Semi‐Crystalline Polymer Blends for Material Extrusion Additive Manufacturing Printability: A Case Study with Poly(ethylene terephthalate) and Polypropylene

Abstract

Semi‐crystalline polymers are an important class of materials for engineering applications due to their high modulus and barrier properties. Traditional manufacturing methods process semi‐crystalline polymers via rigid molds and well‐controlled temperature and pressure environments to handle the significant change in specific volume occurring during crystallization; however, material extrusion additive manufacturing does not use these features. This often leads to warpage‐induced build failure in fused filament fabrication (FFF). To enable FFF of semi‐crystalline polymers, this work investigates characteristics of immiscible polymer blends (e.g., disparate crystallization behavior and phase separation) to mitigate warping failure during printing. A series of poly(ethylene terephthalate)/polypropylene/polypropylene–graft–maleic anhydride blends are explored and the effect of thermal and morphological characteristics on printability is analyzed. It is shown that these blends can be extruded into filament and printed into a 3D structure. Extrapolations indicate that phase‐separated blends with increased total crystallization half‐time are beneficial for FFF printing.

Poly(vinylidene fluoride)/thermoplastic polyurethane flexible and 3D printable conductive composites

“…In this context, the preparation of polymer blends to be used as matrix in polymer composites has been used as a strategy to improve mechanical and electrical properties 31–34 . Recently, many works have been focused on the preparation of co‐continuous immiscible polymer blends to reduce percolation threshold in ECPCs and to improve mechanical properties and printability of composites filaments 22,32–35 .…”

“…The localization of the conductive filler in co‐continuous polymer blends is affected by thermodynamic, kinetic factors and melt viscosity. To the best of our knowledge, the production of insulating polymeric blends to control morphology and properties have been already proposed, 32–35,38–40 however, only a few studies are reported on its use in FFF 31 …”

“…In this context, the preparation of polymer blends to be used as matrix in polymer composites has been used as a strategy to improve mechanical and electrical properties. [31][32][33][34] Recently, many works have been focused on the preparation of co-continuous immiscible polymer blends to reduce percolation threshold in ECPCs and to improve mechanical properties and printability of composites filaments. 22,[32][33][34][35] The development of a material filament based on co-continuous polymer blends containing conductive filler can be an interesting alternative for the production of structural and highly conductive components by FFF.…”

“…To the best of our knowledge, the production of insulating polymeric blends to control morphology and properties have been already proposed, [32][33][34][35][38][39][40] however, only a few studies are reported on its use in FFF. 31 Moreover, among polymer blends, composites based on poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) have been reported due to the possibility of producing high-performance engineering materials for various industrial applications, 41,42 such as electromagnetic interference (EMI) shielding 32 and energy harvesting. 43 In fact, PVDF can display piezoelectric behavior under proper crystalline conditions, 44 and some researchers claim that blending PVDF with TPU is an efficient way to prepare materials with an excellent combination of mechanical flexibility and pyroelectric/piezoelectric properties.…”

Optimization of the Filler Concentration on Fused Filament Fabrication 3D Printed Polypropylene with Titanium Dioxide Nanocomposites

“…PP is widely used by the industry in applications such as operational parts [ 19 ] and in the food industry [ 20 ]. Specifically, PP is characterized as a high-grade engineering material for AM, but it is only recommended for advanced AM users [ 21 ] because it warps easily during the FFF process, and the developed thermal stresses attributed to (i) the 3D printing extruder shear induced crystallization, and (ii) the PP macromolecular chains’ inherent tendency to form crystals on the material coming from the melt to the solid state, resulting in a semi-crystalline polymer [ 22 ]. Hence, research has been conducted into the improvement of PP’s printability [ 17 , 23 ] and their mechanical, thermal, and other properties [ 17 ].…”