A Review of Methods Used to Reduce the Effects of High Temperature Associated with Polyamide 12 and Polypropylene Laser Sintering

Abstract

The polymer laser sintering (PLS) process is one of the most promising additive manufacturing (AM) technologies for polymeric materials. However, the technique has challenges because the physical, mechanical, and chemical properties of the polymeric powder deteriorate due to the high temperatures prevailing in the build chamber during manufacture. These high temperatures cause agglomeration of powder, which leads to a decrease in the flowability of powder. There is also a related drop in the coalescence of the powder granules during PLS, which results in porosity that undermines the mechanical integrity of printed parts. Moreover, the viscosity of the melt increases due to cross-linking of molecular chains. This, in turn, increases the tensile strength of the printed components at the expense of the percentage elongation at break. Thus, high prolonged processing temperatures decrease the reusability of polymeric materials used in PLS. In this paper, a review of the studies conducted to investigate ways of reducing the effects of high temperature on polymeric powders is presented.

Polyamide 12 Materials Study of Morpho-Structural Changes during Laser Sintering of 3D Printing

“…Therefore, we can also examine changes of peaks at 1368 cm −1 corresponded to δ (CH 2 ) twisting vibration, 1159 and 1062 cm −1 to skeletal motion involving CO-NH groups, and 946 cm −1 to in-plane deformation of CO-NH [ 21 ]. However, in this case there aren’t visible changes of these peaks in the infrared spectra for all measured samples ( Figure 7 ) compared to examples of aged samples mentioned in literature [ 7 , 19 ].…”

“…Plastic powders, semi-crystalline or amorphous, are widely used materials in the SLS technique. Among the semi-crystalline polymers, polyamides are the most popular for SLS, where polyamide 12 dominates the production for the capability of generating substantial components for typical applications products [ 7 ]. Parts produced using polyamide 12 powders have superior mechanical and thermal properties.…”

A review of the techniques used to characterize laser sintering of polymeric powders for use and re-use in additive manufacturing

“…The mass of the ejected polymer material is determined using an electronic weighing machine and the value of MFI calculated using Equation (2). The MFI value of virgin PA12 is about 45-50 g/10 min and it degrades from this range with repeated use [36]. After the value reduces below 18 g/10 min, the powder is discarded, which happens after the 7th or 8th re-use cycle [37].…”

3D Printing: An Alternative Microfabrication Approach with Unprecedented Opportunities in Design

“…Electrostatic interactions generated by the powders also lead to powder movements, making it difficult to control the thickness of the print layers below hundreds of micrometers. The formation of defects, or pores, within the structures is also ubiquitous to the sintering process, leading to unwanted diffusion pathways and leakages . Equally, the shrinkage of the structures upon thermal coalescence leads to geometrical deformations which render the design of low-micrometric channels challenging.…”

“…The ability to handle low cost metals or corrosion resistant alloys offers great benefits in this area for extraction from extreme pH or reactivity solutions. Sintering mixed material powders also offers opportunities to develop composite structures, potentially sacrificial, porous, or reactive phases, physically embedded into the matrix of the microfluidic device . The energy costs required for metal or ceramic printing are, however, prohibitive due to the much higher temperatures required for sintering such materials together, and recent research has focused on the development of nonthermal sintering systems based on powder impaction with metal binder jet, direct energy deposition systems employing metal powder or wire feedstock, and FFF’s metallic counterpart as well as bound powder extrusion (BPE) …”