Specific interactions, structure and properties in segmented polyurethane elastomers

Abstract

Abstract. Two sets of segmented polyurethane (PU) elastomers were prepared from 4,4!-methylenebis(phenyl isocyanate) (MDI), 1,4-butanediol (BD) and a polyester or a polyether polyol, respectively. The molecular mass of both polyols was 1000 g/mol. The stoichiometric ratio of isocyanate and hydroxyl groups was 1 and the polyol/total diol ratio changed from 0 to 1 in 0.1 steps. One step bulk polymerization was carried out in an internal mixer and the samples were compression molded for testing. The results proved that specific interactions determine the phase structure and properties of these materials. Crystallinity was approximately the same in the two types of polyurethanes and the amount of relaxing soft segments was also similar. The determination of interaction parameters from solvent absorption and differences in glass transition temperatures indicated stronger interaction between hard and soft segments in the polyester than in the polyether polyurethane. Larger transparency of the polyester PU indicated the formation of smaller dispersed particles of the hard phase. The larger number of smaller hard phase units led to the formation of more physical cross-links distributed more evenly in the polymer. These differences in the phase structure of the polymers resulted in stronger strain hardening tendency, larger strength and smaller deformations for the polyester than for the polyether polyurethane.

Transparent sulfur-containing thermoplastic polyurethanes with polyether and polycarbonate soft segments

“…Segment polarity, length, and crystallizability, the tendency to hard segment-soft segment interaction, overall sample composition, and molar mass are among the factors which have an effect on phase segregation in polyurethanes [2]. It is known that higher polarity polyester and polycarbonate soft segments making up stronger hydrogen bonding with the hard segments exhibit a more limited tendency to phase segregation than lower polarity polyether soft segments [9][10][11]. The use of shorter segments also causes the growth in phase mixing [3,[12][13][14].…”

Interrelationship between ultimate mechanical properties of variously structured polyurethanes and poly(urethane urea)s and stretching rate thereof

“…The chemical structure of SPU soft segments is determined by structure of oligomers used for their synthesis [1,5,[9][10][11]. Hard segments are formed during reaction of diisocyanate with low-molecular bi-functional compounds, e.g., diols or diamines.…”

“…Hydrogen bonds in micro-domains play an important role in stabilization of hard phase structure [9,[12][13][14]. In SPUs, hard domains appear to be strengthening fillers and also physical cross-linking points in specific physical network which is stable in a wide temperature range [15,16].…”

Structure, Mechanical, Thermal and Fire Behavior Assessments of Environmentally Friendly Crude Glycerol-Based Rigid Polyisocyanurate Foams

“…Such effect is related to the increasing heterogeneity of structure and molecular weights of polyol chains, due to the incorporation of biopolyol, whose structure is different than for Lupranol 3300. Used petrochemical polyol is polyether, while CG biopolyol contains in its structure also ester groups, which show different behavior, during DMA analysis [44]. Other important factor is increasing cross-link density of foams [45,46].…”