Grafting of thermotropic fluorinated mesogens on polysiloxane to improve the processability of linear low-density polyethylene

In this study, a series of polysiloxane grafted with thermotropic fluorinated mesogens (TSCPFLCP) is designed and synthesized. The TSCPFLCP exhibits a typical smectic liquid crystal phase, and shows a high thermal decomposition temperature at 335.6 °C. After blending with LLDPE, the balance melt torque of LLDPE/TSCPFLCP is decreased by 42% at 0.5 wt% TSCPFLCP, and the corresponding power law index is increased to 0.45. The flowing activation energy of the optimized LLDPE/TSCPFLCP blend is lower than that of pure LLDPE at the same shear rate, indicating that TSCPFLCP reduced the sensitivity of the apparent melt viscosity of LLDPE to both shear rate and temperature. This contributes to the broadening of the LLDPE processing window. On the other hand, TSCPFLCP is also found beneficial in ameliorating melt fracture during LLDPE extrusion. Furthermore, the mechanical properties of LLDPE/TSCPFLCP blends, such as tensile strength, elastic modulus and elongation at break, are also enhanced significantly at 0.5 wt% TSCPFLCP. Altogether, TSCPFLCP has been proven an effective processing aid to improve the processability and toughness of LLDPE.