Low Warpage Nanophase-Separated Polypropylene/Olefinic Elastomer Reactor Blend Composites With Digitally Tuned Glass Fiber Orientation By Extrusion-Based Additive Manufacturing

Among thermoplastics, polypropylene (PP) is outstanding with respect to its high versatility in terms of its tailoring property profiles for diversified applications, high resource and energy efficiency, environmentally friendly catalytic polymerization process, and recycling capability. However, additive manufacturing of PP by means of fused filament fabrication (FFF), also known as fused deposition modeling, suffers from several drawbacks like high shrinkage, massive warpage, and poor adhesion to common build plates. Herein, we overcome these problems by exploiting glass fiber-reinforced nanophase-separated PP reactor blends (Catalloy process resins). Catalloy is a polymerization process to create PP reactor blends containing dispersed ethylene/1-olefin copolymer rubber nanophases. A warpage quantification method confirms that 3D-printed Catalloy-based PP composites exhibit exceptionally low warpage and successfully compete with amorphous thermoplastics like acrylonitrile-butadiene styrene in printability, build plate adhesion, and printing precision. Microscopic imaging and the measurement of mechanical properties along and perpendicular to the 3D printing direction verify the rapid, highly efficient fusion of the deposited polymer strands. The resulting mechanical properties are very similar to those of injection-molded Catalloy-based composites even at high printing speeds. As evidenced by micro-computer tomography imaging, an unprecedented FFF process-mediated tuning of the fiber orientation is achieved. This allows for precisely tailoring both unidirectional and tuned multidirectional composites via computer design.