Change in mechanical properties, composition, and structure of hydrated polyurethaneurea

Abstract

Relative to the extensive study on the relationship between the structure and properties of polyurethane (PU) and polyurethaneurea (PUU), basic information available on hydrated PUU is limited. In this study, PUU films were immersed in a saline solution (0.9 wt % NaCl, 37°C) for periods of up to 60 days and evaluated by the change in static and dynamic mechanical properties, composition, and hydrogen‐bonding structure. It was found that immersion in a saline solution could greatly increase the average molecular weight and degree of phase separation, which enhanced the mechanical strength and reduced the flexibility. The increase in the average molecular weight is believed to come from the chain extensions or crosslink reactions between intramolecules and/or between intermolecules and from the leaching out of poly(tetramethylene oxide) (PTMO) oligomers. FTIR analysis indicated that H2O molecules did not obviously alter the hydrogen‐bonding structure of PUU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 252–260, 2001

Miktoarm star‐shaped poly(lactic acid) copolymer: Synthesis and stereocomplex crystallization behavior

“…[1][2][3][4][5][6] Unfortunately, the low crystallinity and poor heat resistance of the PLA limit its application. [7][8][9] Many efforts have been made to improve the heat resistance of PLA, such as blending, 10 nucleating agents, [11][12][13][14][15] crosslinking, 16 and nanoparticles. 17 This structure can also have an effect on the heat resistance of PLA, for example, the preparation of stereocomplex (SC) PLA.…”

Insight into selective oxidation of dual‐phase steel after annealing in pure H2 atmosphere at different heating rates and temperatures

“…The mapping and spot analysis results as shown in Figure 3 and Table 2 indicates that the oxides were formed in the order of MnO, Mn 2 SiO 4 , MnSiO 3 , and SiO 2 from the surface of the steel into the matrix, which is very similar to our previous work. [27] Figure 4 shows the effect of different heating rates and temperatures on the internal oxidation depth. It could be seen that the depth of internal oxidation presents a typical parabolic shape.…”

“…In the process of the experiment, the water pressure control device is illustrated in Figure 1 and the experimental equipment is introduced in our previous publication. [27] After reaching the target temperature (700°C, 810°C, and 843°C), the sample was quickly moved to the constant temperature area for oxidation treatment, in which the water pressure was P P / H HO 2 2 = 0.033 bar, the heating stage was 30 and 180 s, and the heat preservation time was 0-30 min. After reaching the predetermined experimental conditions, the samples were rapidly pushed into the cooling chamber to preserve the microstructure of high-temperature precipitates and study their oxidation mechanism.…”

“…In our previous work, we reported the mechanism of oxide growth with different soaking times and water pressures. [27] As part of the project as a whole, the aims of the current study is to further investigate the oxide evolution on DP980 AHSS steel with different soaking temperature and further determining whether the oxidation is influenced by the heating rate. Table 1 shows the chemical compositions of DP980 AHSS.…”

Effect of solvent exposure on the properties of hydroxy‐terminated polybutadiene‐based polyurethanes

“…The improvement in diffusion behavior of HTPB‐based polyurethane as a result of application of stress has been investigated by Sreenivasan 15. Wu et al 16, 17 conducted a series of studies of change relative to the morphology and mechanical properties of polyurethane and polyurethane‐urea exposed to dilute saline.…”