Structural and mechanical properties of polybutadiene‐containing polyurethanes

Abstract

A series of segmented polyurethanes based on hydroxylterminated polybutadienes (HTPBD) and their hydrogenated derivatives(HYPBD) has been synthesized. Thermal, mec:hanic:aL and spectrosc:opic: studies were c:arried out over a wide temperature range to elucidate the structure-property relationships existing in these polymers. Both thermal and dynamic mechanical response showed a soft segment Tu at-74°C forthe unsaturated polyurethanes and at -69"C for the hydrogenated samples. In addition, two hard segment transitions are. observed by differential scanning c:alorimetry (DSC) at 40 and 75°C and a softening region by thermal mechanical analysis (TMA) at 190"C. The low T,,. very dose to that of the free HTPBD and HYPBD and independent of hard segment c:ontent. indicated that these polymers were well phase separated. Results of infrared analysis revealed that at room temperature, 90-95 percent of the urethane N-H groups formed hydrogen bonds. Since hydrogen bonding resides only within the hard segment domain in these butadiene-c:ontaining polyurethanes the extent of H-bonding served as additional evidence for nearly complete phase segregation. From dynamic: mechanical studies, the plateau modulus above the soft segment Tu and stress-strain behavior depended upon the concentration of hard segments. A slight increase in the modulus, a moderate increase in stress (er,,), and decrease in elongation accompanied a higher hard segment content. The thermal and mechanical response of these polyurethanes appears to be consistent with behavior observed for other phase segregated systems. Variations in behavior resulting from hydrogenation of the precursor prepolymer are discussed.

Effect of chain extender structure on the properties and morphology of polyurethanes based on H12MDI and mixed macrodiols (PDMS–PHMO)

“…Most previous studies [1][2][3][4][5][6] on structure-property relationships of polyurethanes have been focused on polyether, polyester, and polycarbonate macrodiols. There has been some recent interest on polyurethanes based on nonpolar macrodiols, such as polydimethylsiloxane (PDMS), 7 polyisobutylene, 8 and polybutadiene 9 macrodiols. Typically, polyurethanes based on nonpolar macrodiols are highly phase separated (poor interfacial adhesion) and, consequently, have poor mechanical properties.…”

Transparent Barrier Urethanes Based on Polyethylene Soft Segments

“…[9] The materials synthesized with the novel soft segment precursors provided by the Tudos group show a superior combination of high stiffness and high elongation relative to other materials prepared in this study and by others. [5,9,11] The barrier properties of these segmented, olefinic polyurethanes are also quite impressive. These elastomers were insoluble in all pure solvents tested, including aprotic solvents such as DMF and tetrahydrofuran (THF).…”

“…[2,[5][6][7][8][9][10][11][12] More emphasis was placed on the latter, because of the commercial availability of butadiene polyols and problematic synthesis leading to inferior performance of the isobutylene-based systems. [10] The physical properties of the hydrogenated polybutadiene (PBD) urethanes, including mechanical performance, thermal transition temperatures, degree of phase separation, and transparency have been found to depend on a number of factors, including degree of hydrogenation [5], soft segment molecular weight [13], and synthesis conditions. [9] A comparison of different studies of polyurethanes having fully saturated soft segments of roughly equal molecular weight also suggests that the use of soft segments supplied by different manufacturers, with the associated differences in branching content and functionality, may alter the properties of the urethanes significantly.…”

Processing and characterization of electrospun trans-polyisoprene nanofibers

“…The sample, of about 4 mg, was placed in a sealed aluminum pan, and the measurements were carried out using heating rates of 10°C/min. The fusion heat of the TPI crystals was taken as 140.82 J/g for calculations of the degree of crystallinity [17]. The calculation was based on the heat of fusion value.…”