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tensi iesce mechanical performance of TLCP. Processing flows play a used to measure the extensional viscosity of LCP melts, Polymer Testing 24 (0142-9418/ $- see front matter q 2004 Elsevier Ltd. All rights rese doi:10.1016/j.polymertesting.2004.11.009central role in defining the orientation on the macroscopic level. Extensional flows have been shown to be much more effective than shear flow in producing a high degree of molecular orientation. In view of the importance of extensional flow in processing of LCPs, the extensional rheological properties of LCPs, such as extensional viscosity, are crucial to understand the microstructural variation in extensional flow. While the shear rheology of liquid crystalline polymer (LCPs) has been studied extensively, little attention was paid to their extensional behavior. Extensional viscosity of including fiber spinning [1,2], rotary clamp method [3,5], lubricated squeezing technique [4], and the Rheometrics Melt Extensional rheometer (RME) [6,7] and entry flow [8]. Metzner and Prilutski [1] reported extensional viscosity data for lyotropic solutions of hydroxypropylcellulose (HPC) in acetic acid obtained by gravity-spinning. They found that the extensional viscosity was independent of rate over a range of 0.02–10 sK1 and that the Trouton ratio at low rates was about 9. Wagner et al. [2] measured the extensional viscosity using a Rheotens fiber-spinning instrument on a commercial TLCP (Vectra B950), and noted behavior similar to polyethylene. Chen et al. [3] measured the transient extensional viscosity of HPC melt at 180 8C usinginterfacial tension between the two components, and covers strain-rate and strain ranges that are very low. Results obtained by the method show extensional rate thinning behavior and strain-hardening behavior. The trends are in agreement with previous measurements using other methods such as fiber spinning. We recommend the thread disintegration method for measuring extensional viscosity at small extensional rates and small strains