Blending, recycling and stress relaxation of binary and ternary semiaromatic LCP/thermoplastic in situ composites

Investigation of the blending, recycling and stress relaxation of binary and ternary semi-aromatic liquid crystalline polymer and thermoplastic in-situ composites have been carried out. A newly developed LCP, Unitika Rodrun LC-5000 LCP with 80/20 molar ratio of PHB/PET was used in this study. Engineering plastics (polycarbonate and polyamide) and general plastics (polyolefins and polystyrene) were used as matrix materials for the composites. Polymer compatibilizers and polyblends were used to improve the mechanical properties of the composites. The test samples were processed by direct injection molding after dry-blending.; The mechanical properties of the Rodrun LC-5000 LCP/TP binary in-situ composites were found to be much lower than those obtained by theoretical prediction. Especially, there is a minimum in the LCP/PP1 and LCP/PA 66 systems. The complicated mechanisms involved in the reinforcement of composites were found to be dependent on not only the type and characteristic nature of the matrix polymer, such as melt flow behavior, but also the processing conditions including processing temperature, shear stress and shear rate, etc.; Ternary LCP/TP in-situ composites were investigated and the results showed that there is a significant increase in tensile properties when polycarbonate was used as a third component in the composites. The addition of the third component resulted in a change in viscosity ratio between the dispersed LCP phase and the thermoplastic matrix phase, as well as the fibrillation and distribution of the LCP fibres and fibrils. At the same time, the interfacial adhesion between the skin layer and the core region was improved.; Rodrun LC-5000 LCP shows high processing stability even after multi-stage recycling. This indicates the possibility of recycling these LCP materials.; Multi-stage recycling of the LCP/TP binary and ternary composites resulted in deterioration of the mechanical properties of the composites. The presence of a third component or compatibilizer contributes more to the deterioration. LCP/PP binary in-situ composites showed high resistance to the multi-stage recycling. A rheology study of the composites indicated a decrease in molecular weight after multi-stage recycling. This coincided with a decrease in mechanical properties. Furthermore, SEM morphology studies revealed that the LCP domains were deformed into smaller pieces after the recycling process.; The stress relaxation phenomenon of semi-flexible LCP and the thermoplastic composites were investigated. A five-element Maxwell body was proposed and found to fit the experimental data well. A Characteristic Stress Relaxation Function (CSRF) was developed for the semi-flexible Rodrun LCP and the composites with thermoplastic matrices.*; *Originally published in DAI  Vol. 59, No. 10. Reprinted here with corrected author name.