Material extrusion‐based additive manufacturing (ME‐AM) is an emerging processing technique that is characterized by the selective deposition of thermoplastic filaments in a layer‐by‐layer manner based on digital part models. Recently, it has attracted considerable attention, as this technique offers manifold benefits over conventional manufacturing technologies. However, to meet the challenges of complex industrial applications, certain shortcomings of ME‐AM still need to be overcome. A case in point is the limited amount of semicrystalline thermoplastics, which are still not established as reliable, commercial filament materials. Particularly, polypropylene (PP) offers attractive properties that are unique among the ME‐AM material portfolio. This review describes the current approaches of fabricating PP components by ME‐AM. Both commercial and scientific strategies to make PP 3D‐printable are elaborated and compared. As dimensional issues are especially problematic for PP, a comprehensive section of this review focuses on the strategies developed for mitigating warpage for PP parts fabricated by ME‐AM. © 2019 The Authors.Journal of Applied Polymer Sciencepublished by Wiley Periodicals, Inc. J. Appl. Polym. Sci.2020,137, 48545.

For parts produced by fused filament fabrication (FFF) the adhesion between the first printed layer and the printing bed is crucial, since it provides the foundation to the subsequent layers. Inadequate adhesion can result in poor printing quality or destroyed bed surfaces. This study aims at understanding and optimising the adhesion process for parts produced by FFF. The consequences of varying printing bed temperatures on the adhesion of two commonly used printing materials on two standard bed surfaces were investigated by means of an in-house built adhesion measurement device and complemented by contact angle measurements. This study shows a significant increase in adhesion forces, when printing parts at a bed temperature slightly above the glass transition temperature of the printing material.

A challenge in extrusion‐based additive manufacturing of polypropylene (PP) filled with spherical particles is the combination of decent processability, excellent warpage control, and the retention of the tensile strength of neat PP. This study addresses this issue by adopting two approaches. Firstly, different size fractions of borosilicate glass spheres incorporated into PP are compared. Secondly, the temperature of the printing chamber (T_Ch) is varied. The effects of these features on the thermal, crystalline, morphological, tensile, impact, and warpage properties of 3D‐printed parts are examined. Smaller glass spheres (<12 µm) are found to be superior to larger fractions in all investigated aspects. Notably, the corresponding composites show higher tensile strengths than neat PP. An increase inT_Chresults in a more homogeneous temperature distribution within the printing chamber and promotes annealing during printing. Consequently, the dimensional accuracy of printed parts is improved. Additionally, β‐crystals and larger spherulites are formed at a higherT_Ch.