Frost-retted hemp fibers were investigated to assess their suitability for composite applications. Chemical analysis of frost-retted hemp fibers highlighted a high amount of solubles (pectins) at the ...fibers surface and a low lignin content in the fibers that was attributed to an unfavorable synthesis of lignin in the cell wall due to the particularly cold temperature during hemp growth in the Nordic countries. The fibers tensile properties were considered at two different scales and the performances of hemp/PLA composites were assessed. Recommendations were provided for the use of frost-retted hemp fibers in the reinforcement of thermoplastic composites.
In the last decade, several studies have been performed on the preparation of smart composite matrix materials by twin-screw extrusion (TSE) followed by its process parametric optimisation based on ...analysis of variance (ANOVA) for 3D printing applications. But, hitherto little has been reported on TSE process optimisation using a hybrid approach, that is, ANOVA in the first stage followed by a technique for order of preference by similarity to ideal solution (TOPSIS) in the second stage for multi-objective selection. In this study, an effort has been made to develop a feedstock filament of polylactic acid (PLA) based composite matrix (comprising polyvinyl chloride (PVC) - wood dust (WD), and Fe
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as reinforcement) with TSE. The result of the study suggests that the proposed hybrid model of analysis is more useful than the single approach (in which the user may first use the ANOVA technique for optimisation followed by TOPSIS for locating the best and worst parametric conditions). Finally, the correlation matrix has been prepared for the mechanical and magnetic properties of the PLA-PVC-WD- Fe
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composite matrix.
This paper reports the printability and thermo-mechanical investigations of poly-lactic acid-polyether ketone-ketone- hydroxyapatite-chitosan (PLA-PEKK-HAp-CS) based functional prototypes printed ...with commercial fused deposition modelling (FDM) setup (without any alteration in software/hardware configuration). The in-house prepared feed stock filament comprising of PLA-PEKK-HAp-CS was used to print flexural samples as per ASTM D790. The samples prepared were investigated for flexural strength (on universal tensile testing (UTM) setup), thermal stability (on differential scanning calorimeter (DSC) setup) followed by morphological analysis (based upon metallurgical image analysis software for porosity evaluation as per ASTM B276). The results of study suggest that from flexural strength viewpoint for PLA-PEKK-HAp-CS based functional prototypes: infill density/percentage followed by infill speed is significant printing parameter. The predicted maximum flexural strength (26.3 MPa) and experimental results (26.17 MPa) are in line to each other and results are valid at 95% confidence level. The best settings of FDM printer from peak strength view point are 100% infill density/percentage, 50 mm s−1 infill speed and 4 no. of perimeters. Further in present case study it has been observed that samples prepared with low infill percentage posses better thermal stability and modulus of toughness as compared to samples prepared with high infill percentage.
The benefits of the fused filament fabrication (FFF) method, including its simplicity, affordability, and accessibility, have made it the most commonly used additive manufacturing technique. ...Polylactic acid (PLA) is the most widely used material in FFF, but its use has been limited by low mechanical properties and a small processing window. To address this, PLA composites are used to improve its properties. Correlating mechanical properties with process parameters is crucial for producing high-quality composite parts. This study investigated the effects of material and process parameters on mechanical properties, such as tensile strength and elongation-at-break, using a customized Delta Rostock FFF printer. Two types of filaments were used, pure PLA and PLA/Aluminum composites. Printing speed (10, 20, and 30 mm/s) and raster angle (0/90, −45/45, and −30/60) were selected as process input parameters. The Taguchi method was used for the experiment design, and signal-to-noise ratio analysis was used for statistical optimization. The optimal values for achieving maximum tensile strength of 61.85 MPa and maximum elongation-at-break of 17.7% were determined. Furthermore, the signal-to-noise ratio analysis indicated that the filament type had the greatest influence on the tensile strength, whereas printing speed had the greatest impact on the elongation-at-break.
Polylactic acid (PLA) is a promising material due to its biodegradability and compatibility. However, the limited resistance to ultraviolet (UV) degradation of PLA composites hinders their use in ...automotive interior materials. In our previous work, we successfully prepared 3D printed filaments by combining KH550-treated micro-nano rice husk (MNRH) fibers with KH570-treated PLA, which exhibited favorable performance. This study aimed to investigate the effects of silane coupling agents, MNRH, and accelerated UV weathering time on the photodegradation behavior of 3D printed PLA-matrix composites reinforced with MNRH. Scanning electron microscopy (SEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were utilized to characterize the 3D printed PLA-matrix composites. Furthermore, an exponential equation between tensile strength and UV weathering time was established, providing theoretical guidance for predicting the service life of automotive interior materials based on PLA composites. The morphological characterization experimental results indicate that with prolonged UV aging time, both PLA and RH6-KH550/KH570 composite materials transitioned from transparency to translucency. This transition can be attributed to the rupture of polylactic acid molecular chains and chemical bonds during the UV aging process. FTIR test results revealed the formation of carboxylic acid in the composite, and the reduction of C = O absorption intensity indicated that MNRH and silane coupling agents exhibited a stabilizing effect on the UV durability of the RH6-KH550/KH570 composite. TGA and DSC results indicated that KH550 and KH570 delayed the photodegradation rate of PLA-matrix composites.
This research was aimed at developing a dental prototype from 3D printing technology using a synthetic filament of polylactic acid (PLA) and zirconium dioxide (ZrO
) with glycerol and silane coupling ...agent as a binder. A face-centered central composite design was used to study the effects of the filament extrusion parameters and the 3D printing parameters. Tensile and compressive testing was conducted to determine the stress-strain relationship of the filaments. The yield strength, elongation percentage and Young's modulus were also calculated. Results showed the melting temperature of 193 °C, ZrO
ratio of 17 wt.% and 25 rpm screw speed contributed to the highest ultimate tensile strength of the synthetic filament. A Nozzle temperature of 210 °C and an infill density of 100% had the most effect on the ultimate compressive strength whilst the printing speed had no significant effects. Differential scanning calorimetry (DSC) was used to study the thermal properties and percentage of crystallinity of PLA filaments. The addition of glycerol and a silane coupling agent increased the tensile strength and filament size. The ZrO
particles induced the crystallization of the PLA matrix. A higher crystallization was also obtained from the annealing treatment resulting in the greater thermal resistance performance of the dental crown prototype.
This study aimed to increase the antibacterial activity of chitosan-polylactic acid (PLA) composite film by adding nisin and ethylenediaminetetraacetic acid (EDTA). We evaluated the mechanical, ...physicochemical, and antibacterial properties of various PLA composite films, as well as the enhancement effect of PLA composite films with EDTA + nisin on the preservation of grouper fillets. Films of PLA alone, PLA plus chitosan (C5), PLA plus nisin + EDTA (EN2), and PLA plus chitosan plus nisin + EDTA (C5EN1 and C5EN2) were prepared. The addition of EDTA + nisin to the chitosan-PLA matrix significantly improved the antibacterial activity of the PLA composite film, with C5EN1 and C5EN2 films showing the highest antibacterial activity among the five films. Compared with the fish samples covered by C5, the counts of several microbial categories (i.e., mesophilic bacteria, psychrotrophic bacteria, coliforms, Aeromonas, Pseudomonas, and Vibrio) and total volatile basic nitrogen content in fish were significantly reduced in the samples covered by C5EN1. In addition, the counts of samples covered by C5EN1 or C5 were significantly lower compared to the uncovered and PLA film-covered samples.
The poly lactic acid (PLA) matrix composites have wide self-assembly non-structural engineering applications. Some studies have reported the use of hybrid blend and multi blend PLA matrix for ...possible 3D printing. This work is an extension of studies reported on optimization of magnetic and surface properties for hybrid blend (PLA-50 wt%, poly vinyl chloride (PVC)-25 wt%, wood powder-5% and Fe3O4-20 wt%) and multi blend (PLA-80 wt% and Fe3O4-20 wt%) in self assembly applications. The hybrid and multi blended feedstock filaments for 3D printing has been prepared by using established conditions of twin screw extrusion (TSE) as per reported literature (i.e. barrel temperature of 170 °C, screw speed 45 rpm and extrusion load of 5 kg). For industrial applications of any process it must be statistically controlled for batch/mass production. Therefore in the present work an effort has been made for comparative process capability analysis based upon magnetic properties (obtained by vibration sample magnetometer, surface porosity (obtained by photomicrographs) and surface hardness (obtained by Shore D hardness) after preparing multi-blend and hybrid blend of PLA matrix composite as feed stock filament. The results of the study suggests that process of multi blend and hybrid blend of PLA matrix is under statistical control as the values of process capability indices (Cp and Cpk) for magnetic as well as surface properties are ≥1. Further X-chart and R-chart also signifies that both multi blend and hybrid blend PLA matrix composite predicts almost similar range of Cp and Cpk. Hence either multi blend or hybrid blend feed stock filament of PLA matrix composite may be used in batch/mass production for non-structural engineering applications.
A novel flame-retardant and toughened bio-based poly(lactic acid) (PLA)/glycidyl methacrylate-grafted natural rubber (GNR) composite was fabricated by sequentially dynamical vulcanizing and reactive ...melt-blending. The surface modification of aluminum hypophosphite (AHP) enhanced the interfacial compatibility between the modified aluminum hypophosphite by silane (SiAHP) and PLA/GNR matrix and the charring ability of the PLA/GNR/SiAHP composites to a certain extent, and the toughness and flame retardancy of the PLA/GNR/SiAHP composites were slightly higher than those of PLA/GNR/AHP composites, respectively. The notched impact strength and elongation of the PLA composite with 20 wt. %GNR and 18 wt.% SiAHP were 13.1 kJ/m
and 72%, approximately 385% and 17 fold higher than those of PLA, respectively, and its limiting oxygen index increased to 26.5% and a UL-94 V-0 rating was achieved. Notedly, the very serious melt-dripping characteristics of PLA during combustion was completely suppressed. The peak heat release rate and total heat release values of the PLA/GNR/SiAHP composites dramatically reduced, and the char yield obviously increased with an increasing SiAHP content in the cone calorimeter test. The good flame retardancy of the PLA/GNR/SiAHP composites was suggested to be the result of a synergistic effect involving gaseous and condensed phase flame-retardant mechanisms. The high-performance flame-retardant PLA/GNR/SiAHP composites have great potential application as replacements for petroleum-based polymers in the automotive interior and building fields.
In this study, the effect of layer thickness on the physicomechanical properties of the wood fiber-polylactic acid composite (WPC) part obtained by fused filament fabrication (FFF) was investigated. ...The results showed that most of the characteristics of the FFF-printed WPC part significantly depended on the printing layer thickness. As the layer thickness increased, the density of the printed WPC part decreased significantly, while the dimensional stability of the water-immersed WPC part decreased. In addition, specific tensile properties increased and the other specific mechanical properties (flexural, compressive, and shear properties) decreased with increasing layer thickness. Furthermore, scanning electronic microscopy micrographs illustrated that the number of voids and defects was more often observed on the surface of the WPC part printed with higher layer thickness. Therefore, these results indicated that the different layer thicknesses in FFF manufacturing have a substantial impact on the dimensional stability and specific mechanical properties of the FFF-printed WPC part.
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