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

TLDR

The study investigates how material modification and filler addition affect dimensional stability and warpage of semi‑crystalline polypropylene in screw‑based large area additive manufacturing. Polypropylene was blended with an amorphous polyolefin‑copolymer and filled with talc, glass fibers, or hollow glass beads to create eight compounds, which were characterized by DSC, TGA, thermal conductivity, and pvT measurements, and then tested for dimensional stability and warpage during processing. Increasing crystallization temperature and thermal conductivity via modification and talc improved dimensional stability, while modification and talc or glass fibers reduced specific volume loss during cooling, leading to a 69 % reduction in warpage with 10 wt % talc and 78 % with 10 wt % glass fibers compared to unmodified, unfilled polypropylene. Other: Warpage reduction percentages: 69 % with 10 wt % talc and 78 % with 10 wt % glass fibers.

Abstract

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.