FTP, name this class of flexible polymeric substances, whose most well-known example is rubber.
Stretching them reduces the total number of conformations in the amorphous form, increasing the order, and causing largely-crystalline regions to appear.  These substances possess cross-linked regions to prevent plastic flow, and rather flexible chains, meaning that "T sub g," the glass temperature, is low.  Their most useful property is their extensibility, which can be more than 1000 times that of ordinary, non-polymeric solids.  FTP, name this class of flexible polymeric substances, whose most well-known example is rubber.
Stretching them reduces the total number of conformations in the amorphous form, increasing the order, and causing largely-crystalline regions to appear.  
elastomers