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As an emerging science, tissue engineering and regenerative medicine focus on developing materials to replace, restore or improve organs or tissues and enhancing the cellular capacity to proliferate, migrate and differentiate into different cell types and specific tissues. Renewable resources have been used to develop new materials, resulting in attempts to produce various environmentally friendly biomaterials. Poly (lactic acid) (PLA) is a biopolymer known to be biodegradable and it is produced from the fermentation of carbohydrates. PLA can be combined with other polymers to produce new biomaterials with suitable physicochemical properties for tissue engineering applications. Here, the advances in modified PLA as tissue engineering materials are discussed in light of its drawbacks, such as biological inertness, low cell adhesion, and low degradation rate, and the efforts conducted to address these challenges toward the design of new enhanced alternative biomaterials. [ABSTRACT FROM AUTHOR]

In order to further explore the feasibility of the application of the residue of Chinese herbal medicine in FDM 3D technology and enrich the kinds of printing materials, Astragalus residue powder(ARP)/poly(lactic acid) (PLA) biocomposite was FDM 3D-printed, meanwhile, two traditional biocomposites, i.e., wood flour (WF)/PLA and rice straw powder (RSP)/PLA, were prepared by the same method, and the properties of the biocomposites were comparatively investigated. The results showed that, the tensile and flexural strengths of ARP/PLA were 28.33 MPa and 97.60 MPa, respectively, which were 2.85% and 10.89% smaller than those of WF/PLA, while 15.73% and 7.04% greater than those of RSP/PLA. WF/PLA showed typical brittle fracture characteristics, ARP/PLA and RSP/PLA both showed ductile fracture, but not obviously. Among the three kinds of biocomposites, ARP/PLA was the most thermally stable, followed by WF/PLA and RSP/PLA in turn. The incorporation of natural plant powder had no significant effect on the glassy transition, melting, and cold-crystallization behaviors of PLA, but the crystallinity of PLA could be increased from 0.3% to 2.0% and 1.9%, respectively, by adding ARP and WF. At 20 °C, the storage modulus of ARP/PLA, WF/PLA and RSP/PLA was 2759.4 MPa, 3361.3 MPa, and 2691.5 MPa, respectively, indicating that WF/PLA has the greatest stiffness, and the stiffness of RSP/PLA was the least. In addition to these, all the biocomposites were hydrophilic, the contact angle of the distilled water on the surface of ARP/PLA, WF/PLA or RSP/PLA was correspondingly 73.5°, 77.6° and 71.2°. Overall, it can be concluded that ARP/PLA has moderate strengths, stiffness and wettability, meanwhile, it is the most thermal stable among the three biocomposites, and can be processed at a temperature close to that of PLA. ARP/PLA is suitable as a new kind of feedstock material for FDM 3D printing. [ABSTRACT FROM AUTHOR]

Thermomechanical pulp (TMP) fibres can serve as renewable, cost-efficient and lightweight reinforcement for thermoplastic polymers such as poly(lactic acid) (PLA). The reinforcing ability of TMP fibres can be reduced due to various factors, e.g., insufficient dispersion of the fibres in the matrix material, fibre shortening under processing and poor surface interaction between fibres and matrix. A two-level factorial design was created and PLA together with TMP fibres and an industrial and recyclable side stream were processed in a twin-screw microcompounder accordingly. From the obtained biocomposites, dogbone specimens were injection-moulded. These specimens were tensile tested, and the compounding parameters statistically evaluated. Additionally, the analysis included the melt flow index (MFI), a dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and three-dimensional X-ray micro tomography (X- μ CT). The assessment provided insight into the microstructure that could affect the mechanical performance of the biocomposites. The temperature turned out to be the major influence factor on tensile strength and elongation, while no significant difference was quantified for the tensile modulus. A temperature of 180 °C, screw speed of 50 rpm and compounding time of 1 min turned out to be the optimal settings. [ABSTRACT FROM AUTHOR]

In our study, the effects of wood waste content (0, 2.5, 5, 7.5, and 10 wt.%) on thermal and dry sliding wear properties of poly(lactic acid) (PLA) biocomposites were investigated. The wear of developed composites was examined under dry contact conditions at different operating parameters, such as sliding velocity (1 m/s, 2 m/s, and 3 m/s) and normal load (10 N, 20 N, and 30 N) at a fixed sliding distance of 2000 m. Thermogravimetric analysis demonstrated that the inclusion of wood waste decreased the thermal stability of PLA biocomposites. The experimental results indicate that wear of biocomposites increased with a rise in load and sliding velocity. There was a 26–38% reduction in wear compared with pure PLA when 2.5 wt.% wood waste was added to composites. The Taguchi method with L25 orthogonal array was used to analyze the sliding wear behavior of the developed biocomposites. The results indicate that the wood waste content with 46.82% contribution emerged as the most crucial parameter affecting the wear of PLA biocomposites. The worn surfaces of the biocomposites were examined by scanning electron microscopy to study possible wear mechanisms and correlate them with the obtained wear results. [ABSTRACT FROM AUTHOR]

Fungal biomass (FB), a by-product of the fermentation processes produced in large volumes, is a promising biomaterial that can be incorporated into poly(lactic acid) (PLA) to develop enhanced biocomposites that fully comply with the biobased circular economy concept. The PLA/FB composites, with the addition of triethyl citrate (TEC) as a biobased plasticizer, were fabricated by a microcompounder at 150 °C followed by injection molding. The effects of FB (10 and 20 wt %) and TEC (5, 10, and 15 wt %) contents on the mechanical, thermal and surface properties of the biocomposites were analyzed by several techniques. The PLA/FB/TEC composites showed a rough surface in their fracture section. A progressive decrease in tensile strength and Young's modulus was observed with increasing FB and TEC, while elongation at break and impact strength started to increase. The neat PLA and biocomposite containing 10% FB and 15% TEC exhibited the lowest (3.84%) and highest (224%) elongation at break, respectively. For all blends containing FB, the glass transition, crystallization and melting temperatures were shifted toward lower values compared to the neat PLA. The incorporation of FB to PLA thus offers the possibility to overcome one of the main drawbacks of PLA, which is brittleness. [ABSTRACT FROM AUTHOR]

This paper presents the study of the properties of objects that were fabricated with fused deposition modeling technology while using Poly (lactic acid)/Walnut shell powder (PLA/WSP) biocomposite filaments. The WSP was treated while using NaOH followed by silane. The infrared spectrum of treated and untreated WSP was characterized. The result was that thermal and mechanical properties could be improved by adjusting the concentration of silane. The experimental results showed: the surface compatibility between WSP and PLA was dramatically improved through treatment with KH550. The crystalline, thermal gravity, and thermal degradation temperatures of biocomposite with untreated WSP were improved from 1.46%, 60.3 °C, and 239.87 °C to 2.84%, 61.3 °C, and 276.37 °C for the biocomposites with treated WSP, respectively. The tensile, flexural, and compressive strengths of biocomposites were raised each by 8.07%, 14.66%, and 23.32%. With the determined silane concentration, PLA/10–15 wt.% treated WSP biocomposites were processed and tested. The results showed that the tensile strength was improved to 56.2 MPa, which is very near to that of pure PLA. Finally, the porous scaffolds with controllable porosity and pore size were manufactured. [ABSTRACT FROM AUTHOR]

Abstract: Over the last few years, intensive research has been devoted to the exploitation of “green products” based on natural resources for both matrices and as reinforcements in composite systems. The mechanical properties of reinforced biocomposites, such as flax/polylactic acid (PLA), are largely governed by interfacial properties between the two constituents apart from their intrinsic properties. Although many papers indirectly demonstrate the importance of optimising the interface between these two polymers, the exact nature of the interaction between the natural fibre and the polymeric matrix has not been clearly investigated on a fundamental level and is presently a major technological limitation of these materials. This work presents the first direct study of adhesion forces, by colloidal force microscopy, between smooth PLA films representing the polymer matrix, and a microbead of cellulose that mimic the cellulose material in flax fibres. Normalised adhesion force measurements have shown the importance of capillary forces when experiments were carried out under ambient conditions. Experiments, conducted under dry air, allowed for the deduction of the contribution of pure van der Waals forces, and our results, through the calculation of the Hamaker constant, show that these forces, for the PLA/cellulose/air system, were lower than those obtained for the cellulose/cellulose/air system and hence underlined the importance of optimising the interface among these materials. This study demonstrates the capacity of AFM to probe direct interactions in complex systems by adjusting the nature of the surface and the probe to mimic the materials in contact. Furthermore, the technique can be operated in a variety of environments, consistent with composite making and provides particular opportunity for testing and improving the properties of these new classes of composite materials. [Copyright &y& Elsevier]

Biodegradable poly(lactic acid) (PLA) presents suitable physicochemical properties and biocompatibility for biomedical engineering. However, PLA has some drawbacks, such as low cell adhesion, biological inertness, low degradation rate, and acid degradation by-products. In this review, recent progress on strategies to address these problems is summarized, including novel fabrication techniques, high-performance PLA composites, and their applications for tissue engineering and drug delivery. The scaffolds, especially for bone regeneration, blood vessels, organs, and skin regeneration are evaluated, in terms of in vivo and in vitro biocompatibility and biodegradability. The enhanced mechanical, thermal, and rheological properties of PLA biocomposites are analyzed in detail. PLA biocomposites for drug encapsulation, sustained release, and tumor-targeting are also reviewed. Furthermore, the challenges and future perspectives on PLA-based biocomposites are discussed. [ABSTRACT FROM AUTHOR]