The purpose of this paper is to investigate the effect of different heating approaches during thermal rounding of polymer powders on powder bulk properties such as particle size, shape and flowability, as well as on the yield of process.,This study focuses on the rounding of commercial high-density polyethylene polymer particles in two different downer reactor designs using heated walls (indirect heating) and preheated carrier gas (direct heating). Powder bulk properties of the product obtained from both designs are characterized and compared.,Particle rounding with direct heating leads to a considerable increase in process yield and a reduction in powder agglomeration compared to the design with indirect heating. This subsequently leads to higher powder flowability. In terms of shape, indirect heating yields not only particles with higher sphericity but also entails substantial agglomeration of the rounded particles.,Shape modification via thermal rounding is the decisive step for the success of a top-down process chain for selective laser sintering powders with excellent flowability, starting with polymer particles from comminution. This report provides new information on the influence of the heating mode (direct/indirect) on the performance of the rounding process and particle properties.

中文翻译：

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下行反应器中微米级聚合物颗粒的热圆化：直接加热与间接加热

本文的目的是研究聚合物粉末热倒圆过程中不同加热方式对粉末体积特性（如粒度、形状和流动性）以及工艺产率的影响。使用加热壁（间接加热）和预热载气（直接加热）的两种不同下行式反应器设计中的商业高密度聚乙烯聚合物颗粒。对从两种设计中获得的产品的粉末松散特性进行表征和比较。与间接加热的设计相比，直接加热使颗粒变圆可显着提高工艺产量并减少粉末团聚。这随后导致更高的粉末流动性。从造型上来说，间接加热不仅会产生具有更高球形度的颗粒，而且还会导致圆形颗粒的大量团聚。,通过热倒圆进行形状改性是具有出色流动性的选择性激光烧结粉末的自上而下工艺链成功的决定性步骤，从来自粉碎的聚合物颗粒。该报告提供了有关加热模式（直接/间接）对倒圆过程性能和颗粒特性的影响的新信息。