Polyurethanes from 2,4-toluene diisocyanate and a mixture of castor oil and hydroxyether of bisphenol-A

Abstract

Polyurethanes (PU) were prepared from 2,4-toluene diisocyanate (TDI) and mixtures of castor oil and hydroxyether of bisphenol-A (HBA). Differential scanning calorimetry and dynamic mechanical measurements studies revealed that each PU so obtained has a single T 8s, increasing with both HBA content and ratio of NCO/OH from 0.85 to 1.1. With increasing HBA/[HBA + castor oil]from 0 to 0.50, the PU samples exhibit various modes of fracture, from the common stress-strain behaviour of elastomers to ductile fracture and to brittle fracture while the Young's modulus increases almost by three orders of magnitude. The curves of Young's modulus vs HBA/[HBA + castor oil] are S-shaped, implying that the PUs are not molecularly homogeneous. Tensile strength increases greatly with HBA content. Increasing NCO/OH ratio from 0.85 to 1.1 also enhances the tensile strength. The elongation at break first increases and then decreases with increasing ratio HBA/[HBA + castor oil].