Pristine PLA Research Articles

Synthesis of a phosphorus-containing L-lactic acid-based flame-retardant plasticizer for simultaneously enhancing flexibility and flame retardancy of poly(lactic acid)

This work provides a straightforward strategy for synthesizing efficient bio-based flame-retardant plasticizers, offering promising prospects for flame-retardant flexible materials. Poly(lactic acid) (PLA) has garnered significant attention as an environmentally friendly polymer among numerous biodegradable materials. However, its high flammability and brittleness severely hinder its application in the field of electronics and electrical devices. To address these challenges, a bio-based flame-retardant plasticizer (EPDL) was designed and synthesized using renewable L-lactic acid, which significantly enhances the flexibility and flame retardancy of PLA. Incorporating 40 phr EPDL resulted in PLA achieving UL94 V-0 grade and a limiting oxygen index of 34.3 %, demonstrating excellent flame-retardant properties. Meanwhile, the peak of heat release rate and total heat release of PLA/EPDL blends exhibited a marked reduction by 23.1 % and 34.1 % compared to that of pristine PLA, respectively. The flame-retardant action mode of EPDL is the combination of gas phase and condensed phase action. Additionally, the introduction of 40 phr EPDL significantly enhanced the ductility of PLA, resulting in a substantial rise in the elongation at break of the PLA/EPDL to 181.8 %, which is approximately 52 times higher than neat PLA. Intriguingly, the crystallization performance of PLA was enhanced by the presence of EPDL.

Enhancing the photostability and mechanical properties of poly‐lactic acid (PLA) composites with glutaric acid functionalized titanium dioxide (TiO2)

AbstractThe performance of Poly(lactic acid) (PLA) composites reinforced with functionalized titanium dioxide (TiO2) nanoparticles in rutile and anatase crystalline phases were systematically investigated. The results underline that the incorporation of TiO2, regardless of its crystalline structure, significantly enhances PLA's crystallinity by 85%. Notably, rutile TiO2, when functionalized with higher glutaric acid concentrations, was an effective crystallinity booster by 95%, passing from 20.39% to 39.58% crystallinity for the PLA/TiO2 R20 + 10% system. Furthermore, this research elucidates that the selection between anatase and rutile phases plays a vital role in the photostabilization. Functionalized Rutile TiO2 exhibited exceptional UV resistance, effectively inhibiting photodegradation; for example, after 15 days of exposure, the functionalized systems exhibited a 497.6% improvement for PLA/TiO2 R10 + 5% (22.1 ± 2.5 MPa), while the PLA/TiO2 R10 + 5% showed an 85.1% increase in composite stiffness (35.5 ± 3.5 MPa) after 7 days of degradation, in comparison with pristine PLA (19.2 ± 2.9 MPa). Anatase, conversely, displayed varying effects depending on concentration, acting as a stabilizer at lower levels and a promoter of degradation at higher concentrations. This knowledge enables the precise modifying of PLA composites for specific applications, balancing crystallinity, mechanical properties, and UV resistance for a diverse array of applications.Highlights TiO2 enhances photostability in PLA confirming its potential as a UV stabilizer. Comparing anatase and rutile phase: Unveiling PLA composite dynamics. Glutaric acid on TiO2 enhances PLA composite strength significantly. Optimal acid concentration key to composite performance. Tailored PLA composites balance crystallinity, mechanics, and UV resistance.

In vitro evaluation and characterization of cisplatin loaded nanofibers for local chemotherapy

Cancer is a disease that affects the quality of life of the patients that are treated with Cisplatin (CDDP), which is needed for adjuvant therapy, however it leads to many secondary and adverse effects. In this study, we manufactured and characterized poly-(lactic acid) (PLA) non-woven fibers loaded with Cisplatin (CDDP) by electrospinning technique to evaluate their cytotoxicity in in vitro assays on HeLa cells (cervical carcinoma cell line). PLA–CDDP solutions with increasing concentrations of CDDP (0.5, 1 and 2% w/w) were used in a TL-01 electrospinning equipment with the same system parameters. We analyzed the chemical, thermal and morphological characteristics of PLA and PLA–CDDP fiber mats. Furthermore, hydrolytic degradation, hemolysis and toxicity in HeLa cells were evaluated. By adding the CDDP to the fibers, the degradation, glass transition and melting temperatures were modified; the 3 µm fiber diameter of pristine PLA fibers was decreased in half the size and the degradation time was extended over 5 months. However, the hemocompatibility of the material with and without CDDP was maintained, while cytotoxicity in HeLa cells increased in the three concentrations of fiber mats of PLA–CDDP compared to the intravenous drug at 24 h (p < 0.01). We concluded that the fiber mats PLA–CDDP could be used for localized therapy in the adjuvant treatment when resection panels are expose after a surgical extirpation of solid tumors.

Strontium-Substituted Nanohydroxyapatite-Incorporated Poly(lactic acid) Composites for Orthopedic Applications: Bioactive, Machinable, and High-Strength Properties.

Traditional metal-alloy bone fixation devices provide structural support for bone repair but have limitations in actively promoting bone healing and often require additional surgeries for implant removal. In this study, we focused on addressing these challenges by fabricating biodegradable composites using poly(lactic acid) (PLA) and strontium-substituted nanohydroxyapatite (SrHAP) via melt compounding and injection molding. Various percentages of SrHAP (5, 10, 20, and 30% w/w) were incorporated into the PLA matrix. We systematically investigated the structural, morphological, thermal, mechanical, rheological, and dynamic mechanical properties of the prepared composites. Notably, the tensile modulus, a critical parameter for orthopedic implants, significantly improved from 2.77 GPa in pristine PLA to 3.73 GPa in the composite containing 10% w/w SrHAP. The incorporation of SrHAP (10% w/w) into the PLA matrix led to an increased storage modulus, indicating a uniform dispersion of SrHAP within the PLA and good compatibility between the polymer and nanoparticles. Moreover, we successfully fabricated screws using PLA composites with 10% (w/w) SrHAP, demonstrating their formability at room temperature and radiopacity when observed under X-ray microtomography (micro-CT). Furthermore, the water contact angle decreased from 93 ± 2° for pristine PLA to 75 ± 3° for the composite containing SrHAP, indicating better surface wettability. To assess the biological behavior of the composites, we conducted in vitro cell-material tests, which confirmed their osteoconductive and osteoinductive properties. These findings highlight the potential of our developed PLA/SrHAP10 (10% w/w) composites as machinable implant materials for orthopedic applications. In conclusion, our study presents the fabrication and comprehensive characterization of biodegradable composites comprising PLA and strontium-substituted nanohydroxyapatite (SrHAP). These composites exhibit improved mechanical properties, formability, and radiopacity while also demonstrating desirable biological behavior. Our results suggest that these PLA/SrHAP10 composites hold promise as machinable implant materials for orthopedic applications.

Bioelectret poly(lactic acid) membranes with simultaneously enhanced physical interception and electrostatic adsorption of airborne PM0.3

Traditional polymeric fibrous membranes have been extensively used to reduce the health risks caused by airborne particulate matter (PM), leading to the dramatically increasing pollution of plastics and microplastics. Although great efforts have been made to develop poly(lactic acid) (PLA)-based membrane filters, they are frequently dwarfed by their relatively poor electret properties and electrostatic adsorptive mechanisms. To resolve this dilemma, a bioelectret approach was proposed in this work, strategically involving the bioinspired adhesion of dielectric hydroxyapatite nanowhiskers as a biodegradable electret to promote the polarization properties of PLA microfibrous membranes. In addition to significant improvements in tensile properties, the incorporation of hydroxyapatite bioelectret (HABE) enabled remarkable increase in the removal efficiencies of ultrafine PM0.3 in a high-voltage electrostatic field (10 and 25 kV). This was exemplified by the largely increased filtering performance (69.75%, 23.1 Pa) for PLA membranes loaded with 10 wt% HABE at the normal airflow rate (32 L/min) compared to the pristine PLA counterpart (32.89%, 7.2 Pa). Although the filtration efficiency of PM0.3 for the counterpart dramatically decreased to 21.6% at 85 L/min, the increment was maintained at nearly 196% for the bioelectret PLA, while an ultralow pressure drop (74.5 Pa) and high humidity resistance (RH 80%) were achieved. The unusual property combination were ascribed to the HABE-enabled realization of multiple filtration mechanisms, including the simultaneous enhancement of physical interception and electrostatic adsorption. The significant filtration applications, unattainable with conventional electret membranes, demonstrate the bioelectret PLA as a promising biodegradable platform that allows high filtration properties and humidity resistance.

Influence of Ambient Temperature and Crystalline Structure on Fracture Toughness and Production of Thermoplastic by Enclosure FDM 3D Printer

Fused deposition modeling (FDM) 3D printing has printed thermoplastic materials layer-by-layer to form three dimensional products whereby interlayer adhesion must be well controlled to obtain high mechanical performance and product integrity. This research studied the effects of ambient temperatures and crystalline structure on the interlayer adhesion and properties of thermoplastic FDM 3D printing. Five kinds of poly(lactic acid) (PLA) filaments, both commercially available and the laboratory-made, were printed using the enclosure FDM 3D printer. The ambient temperatures were set by the temperature-controlled chamber from room temperature to 75 °C with and without a cooling fan. The interlayer adhesion was characterized by the degree of entanglement density, morphology, and fracture toughness. In addition, PLA filament with high crystallinity has induced heat resistance, which could prevent filament clogging and successfully print at higher chamber temperatures. The ambient temperature increased with increased chamber temperature and significantly increased when printed without a cooling fan, resulting in improved interlayer bonding. The crystalline structure and dynamic mechanical properties of the 3D printed products were promoted when the chamber temperature was increased without a cooling fan, especially in PLA composites and PLA containing a high content of L-isomer. However, although the additives in the PLA composite improved crystallinity and the degree of entanglement density in the 3D-printed products, they induced an anisotropic characteristic that resulted in the declination of the interlayer bonding in the transverse orientation products. The increasing of chamber temperatures over 40 °C improved the interlayer bonding in pristine PLA products, which was informed by the increased fracture toughness. Further, it can be noted that the amorphous nature of PLA promotes molecular entanglement, especially when printed at higher chamber temperatures with and without a cooling fan.

Impact fracture mechanism and heat deflection temperature of PLA/PEICT blends reinforced by glass fiber.

To enhance the crack propagation and initiation properties and heat deflection temperature of poly(lactic acid) (PLA), PLA/poly(1,4-cyclohexanedimethylene isosorbide terephthalate) (PEICT) blend systems were prepared and glass fibers (GF) were incorporated as reinforcements. Due to high shear force during extrusion and injection molding the length of GF was reduced and was oriented towards the flow direction. Although the reinforcing effect of the GF deviated from the theoretical values calculated by the Halpin-Tsai equation, both tensile and flexural properties were greatly enhanced with increasing GF content. Dynamic mechanical and thermal testing showed improved storage modulus throughout the entire temperature range showing outstanding reinforcing ability. By incorporating GF into the PLA/PEICT blend, the crack propagation and initiation properties were enhanced compared to pristine PLA. Such an increase in crack propagation properties was the result of enhanced modulus with the added GF. Moreover, because of the increased modulus, the heat deflection temperatures of the GF reinforced blends were drastically increased showing a value of 91.4 °C at 20 wt% GF loading. The high performance reached by the biomass-based composites developed in this research shows great possibility of replacing these conventional petroleum-based polymer systems.

Improvement in thermal stability, elastic modulus, and impact strength of Poly(lactic acid) blends with modified polyketone

We herein report the effect of modified polyketone (PK) on the microstructure, thermal stability, mechanical modulus, and impact strength of poly(lactic acid) (PLA). For this purpose, glycidyl methacrylate-grafted polyketone (PKGMA) was fabricated via in-situ melt-compounding and it was melt-mixed with pristine PLA to obtain PLA-dominant blends with 10–50 wt% PKGMA loadings. The electron microscopic images revealed that PLA/PKGMA blends showed a well-compatibilized microstructure with submicron-sized PKGMA domains in the continuous PLA matrix phase, unlike an immiscible PLA/PK blend. The infrared spectroscopic and melt-rheological analyses confirmed the specific intermolecular interactions and chemical reactions between PLA and PKGMA components in the blends. The differential scanning calorimetric data and X-ray diffraction patterns showed that the PKGMA component serves as a nucleating agent for the crystallization of PLA in the blends. The thermogravimetric analysis demonstrated that the thermal decomposition temperatures and residues of PLA/PKGMA blends were noticeably improved, compared to pristine PLA and an immiscible PLA/PK blend. The dynamic mechanical analysis exhibited that the elastic storage moduli of PLA/PKGMA blends were higher than that of pristine PLA. Furthermore, the Izod impact strength of PLA blends increased with the PKGMA loading. The PLA blend with 50 wt% PKGMA was found to have a maximum impact strength of ∼286.4 J/m, which was ∼94% higher than that (∼147.5 J/m) of pristine PLA. • GMA-grafted polyketone (PKGMA) is fabricated by a facile in-situ melt-mixing. • PLA/PKGMA blends exhibit a highly compatibilized morphological feature. • PLA-g-PKGMA is formed during melt-compounding of PLA/PKGMA blends. • There exist specific interactions between PLA and PKGMA in the blends. • PLA/PKGMA blends have enhanced thermal stability, elastic modulus, and impact strength.

Mechanically robust, stretchable, recyclable, and biodegradable ionogels reinforced by polylactide stereocomplex nanocrystals

Spider silk possesses the combined properties of high strength, great toughness, and good elasticity due to the unique two-phase structures, in which the β-sheet nanocrystals consisting of hydrogen-bonded polypeptide chains are connected by the flexible chains. The spider-silk-like structures provide novel avenues to create functional materials. Herein, a novel yet simple strategy has been developed for the fabrication of spider-silk-like ionogels. The scaffolds of ionogels, polyurethane (scPLA-PEG), were prepared from poly(L-lactide) (PLLA), poly(D-lactide) (PDLA), and poly(ethylene glycol) (PEG). The stereocomplex nanocrystallites (sc) could be formed through the multiple hydrogen-bonds on the enantiomeric PLLA and PDLA chains, thus the as-prepared scPLA-PEG possesses the spider-silk-like two-phase structures, in which the stereocomplex nanocrystallites are cross-linked by the amorphous PEG phases. As compared, the scPLA-PEG exhibit much higher mechanical properties than the pristine PLA counterparts. The scPLA-PEG ionogels also display good mechanical properties, extremely temperature-tolerant flexibility that endures twisting at low temperature (−30 °C) and stretching at high temperature (70 °C). Furthermore, the scPLA-PEG ionogels can be easily recycled owning to the reversible properties of scPLA. The results would present a new insight into designing novel functional ionogels with distinguished mechanical properties, tractable recyclability, and biodegradability, which will promote the sustainable flexible electronics.

Electrochemical activation for sensing of three‐dimensional‐printed poly(lactic acid) using low‐pressure plasma

AbstractIntegrated electrochemical sensors in which plasma‐treated poly(lactic acid) (PLA) single material acts as both selective coating layer and electrochemical transductor (electrode) are prepared. Thus, three‐dimensional‐printed PLA specimens are transformed into electroresponsive material by applying a low‐pressure gas plasma treatment with three different gases: N2, O2, and air (79% N2 + 21% O2). Although all treated samples are able to electrochemically detect dopamine, the one derived from the treatment of low‐pressure O2 plasma exhibits the best performance as a sensor. Finally, cell adhesion assays demonstrate that the cell viability is higher for plasma‐treated PLA modified than for pristine PLA, making the former a promising, versatile, and powerful electroresponsive platform for diverse applications in biomedicine.

Polylactic acid nanocomposites containing functionalized multiwalled carbon nanotubes as antimicrobial packaging materials

Intended for food packaging, nanocomposites films based on poly (lactic acid) reinforced by polydopamine-wrapped carbon nanotubes (PLA/PDA-MWCNTs) or TiO2 modified PDA-MWCNTs (PLA/TiO2-PDA-MWCNTs) as nanofillers were elaborated via melt-blending and characterized by several techniques. The success of the synthesis of the modified MWCNTs was confirmed by transmission electron microscopy, Raman and Fourier transform infrared spectroscopies and thermogravimetric analysis. Properties such as slow crystallization rate, barrier, mechanical, antibacterial and antifungal properties, required for food packaging, have been investigated. As compared to a PLA pristine film, the PLA based modified MWCNTs at 3 wt% loading exhibited better properties, particularly the PLA/TiO2-PDA-MWCNTs nanocomposite film. Indeed, the crystallization rate increased about 10% for PLA/TiO2-PDA-MWCNTs and 7% for PLA/PDA-MWCNTs compared to the neat PLA. Besides, these improved results have positively impacted on the nanomechanical and barrier properties of PLA nanocomposites films. The Young modulus was increased by 161% for PLA/TiO2-PDA-MWCNTs and 113% for PLA/PDA-MWCNTs and the hardness was improved by 815% for PLA/TiO2-PDA-MWCNTs and 79% for PLA/PDA-MWCNTs, respectively, as compared to the pristine PLA. Furthermore, PLA based modified MWCNTs nanocomposite films displayed a strong antimicrobial and antifungal activity compared to pure PLA.

Thermal degradation of various types of polylactides research. The effect of reduced graphite oxide on the composition of the PLA4042D pyrolysis products

This study was aimed to investigate the effect of reduced graphene oxide (rGO) on the pyrolysis of polylactide composites (PLA4042D/rGO) prepared in solution. GC-MS analysis of PLA4042D/rGO pyrolysis products showed that introduction of rGO into the composition with PLA leads to a significant change in the ratio of main degradation products. A sharp decrease of five-membered dioxolanones accompanied by a growth in the content of lactides and cyclic oligomeric lactides was observed in PLA4042D/rGO pyrolysis products as compared with pristine PLA. DSC studies of PLA4042D crystallization in the melt showed that the adsorption of PLA macromolecules on rGO surface can cause the decrease in their segmental mobility. Apparently, a decrease in the segmental mobility of PLA chains hinders the formation of dioxolanones via the intramolecular nonradical ester interchange reaction. At the same time, the role of intermolecular reactions with the formation of cyclic oligomers of lactides increases.

Antioxidant activity of mango seed wax additive on the properties of poly(lactic acid) transparent films for food packaging application

AbstractTo improve the tensile properties of poly(lactic acid) (PLA) biodegradable packaging film, mango seed wax (MSW), an agro‐industrial waste from the mango fruit processing industry has been used as a plasticizing additive. Four different weight ratios of MSW (3, 5, 7, and 9 wt%) in pristine PLA were considered for optimization. The mechanical properties comprising tensile strength, elongation at break, and Young's modulus were studied. Characterizations such as Fourier transform infra‐red (FTIR) spectroscopy, and differential scanning calorimetry were studied. Oxidation induction time (OIT) analysis of samples was also conducted. Other studies such as thermal, barrier, and optical properties were also evaluated. The differential scanning calorimetry (DSC) analysis revealed better compatibility between MSW and PLA matrices. A small decrease in glass transition temperature (10%), and melting point (3%) was observed when increasing the percentage of MSW in PLA. Moreover, the visual transparency of MSW/PLA systems was intact when increasing the loading. The addition of 9% MSW results in a 700% enhancement in elongation at break than that of pristine PLA. The optimized sample (PLA with 5% MSW) showed a 26% improvement in the hydrophobicity of the PLA matrix. The barrier properties (55.6% in WVTR and 10% in oxygen transmission rate (OTR) were also improved by the presence of MSW. These are promising systems as a suitable material for biodegradable food packaging thermoplastic material.

Plasma Sputtered Tungsten Oxide Thin Film on Poly(lactic acid) for Food Packaging Applications

Biodegradable and bio-derived plastics such as poly(lactic acid) (PLA) are a promising solution to solve the huge environmental and economic issues caused by the enormous consumption of conventional oil-derived polymers, especially in food packaging applications. However, their poor gas barrier properties and high transparency to UV radiation limit their currently commercialization. Therefore, this study is focused on the deposition of tungsten oxide (WOx) thin films on commercial PLA in order to enhance its overall performance. Coatings with different thickness (25, 50 and 100 nm) were deposited by means of radiofrequency (RF) plasma magnetron reactive sputtering. Morphological characterization was carried out with atomic force microscopy (AFM) and scanning electron microscopy (SEM). In order to evaluate surface chemical changes due to plasma treatments, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis were performed. The PLA/WOx samples demonstrated remarkable improvements both in UV protection and oxygen barrier properties. In particular, light transmittance was reduced by approximately 95% in the UV-B region, 70% in the UV-A region and 50% in the visible region compared to pristine PLA. Regarding oxygen permeation, a reduction of at least 99.9% was achieved. In addition, the PLA/WOx antibacterial properties against Escherichia coli were also investigated, showing a reduction greater than 5 log10 CFU cm−2 after 24 h for the 50 and 100 nm samples. These results demonstrate the potential of WOx thin coating for sustainable food packaging applications.

Cu(II) adsorption on Poly(Lactic Acid) Microplastics: Significance of microbial colonization and degradation

The current trend towards the use of biodegradable polymers is considered as a sustainable solution to plastic pollution. However, microplastics (MPs) generation due to harsh degradation conditions may impose higher environmental risks on organisms in the aquatic environment, especially when coexisted with various complicated pollutants. This study aimed at investigating the significance of microbial colonization and degradation in the Cu(II) adsorption by poly(lactic acid) (PLA) MPs. The PLA MPs covered with biofilms showed higher monolayer Cu(II) adsorption capacity than the pristine PLA (151.802 ug·g−1 versus 1045.670 ug·g−1), which was attributed to the surface complexation between Cu(II) and functional groups contained in biofilms. The adsorption kinetics of the sewage-incubated PLA was limited by film diffusion and intraparticle diffusion, whereas film diffusion dominated the Cu(II) adsorption by the pristine PLA. Degradation of PLA MPs was detected by Fourier transform infrared spectroscopy (FTIR) with the breakdown of ester bonds, and the biofilm-mediated alterations were further enhanced with the extension of incubation. In addition, removal of biofilms increased the Cu(II) adsorption on PLA MPs by 32.36% due to the higher surface area with more adsorption sites and the pore-filling mechanism. Cu(II) adsorption capacity of PLA MPs was pH-dependent and the biofilm-removed PLA exhibited the lowest adsorption ability at the pH ranging from 4.5 to 6.0. Fulvic acid (FA) inhibited the Cu(II) adsorption due to the complexation of Cu(II) with FA. Our results filled the knowledge gap concerning the influence of microbial colonization and degradation on the adsorption behavior of biodegradable PLA MPs, which can further serve as the cornerstone to understand the environmental interaction between poly(α-hydroxy acid)-type polyesters and heavy metal pollutants.

Improving Recycled Poly(lactic Acid) Biopolymer Properties by Chain Extension Using Block Copolymers Synthesized by Nitroxide-Mediated Polymerization (NMP).

The aim of this contribution is to assess the use poly(styrene-co-glycidyl methacrylate-b-styrene) copolymers synthesized by nitroxide mediated polymerization (NMP) as chain extenders in the recycling of poly(lactic acid) biopolyester. Concisely, the addition of such block copolymers during the melt processing of recycled poly(lactic acid) (rPLA) leads to important increases in the viscosity average molecular weight of modified polymeric materials. Molar masses increase from 31,000 g/mol for rPLA to 48,000 g mol−1 for the resulting rPLA/copolymer blends (bPLA). Fortuitously, this last value is nearly the same as the one for pristine PLA, which constitutes a first piece of evidence of the molar mass increase of the recycled biopolymer. Thermograms of chain extended rPLA show significant decreases in cold crystallization temperature and higher crystallinity degrees due to the chain extension process using NMP-synthesized copolymers. It was found that increasing epoxide content in the NMP-synthesized copolymers leads to increased degrees of crystallinity and lower cold crystallization temperatures. The rheological appraisal has shown that the addition of NMP synthesized copolymers markedly increases complex viscosity and elastic modulus of rPLA. Our results indicate that P(S-co-GMA)-b-S) copolymers act as efficient chain extenders of rPLA, likely due to the reaction between the epoxy groups present in P(S-co-GMA)-b-PS and the carboxyl acid groups present in rPLA. This reaction positively affects viscometric molar mass of PLA and its performance.

Discharge Plasma Treatment as an Efficient Tool for Improved Poly(lactide) Adhesive-Wood Interactions.

Poly(lactide) (PLA) films obtained by thermoforming or solution-casting were modified by diffuse coplanar surface barrier discharge plasma (300 W and 60 s). PLA films were used as hot-melt adhesive in joints in oak wood. It was demonstrated that lap shear strength increased from 3.4 to 8.2 MPa, respectively, for the untreated and plasma-treated series. Pull-off tests performed on particleboard for the untreated and treated PLA films showed 100% cohesive failure. Pull-off strength tests on solid oak demonstrated adhesion enhancement from 3.3 MPa with the adhesion failure mode to 6.6 MPa with the cohesion failure mode for untreated and treated PLA. XPS revealed that carbonyl oxygen content increased by two-to-three-fold, which was confirmed in the Fourier-transform infrared spectroscopy experiments of the treated PLA. The water contact angle decreased from 66.4° for the pristine PLA to 49.8° after treatment. Subsequently, the surface free energy increased from 47.9 to 61.05 mJ/m2. Thus, it was clearly proven that discharge air plasma can be an efficient tool to change surface properties and to strengthen adhesive interactions between PLA and woody substrates.

Cross-sectional microanalysis for tracking the effect of solvent on the morphological evaluation of PLA/AgNWs bionanocomposties

The emphasis of biocompatible polymer applications in medical sciences and biotechnology has remarkably increased. Developing new low-cost, low-toxicity and lightweight composite forms of biopolymers has become even more attractive since the addition of new species into polymer matrices assist to improve biomedical activities of such materials to a higher extend. Developments in nanoscience and nanotechnology recently contribute to controlled fabrication and ultraprecise diagnosis of such materials. This study concerns the observation of solution processing effects in the fabrication of porous PLA/AGNWs bionanocomposite coatings using electron and ion processing based serial cross-sectioning and high-resolution imaging. The nanostructuring and characterization were both performed in a focused ion-beam-scanning electron microscope (FIB-SEM) platform. HR-SEM imaging was conducted on-site to track solvent based morphological property alterations of PLA and PLA/AgNWs structures. Simultaneous SEM-EDS analyses revealed the elemental distribution and the chemical composition along the cross-sectioned regions of the samples. Accordingly, it was observed that, in case of acetone dissolved materials, both pristine PLA and PLA/AgNWs samples sustained their foamy structure. When chloroform was used as the solvent, the porosity of the polymer matrices was less and the resulting structure was found to be denser than samples dissolved in acetone with a lower surface area ratio inside the material. This can be attributed to the rapid volatilization of acetone compared to chloroform, and hence the formation of interconnected pore network. For both nanocomposite biopolymers dissolved in acetone and chloroform, silver nanowires were homogeneously distributed throughout PLA matrices.

Golden Glittering Biocomposite Fibers from Poly(lactic acid) and Nanosilver-Coated Titanium Dioxide with Unique Properties; Antimicrobial, Photocatalytic, and Ion-Sensing Properties.

Golden glittering biocomposite fibers from poly(lactic acid) (PLA) and nanosilver-coated titanium dioxide (Ag/TiO2) were successfully prepared via a melt spinning process. Various contents of 10% Ag/TiO2/PLA masterbatch were diluted with PLA in concentrations of 5, 10, 15, 20, 25, and 30 phr, respectively. The physical, mechanical, thermal, and antibacterial properties of the obtained fibers were investigated. The results indicated that the glittering biocomposite fiber had a light, yellow-gold color and a slightly rough surface. Tenacity and elongation at break of the glittering biocomposite fibers were lower than those of the pristine PLA fiber. The thermal properties of the glittering composite fibers also decreased with increasing masterbatch content. The PLA/PEG-10 biocomposite fiber with good spinnability and mechanical properties was suitably used for preparing the golden glittering composite fabric by the knitting process. Moreover, the golden glittering biocomposite fabrics exhibited antibacterial activity against certain microbes, for example, Staphylococcus aureus, Bacillus subtilis, and Candida albicans. The prepared fabric has significant potential for use in eco-friendly textile products and antibacterial fabrics. Besides, our novel textiles showed not only the photocatalytic property needed to degrade organic dyes such as methylene blue in water but also the ion-sensing property for mercury(II) ions by changing the textile color from yellow to colorless.

Superhydrophobic reduced graphene oxide@poly(lactic acid) foam with electrothermal effect for fast separation of viscous crude oil

In recent years, eco-friendly superhydrophobic materials have aroused much attention. Herein, biodegradable poly(lactic acid) (PLA) was selected as basic material to fabricate superhydrophobic foam with electrothermal effect by dip-coating graphene oxide (GO) on the surface of PLA foam constructed through freeze-drying process and the subsequent reduction with hydroiodic acid. Owing to the micro-nano rough structure of pristine PLA foam and the coverage of low-surface-energy reduced GO (rGO), the obtained rGO@PLA foam exhibited excellent water repellency with a high water contact angle of 150.6°. The foam was able to separate different oil–water mixtures, and the separation efficiencies were all above 96%. Importantly, the rGO layer also endowed the PLA foam with electrothermal conversion capability, and the surface temperature of the rGO@PLA foam rapidly increased to 129.5 °C from 30.8 °C at a low voltage of 15 V within only 120 s. By means of the generated Joule heat, the rGO@PLA foam was successfully applied for separating viscous crude oil from water, and the separation rate was about 14 times higher than that without voltage. Our findings conceivably stand out as a new tool to fabricate functional biodegradable materials for clean-up of viscous crude oil.