Alkyl modified phenolic resins were synthesized by acid catalysed etherification of Phenol formaldehyde resin (PF) using linear (n-propyl-NPA and n-butyl-NBA) and branched (iso-propyl-IPA and t-butyl-TBA) chain alcohols and characterized. Spectroscopic characterization (FTIR and 1H NMR) and hydroxyl value revealed the extent of etherification to be ca. 10–13 %. Enthalpy of curing was not significantly varied with etherification from the control PF resin. Mechanical property evaluation indicated an increase in elongation by 60–80 %. Glass transition temperature was about 135–144 °C vis-a- vis 148 °C for the unmodified PF resin. Thermal stability of the synthesized PF resins was not significantly altered and a marginal improvement in char residue (PF- 49 % and alkyl modified PF- 54–57 %) was observed at 900 °C. Low density carbon composites (0.70 g/cc) were processed using these PF resins as matrix resins and porous graphitic felt as reinforcement and evaluated their thermal and ablative characteristics. Alkyl modification improved the wettability of the graphitic felt and a reduction in backwall temperature was observed when the cured composites were subjected to Plasma arc jet at 220 W/cm2 at the end of 500 s.

中文翻译：

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PF 树脂的线性和支链烷基链改性：高热通量下的合成、热解和烧蚀性能


使用线性（正丙基-NPA 和正丁基-NBA）和支链（异丙基-IPA 和叔丁基-TBA）链醇，通过酚醛树脂 （PF） 的酸催化醚化合成烷基改性酚醛树脂 （PF） 并进行表征。光谱表征（FTIR 和 1H NMR）和羟值显示醚化程度约为 10-13%。固化焓随对照 PF 树脂的醚化反应没有显著变化。机械性能评估表明伸长率增加了 60-80%。玻璃化转变温度约为 135–144 °C，而未改性的 PF 树脂为 148 °C。合成的 PF 树脂的热稳定性没有显着改变，在 900 °C 时观察到残炭（PF- 49% 和烷基改性 PF- 54–57%）略有改善。 使用这些 PF 树脂作为基体树脂和多孔石墨毡作为增强材料加工低密度碳复合材料 （0.70 g/cc），并评估其热和烧蚀特性。烷基改性提高了石墨毡的润湿性，并且在 500 s 结束时，当固化复合材料以 220 W/cm2 的等离子弧射流进行时，观察到底壁温度降低。