Phosphorylated Epoxy Resin: Effect of Phosphorus Content on the Properties of Laminates

Abstract

The paper describes the properties of glass-fabric reinforced composites based on novel phosphorylated epoxy matrix resins. Limiting oxygen index as high as 80 were attained using such novel matrix resins. These resins were prepared by curing diglycidyl ether of bisphenol-A (DGEBA) with phosphorylated amines such as bis(3-aminophenyl) methyl phosphine oxide (B), tris(3-aminophenyl)phosphine oxide (T), bis[3(3′-aminobenzamidophenyl)]-methylphosphine oxide (MB), bis[3(4′-aminobenzamido phenyl)]methylphosphine oxide (PB), tris[3(3′-aminobenzamidophenyl)]phosphine oxide (MT) and tris[3(4′-aminobenzamido phenyl)] phosphine oxide (PT). Phosphorus- containing amide-acid amines were also used for curing and were prepared by reacting T with 1,2,4,5-benzenetetracarboxylic acid anhydride(P); 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride (Z) and 4,4′-(hexafluoroisopropylidene)diphthalic acid anhydride (F). Interlaminar shear strength (ILSS), flexural strength and modulus of composites (32 ± 3% resin content) based on B, T, MB, PB, MT, PT and state-of-the-art curing agent 4,4′-diaminodiphenyl sulfone (D) were higher than the composites prepared using amide-acid amines. Increase in ILSS was observed on heating at 180°C for 200 h. On hygrothermal ageing of the samples for 7 days, the ILSS values decreased but those cured with amide-acid amines showed the least change. A significant improvement in limiting oxygen index (LOI) was observed by increasing the phosphorus content of the composites.