Non-Einstein Viscosity Phenomenon of Acrylonitrile–Butadiene–Styrene Composites Containing Lignin–Polycaprolactone Particulates Highly Dispersed by High-Shear Stress

Lignin powder was modified via ring-opening polymerization of caprolactone to form a lignin–polycaprolactone (LPCL) particulate. The LPCL particulates were mixed with an acrylonitrile–butadiene–styrene (ABS) matrix at an extremely high rotational speed of up to 3000 rpm, which was achieved by a closed-loop screw mixer and in-line melt extruder. Using this high-shear extruding mixer, the LPCL particulate size was controlled in the range of 3395 nm (conventional twin-screw extrusion) down to 638 nm (high-shear mixer of 3000 rpm) by altering the mixing speed and time. The resulting LPCL/ABS composites clearly showed non-Einstein viscosity phenomena, exhibiting reduced viscosity (2130 Pa·s) compared to the general extruded composite one (4270 Pa·s) at 1 s–1 and 210 °C. This is due to the conformational rearrangement and the increased free volume of ABS molecular chains in the vicinity of LPCL particulates. This was supported by the decreased glass transition temperature (Tg, 83.7 °C) of the LPCL/ABS composite specimens, for example, giving a 21.8% decrement compared to that (107 °C) of the neat ABS by the incorporation of 10 wt % LPCL particulates in ABS. The LPCL particulate morphology, damping characteristics, and light transmittance of the developed composites were thoroughly investigated at various levels of applied shear rates and mixing conditions. The non-Einstein rheological phenomena stemming from the incorporation of LPCL particulates suggest an interesting plasticization methodology: to improve the processability of high-loading filler/polymer composites and ultra-high molecular weight polymers that are difficult to process because of their high viscosity

Characterization of dioxane-based and soda-based extraction of lignin from oil palm empty fruit bunches as reinforcement in polylactic acid bio-composite

The study aims to compare the lignin extraction methods of OPEFB using different solvents; soda and dioxane solvent, and the reinforcement effects in polylactic acid (PLA) bio-composite. Different extraction method has been found to produce lignin with different properties and purity. The extraction yield also highly dependent on the types of solvents used in extraction process. Soda treatment had shown a good removal of lignin with 17.4 % of extraction yield, but only 8.08 % for dioxane treatment. In contrast, lower soda lignin content was observed compared to dioxane lignin with 89.65 % and 62.04 % respectively, suggesting lower purity of lignin obtained using soda treatment. Consequently, better performance was shown by PLA/dioxane lignin compared to PLA/soda lignin. Better interfacial bond of higher purity dioxane lignin had increased around 48 % and 38 % for tensile modulus and tensile strength as opposed to only 25 % and 29 % for PLA-soda lignin film

Optimizing tensile strength of PLA-Lignin Bio-composites using machine learning approaches

It is imperative to accurately estimate the final performance of composite parts during the initial design phase of the manufacturing process. In generating sustainable bio composites with superior mechanical properties such as tensile strength, the combination of fillers and plasticizers, as well as their concentration in the mixture, are always deemed crucial. In order to reduce the number of experimental runs and their associated costs and timescales, statistical optimization of the core design elements has become increasingly important. The filler and plasticizer concentrations of extruded bio composites were adjusted in this study utilizing both statistical (analysis of variance (ANOVA) and response surface methodology (RSM)) and machine learning (Multilayer Perceptron (MLP)) approaches. Initial ANOVA results indicated that lignin, epoxidized palm oil (EPO), and their respective combinations were the most influential factors in enhancing the durability of lignin/polylactic acid (PLA) bio composites. In this work, RSM and MLP were used to model and predict the data in order to maximize the various solutions and establish the nonlinear relationship between the concentration of lignin and EPO

Moisture Effects on Qualities and Properties of Laser Powder Bed Fusion (LPBF) Additive Manufacturing of As-Built 17-4PH Stainless Steel Parts

Laser powder bed fusion (LPBF) has the advantages of high resolution and geometric freedom but can be susceptible to process failures and defects caused by inappropriate process parameters and powder conditions. This study aims to reveal and quantify the moisture effect on the qualities and properties of as-built parts with various process parameters. The results showed that the density was decreased by 7.86% with humid powder (60.0% relative humidity (RH)) compared to dry powder (3.4%RH). Expectedly, the observed low density led to the property degradation in the hardness, yield strength (YS), and ultimate tensile strength (UTS) of the humid powder by 11.7, 15.02, and 21.25%, respectively, compared to that of dry powder (3.4%RH). Interestingly, the elongation at break of the parts fabricated with humid powder (60.0%RH) was increased by 2.82%, while their YS and UTS were decreased significantly. It seems that the water molecules on the powder surface hindered the reaction between the N2 shielding gas and melted powder, which resulted in the reduction in the austenite (γ) phase by up to 4.05 wt.%. This could be mainly responsible for the decrease in both the YS and UTS of the humid powder by approximately 100 and 150 MPa, respectively. This study demonstrates that the moisture of the metal powder used for LPBF should be carefully controlled to ensure desirable as-built qualities and properties

Poly(Lactic) acid reinforced with alkaline Lignin Biocomposites prepared by Thermal Extrusion for sustainable 3D printing process

The focus of this work is the mechanical characterization of biomaterials produced by 3D printing based on fused filament fabrication (FFF) process that has been mainly used for prototype rather than functional components due to the limited mechanical properties of pure thermoplastics parts. Addition of reinforcements from natural fiber has been adopted to improve the mechanical properties of the 3D printed parts. In this study, alkaline lignin powder that has been extracted from oil palm empty fruit bunches (OPEFB) via alkaline extraction process were used as filler in the production of biocomposites with poly(lactic) acid (PLA). Poly(lactic) acid filaments filled with 1% of alkaline lignin powder and has been compared with the presence of 5% of epoxidized palm oil (EPO) by means of thermal extrusion and further proceed with 3D printing. The samples were mechanically characterized using tensile tests and the fractography were observed. Tensile test that has been done on the filaments reveal that the filament with addition of lignin and EPO shows improved mechanical properties with higher tensile strength as well as lower stiffness. The 3D printed samples of the filament compositions also exhibit similar trend where the said filament has the best mechanical properties when the EPO is incorporated in the filament

Experimental and numerical investigation of 17–4PH stainless steel fabricated by laser powder bed fusion and hot isostatic pressing

Meticulous design and optimization of additive manufacturing (AM) are essential for obtaining high-quality metallic products, particularly using laser powder bed fusion (L-PBF). However, its potential in applications is limited because of the lack of understanding of AM. This makes the process parameter optimization time and cost-consuming. Here, the L-PBF process is employed to minimize defects and enhance the mechanical properties of 17–4PH stainless steel specimens, coupled with modeling. The optimal manufacturing parameters were determined by evaluating the relative densities of the as-built parts and thermal deformation. Either high or low energy densities resulted in high porosity and a higher energy density results in greater thermal deformation, attributed to the high mismatch in thermal expansion, while the surface roughness of as-built products is not as good as commercially available products. The hot isostatic pressing process improved the mechanical properties of the printed product by reducing the porosity and recrystallizing microstructures

All natural cork composites with suberin-based polyester and lignocellulosic residue

Suberin is an aromatic-aliphatic cross-linked polyester structure which constitutes cell wall structures of cork. It is particularly interesting for its use of monomeric compounds towards renewable bio-based polymers. In this study, the extraction of suberin monomers was successfully done by green method using alkaline hydrolysis combined with mechanical grinding. As the mechanical grinding was applied along with hydrolysis process, the maximum yield of depolymerized suberin monomer (DSM) with relatively low energy and less time was acheived. The polarity and functionality of DSM extracted in this study also showed higher values compared to conventional reflux hydrolysis process. Polyesterification and curing behavior of DSM were examined with molecular weights and mechanical properties of the ensuing polyesters. Tensile properties of suberin-based polyesters are reported for the first time that the maximum strength was found to be 7.3 MPa while Young's modulus was found to be 105 MPa. Furthermore, all natural cork composites were fabricated which comprise suberin-based polyester as matrix and lignocellulosic residue as reinforcement, and also reported their significantly enhanced tensile properties showing the great potential as an alternative green polymer composites for various engineering applications