Inverting Polyurethanes Synthesis: Effects on Nano/Micro-Structure and Mechanical Properties

Abstract

Two sets of new thermoplastic elastomeric polyurethanes were prepared by different routes. One route was the common two shoot polymerization, in which a short diol is added at the last step in order to link prepolymer chains. The new rout that is described here consisted in preparing firstly the hard segments upon 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BD), used in the previous case as chain extender, and adding finally the polydiol in the second step, in a chain extender fashion, in order to form the grown polyurethane. The differences between these two sets of materials were considerable due to the more ordered and crystalline hard segments formed and the subsequent nano-domain distribution that aroused when inverting the common synthesis. Inter-domain distances and domains sizes are measured and also compared with those of the literature. The structure/properties relationships of synthesized polyurethanes with different hard segment content were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and performing tensile and Shore D hardness tests.

Influence of hard segment content and nature on polyurethane/multiwalled carbon nanotube composites

“…These particular polyurethanes hard domains have an average diameter of ~ 15 nm with interdomain distances in the range of 14-32 nm [16] (see Fig. 1).…”

“…Polyurethane (PU) is among the most versatile materials today [13][14][15] and can be tailored according to the desired application requirements choosing carefully the reactants, their ratio and their synthesis procedure [16]. Different combinations of strength, ductility, biodegradability or hardness can be achieved with the proper formulation and preparation.…”

Biostability of polyurethanes. Study from the viewpoint of microphase separated structure

“…In this way, the degradation first stage was governed by the hard segment structure also depending on the hard segment packed structure formed and crystallinity [24,25]. Normally, three mechanisms of decomposition of urethane bonds have been proposed and reactions may proceed simultaneously: dissociation to isocyanate and alcohol, formation of primary amine and olefin and formation Fig.…”

In situ preparation and characterization of biocompatible acrylate‐terminated polyurethane containing chemically modified multiwalled carbon nanotube

“…The constituting monomers/prepolymers provide unique molecular structure for PUs which basically consist of hard (mainly, isocynate constituent) and soft (polydiol) segments. Incompatibility between the soft and hard segments, and the formation of hydrogen bonding between the hard segments of PU macromolecules (between NH and CO groups of urethane) leads to formation of hard domain/phase with average diameter of 5–20 nm distributed in the soft domain. Consequently, PUs are often considered as composite materials in which hard domain with elastic modulus of ∼1 GPa serves as rigid reinforcing particle and resembles thermally reversible crosslink.…”