Influence of material modification and fillers on the dimensional stability and warpage of polypropylene in screw‐extrusion‐based large area additive manufacturing

Abstract In this work, the influence of a modification and fillers on the dimensional stability and warpage of semi‐crystalline polypropylene compounds in screw‐based Large Area Additive Manufacturing is investigated by material characterization and experimental testing. Polypropylene is modified by blending an amorphous polyolefin‐copolymer as well as the addition of three different fillers talc, glass fibers, and hollow glass beads, resulting in eight investigated compounds. A material characterization using Differential Scanning Calorimetry, Thermogravimetric Analysis, thermal conductivity measurements, and pvT‐measurements is carried out. Experimental investigations regarding dimensional stability and warpage deformation during processing are performed. By increasing the crystallization temperature and thermal conductivity from 112.3°C and 0.208 W/(m°C) to 127°C and 0.232 W/(m°C) through the use of a modification and talc, a better dimensional stability during processing is reached. Furthermore, both the modification of the base material and the introduction of talc or glass fibers lead to a significant reduction in the decrease in specific volume during cooling, as determined by pvT‐measurements, thus reducing warpage. The experimentally determined warpage deformation could be reduced by 69% when using 10 wt. % talc‐filler and by 78% when using 10 wt. % glass fibers, compared to the unmodified and unfilled base polypropylene.