Degradation Of PLA Research Articles

Comparative study of PLA composites reinforced with graphene nanoplatelets, graphene oxides, and carbon nanotubes: Mechanical and degradation evaluation

The effect of different reinforcements such as graphene nanoplatelets (GNPs), Graphene oxides (GO), and carbon nanotubes (CNTs), into PLA was studied in this research work. Distinct suspensions of GO, GNPs, and CNTs have been utilized to fabricate the PLA/GO, PLA/GNPs, and PLA/CNTs composites through solution casting. All composites were compared based on mechanical and degradation results. FTIR results confirm the ester and alcohol functional groups in PLA and composites. EDX results indicate the weight % of carbon, oxygen, and chlorine elements. The tensile results showed that adding GO and GNPs significantly enhanced the tensile strength compared to pure PLA, while CNTs slightly increased strength. The ductility of all the composites was decreased by adding carbon-based reinforcements. The addition of GO and GNPs slightly decreases the degradation rate of PLA, while the addition of CNTs accelerates the degradation of PLA. Among the PLA/GO, PLA/CNTs, and PLA/GNP, PLA/GO samples exhibit comparatively better degradation and tensile properties.

3D printed ventilation tubes and their effect on biological models

BackgroundAcute otitis media (AOM) causes inflammation and hearing loss. Ventilation tubes are key in treatment. 3D printing improves prostheses in otorhinolaryngology, offering precision and greater adaptability.Materials and methodsAn experimental study was conducted with Wistar rats from July to December 2020. 3D tympanostomy tube models were designed, with technical specifications and tests performed on inexpensive 3D printers. The tympanostomy tube was inserted endoscopically.ResultsProcedures were performed on five rats with implants in both ears. Pre-intervention pathologies, such as atical retraction and glue ear, were found. The PLA-printed tympanostomy tube showed improvement after adjustments. Histopathological results revealed significant middle and inner ear damage.ConclusionIn our study, the design and 3D printing of implants fulfilled the desired functions when modified, with a height of 5 mm. Complications included PLA degradation and ear damage. There were no adverse events during observation, highlighting the need for further research on 3D-printed implants.

Quantification of PLA degradation in the melt phase using a parallel plate rheometer

Bioplastics like poly(lactic acid) or PLA have received significant attention over the last years, triggered by global environmental and climate concerns linked to the use of petroleum-based plastics. However, the ester bonds in PLA that are responsible for its biodegradable character are also vulnerable linkages during polymer processing. Melt processing of polymers typically involves high temperatures and shear loading. Hence, understanding degradation of PLA in the melt phase is crucial to minimize the molecular weight decrease, since it is directly linked to deterioration of mechanical, thermal and rheological properties. In this study, we performed a 24 full factorial design to investigate melt-phase degradation using a parallel plate rheometer. We investigated the effect of four parameters on the molecular weight: moisture content in the PLA, processing temperature, residence time, and shear stress. In addition, we explored whether the percentage of d-isomer significantly influences the degradation, through selecting three PLA-grades with different optical purity. The results showed that moisture content is the dominant factor in the molecular weight decrease, followed by a significant effect of processing temperature. Notably, the significant interaction between moisture content and processing temperature highlights the importance of studying interaction effects, an aspect often overlooked in current literature. Moreover, only the effect of moisture content is influenced by the percentage of d-isomer, whereas the numerical values of other significant effects are similar across the three PLA-grades. The small, yet significant effect of residence time, along with the unexpected insignificant effect of shear stress, may be explained by the use of small amplitude oscillatory deformations in a parallel plate rheometer as testing method in this study. In conclusion, the findings of this study offer polymer processors and researchers valuable insights, which can help with the selection and prediction of processing conditions that minimize degradation, ultimately saving time and raw materials during production.

TiO2 strengthened PLA nanocomposites: A prospective material for packaging application

Due to its unique mechanical, thermal, photocatalytic, and antibacterial qualities, the ground-breaking bio-based polymer nanocomposite polylactic acid/titanium dioxide (PLA/ TiO2) is a well-known replacement for conventional plastics and is being actively researched. In this work, a route is developed to synthesize nanocomposites based on TiO2-strengthened PLA nanocomposites (PLA/ TiO2). The synthesized nanocomposite was characterized using various spectroscopic techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Transmission electron microscopy (TEM). Using a gas permeameter, the samples oxygen permeability was determined. Water molecules were able to readily penetrate the nanocomposite, and PLA/ TiO2 nanocomposites degraded more quickly than pure PLA. The dispersion of the TiO2 nanoparticles affected the rate of PLA degradation. To regulate the rate at which PLA breaks down during the composting process, a certain amount of dispersed TiO2 nanofiller may also be applied. The photocatalytic activity of the resulting nanocomposites was investigated by monitoring the degradation of methyl orange and malachite green. The PLA/ TiO2 nanoparticles exhibit antibacterial properties as indicated by their zone of inhibition with in addition, PLA/ TiO2 nanoparticles. decrease the amount of extracellular polymeric substance (EPS), indicating up to 17 mm diameter. Their anti -virulence and bio film inhibitory nature, indicating it's potential application as surface disinfectant.

Production and New Green Activation of Conductive 3D-Printed Cu/PLA Electrode: Its Performance in Hydrogen Evolution Reactions in Alkaline Media

In this study, Cu-polylactic acid (PLA) composite filaments were produced with an extruder and three-dimensional (3D) Cu/PLA electrodes were 3D printed with Fused Deposition Modelling (FDM) method. To improve the electrochemical performance of the 3D-Cu/PLA electrode, a novel electrochemical activation method, which differentiates from complex activation methods in the literature, was applied in 1 M KOH solution without using any solvent. Field emission scanning electron microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and RAMAN techniques were used to characterize the 3D-Cu/PLA electrode before and after activation. The results showed that Cu particles were released after the degradation of PLA after activation. In addition, the thermal stability of the 3D electrode was demonstrated by the TGA technique. The performance of the 3D Cu/PLA electrode before and after activation in the hydrogen evolution reaction (HER) in 1M solution was measured using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and cathodic polarization curves methods. The EIS results showed that the charge transfers resistance values of the 3D-Cu/PLA electrode in 1 M KOH decreased significantly after activation. Post-activation hydrogen content measurements of the 3D-Cu/PLA electrode after electrolysis at different potentials and energy efficiency tests at different current densities were also carried out. The results indicate that the electrocatalytic properties of 3D-Cu electrodes were improved for HER through the activation process.

Degradation of polylactic acid/polybutylene adipate-co-terephthalate blend by Papiliotrema laurentii S2P4P isolated from agricultural soils

Polylactic acid/polybutylene adipate-co-terephthalate blend (PLA/PBAT) has been widely used due to their good biodegradation. Recently, the biodegradation of PLA and PBAT has received increasing attention. However, PLA/PBAT blend-degrading strains have been rarely reported in comparison to that for pure PLA and PBAT. A fungus strain, Papiliotrema laurentii S2P4P, was isolated from agricultural soils and identified. S2P4P can efficiently degrade commercial PLA/PBAT films at 30°C in mineral salt medium (MSM) and obtained about 14% of weight loss within 30 days of incubation. Additionally, rough and uneven surface of PLA/PBAT film with cracks and creases, increased hydrophilicity, changes in mechanical property, and decreased intensity of C=O and C-O bonds were observed after S2P4P treatments. The strain secreted esterase to catalyze the degradation of the ester bonds in PLA/PBAT blend, resulting in the production of degradation products such as butanediol, adipic acid, lactic acid and terephthalic acid as well as their oligomers. Furthermore, as carbon and energy sources, the degradation products could participate in the metabolism of S2P4P and then accelerate degradation of PLA/PBAT blend. The advantages of P. laurentii S2P4P in simultaneous degradation of PLA and PBAT indicated that the strain has potential value for the bioremediation of PLA/PBAT blend in the actual environment.

Biodegradable implant of magnesium/polylactic acid composite with enhanced antibacterial and anti-inflammatory properties.

Addressing fracture-related infections (FRI) and impaired bone healing remains a significant challenge in orthopedics and stomatology. Researchers aim to address this issue by utilizing biodegradable biomaterials, such as magnesium/poly lactic acid (Mg/PLA) composites, to offer antibacterial properties during the degradation of biodegradable implants. Existing Mg/PLA composites often lack sufficient Mg content, hindering their ability to achieve the desired antibacterial effect. Additionally, research on the anti-inflammatory effects of these composites during late-stage degradation is limited. To strengthen mechanical properties, bolster antibacterial efficacy, and enhance anti-inflammatory capabilities during degradation, we incorporated elevated Mg content into PLA to yield Mg/PLA composites. These composites underwent in vitro degradation studies, cellular assays, bacterial tests, and simulation of the PLA degradation microenvironment. 20wt% and 40wt% Mg/PLA composites displayed significant antibacterial properties, with three composites exhibiting notable anti-inflammatory effects. In contrast, elevated Mg content detrimentally impacted mechanical properties. The findings suggest that Mg/PLA composites hold promise in augmenting antibacterial and anti-inflammatory attributes within polymers, potentially serving as temporary regenerative materials for treating bone tissue defects complicated by infections.

Exploring the potential of earthworm gut bacteria for plastic degradation

The use of plastic mulch films in agriculture leads to the inevitable accumulation of plastic debris in soils. Here, we explored the potential of earthworm gut-inhabiting bacterial strains (Mycobacterium vanbaalenii (MV), Rhodococcus jostii (RJ), Streptomyces fulvissimus (SF), Bacillus simplex (BS), and Sporosarcina globispora (SG) to degrade plastic films (⌀ = 15 mm) made from commonly used polymers: low-density polyethylene film (LDPE-f), polylactic acid (PLA-f), polybutylene adipate terephthalate film (PBAT-f), and a commercial biodegradable mulch film, Bionov-B® (composed of Mater-Bi, a feedstock with PBAT, PLA and other chemical compounds). A 180-day experiment was conducted at room temperature (x̄ =19.4 °C) for different strain–plastic combinations under a low carbon media (0.1× tryptic soy broth). Results showed that the tested strain–plastic combinations did not facilitate the degradation of LDPE-f (treated with RJ and SF), PBAT-f (treated with BS and SG), and Bionov-B (treated with BS, MV, and SG). However, incubating PLA-f with SF triggered a reduction in the molecular weights and an increase in crystallinity. Therefore, we used PLA-f as model plastic to study the influence of temperature (“room temperature” & “30 °C”), carbon source (“carbon-free” & “low carbon supply”), and strain interactions (“single strains” & “strain mixtures”) on PLA degradation. SF and SF + RJ treatments significantly fostered PLA degradation under 30 °C in a low-carbon media. PLA-f did not show any degradation in carbon-free media treatments. The competition between different strains in the same system likely hindered the performance of PLA-degrading strains. A positive correlation between the final pH of culture media and PLA-f weight loss was observed, which might reflect the pH-dependent hydrolysis mechanism of PLA. Our results situate SF and its co-culture with RJ strains as possible accelerators of PLA degradation in temperatures below PLA glass transition temperature (Tg). Further studies are needed to test the bioremediation feasibility in soils.

Effects of biodegradable poly(butylene adipate‐co‐terephthalate) and poly(lactic acid) plastic degradation on soil ecosystems

AbstractDespite that biodegradable plastics are perceived as environmentally friendly, there is a lack of comprehensive understanding of their fate in soil. Current Environmental, Social, and Governance (ESG) frameworks, along with new UNEP regulations on plastic pollution, necessitate scientific information on plastic degradation in soils for developing sustainable biodegradable plastics. In this study, we examined the degradation rates of two biodegradable plastics, poly(butylene adipate‐co‐terephthalate) (PBAT) and poly(lactic acid) (PLA), in a laboratory microcosm experiment using uncontaminated soil, with PBAT or PLA added at 8.3% (w/w). Our aim was to further understand the impact of these plastic types on soil properties and microbial communities under different incubation temperatures. Both PBAT and PLA treatments elevated cumulative CO2 efflux compared with the control soil incubated at 25 and 58°C. After 33 weeks, 9.2% and 6.1% of the added PBAT and PLA degraded, respectively, at 58°C, while only 2.3% of PBAT and 1.7% of PLA degraded at 25°C, implying slower degradation rates of PBAT and PLA under the lower temperature. Degradation at 58°C increased total soil carbon by 0.6%, 1.9%, and 4.3% for Control, PBAT, and PLA, respectively, and soil electrical conductivity by 0.17, 0.33, and 2.38 dS m−1, respectively, but decreased soil pH. Microbial diversity and richness decreased under thermophilic conditions at 58°C compared with that at 25°C. We conclude that the degradation of PBAT and PLA varies with environmental condition, and influences soil properties.

Exploring the substrate spectrum of phylogenetically distinct bacterial polyesterases.

The rapid escalation of plastic waste accumulation presents a significant threat of the modern world, demanding an immediate solution. Over the last years, utilization of the enzymatic machinery of various microorganisms has emerged as an environmentally friendly asset in tackling this pressing global challenge. Thus, various hydrolases have been demonstrated to effectively degrade polyesters. Plastic waste streams often consist of a variety of different polyesters, as impurities, mainly due to wrong disposal practices, rendering recycling process challenging. The elucidation of the selective degradation of polyesters by hydrolases could offer a proper solution to this problem, enhancing the recyclability performance. Towards this, our study focused on the investigation of four bacterial polyesterases, including DaPUase, IsPETase, PfPHOase, and Se1JFR, a novel PETase-like lipase. The enzymes, which were biochemically characterized and structurally analyzed, demonstrated degradation ability of synthetic plastics. While a consistent pattern of polyesters' degradation was observed across all enzymes, Se1JFR stood out in the degradation of PBS, PLA, and polyether PU. Additionally, it exhibited comparable results to IsPETase, a benchmark mesophilic PETase, in the degradation of PCL and semi-crystalline PET. Our results point out the wide substrate spectrum of bacterial hydrolases and underscore the significant potential of PETase-like enzymes in polyesters degradation.

Structural evaluation of Poly(lactic acid) degradation at standardized composting temperature of 58 degrees

The accumulation of petroleum-based plastics on our planet is causing serious environmental pollution. Biodegradable plastics, promoted as eco-friendly solutions, hold the potential to address this issue. However, their impact on the environment and the mechanisms of their natural degradation remain inadequately understood. Furthermore, the specific conditions set forth in international standards for evaluating the biodegradability of biodegradable plastics have led to misconceptions about their real-world behavior. To properly elucidate the relationship between their degradability and structure, this study mimics the thermal effect on poly(lactic acid) (PLA) under standardized composting temperature. The higher the crystallinity of PLA, the lower the degradation rate, which suggests that crystallinity is a key factor in determining degradation. The composting temperature of 58 °C induces crystallization by having a structural effect on the polymer, which in turn reduces the degradation rate of PLA. Therefore, control over temperature and crystallization during the processing and degradation of PLA is crucial, as it not only determines the biodegradability but also enhances the utility.

Joncryl chain extender reactivity with polylactide: Effect of d-lactide content, Joncryl type, and processing temperature

In this study, a highly crystallizable and an amorphous polylactide (i.e., cPLA and aPLA) with, respectively, low (0.5 mol. %) and high (12 mol. %) d-lactic acid contents and similar molecular weights were melt compounded with two different multifunctional epoxy-based Joncryl chain extenders (CEs, i.e., ADR 4400 and 4468) at 190 °C. Reactivity of Joncryl grades with aPLA was also explored at melt processing temperatures of 150, 170, and 210 °C. Small amplitude oscillatory shear rheological analysis was conducted to understand the extent of the Joncryl reaction with PLA molecules, and the results were confirmed with molecular weight determination using gel permeation chromatography. Extensional viscosity of the processed samples was also compared to control their strain hardening behavior. Results showed that the Joncryl reaction with cPLA and aPLA differs in terms of preference for chain extension or branching, indicating that molecular regularity affected the interactions with both Joncryl grades during reactive melt processing. Moreover, although the increase in processing temperature accelerated PLA degradation, it noticeably increased the reactivity of both Joncryl grades with aPLA. In all cases, ADR 4468 was more reactive in molecular chain extension/branching due to its higher functionality than ADR 4400. Differential scanning calorimetry results also revealed that the crystallization of cPLA was differently affected by the change in the Joncryl content and type.

Morphological adaptation of expanded vermiculite in polylactic acid and polypropylene matrices for superior thermoplastic composites

AbstractThe morphological transformation of expanded vermiculite (VC) during injection molding with brittle PLA and ductile PP polymers along with its positive and negative contribution to mechanical response is investigated. Polymer/VC mixtures with 30 wt. % VC are prepared by thermokinetic high shear mixing at 4000 rpm without any ex‐situ exfoliation agents or compatibilizers. Obtained composite mixtures are then injection molded onto three‐point bending and tensile test specimens. Performed mechanical tests suggested a significant increase in tensile (110%) and flexural modulus (112%) of PP30VC samples. Presented fractographic and morphological investigations suggested that the root cause of measured improved tensile (36%) and bending strength (26%) of PP is the fibrillation of VC associated with PP/VC interactions under high shear. A similarly increasing trend for tensile (147%) and bending modulus (137%) was observed for PLA30VC samples. Contrary to PP30VC, a decreasing pattern was present in the case of tensile (−40%) and bending strength (−13%) of PLA30VC. The root cause for such reduction is determined to be (i) in situ exfoliation of VC inside PLA matrix and transformation of VC into micrometer‐sized platelets; (ii) evaporation of trapped water/crystalline water in the interlayer region of VC which caused in situ degradation of PLA during manufacturing.Highlights Vermiculite‐loaded PP and PLA composites are produced at high shear. Composites have superior modulus compared to neat polymers. Fibrillation of platelet vermiculite is observed in only the PP matrix.

Cheap organocatalyst diphenyl phosphate for efficient chemical recycling of poly(lactic acid), other polyesters and polycarbonates

Bioplastics are regarded as a sustainable alternative to traditional petroleum-based plastics, particularly poly(lactic acid) (PLA). However, due to the slow biodegradation of PLA and the lack of an overall recycling strategy, its large-scale use could make it an acute source of future plastic pollution. Herein, we find that diphenyl phosphate (DPP), a cheap organocatalyst, can efficiently catalyze PLA hydrolysis into valuable oligomers/lactic acid. Without pressure and organic solvents, under mild conditions with 3.5 wt% DPP and a little water (160 °C, 1.5 h), commercial PLA pellets/products are rapidly converted into oligomers with molecular weight below 500 g/mol by random hydrolysis. DPP can catalyze at least 10 batches of PLA without compromising its catalytic performance, and kilogram-scale PLA degradation is facilely achieved. The DPP-containing oligomers can be used directly to synthesize lactide, and subsequently high-quality PLA is obtained using a well-established industrial route to achieve closed-loop recycling. Meanwhile, an aqueous lactic acid solution with comparable commercial quality and intact configuration retention is harvested. Moreover, DPP can also effectively catalyze the hydrolysis of other polyesters and polycarbonates. Overall, this study is expected to address the environmental and engineering challenges associated with plastic waste disposal, in particular fostering a PLA-based green circular bio-economy.

Advancing the additive manufacturing of PLA-ZnO nanocomposites by fused filament fabrication

ABSTRACTPoly(lactic acid)-zinc oxide (PLA-ZnO) nanocomposites for fused filament fabrication have potential applications in the biomedical field as they combine the bio-compatibility of PLA with the antibacterial properties of ZnO. This work investigates the effects of masterbatch mixing strategy, ZnO concentration and ZnO surface treatment (silanisation) on the printability and the mechanical performance of the nanocomposites as a pre-requirement to the wider uptake of these materials. The results showed that the printability decreased as the filler loading increased. However, the surface treatment of the ZnO powder enhanced the matrix-filler interfacial interactions and reduced the thermal degradation of PLA. This ameliorated the printability and the tensile properties of the nanocomposites filled with up to 5 wt.% of ZnO. Moreover, despite the additional thermal treatment, melt-mixing prevented the degradative effect induced by the solvent used for solvent mixing. Future work will focus on assessing the antibacterial properties of the nanocomposite FFF parts.

Effect of accelerated weathering on the properties of poly(lactic acid)/poly(butylene adipate-co-terephthalate) blend and composite containing wood flour and wollastonite

The objective of the present work was to explore the effects of accelerated weathering test on properties of poly(lactic acid) (PLA)/poly(butylene adipate- co-terephthalate) (PBAT) blend and PLA)/PBAT/wood flour (WF)/wollastonite (WT) composite. The 70/30 (wt%/wt%) PLA/PBAT blend and its composite with 25 phr WF and 5 phr WT were prepared on a twin screw extruder and injection molding machine. Resulted blend and hybrid composite were exposed to accelerated weathering conditions of UV-irradiation and moisture cycles at 63°C in a laboratory Xenon Weather-Ometer chamber for various periods (250, 500, 750, and 1000 h). The alterations in the surface quality (color change), chemical structure, surface morphology, tensile properties, thermal behaviors, and thermal stability of the specimens were evaluated by spectrocolorimetry, Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), universal testing machine, differential scanning calorimetry and thermogravimetric analysis, respectively. The photo- and hydrolytic degradations were found to occur during the weathering exposure time. Both blend and composite showed a continuous increase in the total color change with prolonged exposure time, which was mainly due to the degradation of PLA and wood components, especially lignin. The SEM images also confirmed their degradations by illustrating roughness, voids, and cavities on the specimen surfaces after accelerated weathering. Meanwhile, the tensile and thermal properties of both blend and composite were found to decrease. Thus, this study can be used for quality control and material certification.

Accelerating the Biodegradation of Poly(lactic acid) through the Inclusion of Plant Fibers: A Review of Recent Advances.

As the global demand for plastics continues to grow, plastic waste is accumulating at an alarming rate with negative effects on the natural environment. The industrially compostable biopolymer poly(lactic acid) (PLA) is therefore being adopted for use in many applications, but the degradation of this material is slow under many end-of-life conditions. This Perspective explores the feasibility of accelerating the degradation of PLA through the formation of PLA-plant fiber composites. Topics include: (a) key properties of PLA, plant-based fibers, and biocomposites; (b) mechanisms of both hydrolytic degradation and biodegradation of PLA-fiber composites; (c) end-of-life degradation of PLA and PLA-plant fiber composites in aerobic and anaerobic conditions, relevant to compost, soil and seawater (aerobic), and landfills (anaerobic); and (d) sustainability and environmental impact of PLA and PLA-plant fiber composites, as evaluated using life cycle assessment. Additional degradation modes, including thermal and photodegradation, which are relevant during processing and use, have been omitted for clarity, as have other types of PLA biocomposites. Multiple studies have shown that the addition of some types of plant fibers to PLA (to form PLA biocomposites) accelerates both water transport in the material and hydrolysis, presenting a possible avenue for improving the end-of-life degradation of these materials. To facilitate the continued development of materials with enhanced biodegradability, we identify a need to implement testing protocols that can distinguish between different degradation mechanisms.

Hydrolytic degradation of poly(lactic acid): Unraveling correlations between temperature and the three phase structures

Hydrolysis significantly influences both the properties and degradability of poly(lactic acid), PLA. This work investigates the hydrolysis kinetics of PLA films as affected by degree of crystallinity and temperatures by considering the three-phase model structures (i.e., mobile amorphous, rigid amorphous, and crystalline). Molecular weight and three-phase fraction analyses were performed during hydrolysis to estimate the kinetic rates using phenomenological models. Results revealed that temperature significantly impacted PLA degradation, with distinct characteristics observed for each of these three phases. Above the glass transition temperature, the hydrolysis rates of PLA were comparable among samples with different crystallinity due to rapid water-induced crystallization of the amorphous phases, coupled with accelerated hydrolysis. In contrast, at below the glass transition temperature, the higher crystallinity sample exhibited a faster hydrolysis rate attributed to the presence of the rigid amorphous fraction. An increase in crystallinity introduced more defects due to limited mobility in the rigid amorphous fraction, influencing hydrolysis. The study provides valuable insights into the crucial relationship between temperature, crystallinity, and hydrolysis kinetics which are expected to be useful for predicting PLA degradation behavior during its intended applications and at its end of life.

Thermal stabilization of recycled PLA for 3D printing by addition of charcoal

Poly(lactic acid) (PLA) is one of the most widely used thermoplastic materials for 3D printing, particularly in the Fused Filament Fabrication technique. However, the printing process generates waste products and even though PLA is compostable, the possibility of recycling it provides ecological and economical benefits. In this work, a study on the stabilization of recycled PLA using charcoal (CC) was carried out, with the aim of overcoming the well-known problem of degradation (reduction in molecular weight) of PLA, during remelting. Microscopic investigations showed good dispersion of the filler in the polymer matrix, as well as better adhesion between the printed layers. Thermal analyses (Differential scanning calorimetry and thermogravimetry) indicate a stabilization of PLA waste because of the addition of small concentrations of CC to the recycled polymer matrix. These data are confirmed by GPC analyses, which show that the addition of filler is associated with higher molecular weight. Mechanical analysis indicated improved elongation at break and elasticity. Finally, a key ring was printed as an example of the better printability of the filament containing CC. The results indicate that a stabilization of the recycled PLA with a very low concentration of CC has been achieved. Improved 3D printability and properties of the 3D printed objects can be attained through recycling and recovery of wasted PLA, according to sustainability and circular economy matters.

Microbiome dynamics during anaerobic digestion of food waste and the genetic potential for poly (lactic acid) co-digestion

Anaerobic digestion of food waste (FW) and potential co-digestion with biodegradable packaging material (i.e., bioplastics) have been promising resource recovery strategies. Unveiling the microbiome dynamics involved in the digestion process and exploring the genetic potential for poly (lactic acid) hydrolysis therein provide the fundamental basis for further process control and optimization. The current study has shown that the FW-digesting microbiome changed in both composition and activity-dormancy status while consuming available substrates. The microbiome assembly was mainly driven by homogeneous selection (36.7% on average) and drift (59.5% on average), and the homogeneous selection effect scaled with the availability of substrates. Based on the ratio between the relative activity and abundance, the microbiome was clustered into four groups. The Group 1 microbes, including Bacterioidetes_vadinHA17 and Syntrophomonadaceae, accumulated high relative abundance during the early stage of the digestion process but entered dormancy after the preferred substrate was consumed. Other members, i.e., the Group 4 Syntrophobacteraceae and Pseudomonadaceae, showed low abundance but disproportional activity during the later stage of the digestion process. The genome-centric metagenomics revealed that inherent AD microbes, especially the Group 1 microbes, harbored robust hydrolase genes, facilitating the PLA degradation. In fact, PLA addition to FW digestor led to significant methane production enhancement (14%) but negligible changes in microbiome composition. The outcome of this study provided the theoretical basis for developing microbiome management and engineering strategies that prospect efficient FW and PLA co-digestion processes.