Thermochemical Behavior and Mechanical Strength of Liquid Crystalline Polymers-Magnesium Silicate Based Nanocomposites Investigated by Pyrolysis GCMS, Scanning Electron Microscopy and DSC

摘要

Compared to traditional thermoplastic polymers liquid crystalline polymers would be superior in demanding material applications. Having a very small specific heat and a very good environmental stress and thermal stability liquid crystalline polymers also have competitive mechanical materials properties compared to conventional thermoplastics. LCP's characteristic feature is it's rigid rod-shaped aromatic polymer structure. Because of highly oriented macromolecules LCP's mechanical strength properties are different in fiber direction compared to transverse direction. Thermal expansion coefficients are smaller in the direction of melt orientation (machine direction with injection molded parts) but higher in transverse directions. Other drawbacks of injection molded LCP products have sometimes been poor surface quality and weak weld and knit line strengths. Significant progress has been achieved during recent years in development of LCP combination materials and their processing techniques. Particular LCP injection molding tools have been developed for pilot and commercial production of various parts in electronics and medical applications. Our research team has studied molecular structure - materials property relationships of LCPs and LCP based nanocomposites in order to decrease anisotropy and improve strength and toughness of weld and knit lines in injection molded parts. Electron microscopy (SEM and EDX) was used in this investigation for analyzing changes in microstructure as a consequence of changes in LCP materials compositions and processing parameters, differential scanning calorimetry (DSC) for monitoring and understanding of changes of LCP crystal structures in melting and solidifying processes and pyrolysis gas chromatography - mass spectrometry (GCMS) for analyzing potential thermal degradation of LCP materials in mechanochemical processing, compounding and injection molding processes, as well as in DSC analysis.