Developing a Renewable Hybrid Resin System. Part I: Characterization of Co-Polymers of Isocyanate with Different Molecular Weights of Phenolic Resins

Abstract

Co-polymer systems of methylene diphenyl diisocyanate (MDI) and phenol-formaldehyde (PF) resins with different molecular weights were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The FTIR and TGA coupled with differential thermogravimetric (DTG) results showed that higher molecular weight of PF resins not only promoted the reaction of isocyanate and PF co-polymer system, but also resulted in a better thermal property of prepared co-polymers. The XRD results revealed that higher molecular weight led to a higher proportion of ordered or crosslinking structures in the hybrid resin system. The relationship between the thermal resistance, mechanical properties and the molecular weights of phenolic resins needs further study.

Optimization of Isocyanate Content in PF/pMDI Adhesive for the Production of High-Performing Particleboards

“…In the next stages, the mixture containing 20% of pMDI also experienced a significant mass loss; however, the residual mass was slightly higher than observed for resins enhanced with smaller amounts of pMDI but still lower than in the case of pure PF resin. It is worth emphasizing that the results of TG/DTG are consistent with the outcomes obtained by Liu et al [60] who showed that the mixture of PF resin with pMDI in a 1:1 weight ratio was characterized by better thermal properties than pure PF resin at temperatures below 500 • C. Reduced thermal stability of PF/pMDI resins containing small amounts of pMDI (5-15%) was probably related to the fact that, with such small loadings of isocyanate, the dominant reaction was slow condensation of PF resin [52]. The second reaction was between pMDI and hydroxyl of the methylol group (-CH 2 OH) of resol PF with the formation of a relatively small number of urethane linkages.…”

“…Observed improvement in the reactivity of PF resin, which is shown mainly by the reduction in T p , results from the fact that, in addition to the typical slow condensation reaction leading to the formation of methylene bonds (-CH 2 -), a second reaction takes place (almost simultaneously) as well. The reaction of the hydroxyl groups of PF resin with the isocyanate groups of pMDI leads to the formation of durable urethane linkages (-NH-CO-O-) [ 57 , 58 , 59 , 60 ]. The reaction of pMDI with the functional groups of PF resin is probably hindered by the considerable amount of water introduced with the PF resin and released during its condensation.…”

“…Overall, the thermal degradation process of PF resin includes three main degradation stages: post-curing, thermal reforming, and ring stripping [ 60 , 61 ]. Based on the analysis of TG/DTG curves, three mass-loss stages can be noted: a first in the temperature range up to 270 °C, a second between 270 and 450 °C, and a third between 450 and 550 °C.…”

“…Despite the recorded improvement in the reactivity of PF/pMDI hybrid resin, we also noticed that the introduction of pMDI in the amount ranging from 5 to 15% resulted in a gradual decrease in resin's thermal stability, especially at temperatures exceeding 300 °C (Figure 3, Table 4). Overall, the thermal degradation process of PF resin includes three main degradation stages: post-curing, thermal reforming, and ring stripping [60,61]. Based on the analysis of TG/DTG curves, three mass-loss stages can be noted: a first in the temperature range up to 270 • C, a second between 270 and 450 • C, and a third between 450 and 550 • C. In the first stage of pyrolysis, usually occurring below 270 • C, a mass loss mainly related to the release of free formaldehyde, phenol, oligomer, and water introduced with PF resin and resulting from the progressing cross-linking reaction can be observed.…”

Waste to Energy from Flue Gas of Industrial Plants to Biodiesel: Effect of CO2 on Microalgae Growth

“…The biomass of microalgae can be used as the source of biofuel, biopolymers and nutraceutical products [8,9]. The recent researches for production of polymer can be employed for efficient conversion of algal organic acids to high quality products [10,11]. For biofuel production hydrodeoxygenation can efficiently convert biomass to bio-oil [12].…”