Having even particle size and regular morphology of biochar microspheres (BM) provides the possibility for preparing polylactic acid (PLA) films. Hence, the novelty is proposing a strategy for ...reinforcing PLA by BM. It was found that BM exhibited regular morphology, higher thermal stability, even particle size, and better pore characteristics. Although adding BM decreased the toughness of PLA due to the poor compatibility between BM and PLA, the nucleation effect of BM facilitated the crystallization in the PLA system. The tensile strength and modulus of BM/PLA composite films increased first and then decreased with increasing BM content. The stress concentration formed by BM particle agglomeration was responsible for the tensile strength and modulus decreases of BM/PLA composite films under higher BM addition. 2% BM added and 3% added composite films exhibited the best tensile strength and modulus with 64.99 MPa and 1.59 GPa, which was mainly attributed to the proper proportion of BM to PLA and the uniform distribution of BM in PLA. The results of this study confirmed the positive reinforcing effect of BM in PLA and are expected to be available in the composite film field.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, the physicochemical properties of torrefied biomass (larch and yellow poplar) were investigated based on torrefaction temperature. The effect of torrefied biomass on the hydrophobicity ...and mechanical properties of a polylactic acid (PLA) composites was evaluated. Hemicellulose was removed from the biomass during torrefaction, whereas the cellulose and lignin contents increased slightly. The color of the biomass changed from brown to black. The grindability of the torrefied biomass improved as the torrefaction temperature increased, which contributed to the production of fine particles (>100 mesh). A PLA composite was prepared using torrefied biomass (10 %) and polylactic acid. At 280 °C, water contact angle was the highest, regardless of the particle size and biomass species. Tensile strength of the PLA composite was slightly lower than that of PLA alone, regardless of the particle size of torrefied biomass. Nevertheless, the strength increased with the torrefaction temperature, except for larch with a relatively large particle size (<100 mesh). The tensile strength of the control was 68.0 MPa, whereas that of the torrefied biomass ranged from 61.1 to 65.8 MPa.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, the influence of layer thickness (LT), infill percentage (IP), and extruder temperature (ET) on the maximum failure load, thickness, and build time of bronze polylactic acid (Br-PLA) ...composites 3D printed by the fused deposition modeling (FDM) was investigated via an optimization method. PLA is a thermoplastic aliphatic polyester obtained from renewable sources, such as fermented plant starch, especially made by corn starch. The design of experiment (DOE) approach was used for optimization parameters, and 3D printings were optimized according to the applied statistical analyses to reach the best features. The maximum value of failure load and minimum value of the build time were considered as optimization criteria. Analysis of variance results identified the layer thickness as the main controlled variable for all responses. Optimum solutions were examined by experimental preparation to assess the efficiency of the optimization method. There was a superb compromise among experimental outcomes and predictions of the response surface method, confirming the reliability of predictive models. The optimum setting for fulfilling the first criterion could result in a sample with more than 1021 N maximum failure load. Finally, a comparison of maximum failure from PLA with Br-PLA was studied.
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•3D printing of continuous wire polymer composite (CWPC) for strain sensor.•Integrated Copper wire in PLA and PU CWPCs enhances their mechanical properties.•The gauge factor of both ...PLA and PU CWPCs was statistically insignificant.•Gauge factor results were verified by an analytical model.•Rigid PLA and flexible PU CWPCs can fit different applications based on strain needed.
In this study, the electromechanical properties of two different three-dimensional (3D) printed continuous wire polymer composites (CWPC) were characterized and compared. The two composite materials were copper wire polylactic acid (PLA) composite (rigid material) and copper wire polyurethane (PU) composite (flexible material). The electromechanical measurements were based on piezoresistive properties of the sensor at which the mechanical strain and the electrical resistance were correlated under a uniaxial loading condition. Both types of materials exhibited a direct linear relationship between the two quantities, indicating the ability of CWPC to be used for strain sensing applications. The gauge factor (GF) sensitivity was compared for the two types of materials. It was found that there is no statistical significance difference between the GF of PLA CWPC (1.36 ± 0.14) and PU CWPC (1.29 ± 0.07)); therefore, the sensing property depends mainly on the wire integrated into the 3D-printed structure rather than the matrix. Thus, different matrices can be used to fit different applications. An analytical model for GF showed agreement with the experimental results for both materials. PU CWPC showed significant improvement in both Young’s modulus (E) and ultimate tensile strength (UTS) (210.5 % and 31.86 %, respectively), compared with pure PU, while the change in Poisson’s ratio (ν) was insignificant. Young’s modulus of PLA CWPC was significantly increased by 80.3 % compared with PLA, while UTS and ν did not significantly change. The experimental mechanical properties showed good agreement with data from the analytical models. The outcome of this study focused on the manufacturing of 3D-printed functionalized structure for strain sensing applications with improved mechanical properties. The wide range of attained strain allowed their use in different applications based on the range of strain needed, such as rigid sports equipment and flexible wearable sensors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Pediococcus pentosaceus, a bacterium recently used in human and animal probiotics, was used in combination with supports made from polylactic acid composite soybean meal was used to study biofilm ...formation, and it was found that dense biofilms developed by Day 1. Proteomic comparison between planktonic and biofilm cultures of P. pentosaceus showed distinct expression patterns of intracellular and extracellular proteins. Type I glyceraldehyde‐3‐phosphate dehydrogenase was upregulated in biofilm cultures and mediated cell adhesion and encouraged biofilm production. GMP synthase, which regulates GMP synthesis and acts as an intracellular signal molecule to control cell mechanisms and has been exploited in the development of new therapeutic agents, was also upregulated in the biofilm mode of growth. The present work serves as a basis for future studies examining the complex network of systems that regulate lactic acid bacterial (LAB) biofilm formation and can serve as a framework for studies of production of therapeutic agents from LAB.
Significance and Impact of the Study: This work studied the biofilm forming ability of Pediococcus pentosaceus and elucidated the differing protein profiles of the micro‐organism grown in planktonic versus biofilm conditions. Many proteins related to biofilm formation and antibiotic production were overexpressed in the biofilm mode of growth. The novel use of polylactic acid composite soybean meal as a biodegraded carrier for P. pentosaceus biofilm formation is described.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Herein, a hydroxyl-terminated hyperbranched polymer (HPN) with abundant terminal hydroxyl groups was employed to modify straw-plastic composites and studied the effect of HPN concentration on straw ...fiber reinforced polylactic acid (SF/PLA). Silane coupling agent (CA) was used to improve the interfacial compatibility between SF, HPN and PLA matrix. The mechanical strength, thermal properties and water resistance of different SF/PLA composites were tested and analyzed. When the concentration of HPN is 6%, the HPN-SF/PLA has the best mechanical strength index. HPN modification, CA modification and the combination of both have positive effect on improving mechanical performance. Compared with the UN-SF/PLA, the tensile, flexural and impact strength of HPN+CA-SF/PLA composites were increased by 24.7%,16.6% and 10.8%, respectively. The crystallinity of SF/PLA treated with HPN, CA, and their combination increased from 28% to 29.4%, 36.9%, and 42.3%, respectively. However, low melting point of HPN caused a decrease in the Tg, Tm, Tc, Td5% and Tdmax of SF/PLA. These characteristic temperatures can be enhanced by adding CA for co-modification. In addition, the three modified approach were able to enhance the water resistance of SF/PLA composites due to the reduction of the number of hydroxyl groups on the SF surface and the enhancement of the interfacial bonding properties.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Polylactic acid (PLA) films with good sustainable and biodegradable properties have been increasingly explored recently, while the poor mechanical property of PLA limits its further application. ...Herein, three kinds of nano-sized cellulose formate (NCF: cellulose nanofibril (CNF), cellulose nanocrystal (CNC), and regenerated cellulose formate (CF)) with different properties were fabricated via a one-step formic acid (FA) hydrolysis of tobacco stalk, and the influence of the properties of NCF with different morphologies, crystallinity index (
), and degree of substitution (
) on the end quality of PLA composite film was systematically compared. Results showed that the PLA/CNC film showed the highest increase (106%) of tensile strength compared to the CNF- and CF-based films, which was induced by the rod-like CNC with higher
. PLA/CF film showed the largest increase (50%) of elongation at the break and more even surface, which was due to the stronger interfacial interaction between PLA and the CF with higher
. Moreover, the degradation property of PLA/CNF film was better than that of other composite films. This fundamental study was very beneficial for the development of high-quality, sustainable packaging as an alternative to petroleum-based products.
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