Abstract
Aliphatic segmented polyurethanes were prepared by one-step procedure in catalytic reaction between polycarbonate diol, hexamethylene-diisocyanate and 1,4-butandiol (as chain extender). The hard segment content TS was varied (17, 24, 30 and 42 wt. %) by changing the ratio of starting compounds. The soft segment is made from flexible aliphatic polycarbonate diol, while hard segments consist of chain extender and diisocyanate component. In order to study the hydrogen bonding formation and phase separation, Fourier transform infrared spectroscopy (FT-IR) was used. Wide angle X-ray scattering (WAXS) was performed to determine a degree of crystallinity and to investigate the phase behavior of prepared elastomers. The effect of TS content on mechanical properties (tensile strength, elongation at break and hardness) was tested. Thermal behavior of prepared novel polycarbonate-based polyurethanes was investigated using differential scanning callorimetry (DSC). It was determined that the elastomer which contains the highest amount of urethane groups in its structure (TS content of 42 wt. %) exhibits the most pronounced phase separation and the highest degree of crystallinity. All prepared polyurethanes exhibit high elongation at break (over 700%). The glass transition temperature Tg of prepared samples was in the temperature region from ?39 to ?36?C, and it was found to be slightly influenced by the soft segment content. The enthalpy of chain segments relaxation in diffused region between hard and soft domains (detected in the temperature range from 35 to 55 ?C) was decreased with the increase of hard segment content. The multiple melting of hard segments (connected with the dissruption of physical crosslinks) appeared above 100 ?C. It was found that the melting enthalpy linearly increases with the increase of urethane group content. Sample with 42 wt. % of TS has the highest value of melting enthalpy (41.5 J/g).
Highlights
Makrodiol T5651 ima sledeće karakteristike: hidroksilni broj, 111,4 mg KOH/g; sadržaj vode, 0,0052 mas.% i viskoznost od 1619 mPa·s na 5 °C
Na talasnom broju od 2270 cm−1, koji odgovara NCO grupi, nije uočen pik na Fourier transform infrared spectroscopy (FT-IR) spektrima svih ispitivanih uzoraka, što predstavlja potvrdu da su izreagovale sve izocijanatne grupe sa alkoholnim grupama u toku sinteze segmentiranih poliuretana
Karbonilne grupe prisutne u kristalnim, tvrdim oblastima su uočene na talasnom broju od 1682 cm−1, dok traka 4 (u obliku ramena), koja se nalazi na 1657 cm–1, potiče od karbonilnih grupa za koje je vezan atom vodonika, a koje su prisutne u mekim segmentima sintetisanih poliuretanskih elastomera [27]
Summary
Alifatski polikarbonatni diol oznake proizvođača T5651, molekulske mase oko 1000 g/mol, koji u struk-. Turi sadrži isti broj pentanskih i heksanskih jedinica, dobijen je od Asahi Kasei korporacije. Makrodiol T5651 ima sledeće karakteristike: hidroksilni broj, 111,4 mg KOH/g; sadržaj vode, 0,0052 mas.% i viskoznost od 1619 mPa·s na 5 °C. Heksametilen-diizocijanat (HDI), 1,4-butandiol (BD) i katalizator, dibutil-kalaj-dilaurat (DBTDL) dobijeni su od proizvođača Fluka
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