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DSC curves (First heating) of PET films: starting material and PET following different treatments and storage conditions (storage for 5 months at room conditions, previously equilibrated with CO 2 at 1 bar and previously submitted to CO 2 sorption isotherm determination up to 25 bar)
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This work investigated the sorption and the diffusion properties of CO2 under high pressure and the further modifications induced in Poly (lactic acid) (PLA) thin layers. Poly (ethylene terephtalate) (PET) was also considered for comparative purposes. Firstly, from thermodynamic equilibrium, the CO2 sorption isotherm (two sorption-desorption cycles...
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Citations
... The presence of peak at 1182 cm −1 relates to the asymmetric stretching of -C-O-C. The peaks at 1087 and 866 cm −1 are associated with the stretching behaviour of − C − O and − C − C functional groups of PLA [29]. Furthermore, an additional peak that appears at 750 cm −1 corresponds to -C-C-stretching in the semi-crystalline phase of PLA biopolymer [30]. ...
Sustainable poly(lactic acid) (PLA)/propylparaben (PPB) composite based films were fabricated via solution casting approach. The assessment of PLA/PPB composite films in terms of active food packaging characteristics like thermal, mechanical, UV–Vis, oxygen barrier, anti-bacterial as well as anti-oxidant effect is carried out. The PLA/PPB-5 composite film resulted in three-fold (23%) increase of elongation-at-break while maintaining a tensile strength (42 MPa) in comparison with PLA film. Consequently, the PLA/PPB-5 composite film displayed a 70% UV–B blockage and reduced the oxygen transmission rate by 52% as compared to PLA film. Further, the PLA/PPB-5 composite film exhibited significant improvement (52%) in the radical scavenging activity which can be really helpful to keep the food products fresh for longer periods. The PLA/PPB filler showed good antibacterial activity against food-borne bacteria [Staphylococcus aureus and Escherichia coli]. The fabricated PLA/PPB composite films have shown desirable active food packaging characteristics and therefore may be suitable for food packaging applications.
Graphical Abstract
... These peaks were only visible in Fig.1 (b) of the pure PLA, since there were no obvious peaks in the mixture samples. The finding was similar to Rocca-Smith et al. (2017), who noticed peaks at 863 and 758 cm -1 in the FTIR result of a PLA film. The peaks of PLA/C in Fig. 1 (e) were more pronounced than the spectra of PLA/C/AC and PLA/C/AC/MMT mixtures in Figs. 1 (f) and (g). ...
A new bio-sorbent derived from green algae biomass, Arthrospira platensis (Spirulina), was found to be economically practical for water decontamination. This biosorbent comprised of microalgae cellulose, poly(lactic acid) (PLA), Dabai activated carbon (AC), and montmorillonite (MMT), each plays a distinctive role in removing methylene blue (MB) dye. The presence of hydroxyl and carbonyl functional groups in algae cellulose, confirmed by the FTIR analysis, offered binding sites for dye removal. Scanning electron microscopy demonstrated the morphological structure of the biosorbent, highlighting the combined effect of microalgae cellulose, PLA, Dabai AC, and MMT mixtures. The inclusion of Dabai AC and MMT improved micropores and mesopores, enhancing adsorption reactions. The Brunauer-Emmett-Teller (BET) analysis confirmed that the sample containing microalgae cellulose, Dabai AC, and MMT clay in PLA had a specific surface area of 0.784 m 2 /g, three times higher than the PLA + cellulose sample. Additionally, adding 1% MMT to the sample improved the particle dispersion on the surface of the hydrophobic PLA, thereby improving its thermal properties. Remarkably, the biosorbent effectively eliminated 86.8% of MB dye from an initial concentration of 50 mg/L after 60 min of Vis-light irradiation using Ultraviolet-visible spectroscopy.
... It can be seen from Fig. 4b that the characteristic peak for PLA appears at 1754 cm −1 and this is attributed to the -C=O stretching of carbonyl backbone present in PLA [38]. The appearance of peak position at 1450 cm −1 represents the bending of methyl groups in PLA [39]. The presence of band position at 1367 cm −1 corresponds to the asymmetric bending of -CH-groups present in PLA [40]. ...
In the current work, poly(lactic acid) (PLA) based composite films are developed via incorporation of “menadione” (MD) as additive agent and solution casting approach is followed for fabrication of composite films. The impact of MD on the physico-chemical properties of PLA and its active food packaging characteristics is envisaged herein. The incorporation of MD in the PLA matrix helps in favour of four-fold enhancement in elongation property for the composite films. Interestingly, the PLA/MD composite films demonstrate complete UV-barrier property and presents an UV protection factor (UPF) value > 50. The oxygen permeability analysis reveals that the MD could help in reducing the oxygen transmission rate by ~ 30% for PLA composites than PLA. The PLA/MD composite films act as potential 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenger by presenting ~ 97% antioxidant activity. The increase in wt% loadings of MD in the PLA matrix show improved antibacterial properties against Gram positive Staphylococcus aureus (S. aureus) and Gram negative Escherichia coli (E. coli). The PLA/MD composite films registered values within the EU limit of 10 mg/dm² for dry food migration. Thus, the PLA/MD composite formulation envisaged in this work presents promising characteristics pre-requisite for both watery and dry active food packaging application.
Graphical Abstract
... Briefly, for PET, there were C H stretching at 2950 cm −1 , C=O stretching at 1712 cm −1 , CH 2 bending at 1444 cm −1 , C=O bending at 1240 cm −1 , O C stretching at 1108 and 1092 cm −1 , and vibrational modes resulting from the terephthalate group at 1578, 1506, 1016, 872, and 724 cm −1 . 39,40 For PLA, there were CH stretching at 2988 and 2954 cm −1 , C=O stretching at 1748 cm −1 , CH 3 bending at 1452 cm −1 , C=O bending at 1452 cm −1 , C=O bending at 1268 cm −1 , C O C stretching at 1182 cm −1 , C O stretching at 1130 and 1086 cm −1 , OH bending at 1044 cm −1 , and C C stretching at 872 and 754 cm −1 . 39,41 For PP, there were CH 3 stretching at 2950 cm −1 , CH 2 symmetric stretching at 2838 cm −1 and asymmetrical stretching at 2916 cm −1 , CH 2 bending at 1450 cm −1 , and C H bending at 1168 and 842 cm −1 . ...
... 39,40 For PLA, there were CH stretching at 2988 and 2954 cm −1 , C=O stretching at 1748 cm −1 , CH 3 bending at 1452 cm −1 , C=O bending at 1452 cm −1 , C=O bending at 1268 cm −1 , C O C stretching at 1182 cm −1 , C O stretching at 1130 and 1086 cm −1 , OH bending at 1044 cm −1 , and C C stretching at 872 and 754 cm −1 . 39,41 For PP, there were CH 3 stretching at 2950 cm −1 , CH 2 symmetric stretching at 2838 cm −1 and asymmetrical stretching at 2916 cm −1 , CH 2 bending at 1450 cm −1 , and C H bending at 1168 and 842 cm −1 . 42,43 A low intensity peak at 2350 cm −1 was seen in PET samples not treated and disappeared after scCO 2 treatment. ...
BACKGROUND
EU policies towards a circular economy address plastic packaging as one of the significant concerns and sets ambitious recycling targets. Polyolefins (POs) cannot be recycled for food contact using conventional polyethylene terephthalate (PET) recycling approaches. Thermal degradation prevents the use of high temperatures and, consequently, decontamination of POs may be insufficient when using lower temperatures. Polypropylene (PP) beverage cups were decontaminated using supercritical fluid extraction with carbon dioxide (scCO2). Decontamination efficiencies (DEs) of selected markers were determined in challenge tests following European Food Safety Authority guidelines. The effects of time (10–60 min) for PET, polylactic acid (PLA), and PP and temperature (60–80 °C) for PP were studied at constant pressure. The physical properties, sensorial properties, and overall migration of treated scCO2 PP were analysed and compared with virgin PP.
RESULTS
PP showed the highest average DE, and PET the lowest, for all the surrogates and in all time conditions. A relative increase in the DE with the increase in process time, particularly for PET and to some extent for PLA, was seen. For PP, no significant impact of time and temperature was observed under the conditions tested. The DE of volatile surrogates was higher than that of semi‐volatiles. Results indicate that the scCO2 treatment did not affect the physical and sensorial properties, nor the overall migration of PP, although it contributes to a considerable reduction in extractable n < C24 alkanes.
CONCLUSIONS
Results indicate that scCO2 can be used to decontaminate post‐consumption PP beverage cups with higher DEs than those for PET and PLA, applying mild processing conditions. © 2022 Society of Chemical Industry.
... The study of the barrier properties of PLA films after processing with high pressure-CO 2 has also been very rare. The impact of high-pressure CO 2 on water vapor barrier properties was analyzed and revealed an increase in WVPC more significant than expected, due to scCO 2 acting as plasticizer and being physically intercalated between polymer chains, increasing the sites for sorption of water molecules [75]. 30 µm-thick PLA films presented an initial WVPC coefficient of 5.1 × 10 −6 kg m −1 s −1 Pa −1 and, after CO 2 sorption at 25 bar, WVPC increased to 7.2 × 10 −6 kg m −1 s −1 Pa −1 . ...
The performance characteristics of polylactic acid (PLA) as an active food packaging film can be highly influenced by the incorporation of active agents (AAs) into PLA, and the type of processing technique. In this review, the effect of processing techniques and the addition of natural AAs on the properties related to PLA performance as a packaging material are summarized and described through a systematic analysis, giving new insights about the relation between processing techniques, types of AA, physical–mechanical properties, barriers, optical properties, compostability, controlled release, and functionalities in order to contribute to the progress made in designing antioxidant and antimicrobial PLA packaging films. The addition of AAs into PLA films affected their optical properties and influenced polymer chain reordering, modifying their thermal properties, functionality, and compostability in terms of the chemical nature of AAs. The mechanical and barrier performance of PLA was affected by the AA’s dispersion degree and crystallinity changes resulting from specific processing techniques. In addition, hydrophobicity and AA concentration also modified the barrier properties of PLA. The release kinetics of AAs from PLA were tuned, modifying diffusion coefficient of the AAs in terms of the different physical properties of the films that resulted from specific processing techniques. Several developments based on the incorporation of antimicrobial and antioxidant substances into PLA have displayed outstanding activities for food protection against microbial growth and oxidation.
... These variations indeed agree with the DSC measurements, indicating the highest degree of crystallinity for PLA/char 80/20 and PLA/char 70/30. In the lower wavenumber region, the 863 cm -1 bands (C-C, amorphous) and 758 cm -1 bands (C-C, crystalline) [59] indeed show slight changes that qualitatively can be related to small crystalline variations by the addition of char. Supplementary effects with a TPS plasticizer are observed (Figure 5b), including an overlapping band originating from both the carbonyl stretching peak at around 1760 cm -1 of PLA and the corresponding TPS peak at around 1730 cm -1 , of which the ratio is changing in agreement with the composition. ...
Biochar has emerged as a filler material for bio-degradable composites with favorable thermal and mechanical properties. Therefore, biochar is used in poly (lactic acid) (PLA) and PLA/thermoplastic starch (TPS) based composites. The crystallization and thermo-analytical properties of these blends with increasing amounts (20 to 50 wt%) of biochar are investigated. In the thermogravimetric analysis, the PLA/char composites’ onset degradation temperature and temperature of maximum weight loss decrease with increasing biochar concentrations (320 to 275 °C and 380 to 350°C, respectively). Contrastingly, in the PLA/TPS/char composites, the impact of the biochar is shielded by the TPS. The unaltered glass transition demonstrates that biochar does not act as a plasticizer in any of the composites, while TPS does. Biochar acts as a nu-cleation agent, but hinders further crystal growth at high concentrations, as confirmed by isothermal crystallization and infrared spectroscopy. The TPS smoothens the PLA/biochar interface, leading to an obstructed nucleation effect of biochar, proven by differential scanning calorimetry, infrared spectroscopy, and scanning electron microscopy. This work demonstrates the shielding effect TPS has on biochar and can help to understand further and optimize the production and biodegradability of these composites.
... Over the years, several PLA and PLA stereoisomer-based consumables for tissue engineering applications have been commercialized, and this is summarised in Table 1. Although PLA has been around for numerous decades, due to high production costs, its use has only been limited to the fabrication of medical devices like sutures [45]. However, Cargill Dow LLC developed a patented, low-cost continuous process to produce lactic acid-based polymers that combines the substantial economic and environmental benefits of both lactide and PLA synthesis in the melt instead of a solution. ...
Patients sometimes lose organs and/or organ functions due to disease and injury, which may result in permanent
disabilities. Advanced biotechnological practices can now afford victims of these incidences an opportunity to repair some
of the damaged tissues or organs without the need for a donor. This can be achieved by reconstruction of the damaged tissue
or organ through scaffold and cell technologies. Scaffolds serve as template material for neo-organs to guide and accelerate
cell growth. The structure of a scaffold material must meet certain design parameters to achieve optimal functionality in
tissue engineering. Pre-requisites include surface compatibility and architectural suitability with the host environment. Polymeric scaffolds derived from polymer blends have the prospects to control the physical and chemical environment of the biological system. In this review, potential roles, general properties, advantages, and disadvantages of poly (lactic acid) and
its composites as functional materials for scaffolding will be outlined. PLA and its composites have been subjects of research
for some decades due to non-toxicity and the ability to mimic native tissue. Though PLA and composites have demonstrated
great potential for various biomedical applications, a lot still needs to be done for them to compete with donor and prosthetic
organs.
... Up to now, the related literature is mainly focused on the effects of supercritical CO 2 on the PLA properties and so there is not enough available information related to the effects of CO 2 at conditions lower than its supercritical point. [49] Properties of PLA depend on its component isomers, processing temperature, annealing time, and molecular weight (Mw). [50] In particular, the PLA lactides are formed by the condensation of two molecules of lactic acid, so three types of lactides can be obtained: dd-lactide, ld-lactide Poly-Dlactide acid (PDLA) and ll-lactide poly l-lactic acid (PLLA). ...
... [51] At this regard, several authors, using a quartz crystal microbalance, studied the influence of the thermal history of a polymer film in the gas sorption and concluded that the polymer film thermal history only has significant impact in gas sorption for pressures higher than 2 MPa. [52][53][54] At the same time, Rocca-Smith et al. [49] studied the sorption and the diffusion properties of CO 2 at high pressure and the changes induced by physisoprtion on the PLA films. They proved a good CO 2 adsorption capacity of PLA film with a small hysteresis cycle and the modification inducted by CO 2 pressure on the PLA film. ...
... The sorbed quantity was rather high than the values reported in the literature for PLA films under similar pressure and temperature conditions. [45,47,52] In the same conditions (15 bar and room temperature (RT)), Rocca-Smith et al. [49] reported, in fact, an adsorbed quantity of CO 2 equal to 4%, which is similar to the adsorption capacity of cPLA and pPLA, while it is half of that recorded for the fPLA sample. The highest absorption of fPLA can be attributed to the morphology and crystalline structure of the sample. ...
Carbon capture and storage (CCS) in conjunction with an increasing use of renewables provides a clean pathway to sustainable development and climate change mitigation. In selecting a low temperature CCS adsorbent, parameters such as selectivity, regeneration energy, and economicity play a crucial role. Poly(L‐lactide) (PLA) is one of the most promising materials in science and engineering, not only because it is a green polymer progressively replacing petrobased plastics, but also for its carbon dioxide (CO2)‐philic nature that makes it a suitable candidate for greenhouse gas capture and climate change mitigation. Literature data point to PLA as a valid CCS candidate, although no direct gaseous CO2 adsorption investigation or with mild preparation/regenerative energy was reported. In the present experimental work, a deeper investigation of the adsorption/desorption properties of PLA in presence of gaseous CO2 at room temperature was undertaken by means of a home‐made Sievert‐type apparatus. The effects of pressure (0–15 bar), morphology (commercial pellets, powder, and flakes), and regenerative energy (303 and 333 K) were investigated. PLA samples were also characterized by helium picnometry to obtain skeletal density and by XRD and SEM to obtain morphological and structural information. Results show that PLA represents a valid and ecological alternative among the materials for the capture of CO2. The PLA absorption capacity reaches 16 wt% at 15 bar and 303 K, and is closely linked to the thermal treatment, morphology, and crystalline structure of the material.
... In all cases, we see the typical peaks of the PLA backbone ester group, i.e., 1748 cm -1 (-C=O stretching), 1182 cm -1 (-C-O-C stretching), 1133 cm -1 and 1079 cm -1 (both -C-O-stretching) (all marked by solid lines) [24]. Additional typical PLA peaks can be found at 1452 cm -1 (-CH 3 bending), 1268 cm -1 (-C=O bending), 1038 cm -1 (-OH bending) as well as 872 cm -1 and 754 cm -1 (-C-C-stretching of amorphous and crystalline phases, respectively) (all marked by dashed lines) [25]. Finally, the small peaks around 1358 cm -1 and 1384 cm -1 can be attributed to -CH vibration and symmetric -CH 3 bending, respectively (dotted lines) ( [26] and [27]). ...
Additive manufacturing technologies are nowadays used in all kinds of industries. In most cases, however, the surface texture of the produced models is unsatisfactory and requires further processing, aiming to reduce surface roughness and waviness. The quality of the surface layer in many cases plays not only an aesthetic role, but also affects, for example, the process of wear and tribological properties. In the presented work, samples prepared by fused deposition modeling technology from polylactic acid (PLA) material were subjected to tests. The samples were subjected to heat or chemical treatment through the use of acetone. The quality of the surface texture was tested both before and after the treatments. In addition, tests were carried out to determine the effect of the presented finishing treatment on the tensile strength of the tested sample models. The test results showed that both thermal treatment and acetone treatment influence the surface texture quality, especially the waviness, and that the acetone treatment can improve some mechanical properties.
... Due to the strong relaxation of nanofiber mats during evaporation of residual solvent [49], the opposite procedure of electrospinning on 3D printed layers does not seem to be suitable, but can be expected to result in breaking of the nanofiber mats, which may also happen during electrospinning on the commonly used polypropylene nonwoven. Next, Figure 6b shows FTIR measurements of PAN nanofiber mats on 3D printed PLA. Figure 6a gives an overview of typical peaks of PLA [51][52][53][54] (grey lines) and PAN [55] (red lines), respectively. ...
Electrospinning is a well-known technology used to create nanofiber mats from diverse polymers and other materials. Due to their large surface-to-volume ratio, such nanofiber mats are often applied as air or water filters. Especially the latter, however, have to be mechanically highly stable, which is challenging for common nanofiber mats. One of the approaches to overcome this problem is gluing them on top of more rigid objects, integrating them in composites, or reinforcing them using other technologies to avoid damage due to the water pressure. Here, we suggest another solution. While direct 3D printing with the fused deposition modeling (FDM) technique on macroscopic textile fabrics has been under examination by several research groups for years, here we report on direct FDM printing on nanofiber mats for the first time. We show that by choosing the proper height of the printing nozzle above the nanofiber mat, printing is possible for raw polyacrylonitrile (PAN) nanofiber mats, as well as for stabilized and even more brittle carbonized material. Under these conditions, the adhesion between both parts of the composite is high enough to prevent the nanofiber mat from being peeled off the 3D printed polymer. Abrasion tests emphasize the significantly increased mechanical properties, while contact angle examinations reveal a hydrophilicity between the original values of the electrospun and the 3D printed materials.
