Hardness evaluation of cured urea–formaldehyde resins with different formaldehyde/urea mole ratios using nanoindentation method.

Highlights: [•] Hardness of cured UF resins was evaluated by nanoindentation technique. [•] Both HB and HM value was consistently changed as a function of F/U mole ratio. [•] However, both Er and Es of cured UF resins displayed inconsistent trend. [•] Both HM and Er showed much greater in the COV at lower F/U mole ratios 1.0 and 1.2. [•] Crystalline structures in the low F/U mole UF resins contributed to this variability. [ABSTRACT FROM AUTHOR]