Synthesis and characterization of phenolic resole resins for composite applications

Shafizadeh, J. E.; Guionnet, S.; Tillman, M. S.; Seferis, James C.

doi:10.1002/(sici)1097-4628(19990725)73:4<505::aid-app6>3.0.co;2-l

Cited by 11 publications

(2 citation statements)

References 18 publications

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“…According to Shafizadeh et al ., 53 the high degree of crosslinking that R undergoes during its synthesis using NaOH as a catalyst and the high curing/post‐curing temperature profiles (150 °C for 2 h followed by 177 °C for 2 h) render it very brittle with low toughness and fracture energy. Since the unreinforced N (catalyst: oxalic acid) and R (catalyst: BaOH) in the present study both show comparable values of flexural strength after being post‐cured at 170 °C for 1 h, the lower flexural strength of the R‐based composite is most likely to occur due to manufacturing flaws, as mentioned above.…”

Section: Resultsmentioning

confidence: 99%

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

Georgiou,

Kyriakopoulou,

Zoumpoulakis

2024

Polymer International

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The demands of cost‐driven industrial applications can be satisfied by manufacturing composites with a low volume fraction of carbon fibres as phenolic carbon fibre‐reinforced composites and C/C composites, both with acceptable performances, for low‐ or high‐temperature applications, respectively. Polymeric composites reinforced with a low volume fraction (7.5% v/v) of carbon fibres were fabricated using laboratory‐produced phenolic resins, novolac (N) and resole (R), as matrices after different curing/post‐curing temperature profiles. By optimising the manufacturing conditions, the N‐based polymeric composites exhibited higher flexural strength, whereas the R‐based composites showed higher shear strength. C/C composites, namely N‐based and R‐based, were manufactured by pyrolysis of the previous polymeric composites up to 1000 °C. The pyrolysed composites were then densified by impregnation with an appropriate resin solution, followed by curing and new pyrolysis, and particularly by employing 1 up to 4 consecutive cycles of ‘impregnation‐curing / pyrolysis’. Weight changes resulting from the impregnation‐curing and pyrolysis stages were determined. The curing of both resins was verified by FTIR. The apparent density and X‐ray diffraction data of the C/C composites were used to calculate their total percent porosities. The morphology and elemental analyses of C/C composites at their failure region (after flexural testing) were examined by SEM/EDS analyses. In comparison to N‐based C/C composites, R‐based ones exhibited: higher shear strength, lower flexural strength, higher Shore D hardness, slightly higher surface conductivity, and lower volume conductivity. The optimum conditions for the manufacture of C/C composites were achieved by applying two consecutive cycles of ‘pyrolysis‐impregnation‐pyrolysis’ to the polymeric composites.This article is protected by copyright. All rights reserved.

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Section: Resultsmentioning

confidence: 99%

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

Georgiou,

Kyriakopoulou,

Zoumpoulakis

2024

Polymer International

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“…For the same reason, although NaOH is often chosen as a catalyst for the synthesis of resoles, ammonia catalysis was preferred in this work. Furthermore, resins synthesized with ammonia versus NaOH are described as being more heat resistant, having a higher molecular weight, having lower water solubility, higher glass transition temperature, and being slightly less crosslinked (associated with better mechanical properties). − To the best of our knowledge, formaldehyde scavengers with ammonia-catalyzed phenolic resins have not been studied.…”

Section: Introductionmentioning

confidence: 99%

Versatile Method To Reduce the Free Formaldehyde Content in Phenolic Resins for High-Temperature Applications

Chaussoy

Brandt

Gerard

2022

ACS Appl. Polym. Mater.

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Discovered by Baekeland a century ago, phenolic resins are still widely used today with a global production of about 12 million tons/year. Typically, these resins contain residual free formaldehyde, which is highly toxic and carcinogenic and will soon be banned by the European REACh regulation. Consequently, phenolic resins must be substituted. These resins are extensively used as a char precursor for composite-based thermal protection systems. Commonly, urea is a widely used formaldehyde scavenger and can be added to phenolic resins to decrease their free formaldehyde content, but urea is not suitable for high-temperature applications. Thus, an easy-to-implement method was developed with an aminophenol, giving access to a noncarcinogenic resin while maintaining the thermomechanical properties. The chemistry and the reaction mechanism of aminophenols with formaldehyde were also studied. The interest of this additive is multiple: it allows trapping of formaldehyde, to comply with the European REACh regulation (wt % free formaldehyde <0.1%), while the modifying agent is integrated into the polymer network, maintaining the thermostability (Td5% = 395 °C and char yield = 63%). This method is also applicable on an industrial scale. In addition, this method uses mild reaction conditions and limits volatile organic compound emissions by trapping free formaldehyde, which are two ways to improve durability and reduce toxicity of the resin.

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Kinetics of hydroxymethyl phenols formation by in‐line FTIR spectroscopy

Poljanšek

Likozar

Krajnc

2007

J of Applied Polymer Sci

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The kinetics of phenol-formaldehyde prepolymers catalyzed by sodium hydroxide at various temperatures was studied. Several reactions were conducted with different phenol to formaldehyde as well as phenol to sodium hydroxide molar ratios. The React-IR system was used to monitor the reaction as well as to determine residual free phenol and formaldehyde.The changes in the concentrations of phenol and formaldehyde with the reaction time were determined. The value of the concentration of the hydroxide ion, [OH 2 ], was obtained by measuring the pH value of reaction mixture. The concentration of the hydroxide ion, [OH 2 ], expressed as a function of reaction time, was fitted by the six-order polynomial to the experimental data. On the basis of the proposed reaction scheme the kinetic model was developed.The kinetic parameters were obtained by adjusting the experimental evolution of phenol and formaldehyde during the synthesis. Using this method the changes in the concentrations of five species of hydroxymethyl phenols with the reaction time was also been calculated. The activation energy and preexponential factor have been calculated for individual reactions. The accuracy of the kinetic model was confirmed by comparing experimental concentration profiles of formaldehyde and phenol with the calculated ones for different molar ratios. The experimental tendencies are in agreement with the results of the model.

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Synthesis and characterization of phenolic resole resins for composite applications

Cited by 11 publications

References 18 publications

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

Versatile Method To Reduce the Free Formaldehyde Content in Phenolic Resins for High-Temperature Applications

Kinetics of hydroxymethyl phenols formation by in‐line FTIR spectroscopy

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