| 초록 |
This paper presents properties of urea-formaldehyde (UF) resins with different formaldehyde/urea (F/U) mole ratios by measuring their crystallinity and hardness, using X-ray diffraction, SAXS and nanoindentation techniques. As the F/U mole ratio decreased, the crystallinity of cured UF resins increased up to 48%. The average distance between domains decreased from 39 nm to 34 nm while the crystallite size increased from 1.3 nm to 5 nm. The Brinell hardness (HB) decreased continuously, and the hardness (HN) obtained by nanoindentation demonstrated a similar trend as a function of F/U mole ratio. However, the nanoindentation also provided the Er and calculated elastic modulus, which did not show a consistent trend as the HN and HB did. These results could be ascribed to the presence of crystalline structure in cured UF resins with low F/U mole ratios. |
