Phase structure and thermal stability of crosslinked polyurethane elastomers based on well‐defined prepolymers

Abstract

Taking advantage of the DSC method, general procedures were presented for qualitative and quantitative evaluation of the phase separation degree and the crystalline phase content in polyurethane elastomers with well-defined structures. Those elastomers were obtained not only in a typical one-step method but also in the prepolymer method with the use of urethane oligomers with controlled molecular weight distribution (MWD). Prepolymers with well defined chain structures and narrow distributions of their molecular weights (MWD) M w /M n ¼ 1.1-1.3 were produced in a multistage method, i.e., in step-by-step polyaddition of 2,4-and 2,6-TDI with polyoxyethylenediols or with polycaprolactonediols of varied molecular weights. Isocyanate oligomers obtained at individual stages were then crosslinked with triethanolamine, whereas hydroxyl-terminated oligomers were crosslinked with 4,4 0 ,4 00 -triphenylmethane triisocyanate (Desmodur RE). The obtained polyurethane elastomers were found to be characterized by the presence of five phases: soft phase consisted of flexible polyol-type segments, crystalline phase made of soft segments, crystalline and amorphous hard phase made of hard segments, and intermediate phase, which was a composition of the soft and hard segments. The polyurethanes obtained out of prepolymers with defined MWD were characterized by better phase separation of the soft segments and increased structural order inside the hard phase as well as by better thermal stability than polyurethanes obtained from the typical one-step method. The structural effects were also discussed on the thermal properties of the synthesized elastomers as analyzed by the TG and DTA methods.

Modeling of segmented pure polyurethane electrostriction behaviors based on their nanostructural properties

“…16 | P a g e could correspond to the fusion of crystalline hard segments with two different chain lengths [1921,224]. Alternatively, it can be related to rearrangements within the HDs and SDs, followed by the fusion of crystalline HDs [235,2419].…”

Specific interactions, structure and properties in segmented polyurethane elastomers

“…Phase separation has been the subject of many studies [11,12]. The results showed that structural units of various forms and sizes develop during polymerization [13][14][15]. Besides a crystalline or at least highly ordered phase, soft and hard segments form corresponding phases which are partially soluble in each other [16][17][18][19][20][21].…”

Stress–Strain Dependence of Segmented Polyurethanes and Polyurethane Ureas

“…Earlier we proved that the effect of a strong decrease in the slope of the stress-strain plot could not be described using Eq. (7). [31,32] In our opinion, simple approaches with a minimum number of parameters are the most interesting.…”

“…Hard domains can destruct partially or completely at elevated temperatures, at high strain degrees, or when immersed in solvents or plasticizers. [6,7] A number of papers containing experimental stress-strain data of segmented polyurethanes under simple stretching have been published. [e.g., ] The majority of these works are characterized by a descriptive consideration of the obtained data.…”