Solid viscoelasticity of glass fiber and carbon fiber filled liquid crystalline polymers

摘要

Two types of thermotropic liquid crystalline polymers (fully-aromatic type. VA and semi-aromatic type. NE) were filled with glass fiber (GF) and carbon fiber (CF) to produce composite materials. These composite materials were processed using a capillary rheometer under different pressure and cooling temperature conditions to prepare four types of strands, and their dynamic viscoelastic properties were measured at 1 and 104 Hz. The results of the measurement were as follows. For unfilled liquid crystalline polymers, VA and NE, the storage modulus (E') and loss modulus (E") were markedly affected by the strand processing conditions, with both E' and E" decreasing with increasing frequency. For both GF- and CF-filled VA systems, E' and E" increased with increasing fiber content. The degree of the influence of the processing conditions on viscoelastic properties of CF/VA was higher than that for the GF/VA system. E' and E" of the CF-filled system also showed a larger fiber-content dependency than the CF-filled system. In both systems, E' and E" showed little difference in their values measured at 1 and 104 Hz, suggesting that their frequency dependency was small. In GF- and CF-filled NE systems, both E' and E" showed a small frequency dependency. When comparing the fiber content dependency on viscoelastic properties for both systems at 1 and 104 Hz, that for the GF/NE system was higher than for the CF/NE system. The dependency of E' and E" on processing conditions in the fiber-filled NE systems showed different behavior from those of the fiber-filled VA systems, i.e. the degree of the influence of the processing condition on E' and E" of the CF/NE system was higher than that for the CF/NE system. The glass transition temperature (TG) of the VA and NE systems determined from their tanδ curves at 1 Hz were larger than those by the DSC method. Fiber content dependency of Tg for the GF- and CF- filled VA systems were different from those of the GF- and CF-filled NE systems. In all the systems, the inflection points (Tc) of the tanδ curves at 104 Hz were larger than the corresponding Tg at 1 Hz. floth unfilled and fiber-filled VA and NE systems showed processing dependency for their Tg and Tc values.