Elongation, molecular machines

Compared to most isotropic polymers, thermotropic LCPs possess outstanding mechanical properties due to their rigid rod-like backbones. It has been reported that LCPs have tensile strength in a range of 150 to 400 MPa and tensile modulus from 13 to 25 GPa, while LCP fibers have tensile strength ranging from 500 to 650 MPa and tensile modulus from 50 to 100 GPa. When LCPs are blended with thermoplastics in a process where an elongational flow field exists, the LCP phase will deform into molecularly oriented fibers that reinforce the thermoplastic matrix. So, until now, many isotropic polymers have been blended with LCPs. Table 7.5 summarizes various in situ composites reported, with their machine direction mechanical properties. 

Blown films can be produced from these high molecular weight resins on conventional equipment. These films are transparent and amber as produced. If films are biaxially oriented, this transparency is retained on annealing. At a blow-up ratio of 3.0, the tensile strength and elongations are essentially the same in both the machine and transverse directions (Table V). Electrical properties are typical for polyphenylene sulfide resins. 

Sheet (20 mils) can be extruded readily from the new high molecular weight polymer. Quenched sheet is transparent and amber in color, while annealed sheet is opaque (Table VI). Tensile strength increases somewhat on annealing and elongation decreases. There is essentially no difference between machine direction and transverse direction in mechanical properties-... 

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