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Influence of hard segments content on thermal, morphological and mechanical properties of homo and co-polyurethanes: a comparative study

Alobad Z.K., Albozahid M., Naji H.Z., Alraheem H.S., Saiani A.

Archives of Materials Science and Engineering

2021

Vol. 109, nr 1

5--16

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)-block-poly(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 (ΔHM) and heat capacity (ΔCP) 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). Practical implications: Thermoplastic polyurethanes (TPUs) can be used in various application such as backageing, foot,automobiles and constructions. Originality/value: A new type of TPUs that synthesized using different type of chain extender (1.5 pentanediol). Two different types of TPUs were synthesized one contained 30% SS and 70% HS and a second one contained 100% HS.

Effect of structure on the thermal stability of crosslinked poly(ester-urethane)

Oprea S.

Polimery

2009

T. 54, nr 2

120-125

Polyurethane (PUR) crosslinked copolymers composed of 4,4'-diphenylmethane diisocyanate (MDI), poly(ethylene adipate)diol (PEA), glycerine (Gly), and diol [1,2-ethanediol (ED), diethylene glycol (DEG), 1,3-propanediol (PD), 1,4-butanediol (BD), 1,5-pentanediol (PTD) or 1,6-hexanediol (HD)] as a chain extender were synthesized in a two-step process. The effect of structural hard segments on the thermal stability of crosslinked poly(ester-urethane) was studied. Increase in the length of the hard segment decreased the thermal stability within a given series of compounds. The thermal oxidative stability of the polyurethane crosslinked system was investigated under an air atmosphere using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Interchain crosslinking improves thermal stability and chemically crosslinked PUR behaves as an elastomer capable of shape memory. The decomposition of PUR crosslinked with various hard segments has been compared.

Usieciowane koplimery poliuretanowe (PUR) syntezowano dwuetapowo z diizocyjanianu 4,4'-difenylometanu (MDI), diolu poli(adipinianu etylenu) (PEA), glicerolu (Gly) i diolu jako przedłużacza łańcucha [1,2-etanodiolu (ED), glikolu dietylowego (DEG), 1,3-propanodiolu (PD), 1,4-butanodiolu (BD), 1,5-pentanodiolu (PTD) lub 1,6-heksanodiolu (HD)] (tabela 1). Metodą analizy termograwimetrycznej (TGA) i skaningowej kalorymetrii różnicowej (DSC) badano w atmosferze powietrza stabilność termiczną otrzymanych materiałów. W badanych seriach związków różniących się stosunkiem substratów (PUR1-PUR2 i PUR7-PUR12) metodą TGA stwierdzono zmniejszanie się stabilności termicznej ze wzrostem długości segmentów sztywnych (tabela 2, rys. 1-4). Wyznaczono energię aktywacji (Ea) procesu degradacji w funkcji stopnia przemiany (a) (rys. 5 i 6). Zaobserwowano zwiększanie się wartości Ea ze wzrostem ciężaru cząsteczkowego segmentów sztywnych podczas pierwszego etapu degradacji, a zmniejszanie się podczas drugiego etapu. Metodą DSC wyznaczono temperaturę zeszklenia (Tg) otrzymanych materiałów. Stwierdzono zmniejszanie się wartości Tg ze wzrostem zawartości grup metylenowych w segmentach sztywnych PUR.