Effect of Monol Content on One-Shot Elastomer Processability and Properties

2 Effect of Monol Content on One-Shot Elastomer Processability and Properties 

The effect of monol content on the processability and properties of one-shot elastomers is shown in Table 9.9. We prepared 80 Shore A elastomers based on carbodiimide-modified MDI and BDO using a 4000-MW, EO-capped, ultra-low monol diol containing 3% monol content and a conventional EO-capped diol containing 15% monol. These polyols had comparable primary hydroxyl concentrations of 87 and 89%, respectively. 

As expected, the monol content of the EO-capped PPG diols has a significant effect on the elastomer processability. The Shore hardness of the conventional elastomer was only 57A after 16 hours cure at 100 C, whereas the elastomer based on ultra-low monol PPG had a hardness of 78A. It took three weeks for the conventional 

Virtually all elastomer properties improved with lower monol contents (see Table 9.9). Of particular note, the rebound increased from 59 to 68 percent, the elongation from 470 to 550%, tensile strength from 10 to 19 MPa, tear strength from 49 to 68 kN/m, compression set decreased from 64 to 23 %, and the Taber abrasion loss (ASTM D4060-95 [26]) decreased from 220 to 80 mg loss/1000 cycles. The improvement in the stress/strain curves is shown in Eigure 9.7. Lower monol content results in significantly higher ultimate polymer MW, which results in improved mechanical properties. 

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