Curing of novolac–lignocellulosic composites

Abstract

Novalac resin (N) with hexamethylenetetramine (HTA) was cured with biomass (B) or Kraft lignin (KL) or hydroxymethylated Kraft lignin (KLH) or cellulose (CEL). The agriculturalfindustrial by-product of olive stones was used as biomass. Kraft lignin, hydroxymethylated Kraft lignin and cellulose were isolated from the biomass. The cure was followed by DSC and IR spectroscopy. Based on the IR spectra of cured materials and their characteristic bands, the proportion of N/B = 50/50 was chosen for the preparation of novolac mixtures with other components. Only N-KLH exhibited values of AH higher than AH,, calculated from the law of mixtures, indicating that KLH participates in the cure reaction. The kinetic parameters E and k, of the total cure reactions, calculated by DSC scans, increased in the order N < N-KLH < N-B < N-KL < N-CEL.The incorporation of KLH in the mass of N-HTA led to a slight increase in E and k,. On the other hand, KL, CEL and B acted as diluents in the mass of novolac. Generally, the cure of all materials was a first order reaction, indicating that the cure mechanism of novolac remains the same.

Ion exchange resins from phenol/formaldehyde resin‐modified lignin

“…Lignin reacts through the aromatic ring and the lateral chain of its units and its incorporation into the novolac resin causes differences in the resin glass transition temperature 19. Lignin exhibits larger reactivity in hydroxymethylation, so is likely to react efficiently with the initial amount of phenol 9. As observed from the swelling of sulfonated materials in different solvents, the materials show very strong cross‐linking of their networks.…”

“…The cost of isolated lignin is lower than that of phenol. The effect of replacement of phenol by lignin on the properties of novolac resins was experimentally investigated8 and the kinetics of curing of novolac in the presence of agricultural biomass or its constituent such as lignin was also determined 9. 10…”

Lignins for phenol replacement in novolac‐type phenolic formulations, part I: Lignophenolic resins synthesis and characterization

“…Since then, much research work has been done trying to optimize L incorporation in PF formulations, being most of the works dedicated to resole-type resins [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and only a few of them to novolac-type lignophenolic resins. [22][23][24][25][26] In both cases, L from different origins have been tested either nonmodified [12][13][14][15][16][17][18][23][24][25] or after several modifications such as fractionation, 3,8,9,[27][28][29][30][31] hydroxymethylation, 10,11,20,22,26,32,33 or phenolation. 6,7,34,…”

A preliminary experimental feasibility case study of energy upgrade of pellets of lignite and plastic waste mixtures

“…Blesa, Miranda, Izquierdo, and Moliner () found that the best curing temperature for some biomasses was around 200 degrees Celsius (°C). Simitzis, Karagiannis, and Zoumpoulakis () used hardening times of varying lengths at 110°C. Blesa et al.…”

“…Simitzis, Sfyrakis, and Faliagas () used mixtures of epoxy resins and coke cake and, after hardening and pyrolyzing the mixture at temperatures of 800°C and higher, investigated their porosity. The same group (Simitzis et al., ) used several mixtures of novolac and hexamethylenetetramine (HEXA) as a hardener for the biomass, which they cured at 110°C. Blesa et al.…”