Phenols pdf

The objective of this study is to prepare PF resoles from hydrolytically depolymerized Kraft lignin DKL , and to investigate the effect of Mw of DKL, percent substitution of phenol-to-lignin, and formaldehyde-to-phenol ratio using Box-Behnken Design BBD to find the optimum curing temperature for BPF resoles without compromising the properties of resoles. Molecules , 22, 3 of 20 2. Results and Discussion 2. These results suggest that the depolymerization process effectively cleaved the intermolecular bonds, such as ether bonds, which decreased the molecular weight of lignin, increased the contents of total hydroxyl groups in DL and hence greatly promoted the reactivity of the DL for the preparation of resoles.

Given the limited or no research work on the impact of lignin Mw on the properties of BPF resins, the Mw of DL products is of interest in this research project, where it is used as one of the process parameters to produce BPF resoles at high phenol substitutions.

The relative Mw of the three DL products were obtained and listed in Table 1, along with the DL yields from the hydrolysis experiments at various severities. Table 1. Mw of DL Reaction Temp.

As the treatment severity increase, the Mw of DLs reduced because the depolymerization reactions are endothermic, higher temperatures were thermodynamically favorable in promoting greater cleavage of aryl-ether linkages within the polymer chains of the lignin molecule [13,14].

At the same time the yield of DLs also reduces with increase in treatment severity due to the occurrence of prominent crosslinking reaction lead to solid residues [6,13]. DL with lower Mw can be particularly advantageous in applications for the synthesis of BPF resins, where lignin with lower Mw would result in reduced steric hindrance and provide more phenolic hydroxyl contents, which increases the reactive sites towards formaldehyde, thus facilitating the resinification reactions and enabling production of BPF resins at higher phenol substitutions [13].

Molecules , 22, 4 of 20 Table 2. These results consistent with 1H-NMR analysis lignin molecular structure. These results consistent with 1 H-NMR analysis treatment of hydrolytic processing resulted in increases of phenolic hydroxyl groups in the products performed on DKL products by Mahmood et al. Averages of three measurements were recorded. Viscosity measurements of phenolic resins provide important information about the advancement of resole resin synthesis and the degree of condensation reactions [15,16].

Low resin viscosities or low Table 3. Viscosity of all BPF resoles synthesized in this study. The increase in viscosity of BPF with higher percent substitutions can be attributed to incorporation of greater lignin content in the BPF resole synthesis. Research findings from Cheng et al.

Table 3. This is actually confirmed by the measurements of pH and non-volatile content for the corresponding resoles. Using higher Mw of DL in the synthesis of lignin-based phenol formaldehyde resins will likely result in BPF resin with higher molecular weights and increased viscosities [18].

Given the complex structure of lignin, higher Mw of depolymerized lignin could result in lengthening of polymeric chains or additional branching within the structure of BPF resoles, which would then significantly increase the viscosities of the BPF resins [16]. Table 4. However, increased to 3—4care must be taken h. However, care not mustto cause be drastic taken not increases to cause in the viscosities drastic increasesofin BPF as viscosities the a result of potential of BPF as polymer a resultgelation.

Figurepolymer of potential 2 clearly indicatesFigure gelation. As discussed and reduces the pHearlier, of thehigher resoles. As can be seen, there BPF curing temperature. The peak exothermic first exothermic might be duepeak to might additionbe reactions due to addition of free reactions of free formaldehyde to phenolic rings while the second and third exothermic peaks could be attributed to curing reactions of methylolphenols and phenols to form methylene bridges and condensation reactions of two methylol groups to form dimethylene ether bridges [4].

The first exothermic peak might be due to addition reactions of free formaldehyde toformaldehyde phenolic ringstowhile phenolic the rings secondwhile and the second third and third exothermic exothermic peaks could bepeaks could attributed becuring to attributed to curing reactions reactions of methylolphenols of methylolphenols and phenols toandformphenols to form methylene methylene bridges bridges and and condensation condensation reactions of two methylol groups to form dimethylene reactions of two methylol groups to form dimethylene ether bridges [4].

Effect Figure of lignin 4. It suggests that for BPF synthesized resoles at low with phenol Mw DKL has incorporation lowersubstitutions, a slightly lower ofcuring lignin temperatures. In contrast, as revealed by hydroxyl Figure content 4, the curingattemperature would accelerate of BPF the curing resins with rate of the phenol resoles [18].

Model Building and Analysis of Variance ANOVA The curing temperature response from all the synthesis runs based on the experimental design The curingand was measured temperature the results response from are provided in all thethe synthesis Table runs 7. These based results on the show thatexperimental design curing temperature was measured and the results are provided in the change with the variation of the synthesis conditions.

Table 7. These results show that curing temperature change with the variation of the synthesis conditions. Using Minitab, the regression coefficients coefficients were estimatedwereand estimated and a mathematical a mathematical model for predicting model for predicting the curingthe curing temperature temperature was built was built and used and used to to predict thepredict the response.

The response and also interpreted using surface and contour plots. The response curing temperature was curing temperature was determined determined using using DSC. The one exception was BPF, 0 ,1.

A box-plot of the response curing temperature in Figure 5 shows that the curing temperature for BPF, 0 ,1. Thus, outlier. Figure 5. R2 2 adj was used to ensure that the model is not over-fitted. The statistical significance of the coefficients, regression, and residual errors was checked using the F-test and the p-value test as shown in Tables 8 and 9.

Table 8. Statistical significance of the coefficient of regression. ANOVA for the regression. Thus, these coefficients were not included in the regression model. The normal probability plot Figure 6 indicates that assumption that the errors are normally distributed was a good prediction.

The absence of a visible pattern in the residual versus fitted plot Figure 7 indicates model adequacy. Figure 8 shows the actual curing temperatures of the BPF resoles plotted against the predicted curing temperatures from the model.

As can be seen, there was an agreement between the predicted data and the actual data for the curing temperature. Table Table 9. Normal 6. Normalprobability Normal probabilityplot probability plotfor plot forcuring for curingtemperature curing temperature response.

Molecules , 22, 10 of 19 Figure 8 shows the actual curing temperatures of the BPF resoles plotted against the predicted curing temperatures from the model.

As can be seen, there was an agreement between the predicted Figure7. Figure 7. Residual 7. Residual vs. Figure 8. Predicted vs actual curing temperatures. Predicted vs. Interaction Effects Figure 9 shows the interaction effects of the regression model, where the plots for means of each level of a factor are given while keeping the second factor constant.

Absence of parallel lines indicates that the response of one variable depends upon the levels of other variables. As such, assessment of the effect of any of the variables substitution of phenol with lignin, Lignin Mw, and formaldehyde- to-phenol ratio should be done with respect to the other variables.

Molecules , 22, 11 of 20 Figure 8. Febrian Ardwianto. Nimish Jain. Khusbu Patel. Priya dharshini. Victor Mondine. John Bryan Aldovino. Ritwick Bose. Josephine Torres. Boj Lucero. Stephannie Sy. Quarter 3 Thermodynamics Review Regents Style 1. Rituraj Tripathy. Bea Abis. Sudhakar Kolanu.

Shubham Raj. Popular in Fries Rearrangement. Nova sounds - No copyright music. Awad Said. Maggie Zhu. Abhishek Gumwant. Abhay Kumar Nayak. Sukumar Pani. Now, the start to learn the examples of phenol in brief. The difference between alcohol and phenol are the following Now, we shall learn about ether as well as the definition, examples, classification and much more.

Ether:- It is an alcohol or phenolic hydrocarbon compound in which the alkyl or aryl group replace the hydrogen atom of hydroxyl radical of alcohol or phenol compound, which is known as ether. Now, the start to learn the examples of ether in brief. The examples of ether are following Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.