S of frequency sweep tests at T . TCO (T ?1658C) and also the final results are reported in figure three. The cross-over frequency was low (v ?2 rad s21), as is common for incredibly high molecular weight polymers (figure 3a) [17]. The PU complex viscosity as a function of frequency showed a shear thinning behaviour in a wide range of frequencies (figure 3b). The outcomes of time sweep test (isothermal rheological characterization) are reported in figure four. G0 and G00 had been about constant through the test, suggesting that samples didn’t undergo thermal degradation. Additionally, PU stability was confirmed by the absence of substantial variations in terms of the polymer molecular weight and polydispersity index following this thermo-mechanical remedy (Mn ?71 500 Da and D ?1.96; table 1).3.1.3. Thermal properties three.1.three.1. Differential scanning calorimetryDSC was performed to characterize the thermal properties of PU films in terms of glass transition, melting and crystallization temperatures (Tg, Tm, Tc, respectively) and melting and crystallization enthalpies (DHm, DHc, respectively).4-Bromo-5-chloronaphthalen-2-ol Chemical name Results are shown in table 2 for each and every DSC scan. The DSC thermograms of PU films are reported in figure 5. The very first heating scan from the PU films showed two melting peaks at 768C and 1568C, each characterized by a melting enthalpy of 2.four J g ?1. These two endothermic peaks areTable 2. Thermal parameters of PU measured by non-isothermal DSC evaluation (initially heating: from 208C to 2008C; cooling: from 2008C to 2608C; second heating: from 2608C to 2008C; scan rate: 108C min21). initial heating Tg (8C) 45.4 Tm (8C) 76 155 DHm (J g ?1) 2.4 2.four cooling Tc (8C) 222 DHc (J g ?1) 13.six second heating Tg (8C) — Tc (8C) 24 DHc (J g ?1) 7.2 Tm (8C) 39 DHm (J g ?1) 24.rsfs.royalsocietypublishing.org Interface Focus four:0.4 0.cooling0 ?.2 second heating initial heating ?.four ?.6 ??35 85 temperature ( )Figure 5. DSC thermograms of PU sample. 1st heating scan: heating from 208C to 2008C at 108C min21 and isotherm at 2008C for three min; cooling scan: cooling from 2008C to 2608C at 108C min21 and isotherm at 2608C for three min; second heating scan: heating from 2608C to 2008C at 108C min21.tough segment Tg for many minutes. Having said that, this thermal remedy is just not anticipated to result in any modification within the difficult segment melting temperature. A processing temperature higher than the tough segment melting temperature (1558C) was selected for the fabrication of PU scaffolds by AM.Price of 3-Bromo-5-methylbenzonitrile at 1558C.PMID:24182988 The uniformity in the layered pattern, with precisely aligned and often spaced fibres and completely interconnected inner architecture, demonstrated the suitability of this polymer to be melt-extruded in three-dimensional structures. The results of image analysis on SEM micrographs showed good agreement involving the computer-generated geometry plus the obtained scaffolds. A imply fibre diameter of 152 + 5 mm along with a imply spacing of 505 + 5 mm were measured. Scaffold height was 280 mm, suggesting interpenetration in between adjacent layers of about 20 mm. Uniaxial tensile tests had been performed on scaffolds and relative mechanical parameters had been measured (E ?10.2 + 2.two MPa; UTS ?three.three + 0.two MPa; strain at UTS ?693.0 + 15.0 ). A representative tensile stress train curve is reported in figure 9. Cyclic tensile tests (five cycles; 0?0 deformation; table three) evidenced a permanent strain of about 2.5 immediately after the first cycle, probably owing to chain orientation along the anxiety path [19]. During the following deformation cycles, permanent.
