Nonlinear Viscoelasticity of Fiber-Filled Liquid Crystalline Polymer Melts

Melts of semi-aromatic liquid crystalline polymer (LCP) filled with carbon fiber (CF) and glass fiber (GE) were measured for dynamic viscoelasticity to quantitatively analyze their nonlinear viscoelastic properties. The LCP and its CF and GF filled polymer systems were examined for dynamic viscoelastic behaviors by Fourier expansion of shear stress wave.For LCP the tertiary terms G'3 and G''3 are considerably smaller than their primary terms G'1 and G''1, ;the viscoelastic property is almost linear.On the other hand, the two types of CF filled LCP systems showed that an increase in the oscillatory angle decreased G'1 and G''1 in sequence with increasing i.However, the G'3 and G''3 values are large enough not to be negligible, i.e.both polymer systems show similar nonlinear viscoelastic behaviors.A study on the GF filled LCP systems showed the same tendency as the CF filled systems;both G'1 and G''1 have apparently a plateau region.Furthermore, the values of G3 /G1, G'3/G'1 and G''3/G''1 are recognized as the indicator of the degrees of their nonlinearity, and the fiber filled LCP systems showed no significant difference in their dependency on co, although the GF filled systems showed a markedly higher nonlinearity of G''3/G''1 than the CF filled systems in a high co region.