Soft segment content

Elastomeric, lignin-derived polyurethanes can be produced from a three-component system, in which a polyether diol (like PEG) is used as soft segment, provided that the crosslink density is held at a low level and that the soft segment content is high enough to keep T below room temperature. 

Effect of Soft-Segment Content on the Properties of Lignin-Based Polyurethanes... 

The Tg of polyurethanes crosslinked with aromatic isocyanates shows no difference between the PEG-extended and the CEHPL networks. The Tg values for both types of networks follow the same relationship. Networks without soft segment content generally have a higher Ttf than those with... 

KELLEY et al. Soft-Segment Content of Lignin-Based Polyurethanes 407... 

Figure 7. Surface chemical composition—depth profile of Avothane. (O) Based on 1710 cm 1 based on 1600 cm 1, (a) The calibrated soft-segment content in air surface/substrate surface, (b) the calibrated silicone polymer content in air surface/substrate surface.

Here we consider a series of new poly(ester ether carbonate) (PEEC) multiblock terpolymers with varying amount of ether and carbonate soft-segment content. Dielectric relaxation experiments on the same PEECs revealed the existence of two relaxation processes (Roslaniec et al, 1995). The dielectric loss values show the existence of a relaxation maximum appearing at about 0 °C for 10 kHz relaxation) accompanied by a lower temperature relaxation (y relaxation) which appears at about —50 °C. 

By decreasing the soft segment content we are increasing the length of the hard segments that exist at a particular degree of reaction. Table II lists the number and weight... 

Figure 8. Effect of soft segment content on point of phase separation during polyurethane polymerization as indicated by discontinuity in DSC reaction profile. Dotted line shows theoretical prediction assuming separation at constant number-average sequence length (1.3) of hard segments ("see text).

Number Average and Weight Average Hard Segment Sequence Lengths at Separation As a Function of Soft Segment Content. 

Segmented polyurethanes having as soft segment content, mixtures of PEO, PPO, and diblocks of PEO-PPO, have very low p, around 0.04, suggesting that molecular disorder, thereby created, is useful. 

Cast Elastomers and Their Hard and Soft Segment Contents... 

The soft segment content is a major variable in this system. Table 4, as it is in the case of polystyrene/polybutadiene/poly styrene triblock polymer. A comparison of the data in Tables 3 and 4 shows that at the same "B" segment content these polymers have similar tensile elongations at break, even though their chemical composition is in no way similar. The arrangement of glassy and rubbery segments and their concentrations dominate. 

Petrovic and co-workers [127] used a polyricinoleic acid diol of 2,580 Da as a soft-segment to prepare a series of PU TPE based on an aromatic diisocyanate and 1,4-BD, with soft-segment sizes ranging from 40 to 70% (Scheme 4.28). These materials displayed a microphase separation and two Tg at around -50 and 100 °C. T values in the range 170-220 °C were observed depending on the soft-segment content. Their mechanical and thermal properties suggested that they could be used in conventional TPE applications. 

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