This work is concerned with the generation of thermoplastic filaments (polypropylene initially) reinforced with thermotropic liquid crystalline polymers, TLCP’s, of higher melting point than the matrix using a unique dual extrusion technology developed in our laboratory. In this technology, TLCP’s and thermoplastic polymers are plasticated in two different extruders at different temperatures producing mechanically stronger filaments than in situ processed filaments in which both the TLCP and matrix are processed in one extruder. TLCP’s are plasticated at a higher temperature in the dual extrusion method and then cooled and introduced into the matrix which has usually a degradation temperature lower than the processing temperature of the TLCP’s. Because the TLCP’s super-cool significantly they can be processed below their melting points. The mixture is then passed through static mixers and a capillary die, producing continuous reinforcement by means of the TLCP phase in the matrix. Initially, polypropylene is used as the matrix with different concentrations (&gt;50%) of a TLCP. The TLCP nearly continuous microfibrils have a modulus and strength which approach those of the lower end of carbon fiber leading to filaments with a modulus approaching 80 GPa and a strength of 700 MPa (60 wt% TLCP/40wt% PP). These filaments are then used in Fused Filament Fabrication (FFF) to generate simple plaques with various layup directions. The advantage of these materials is that they can be severed at the end of the layup process whereas continuous glass and carbon fibers can’t. At a later stage, higher performance matrices, such as polyethyleneterephthalate (PET) and polyphenylenesulfide (PPS), will be used. This will address the need for mechanically stronger filaments for FFF which has a major share in the growth of 3D printing technology.

Generation of thermotropic liquid crystalline polymer thermoplastic composite filaments and their processing in fused filament fabrication

251st National Meeting (2016)

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