Hard-segment characterization

Hard Segment Characterization The preparation of copolymers of aminopropyl endcapped dimethylsiloxane oligomers and isophorone diisocyanate with 1,4-benzenedimethanol as the chain extender outlined in Scheme 1 is similar to the method used by Pascault and co-workers to prepare alkoxy-silane terminated... 

In addition to microphase structures, MDI/BDO-based polyurethane systems have exhibited spherulitic superstructure. Characterization of the birefringence of the spherulites was used to determine the orientation of the hard-segment domains (7). However, because of the sensi-... 

TDI Polyurethanes. Two 2,4-T-lP samples with different hard-segment concentrations were studied and found to display a broad a-relaxation maximum, also characterized by a decline in storage modulus of about two and one half orders of magnitude, as shown in Figure 5, a plot of storage and loss modulus vs. temperature at 11 Hz. The position... 

Both series of polyurethanes were prepared using a prepolymer technique in which reactants were mixed at 70 °C/1 hour, cast into molds at 105 °C/2 hours, and cured at 80 °C/14 hours. The BD/MDI hard segment contents ranged from 0% (transparent, colorless homopolyurethanes) to 30% w/w (opaque, white copolyurethanes). All elastomers were characterized using DSC, dynamic mechanical, and tensile stress-strain measurements. 

Urethane polymer morphology can be quickly characterized by means of DSC and TMA analyses. These thermal analyses are valuable tools in determining the interrelationship of the many formulation variables of urethane polymer systems polyol type and molecular weight, hard segment type and concentration, and various prepolymer compositions. 

These premises can be taken as the major reasons for the rationale that brought us to contribute to meetings, such as the first and the second Joint Polish-Italian Seminar, expressely devoted to "polymer blends". In this context, we present the results of the work done in part at the University of Pisa and in part at the University of Massachusetts in the field of the preparation and characterization of polyester systems containing p-oxybenzoate residues, as the anisotropic moieties, embedded in structurally ordered macro-molecular segments. Linking units in the hard segments are the terephthaloyl (Series I, IV, and V), oxalyl (Series II) and carbonyl... 

Versteegen RM, Sijbesma RP, Meijer EW (2005) Synthesis and characterization of segmented copoly(ether urea)s with uniform hard segments. Macromolecules 38(8) 3176-3184... 

PUs comprise a polyether, or polyester soft segment, and a diisocyanate-based hard segment. This can be characterized by a two-phase morphology, which is due to the fact that the hard and soft phases are immiscible, leading to the formation of a hard-segment domain, a soft-segment matrix, and an ill-defined interphase. 

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