Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer.

Shazia Naheed,Abdelatty Abdelgawad,Mohammed A F Sharaf,Mohammad Zuber,Mohammed Rafi Shaik,Doumbia Sekou,Zumaira Siddique,Emad Mahrous Awwad,Nasir Rasool,Mahwish Salman

doi:10.3390/polym13132060

Abstract

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

Highlights

The importance of PU elastomers is increasing because of their broad range of properties and increasing number of applications [1,2,3]
Clear phase segregation was observed in the high molecular weight polycaprolactone diol (PCL) samples
Micrographs demonstrated that phase segregation depended upon the increasing molecular weight of the macrodiol

Summary

Introduction

The importance of PU elastomers is increasing because of their broad range of properties and increasing number of applications [1,2,3]. The macromolecules of PUEs are composed of relatively long, flexible segments (SSs) and short, rigid segments (HSs), with alternating polydisperse blocks. As a result of the phase separation process, a soft phase is formed from the SSs, and a hard phase is formed from the HSs. The soft phases, with minor glass transition temperature (Tg) values, usually consist of polyethers, polyesters or polyols, whose molecular weight range is from 400 to 5000. Polyurethane elastomers demonstrated microphase separation due to thermodynamic immiscibility between the polyol (soft segment) and urethane (hard segment). This doublephase microdomain structure shown by PUEs provides them with their better mechanical properties [2,4,8,9]

Methods

Results

Conclusion