Effect of Hard Segment Molecular Weight on Dilute Solution Properties of Ether Based Thermoplastic Polyurethanes

K W Lem,C Brumlik,G S Song,J R Haw,S E Sund,D S Lee,S Curran

doi:10.13189/nn.2013.010301

K W Lem, C Brumlik + Show 5 more

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https://doi.org/10.13189/nn.2013.010301

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Abstract

A systematic study was conducted on the effect of hard segment molecular weight (or length) on solution and bulk properties of ether based thermoplastic polyurethanes (TPUs). The purpose of this study is to provide a roadmap to deliver the desired end-use performance of a polyurethane product based on the optimal design of the starting materials. In this paper, we report our findings on the effects of hard segment molecular weight on properties of a dilute solution of TPUs in N, N-dimethyl formamide (DMF). The molar feed was used to determine the molecular weight of the hard segment. Then, the weight fraction of the hard segment is determined by calculating the ratio of the molecular weight of the hard segment to the number average molecular weight of the TPU determined by Gel Permeation Chromatography. It was found at low hard segment weight fraction there is a significant impact on the weight average molecular weight and molecular weight distribution, intrinsic viscosity, critical concentration, hydrodynamic diameter, polymer-solvent interaction parameter and second virial coefficient. However, at high weight fractions at around 0.4, the impact is minimal. Furthermore, the weight fraction has a minimal impact on number average molecular weight, and the expansion parameter in the Flory-Huggins analysis.

Highlights

Polyurethane is one of the most diversified traditionaland nano-structured polymers known
We report the highlights of our study on the effects of hard segment
A segmented di-block thermoplastic polyurethane (TPU) is synthesized in this study, following the procedure and the analysis described by Kim and Lee [47] and Nguyen et al [48]

Summary

Introduction

Polyurethane is one of the most diversified traditionaland nano-structured polymers known. The soft segment contributes “elastomeric” properties such as hardness, compression and tension set, flexibility, and low-temperature performance. Five potential morphologies are illustrated in the segmented polyurethane as seen in Fig. 1: 1) pure hard segment, 2) pure soft segment, 3) soft segment and soft segment mixing, 4) hard segment and hard segment mixing, 5) hard and soft segment mixing. These hard and soft segments play a critical role in determining the properties at the nano- or micro-scale in the solid state.

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