Effect of sepiolite on the biodegradation of poly(lactic acid) and polycaprolactone

Key insights into mechanism and kinetics of biodegradation of poly (3-hydroxybutyrate)-based nanocomposite films in natural soil and river water environments

The biodegradability of poly (3-hydroxybutyrate) (PHB)-based food packaging material PHB/5GS/0.7MgO, developed by incorporating 5 wt% grapeseed oil (GS) and 0.7 wt% MgO nanoparticles using solution casting route, was investigated in soil and river water environments. For comparison, the biodegradability of neat PHB films and PHB-based films loaded only with 5 wt% GS (PHB/5GS) was also studied. Remarkably, all PHB-based films showed 100 % weight loss in soil within 25 days. In contrast, the weight loss of PHB, PHB/5GS, and PHB/5GS/MgO films in river water was 27, 24, and 20 %, respectively, in 120 days. Gradual reduction in average molecular weight and carbonyl index, alongside an increase in crystallinity, opacity, and the number of chain scissions per unit mass, was observed for various PHB-based films during their degradation in soil and river water. Overall, this study demonstrated high degradation efficiency of PHB-based food packaging material in soil than in river water.

Enhanced Crystallization of Sustainable Polylactic Acid Composites Incorporating Recycled Industrial Cement

Globally, the demand for single-use plastics has increased due to the rising demand for food delivery and household goods. This has led to environmental challenges caused by indiscriminate dumping and disposal. To address this issue, non-degradable plastics are being replaced with biodegradable alternatives. Polylactic acid (PLA) is a type of biodegradable plastic that has excellent mechanical properties. However, its applications are limited due to its low crystallinity and brittleness. Studies have been conducted to combat these limitations using carbon or inorganic nucleating agents. In this study, waste cement and PLA were mixed to investigate the effect of the hybrid inorganic nucleating agent on the crystallinity and mechanical properties of PLA. Waste cement accelerated the lamellar growth of PLA and improved its crystallinity. The results indicate that the flexural and impact strengths increased by approximately 3.63% and 76.18%, respectively.

Going beyond Cellulose and Chitosan: Synthetic Biodegradable Membranes for Drinking Water, Wastewater, and Oil-Water Remediation

Membrane technology is an efficient way to purify water, but it generates non-biodegradable biohazardous waste. This waste ends up in landfills, incinerators, or microplastics, threatening the environment. To address this, research is being conducted to develop compostable alternatives that are sustainable and ecofriendly. Bioplastics, which are expected to capture 40% of the market share by 2030, represent one such alternative. This review examines the feasibility of using synthetic biodegradable materials beyond cellulose and chitosan for water treatment, considering cost, carbon footprint, and stability in mechanical, thermal, and chemical environments. Although biodegradable membranes have the potential to close the recycling loop, challenges such as brittleness and water stability limit their use in membrane applications. The review suggests approaches to tackle these issues and highlights recent advances in the field of biodegradable membranes for water purification. The end-of-life perspective of these materials is also discussed, as their recyclability and compostability are critical factors in reducing the environmental impact of membrane technology. This review underscores the need to develop sustainable alternatives to conventional membrane materials and suggests that biodegradable membranes have great potential to address this challenge.

Bottom-Up Design of a Green and Transient Zinc-Ion Battery with Ultralong Lifespan

Transient batteries are expected to lessen the inherent environmental impact of traditional batteries that rely on toxic and critical raw materials. This work presents the bottom-up design of a fully transient Zn-ion battery (ZIB) made of nontoxic and earth-abundant elements, including a novel hydrogel electrolyte prepared by cross-linking agarose and carboxymethyl cellulose. Facilitated by a high ionic conductivity and a high positive zinc-ion species transference number, the optimized hydrogel electrolyte enables stable cycling of the Zn anode with a lifespan extending over 8500 h for 0.25 mA cm^-2 - 0.25 mAh cm^-2 . On pairing with a biocompatible organic polydopamine-based cathode, the full cell ZIB delivers a capacity of 196 mAh g^-1 after 1000 cycles at a current density of 0.5 A g^-1 and a capacity of 110 mAh g^-1 after 10 000 cycles at a current density of 1 A g^-1 . A transient ZIB with a biodegradable agarose casing displays an open circuit voltage of 1.123 V and provides a specific capacity of 157 mAh g^-1 after 200 cycles at a current density of 50 mA g^-1 . After completing its service life, the battery can disintegrate under composting conditions.

Poly(Lactic Acid) (PLA)-Based Nanocomposites: Impact of Vermiculite, Silver, and Graphene Oxide on Thermal Stability, Isothermal Crystallization, and Local Mechanical Behavior

The structural, thermal, and mechanical properties of unreinforced and reinforced polylactic acid (PLA) were investigated. The PLA was a biopolymer that was reinforced with four fillers (i.e., graphene oxide (GO) and silver (Ag); vermiculite (VMT) and silver (Ag); and two organically modified vermiculites). The processing technique for the production of the composite materials were carefully planned. The PLA nanocomposites were investigated by examining their morphological aspects, changes in PLA phases and transitions and, most importantly, the effect on certain final properties. X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that the sample was completely amorphous. Thermogravimetric analysis (TGA) results indicated that the presence of reinforcing particles in the PLA matrix did not affect the thermal degradation of these composites. Furthermore, the local mechanical properties were investigated using the microindentation method to evaluate the effect of different nanofillers. Scanning electron microscopy (SEM) and a VHX-500 optical digital microscope (Keyence International, Mechelen, Belgium) were also used to examine the surface morphology of the PLA polymer composites. These results can help to select suitable fillers to enhance the PLA performance of biopolymers.

Comparative Study of the Properties of Plasticized Polylactic Acid with Maleinized Hemp Seed Oil and a Novel Maleinized Brazil Nut Seed Oil

In this study, for the first time, Brazil nut seed oil was chemically modified with maleic anhydride to obtain maleinized Brazil nut seed oil (MBNO). The same process was developed to obtain maleinized hemp seed oil (MHO). The use of MBNO and MHO was studied as bio-based plasticizers by incorporating them with different contents ranging from 0 to 10 phr in a polylactic acid (PLA) matrix. By means of mechanical, thermal and thermomechanical characterization techniques, the properties of the different formulations were studied to evaluate the plasticizing effect of the MBNO and MHO. With the addition of both plasticizers, a significant increase in ductile properties was observed, reaching an increase in elongation at break of 643% with 7.5 phr MBNO and 771% with 10 phr MHO compared to neat PLA. In addition, it has been observed that the mechanical resistant properties do not decrease, since the oils enhance the crystallization of PLA by increasing the free volume between its chains and counteracting the effect. Finally, a disintegration test was carried out under thermophilic conditions at 58 °C for 27 days, demonstrating that the incorporation of MHO and MBNO does not significantly affect the biodegradability of neat PLA.

Phylogenetic Distribution of Plastic-Degrading Microorganisms

The number of plastic-degrading microorganisms reported is rapidly increasing, making it possible to explore the conservation and distribution of presumed plastic-degrading traits across the diverse microbial tree of life. Putative degraders of conventional high-molecular-weight polymers, including polyamide, polystyrene, polyvinylchloride, and polypropylene, are spread widely across bacterial and fungal branches of the tree of life, although evidence for plastic degradation by a majority of these taxa appears limited. In contrast, we found strong degradation evidence for the synthetic polymer polylactic acid (PLA), and the microbial species related to its degradation are phylogenetically conserved among the bacterial family Pseudonocardiaceae We collated data on genes and enzymes related to the degradation of all types of plastic to identify 16,170 putative plastic degradation orthologs by mining publicly available microbial genomes. The plastic with the largest number of putative orthologs, 10,969, was the natural polymer polyhydroxybutyrate (PHB), followed by the synthetic polymers polyethylene terephthalate (PET) and polycaprolactone (PCL), with 8,233 and 6,809 orthologs, respectively. These orthologous genes were discovered in the genomes of 6,000 microbial species, and most of them are as yet not identified as plastic degraders. Furthermore, all these species belong to 12 different microbial phyla, of which just 7 phyla have reported degraders to date. We have centralized information on reported plastic-degrading microorganisms within an interactive and updatable phylogenetic tree and database to confirm the global and phylogenetic diversity of putative plastic-degrading taxa and provide new insights into the evolution of microbial plastic-degrading capabilities and avenues for future discovery.IMPORTANCE We have collated the most complete database of microorganisms identified as being capable of degrading plastics to date. These data allow us to explore the phylogenetic distribution of these organisms and their enzymes, showing that traits for plastic degradation are predominantly not phylogenetically conserved. We found 16,170 putative plastic degradation orthologs in the genomes of 12 different phyla, which suggests a vast potential for the exploration of these traits in other taxa. Besides making the database available to the scientific community, we also created an interactive phylogenetic tree that can display all of the collated information, facilitating visualization and exploration of the data. Both the database and the tree are regularly updated to keep up with new scientific reports. We expect that our work will contribute to the field by increasing the understanding of the genetic diversity and evolution of microbial plastic-degrading traits.

UV Protective, Antioxidant, Antibacterial and Compostable Polylactic Acid Composites Containing Pristine and Chemically Modified Lignin Nanoparticles

Polylactic acid (PLA) films containing 1 wt % and 3 wt % of lignin nanoparticles (pristine (LNP), chemically modified with citric acid (caLNP) and acetylated (aLNP)) were prepared by extrusion and characterized in terms of their overall performance as food packaging materials. Morphological, mechanical, thermal, UV–Vis barrier, antioxidant and antibacterial properties were assayed; appropriate migration values in food simulants and disintegration in simulated composting conditions were also verified. The results obtained indicated that all lignin nanoparticles succeeded in conferring UV-blocking, antioxidant and antibacterial properties to the PLA films, especially at the higher filler loadings assayed. Chemical modification of the fillers partially reduced the UV protection and the antioxidant properties of the resulting composites, but it induced better nanoparticles dispersion, reduced aggregates size, enhanced ductility and improved aesthetic quality of the films through reduction of the characteristic dark color of lignin. Migration tests and disintegration assays of the nanocomposites in simulated composting conditions indicated that, irrespectively of their formulation, the multifunctional nanocomposite films prepared behaved similarly to neat PLA.

Mussel-inspired polydopamine-mediated surface modification of freeze-cast poly (ε-caprolactone) scaffolds for bone tissue engineering applications

There are many methods used to fabricate the scaffolds for tissue regeneration, among which freeze casting has attracted a great deal of attention due to the capability to create a unidirectional structure. In this study, polycaprolactone (PCL) scaffolds were fabricated by freeze-casting technology in order to create porous microstructure with oriented open-pore channels. To induce biomineralization, and to improve hydrophilicity and cell interactions, mussel-inspired polydopamine (PDA) was coated on the surface of the freeze-cast PCL constructs. Then, the synergistic effects of oriented microstructure and deposited layer on efficient reconstruction of injured bone were studied. Microscopic observations demonstrated that, the coated layer did not show any special change in lamellar microstructure of the scaffolds. Water-scaffold interactions were evaluated by contact angle measurements, and they demonstrated strong enhancement in the hydrophilicity of the polymeric scaffolds after PDA coating. Biodegradation ratio and water uptake evaluation confirmed an increase in the measured values after PDA precipitation. The biomineralization of the PDA-coated scaffolds was characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Obtained results confirmed biomineralization of the constructs after a 28-day immersion in a simulated body fluid (SBF) solution. Mechanical analysis demonstrated higher compressive strength after PDA coating. L929 fibroblast cell viability and attachment illustrated that PDA-coated PCL scaffolds are able to support cell adhesion and proliferation. The increased secretion of alkaline phosphatase (ALP) after culturing osteosarcoma cell lines (MG-63) revealed the initial capability of scaffolds to induce bone regeneration. Therefore, the PDA-coated scaffolds introduce a promising approach for bone tissue engineering application.

Thermal and Mechanical Properties of Silica⁻Lignin/Polylactide Composites Subjected to Biodegradation

In this paper, silica–lignin hybrid materials were used as fillers for a polylactide (PLA) matrix. In order to simulate biodegradation, PLA/hybrid filler composite films were kept in soil of neutral pH for six months. Differential scanning calorimetry (DSC) allowed analysis of nonisothermal crystallization behavior of composites, thermal analysis provided information about their thermal stability, and scanning electron microscopy (SEM) was applied to define morphology of films. The influence of biodegradation was also investigated in terms of changes in mechanical properties and color of samples. It was found that application of silica–lignin hybrids as fillers for PLA matrix may be interesting not only in terms of increasing thermal stability, but also controlled biodegradation. To the best knowledge of the authors, this is the first publication regarding biodegradation of PLA composites loaded with silica–lignin hybrid fillers.

Functional Nanocomposites Based on Fibrous Clays

This chapter is focused on functional nanocomposites based on the use of the microfibrous clays sepiolite and palygorskite as efficient fillers for diverse types of polymer matrices, from typical thermoplastics to biopolymers. The main features that govern the interaction between the silicates and the polymer matrix are discussed. The introduction addresses the structural and textural features of the fibrous silicates, as well as the possible synthetic approaches to increase the compatibility of these nanofillers with the polymeric matrix. Additionally, these clays can be easily functionalized through their surface silanol groups based on chemical reactions or by anchoring of nanoparticles. This allows for the preparation of a wide variety of functional polymer–clay nanocomposites. Thereafter, some relevant examples of nanocomposites derived from conventional polymers are reported, as well as of those based on polymers that exhibit electrical conductivity. Lastly, selected works employing sepiolite or palygorskite as fillers in polymeric matrixes of natural origin are discussed, showing the wide application of these resulting nanocomposites as bioplastics, as well as in biomedicine, environmental remediation and the development of sensor devices.

Effect of Extrusion on the Mechanical and Rheological Properties of a Reinforced Poly(Lactic Acid): Reprocessing and Recycling of Biobased Materials

The aim of this research paper is to study the behaviour of a common used biopolymer (Poly(Lactic Acid) (PLA)) after several reprocesses and how two different types of additives (a melt strength enhancer and a nanoadditive) affect its mechanical and rheological properties. Systematic extraction of extrudate samples from a twin-screw compounder was done in order to study the effect in the properties of the reprocessed material. Detailed rheological tests on a capillary rheometer as well as mechanical studies on a universal tensile machine after preparation of injected specimens were carried out. Results evidenced that PLA and reinforced PLA materials can be reprocessed and recycled without a remarkable loss in their mechanical properties. Several processing restrictions and specific phenomena were identified and are explained in the present manuscript.

Enhanced removal of nitrate using starch/PCL blends as solid carbon source in a constructed wetland

Cornstarch/polycaprolactone (SPCL) blends were prepared and used as external carbon source for biological denitrification in a constructed wetland. The denitrification performances, components of dissolved organic matter (DOM) and microbial diversity were investigated. The results showed that nitrate was removed mainly in the layer filled with SPCL, and the average denitrification rate was 0.069kg/m(3)d (nitrate removal efficiency was 98.23%). The major component of DOM was polysaccharides which mainly consisted of reducing sugar. Besides, the concentrations of polysaccharides and reducing sugar decreased along the height of the constructed wetland. Therefore, the dissolved organic carbon (DOC) of effluent decreased to 6.54mg/L. Denitrifying bacteria Bacillus (24.25%) and Thauera (9.36%) were the most abundant genera in the biofilm attached on the surface of SPCL.