SYNTHESIS AND PROPERTIES OF UV/MOISTURE DUAL CURABLE HYPERBRANCHED POLYURETHANE COATINGS

Hyperbranched polyurethane (HPU) was synthesized from toluene-2, 4-diisocyanate (TDI) and diethanolamine (DEOA) by one-step method, which was further modified to prepare UV-curable hyperbranched polyurethane acrylate (UV-HPUA) and a series of dual curable hyperbranched polyurethane acrylate (DHPUA) with different ratios of acrylate and trimethoxysilane end groups. All resins were characterized by Fourior-transformed infrared spectroscopy (FTIR), H-1 and C-13 nuclear magnetic resonance (H-1- C-13-NMR) and gel permeation chromatography (GPC) Then the resins were used as oligomers to prepare UV/moisture dual curable coatings. The surface topographies of the UV cured coatings were investigated by atomic force microscopy (AFM) before and after moisture cure. The results showed that the superficial degree of roughness of the coatings, with acrylate and trimethoxysilane end groups ratio 3 similar to 1 or 1 similar to 1 decreased after moisture cure. However, UV-HPUA and acrylate and trimethoxysilane end groups ratio 1 similar to 3 coatings increased after moisture cure. Thermal gravimetric analysis (TGA) results indicated that the coating thermal stability increased with increasing trimethoxysilane end groups. Moreover the physical properties of the UV cured coating were also measured before and after moisture cure, which indicated that physical properties of the UV-HPUA coating were slight improved through moisture curing process. However, the physical properties were greatly improved for DHPUA coatings, the pencil hardness increased from 6B to 3H and 4H.