Purpose: This work aims to study the effect of hard segments (HS) content on the
thermal, morphological and mechanical properties of polyurethane polymers based on 1.5
pentanediol chain extenders.
Design/methodology/approach: Two comparable series of polyurethanes were
synthesised including homo-polyurethane (Homo-PU) and copolyurethane (Co-PU). The
Homo-PU consists of 100% wt. of hard segments (HS). The Co-PU composes of 30%wt.
of soft segments (SS) using a poly(ethylene glycol)-block-poly(propylene glycol)-blockpoly(ethylene glycol) material. The effect of hard segments content on the morphology of
Homo-PU and Co-PU was also studied.
Findings: The Homo-PU and Co-PU materials show three distinct degradation steps with
the higher thermal stability of the Co-PU compared to the Homo-PU. Enthalpy of fusion
(?HM) and heat capacity (?CP) of polyurethane (PU) samples decrease with decreasing HS
content. In the cooling cycle, the higher exothermic peak of crystallization is observed in
the Co-PU. In contrast, the cold crystalline peak is observed in the 2nd heating cycle of the
Homo-PU. Melting temperature (TM) increases with increasing SS content. Glass transition
temperature (Tg) of PU samples shifts to higher temperature with increasing HS content.
Storage modulus (E’) of the Co-PU is higher than E’ of the Homo-PU. All N-H groups in PU
samples are hydrogen-bonded, whilst most of the C=O groups are hydrogen-bonded. The
degree of hydrogen bonding in PU samples decreases with decreasing HS content. The
Homo-PU shows better hardness than the Co-PU and higher brittleness at low temperature.
WAXS results of the Homo-PU display better crystallinity compared to the Co-PU.
Research limitations/implications: The main challenge in this work was how to
synthesis Thermoplastic polyurethanes (TPUs) with specific properties to compete other
common polymer such as Polyamides (PA) and Polypropylene (PP)