Abrasion-Induced Acceleration of Melt Crystallisation of Wet Comminuted Polybutylene Terephthalate (PBT)

Abstract

Within this contribution, the effect of grinding media wear on the melt crystallisation of polybutylene terephthalate (PBT) is addressed. PBT was wet ground in a stirred media mill in ethanol using different grinding media beads (silica, chrome steel, cerium-stabilised and yttrium-stabilised zirconia) at comparable stress energies with the intention to use the obtained particles as feed materials for the production of feedstocks for laser powder bed fusion additive manufacturing (PBF-AM). In PBF‑AM, the feedstock’s optical, rheological and especially thermal properties—including melt crystallisation kinetics—strongly influence the processability and properties of the manufactured parts. The influence of process parameters and used grinding media during wet comminution on the optical properties, crystal structure, molar mass distribution, inorganic content (wear) and thermal properties of the obtained powders is discussed. A grinding media-dependent acceleration of the melt crystallisation could be attributed to wear particles serving as nuclei for heterogeneous crystallisation. Yttrium-stabilised zirconia grinding beads proved to be the most suitable for the production of polymer powders for the PBF process in terms of (fast) comminution kinetics, unchanged optical properties and the least accelerated crystallisation kinetics.

You get what you screen for: a benchmark analysis of leaf branch compost cutinase variants for polyethylene terephthalate (PET) degradation

“…35 The particle size distribution of the polymer powder predispersed in water was measured by laser diffraction (Mastersizer 2000/Hydro 2000S, Malvern Panalytical, Malvern, United Kingdom). 35…”

“…Morphology and surface of the PET fibres was assessed via scanning electron microscopy (SEM) using a Gemini Ultra 55 (Carl Zeiss AG, Oberkochen, Germany) operated at an acceleration voltage of 1.0 kV as described previously. 35 The particle size distribution of the polymer powder predispersed in water was measured by laser diffraction (Mastersizer 2000/ Hydro 2000S, Malvern Panalytical, Malvern, United Kingdom). 35 The mass-specific surface area S M was measured using a volumetric gas sorption analyser (Nova 4200e, Quantachrome, FL, USA) at liquid nitrogen temperature.…”

“…35 The particle size distribution of the polymer powder predispersed in water was measured by laser diffraction (Mastersizer 2000/ Hydro 2000S, Malvern Panalytical, Malvern, United Kingdom). 35 The mass-specific surface area S M was measured using a volumetric gas sorption analyser (Nova 4200e, Quantachrome, FL, USA) at liquid nitrogen temperature. Five pressure points of the adsorption isotherm were evenly spread in the relative pressure range between 0.02 and 0.35 p/p 0 and evaluated according to the Brunauer-Emmet-Teller (BET) theory.…”

Dry powder coating in additive manufacturing

“…This is explained by a much better dispersion of the nanoparticles by the direct synthesis in contrast to the tumbling mixer with only moderate dispersion of agglomerates. The amount of flowing aid in an AM feedstock powder should be kept as low as possible, as it might impair the isothermal crystallization behavior under process conditions (Tischer et al, 2022), i.e. lead to unwanted effects during processing, such as premature crystallization and, thus, deterioration of part geometry or termination of the built.…”