Selective laser melting using holographic beam manipulation: influence of polypropylene molecular weight

Abstract

Purpose-There is a requirement to match selective laser melting (SLM) technologies to a wider range of polymeric materials, since the existing market for SLM powders is dominated by polyamide PA12. Drivers include the tailoring of physical properties to individual applications, or cost reduction. Polypropylene (PP) currently has limited use in SLM, so the potential use of PP materials of varying molecular weight (Mw) is explored here. Design / methodology / approach-PP polymers of differing molecular weight were characterised using a range of analytical techniques, including DSC, thermogravimetric analysis (TGA), rotational rheometry and real-time hot-stage (optical) microscopy. Findings-The techniques are sufficiently sensitive to distinguish molecular weight effects, notably in terms of material viscosity. The stable sintering region for SLM has been defined clearly. Some success was achieved in melting parts using some grades of PP, including higher molecular weight grades, which potentially offer improved mechanical performance. Research limitations / implications-The range of techniques (DSC, OIT and TGA) form an effective analytical package with which to consider new polymeric materials for SLM. Practical implications-High-MW PP polymers, in tape or powder form, have potential use in SLM processes, providing scope to enhance part properties in future. Originality / value-This is believed to be the first in-depth study noting the influence of PP molecular weight on important physical performance in a proprietary SLM process, using holographic beam manipulation (HBM).

Comparative study on the selective laser sintering of polypropylene homopolymer and copolymer: processability, crystallization kinetics, crystal phases and mechanical properties

“…Out of the various commodity polymers, polypropylene (PP), in particular isotactic PP, is one of the most widely used due to its low cost, balanced mechanical properties, and high chemical resistance. Isotactic PP is commonly available in the form of a homopolymer, and till date, most studies investigating the SLS of PP have focused on the homopolymer, [7][8][9][10][11][12][13][14][15] or its composites. [16][17][18] Majority of those studies largely focus on the optimization of the process J o u r n a l P r e -p r o o f parameters and mechanical performance of the sintered PP parts.…”

Development of organically modified montmorillonite/polypropylene composite powders for selective laser sintering

“…Recently, the use of PP for SLS has been on the rise, with several SLS material companies commercializing PP powders. [9][10][11][12][13][14][15] However, a major disadvantage of PP is its relatively poor thermal stability that has thus far not been addressed for SLS. The poor thermal stability of PP makes it prone to degradation, thus negatively affecting the product lifetime, and at the same time puts it at a significant disadvantage especially for use in SLS due to the prolonged heating during part fabrication.…”

An investigation of post treatment on properties and structure of ultrahigh molecular weight polyethylene parts prepared by selective laser sintering for biomedical application

“…SLS is more widely used owing to great advantages of higher molding precision, more environmentally friendly molding process, and with no need for supporting structures compared with other AM technologies . Based on the perspective of inherit properties of raw materials and processing properties in SLS, some researchers focused on studying the influence of formability of material, such as molecular weight, particle morphology, and technological parameters such as laser power, preheating temperature, and scanning interval on structure and properties of sintered parts . Other researchers utilized the processing characteristics of SLS to realize the functionalization of products with composite powder materials, such as electrical conductivity, thermal conductivity and biocompatibility .…”