Development and Characterization of Palm Flower Carbon Reinforced DOPO‐Urea Diamine Based Cardanol Benzoxazine‐Epoxy Hybrid Composites

Two high toughness and flame retardant DOPO-containing polybenzoxazines based on polyether-urea

In this current work, two new-style DOPO-containing benzoxazines based on polyether-urea were successfully synthesized by a modified version via three-step procedures, and the corresponding polybenzoxazines with high toughness and flame retardancy were obtained by thermal activated polymerization. The single and double DOPO-containing benzoxazines were named as BzD1 and BzD2, respectively. The corresponding polymers followed were named as PBzD1 and PBzD2, respectively. The curing behaviors of the two new benzoxazines were investigated by differential scanning calorimetry. The thermal and mechanical properties of the materials were evaluated by TGA and dynamic mechanical analysis. The flame retardant properties were elucidated via limiting oxygen index (LOI). The toughness properties were expressed by bending tests. The results showed that the Yc for PBzD1 and PBzD2 were approximately 22.2% and 24%, respectively, distinctively higher than the value 2.57% of pristine polybenzoxazine PBz1, at 800 °C in N2 atmosphere. The Tgs of PBzD1 and PBzD2 distinctly increased by 42.8 °C and 20 °C, respectively, in comparison to −35 °C for pristine PBz1. The LOI values of PBzD1 and PBzD2 were 28.5 and 31, respectively. The length and weight-loss of PBzD1 and PBzD2 samples were significantly less than that of PBz1 when they were burned in the air environmental condition. The burning behavior demonstrated that the flame retardant properties was obviously improved as DOPO was introduced. All of the three specimens of PBz1, PBzD1 and PBzD2 presented excellent flexible property.

Bio-based polybenzoxazines as an efficient coatings to protect mild steel surfaces from corrosion

New types of mono and bi-functional benzoxazine monomers were synthesized using cardanol (C) and 4-aminobenzonitrile (abn), p-phenylediamine ( ppda) along with paraformaldehyde. The synthesized benzoxazine monomers structure was elucidated by 1H, 13C-NMR and FTIR spectroscopic techniques. The polymerization temperature (Tp) of C-abn and C- ppda are noticed at 280oC and 237oC, respectively. It was also noticed that bi-functional benzoxazine (C- ppda) possesses lower curing temperature than mono-functional benzoxazine (C-abn). The ring opening polymerization of benzoxazine was confirmed by FTIR spectroscopy. Thermal analyses indicate that, benzoxazine [poly(C- ppda)] possesses higher thermal stability than poly(C-abn). The surface roughness of the benzoxazine coated MS specimen was analysed by atomic force microscope. The values of water contact angles obtained for poly(C-abn) and poly(C- ppda) are 145o and 148o, respectively. It was noticed that the mild steel specimen coated with bio-based benzoxazine C-abn exhibit excellent resistance to corrosion.