Preparation and characterization of novel PA6/SiO^sub 2^ composite microsphere applied for selective laser sintering

Headnote

Abstract. The high cost and less variety of raw materials has greatly restricted the wide application of selective laser sintering (SLS) technology. In order to make the material cheaper and more diverse, PA6 is the most preferable material. In this work, a new PA6/SiO₂ composite microsphere used for SLS was designed and fabricated. To construct the material, PA6 porous microspheres with diameters of 20-80 gm and a certain pore volume were firstly prepared by the dissolution precipitation method. Then, SiO₂ was generated in situ in the PA6 porous microsphere framework, thus achieving a special structured PA6/SiO₂ composite microsphere. These microspheres with much well dispersed SiO₂ in PA6 matrices formed a powder with high bulk density and good electron conductivity. The particle size and weight fraction of the two components can be well controlled by adjusting the experimental conditions. Differential scanning calorimetry (DSC) data showed that the composite powder had a larger sintering window, which would be beneficial for SLS processing. The introduction of SiO₂ reduced the rate of water absorption in the composite powder, which could improve the accuracy of SLS forming. This work has certain significance as a reference for the design and development of SLS polymer-based composite materials.

Keywords: polymer composites, PA6 microspheres, selective laser sintering, preparation and characterization

1.Introduction

SLS is one of the most developed and widely used 3D printing technologies [1, 2]. The laser sintering process allows complex 3D objects to be built by selectively fusing together successive layers of powdered material. Theoretically, the wide range of material choices is a major advantage of SLS technology, because any powder that can be bonded after heating can be applied in SLS technology, but in practical applications, powder materials that can be successfully used are scarce [3-8]. The main reason for this scarcity is that SLS technology requires high-performance powder materials. For example, in order to create molded parts with good dimensional accuracy and mechanical strength, the resin material used to prepare the powder should have an appropriate melting point, high thermal stability, small shrinkage rate, and suitable melt viscosity. Furthermore, the prepared powder particles should have approximately spherical structures with diameters of 20-80 gm, permitting greater powder fluidity and higher bulk density [9, 10].

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