA) resins. Simultaneously, two concentrations of hydrochloric acid catalyst (1% and 10%) were examined to understand the effect of the catalyst on the reaction between bio-oil and aldehyde. The kinetic parameters of the curing reaction using Bisphenol A diglycidyl ether (DGEBA), as a formaldehyde-free cross-linker for bio-oil based novolac resins were evaluated with model-free methods using data obtained from differential scanning calorimetry (DSC). Physicochemical and thermal properties of BPA resins were determined before and after curing and compared in the function of different synthesis conditions.
The results showed that the higher the proportion of bio-oil is, the more the properties of Novolac resin deviated from standard phenol resins. The presence of bio-oil promoted the curing reactions. Indeed, the curing reaction of all the BPA resins started early than PA resin. The peak temperature at maximum rate and the activation energy (Ea) of BPA resins were lower than that of PA at a low bio-oil ratio (≤75 wt %). It was also observed that the char yield at 800? of resins increased and reached the highest value at 100% BPA due to the occurrence of cross-linking reaction between novolac resins and DGEBA.
Under 10% of HCl catalyst, all cured and uncured Novolac BPA resins are more stable. The high catalyst content can shorten the defect of incorporating bio-oil and can produce excellent bio-oil based resins with less free phenols and aldehydes, higher yield, and higher molecular weight. High content of catalyst allows BPA to decrease the activation energy (Ea) when curing with DGEBA and its properties are also closer to PA resin.
Audience take-away:
- The audience will be able to learn some skills of applying bio-oil to replace phenol to synthesize bio-oil novolac resin.
- At the same time, many analytical instruments have also been applied to characterize the physical and chemical properties of the prepared resin (FT-IR, H-NMR, GPC, HPLC, GC-FID, GC-MS, DSC, and TGA), which will also help readers in their future studies.
- The audience will know how to use differential scanning calorimetry (DSC) to study the curing reaction of bio-oil based novolac resin and DGEBA. The obtained data will further use model-free methods to calculate the kinetic parameters of curing (Ea, reaction order).
