In the present study, recyclability of Laser PP CP 75 polypropylene powder from Diamond Plastics GmbH was determined by characterizing and comparing the used powder after each cycle with material from previous cycles and with fresh powder. The melt flow index of Laser PP CP 75 was affected by recycling since it was observed to change by 30.62% after the 8th 100% re-use cycle, a lower value than PA 12 of 66.04%, for the 6th re-use cycle. Parts printed with virgin Laser PP CP 75 had an average dimensional error of 3.02% (virgin material) and 4.06% after the 4th 100% re-use cycle, which raises concerns about the commercial viability of the material. After the 4th re-use cycle, the printed parts had distorted edges and failed to print after the 9th print cycle. Lastly, tensile testing revealed a skewed bell-shaped curve of strength versus the number of recycles with the highest ultimate tensile strength occurring for the second 100% re-use cycle (7.4 MPa). The curves for elastic modulus and percentage elongation were inverted with minimum points for the 2nd 100% re-use cycle. Overall, the experimental work confirmed that the properties of polypropylene powder were affected by recycling in polymer laser sintering, but the powder exhibited superior characteristics upon recycling to those of the predominantly used PA 12 powder.

Preliminary Testing to Determine the Best Process Parameters for Polymer Laser Sintering of a New Polypropylene Polymeric Material: Polymer laser sintering is an elaborate additive manufacturing technique because it is subject to process parameters and material properties. In this regard, each polymeric material necessitates a different set of process conditions. To this end, testing was done to determine the most suitable process parameters for a new commercially available polymer (Laser PP CP 60), from Diamond Plastics GmbH. It was established that the material requires slightly different settings from those provided by the supplier for the values for the removal chamber temperature, building chamber temperatures, and laser power to achieve the best mechanical properties (ultimate tensile strength). The preliminary testing indicates that the process parameters that yielded the best mechanical properties for the laser PP CP 60 powder were 125C, 125C, 0.15mm, 250μm, 4500mm/s, 34.7W, 1500mm/s, and 21.3W for the removal chamber temperature, building chamber temperature layer thickness, hatch distance, scanning speed fill, laser power fill, scanning speed contour, and laser power contour, respectively.

Currently, the world is undergoing the fourth industrial revolution, also referred to as Industry 4.0, which is characterised by a set of new technological advances in the industrial and production sectors. Additive manufacturing (AM) is considered an essential factor in this new era because of its ability to process a wide spectra of materials, produce customised products, promote sustainability and develop intricate components which are unachievable using conventional manufacturing techniques. The field of AM is rapidly evolving and has seen unprecedented uptake in many industries. Different types of AM technologies have been developed over the last three decades to process different materials, such as polymers, composites, metals, ceramics and alloys. Both industry and academia have made a considerable effort to investigate the use of AM technologies to print different types of polymers because of the possibility to reach new markets. This comprehensive review focuses on polymer laser sintering (PLS) and fused deposition modelling (FDM), which are the most commonly employed AM methods for polymers. This review outlines the processes, process parameters, available commercial polymeric materials, benefits, challenges, and applications of the two technologies. PLS and FDM are multifactorial processes that produce final components whose quality is subject to the process parameters. This review, therefore, delves into the different process parameters for the two technologies and their impacts. The article also lists the available commercial polymeric materials, for each of the methods, to assist researchers and industries to select most suitable materials based on their processability and characteristics. A detailed discussion of applications of the two technologies is outlined in this review. The study provides a comprehensive detail of the benefits and challenges of PLS and FDM. Last, the study also outlines the future works for the two techniques.

The current study examines the feasibility of Ultrasint PP nat 01 polypropylene material in powder bed fusion through powder characterisation. The results obtained are also deemed to be pertinent when developing or validating analytical and numerical models of Polymer Laser Sintering, which were not within the scope of this paper. The following critical characteristics were examined: powder morphology, powder particle size distribution (PSD), bulk density, tapped density, melt flow index, thermal characteristics of the material, degree of crystallinity, and optical properties. Ultrasint PP nat 01 powder has a PSD in the range of 20–80 µm, which is within the recommended particle size distribution. The Hausner ratio, tapped density, and bulk density of the material were calculated and measured as 1.230 ± 0.05, 0.455 ± 0.02 g/cm³, and 0.370 ± 0.03 g/cm³, respectively. The melt flow index of Ultrasint PP nat 01 was measured as 15.8 g/10 min. The initial melting point of the material was determined to be 133.8 °C. The powder used had a relatively high sintering window of 30.7 °C, a degree of crystallinity of around 31.8%, and a high thermal stability of around 461.52 °C. The material was found to attain full fusion of particles at around 170 °C. Fourier Transform Infrared Spectroscopy indicated that Ultrasint PP nat 01 powder has poor radiation absorption, but high transmission properties.

High‐density polyethylene (HDPE) is largely processed using conventional manufacturing techniques. However, there is a need to investigate its processability when fabricated using additive manufacturing (AM) in an effort to use this polymer for high‐end applications, such as the fabrication of human implants. In this regard, the current study investigated the intrinsic and extrinsic properties of HDPE powders (DiaPow HDPE HX R) from Diamond Plastics GmbH, to determine its feasibility of use in powder bed fusion (PBF). Powder characterisation was undertaken using a scanning electron microscope (SEM), melt flow index (MFI) testing, tapped density testing, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) spectroscopy, and hot‐stage microscopy. The analysis revealed that this high‐density polyethylene powder is suitable for processing using PBF based on the particle size distribution (PSD) (65–92 μm), flowability (Hausner ratio = 1.22 ± 0.02), melting point range (125.7–135.2 degrees Celsius), enthalpy of melting (170.51 J/g), and thermal stability (the materials starts to degrade at 350.0 degrees Celsius and completely degrades at 500.0 degrees Celsius). It also showed good coalescence behaviour. However, the narrow sintering window (7.9 degrees Celsius) of the material indicates possible challenges of shrinkage and curling during printing. The material was also found to have poor absorptive properties of infrared radiation at 10.6 μm, which might make sintering using CO₂ lasers challenging.

The laser-powder bed fusion (L-PBF) process presents advantages over other polymer additive manufacturing processes in terms of part strength and high production rate possible with the technology. The high cost and limited re-use of nylon powder used in the process however limit the large-scale adoption of the technology in industry. This paper investigated the re-use of PA12 powder that is no longer suitable for the L-PBF process through producing filament for the fused deposition modelling (FDM) process. Results from the study showed that parts with good mechanical strength and reasonable dimensional accuracy can be produced using FDM.