Novel phenolic resins with improved mechanical and toughness properties

Novel phenolic resins with improved mechanical and toughness properties

Novel phenolic type of thermoset resins were synthesized, and their mechanical and toughness properties were evaluated. Phenol Formaldehyde (PF) phenolic resins were modified to broaden their applications for modern composite structures. A first modification consisted of copolymerization of Phenol with Cardanol during the synthesis of resole phenolic (CPF) resins. The modified
phenolic resins (CPF) were prepared at various molar ratios of total Phenol to Formaldehyde (F : P ratio) and with different weight ratios of Phenol to Cardanol. CPF resins with a maximum content of 40 wt % of Cardanol were synthesized and used. The CPF resins were applied as a plasticizer and toughening agent to the base PF resins. Both resins (CPF/PF) were mixed in different proportions,
and their thermal and mechanical properties were then
established. A full miscibility of the two resins was
observed with the formation of a single-phase system. An
increase in the content of Cardanol resulted in a propor-
tional increase of the flexural strength and fracture tough-
ness together with a decrease of the flexural modulus of
the cured CPF/PF resins. Further increased plasticizing
and toughening effect was also observed by the blending
of the CPF resins with propylene glycol. The higher tough-
ness and flexibility effect of the CPF resins was obtained
with a F : P molar ratio equal to 1.25 and with a Cardanol
content of 40% (w/w).

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