Effect of Chemical Composition on Large Deformation Mechanooptical Properties of High Strength Thermoplastic Poly(urethane urea)s

Abstract

The effect of composition on the true mechanooptical properties of thermoplastic poly-(urethane urea)s was investigated by selectively varying the type and content of soft and hard segments. Real-time stress-strain-birefringence data together with off-line wide-angle X-ray scattering measurements revealed that soft segment and chain extender play dominant roles on the chemical structures of the poly(urethane urea)s. All poly(tetramethylene oxide) glycol-based samples showed the same crystal structure. The samples containing ethylenediamine as the chain extender showed enhanced crystallizability as compared to those with 1,6-diaminohexane no matter which soft segment was used. In general, samples with lower fraction of hard segment exhibited higher crystallizability than their high hard segment counterparts. Long-term holding of poly(ethylene oxide) samples in stretched state was found to increase crystallinity. The strain-induced crystallization in low hard segment content poly(tetramethylene oxide)based samples was only observed at very high deformation levels. On the other hand, crystallization in the samples containing high hard segment was found to evolve gradually over large deformation range. The strain rate has a considerable effect on the crystallization behavior of poly(tetramethylene oxide)based samples. While the low hard segment content poly(tetramethylene oxide) sample experiences decreasing crystallizability as the strain rate increases, its counterpart containing higher fraction of hard segments exhibits opposite behavior. We have investigated linear and nonlinear stress optical behavior and observed that the span of the initial linear stress optical region varied primarily with composition (slope ranging from 0.1 to 2.2 GPa -1 ) and secondarily with the deformation rate. Hysteresis experiments show that there is a considerable loss of energy in cyclic loading of these materials, and hysteresis increases as the chain extender is changed from 1,6-diaminohexane to ethylenediamine.

Development in Synthesis and Coating Applications of Polyurethane

“…PUs are segmented linear macromolecules having alternate sequence of soft and hard segments. The soft segments consist of polyether / polyester diols, whereas hard segments consist of diisocyanate and diols/diamines which act as chain extenders [3]. The soft segments exhibit the elastomeric property while hard segments show crosslinking and high strength.…”

Relationship between Photoelasticity of Polyurethane and Dielectric Anisotropy of Diisocyanate, and Application of High-Photoelasticity Polyurethane to Tactile Sensor for Robot Hands

“…Photoelasticity is a property in which a change in an optical parameter (refractive index) is caused by elastic deformation [ 17 , 18 , 19 , 20 ]. There are two constants: a photoelastic constant ( P ) and an elasto-optical constant ( E ).…”

Electrospinning-induced shape memory effect in thermoplastic polyurethane characterization and thermoviscoelastic modeling

“…Thermoplastic polyurethanes (TPUs) are very versatile polymers, owing to the numerous options for combining the hard and soft segment‐forming macromolecules through urethane bonds . Indeed, a variety of nanoscale morphologies may be achieved by manipulation of the hard and soft segment types and their relative concentrations .…”