Comparison of the Structure-Properties in 2,4 TDI Based Polyether Polyurethanes and Polyurethaneureas

Abstract

The objective of this paper is to review and compare the structure-property relationships in segmented polyurethanes and polyurethaneureas based on 2,4 toluene diisocyanate. In this paper, polyurethanes refer to polymers extended with butane diol, while polyurethaneureas refer to polymers extended with ethylene diamine. Both polyurethanes and polyurethaneureas consist of alternating soft segment (aliphatic polyether) and hard segment (aromatic urethane or urea). Due to the thermodynamic incompatibility of the hard segments with the soft segments, microphase segregation occurs in these polymers to a varying degree, which is strongly influenced by the compositional variables (1–4). In this paper, the effect of urethane linkage (as in polyurethanes) versus urea linkage (as in polyurethaneureas) in the hard segment will be discussed with polymers based on asymmetric diisocyanates, such as 2,4 toluene diisocyanate. Due to its asymmetry, the hard segment domains in these polymers are amorphous (2,5), thus complications arising from a partial crystallinity in the hard segment domains (as in MDI based polyurethanes) are absent. The soft segment used in these polymers is polytetramethylene oxide (M.W. 1000 or M.W. 2000), which was found to be amorphous in segmented polyurethanes or polyurethaneureas.