Polypropylene Surface Research Articles

Wastewater-associated plastispheres: A hidden habitat for microbial pathogens?

Wastewater treatment plants (WWTPs) receive wastewater from various sources. Despite wastewater treatment aiming to remove contaminants, microplastics persist. Plastic surfaces are quickly colonized by microbial biofilm ("plastispheres"). Plastisphere communities are suggested to promote the spread and survival of potential human pathogens, suggesting that the transfer of plastispheres from wastewater to the environment could pose a risk to human and environmental health. The study aimed to identify pathogens in wastewater plastispheres, specifically food-borne pathogens, in addition to characterizing the taxonomic diversity and composition of the wastewater plastispheres. Plastispheres that accumulated on polypropylene (PP), polyvinyl chloride (PVC), and high-density polyethylene propylene (HDPE) surfaces exposed to raw and treated wastewater were analyzed via cultivation methods, quantitative reverse transcription PCR (RT‒qPCR) and 16S rRNA amplicon sequencing. RT‒qPCR revealed the presence of potential foodborne pathogenic bacteria and viruses, such as Listeria monocytogenes, Escherichia coli, norovirus, and adenovirus. Viable isolates of the emerging pathogenic species Klebsiella pneumoniae and Acinetobacter spp. were identified in the plastispheres from raw and treated wastewater, indicating that potential pathogenic bacteria might survive in the plastispheres during the wastewater treatment. These findings underscore the potential of plastispheres to harbor and disseminate pathogenic species, posing challenges to water reuse initiatives. The taxonomic diversity and composition of the plastispheres, as explored through 16S rRNA amplicon sequencing, were significantly influenced by the wastewater environment and the duration of time the plastic spent in the wastewater. In contrast, the specific plastic material did not influence the bacterial composition, while the bacterial diversity was affected. Without efficient wastewater treatment and proper plastic waste management, wastewater could act as a source of transferring plastic-associated pathogens into the food chain and possibly pose a threat to human health. Continued research and innovation are essential to improve the removal of microplastics and associated pathogenic microorganisms in wastewater.

Track of methylparaben in the bulk phase and on the extracellular matrix of dual-species biofilms: Biodegradation and bioaccumulation

Methylparaben (MP) is a preservative considered an environmental contaminant of emerging concern due to its persistence in water sources, including drinking water (DW). This study assesses the interaction between MP and dual-species biofilms of Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. These biofilms were grown under realism-based conditions in a multiple-cylinder biofilm reactor on polypropylene (PPL) surfaces, for 7 days, and then exposed to MP at 0.5 mg/L for three consecutive days. S. maltophilia predominantly succeeds within these biofilms compared to A. calcoaceticus. Exposure to MP resulted in a 4-fold increase in the number of culturable cells and a 1.4-fold rise in polysaccharide content, suggesting that bacterial cells may utilize MP as a carbon source to enhance biofilm fitness. MP was found to adsorb to PPL with biofilms following a pseudo-second-order kinetic model. Circa 37 % of MP adsorbed to PPL after 3 days of exposure. Besides that, MP was biodegraded by biofilms following an apparent first-order kinetic model. Part (25 %) of the MP was biodegraded whereas only 0.02 % bioaccumulated on the biofilm matrix. Biodegradation was related to esterase and lipase activity. The results provide new insights into the interaction between MP with biofilms and materials used in DW industries.

Analysis of time-dependent hydrophobic recovery on plasma-treated superhydrophobic polypropylene using XPS and wettability measurements

In specific applications like ice-repellent coatings or membrane separation technology, wettability is a key parameter affecting the applicability of commodity polymers. This study presents a technique to fine-control the wetting properties of a hierarchically structured polypropylene surface, enabling the transition between superhydrophobic and superhydrophilic states. To demonstrate the tunability of the wetting properties of polypropylene (PP) substrate, we prepared in a consecutive way superhydrophobic (advancing contact angle (CAadv) of 152°) and superhydrophilic (CAadv of 0°) material by solvent-treatment and mild air plasma treatment. The optimal plasma treatment parameters to achieve superhydrophilic wetting behaviour, which is stable for at least one week of storage in air was also explored. Water contact angle measurement and X-ray photoelectron spectroscopy were used to monitor the time dependency of hydrophobic recovery on a hierarchically structured PP surface. With a simple model considering structural and wetting parameters, we characterized the droplet spreading behaviour of plasma-treated roughened surfaces, which exhibited superhydrophilic wetting behaviour with equilibrium CAadv of nearly 0°. The proposed model, which aligns well with experimental data, can be used to compare the droplet spreading behaviour of plasma-treated roughened surfaces.

Cu-ZnO Embedded in a Polydopamine Shell for the Generation of Antibacterial Surgical Face Masks.

A new easy protocol to functionalize the middle layer of commercial surgical face masks (FMs) with Zn and Cu oxides is proposed in order to obtain antibacterial personal protective equipment. Zinc and copper oxides were synthesized embedded in a polydopamine (PDA) shell as potential antibacterial agents; they were analyzed by XRD and TEM, revealing, in all the cases, the formation of metal oxide nanoparticles (NPs). PDA is a natural polymer appreciated for its simple and rapid synthesis, biocompatibility, and high functionalization; it is used in this work as an organic matrix that, in addition to stabilizing NPs, also acts as a diluent in the functionalization step, decreasing the metal loading on the polypropylene (PP) surface. The functionalized middle layers of the FMs were characterized by SEM, XRD, FTIR, and TXRF and tested in their bacterial-growth-inhibiting effect against Klebsiella pneumoniae and Staphylococcus aureus. Among all functionalizing agents, Cu2O-doped-ZnO NPs enclosed in PDA shell, prepared by an ultrasound-assisted method, showed the best antibacterial effect, even at low metal loading, without changing the hydrophobicity of the FM. This approach offers a sustainable solution by prolonging FM lifespan and reducing material waste.

Polypropylene Blends with Durable Hydrophobicity and Enhanced Mechanical Properties Based on POSS and Alkane Modified Polypentafluorophenyl Methacrylate.

Durable functionalization on polypropylene (PP) surfaces is always a key problem to besolved. Coatings with low surface energy peel off easily especially under extreme conditions, owing to their weak adhesion. In this paper, side groups of both polyhedral oligomeric silsesquioxane (POSS) and alkane are grafted to polypentafluorophenyl methacrylate (PFP), and then PP blends with these side-group modified PFP are obtained through a melt-blending process. It is found that POSS can result in surface segregation and provide hydrophobicity in blends. Microfibers are formed because of the orientation effect during the tensile testing, which furtherly promotes mechanical strength. Significantly, alkaneside-groups can be entangled with PP segments, which brings about cross linking. Therefore, with crosslinking and synchronous orientation of POSS, the elongation at the break of blends is greatly increased up to 974%. The final blend demonstrates quite durable hydrophobicity under many extreme conditions, such as repeated tape peeling, ultrasonic washing, strong friction, and soaking in strong acid (pH = 1), strong alkali (pH = 14) and alcohol. The heat and UV resistance of the blend are also obviously improved. This study will develop anovel and facile strategy to endow PP with durable hydrophobicity as well as greatly enhanced mechanical properties.

Enhancing the coloration of polypropylene surfaces through low-frequency plasma modification with disperse dyes

This study focuses on the effective coloring of nonwoven polypropylene surfaces, achieved through the application of oxygen and nitrogen plasma treatments in a vacuum environment using cold plasma. Various plasma durations were employed to introduce experimental diversity into the samples. Following surface modification, dispersal dyeing based on benzenesulphonamide was performed. To evaluate the impact of surface modification, comprehensive characterization tests, including SEM, FTIR-ATR, XRD, and XPS, were conducted. Performance effects were scrutinized through color spectrum values (CIE L*, a*, b*, and K/S values), tearing strengths and contact angle measurements. Furthermore, fastness tests for washing (color change and staining) and for rubbing (dry and wet) were carried out to examine the effect of surface modification on dyed polypropylene nonwoven fabrics. According to the test results, a notable increase in K/S values was observed after plasma treatments. The impact of nitrogen and oxygen plasma treatment on polypropylene surfaces was comprehensively evaluated, considering performance properties across all characterization processes.

Vaterite-based in situ surface modification and process-dependent biocompatibility of laser sintered polypropylene

Polypropylene (PP) rapidly gains scientific attention as fatigue-resistant and lightweight tissue repair and implant material, while emerging laser-sintering based methods for PP processing further allow unlimited versatility of PP specimens and often reduced numbers of process steps, substituting traditional manufacturing approaches. Generally, PP is considered biocompatible for a variety of medical applications while showing superior long-term stability, however, thermoplastic processing of polypropylene may induce the formation of cytotoxic degradation products, necessitating its cytotoxicological assessment. In the present study, PP specimens have been fabricated using warm, quasi-isothermal and complementary cold, non-isothermal powder bed fusion (PBF), allowing processing PP at ambient powder bed temperature of 25 °C for minimizing thermal exposure and the formation of decomposition products. The surface of manufactured specimens has been modified with hybrid coatings consisting of mesoporous inorganic microcrystals of vaterite laden with model biomacromolecules, i.e., fluorescently labelled dextran, demonstrating the stable coating and attachment of dextran-loaded vaterite crystals independent of the applied PBF processing regime. Vaterite coating is degradable and enables the opportunity to endow the surface of PP with sustained release functionalities. Both coated and uncoated specimens demonstrated excellent biocompatibility independent of the applied processing regime, as evaluated in an ex ovo shell-less hen's egg model.

Water Impact Dynamics and Mechanism Analysis of Polypropylene and Polypropylene/poly(ethylene-co-octene) Replica Surfaces with Nanowires under Low Temperature Conditions.

In this work, polypropylene (PP) and PP/poly(ethylene-co-octene) (PP/POE) blend replica surfaces with densely arranged nanowires are fabricated using a molding process. Morphology analysis shows that the nanowires on these replica surfaces have sharp tips and high aspect ratios. The droplet impact behaviors on the surfaces of the PP/POE blend replicas and PP replicas are investigated before and after freezing at -20 °C for 4 h. The height of the nanowires on the PP/POE blend replica surfaces is higher than that on the PP surface before and after freezing. The static wettability and droplet impact tests on the surfaces of PP/POE blend replicas and PP replica show that adding POE into the PP matrix can significantly increase the toughness of the nanowires on the PP/POE blend replica surfaces during the droplet impact at low temperatures. These investigations are favorable to broaden the practical applications of superhydrophobic surfaces in some severe environments.

Interfacial engineering assists dendrite-inhibiting separators for high-safety Li-S batteries

The impediments to the safety and cyclic performance of lithium-sulfur (Li-S) batteries arise from the lithium dendrite growth and “shuttle effect” of polysulfides. Herein, an interfacial engineering was proposed by pre-irradiation grafting acrylic acid (AA) into polypropylene (PP) separator to achieve a dendrite-inhibiting and high stability functional separators. The abundant –COOH groups, introduced to the surface of PP along with AA, effectively modulate lithium dendrite growth by eliminating the local aggregation of Li+ on the surface of the anode and restrain the “shuttle effect” of polysulfides by the physical confinement and electrostatic interaction. Lithium-sulfur batteries with the grafted separator achieved a high initial capacity of 1108.7 mAh g−1 with an ultralow attenuation rate of 0.012 % per cycle at 1C, outperforming the traditional commercial PP separator. Additionally, the grafted separator also appeared a remarkable flexibility owing to the chemical bond between AA and PP-chain. Notably, the pre-irradiation grafting process, characterized by a mild reaction condition and high economic benefit, endowed the grafted separator with outstanding potential for industrialization. Those results showed the practical prospects of the grafted separator, offering a promising new option for high-safety Li-S batteries.

New click chemistry scheme towards improvement of filler/polymer crosslinking in bio-based polymer composites

ABSTRACT The current study aims to develop a cutting-edge methodology to enhance compatibility between natural fiber and polymeric matrix in bio-composites. To achieve this, an innovative approach for grafting an azide functional group (Az) onto the surface of polypropylene (PP) was successfully developed and confirmed. The Az group contributed to enhancing the interfacial interaction between the polymer matrix and the bio-filler through chemical crosslinking. Crosslinking is achieved through an innovative and efficient chemical process known as click chemistry. In particular, a click reaction is established between the functionalized PP with an azide group and functionalized natural filler with an alkyne group. The effectiveness of the proposed technique is verified using Fourier Transform Infrared (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). The resulting bio-composite exhibits higher mechanical properties, better thermal stability, and improved biocompatibility compared to conventional materials. Specifically, the maximum tensile strength was achieved at 10% DPP loading, showing a 22% increase over the base material (DPP/PP) and a 7% increase over neat PP. A more significant enhancement was observed in Young’s modulus results across all samples. Therefore, the established method is beneficial for polymer modification, promoting the production of high-performance bio-composite materials.

Generation of nano-to-microplastics from polypropylene surfaces via femtosecond laser ablation in liquids with different viscosities

Preparation of polypropylene (PP) nano and microparticles, crucial for investigating the effects of plastics on both human health and the environment, presents a significant and immediate challenge. Utilizing an fs laser system in different liquid mediums such as water, dodecane, and hexadecane, we have successfully generated PP particles with sizes ranging from 1.8 to 4911 nm. This outcome is partly attributed to the constraint on plasma expansion caused by the viscosity of the liquid media. We investigated the areas of material removal and observed a transition from ordered to disordered removal patterns during this process. The formation of filaments and pillars within the material removal cavity, along with the deposition layer at the cavity edge, primarily occurred due to insufficient plasma formation at low laser energy levels. Furthermore, we observed neck-shaped filaments and nano cracks on the deposition surface, which were attributed to the heat effect during laser interaction with the PP substrate. Moreover, we collected distinct nano-Fourier transform infrared spectroscopy (FTIR) signals from both the nanoparticle area and the deposition layer, revealing a 2 cm−1 wavenumber difference between the two regions. This discrepancy proved to be a valuable method for distinguishing between the nanoparticle area and the deposition layer.

Post-polymerization modification of polypropylene with different functional groups utilizing non-catalytic C–H insertion of sulfonyl azide

This study presents a comprehensive investigation into the preparation of functionalized polypropylene (PP) with different functional groups, such as amino-, hydroxyl-, acetamido-, and carboxyl-groups, utilizing efficient C–H insertion capability of sulfonyl azide (SA) compounds with the functional groups. The reactive melt mixing of PP and the SA compounds was performed at temperatures determined by the decomposition temperatures of the SA groups, followed by purification processes to remove unreacted SA compounds, confirming the establishment of stable covalent linkages between the SA compounds and PP chains. Grafting efficiency (GE) values were determined using FT-IR spectroscopy, showcasing efficient grafting of the SA compounds onto PP chains with GE values ranging from 60 % to 70 %. Remarkably, SA compound with carboxyl functional group exhibited an exceptionally high GE value of ∼90 %, likely attributed to its electron-withdrawing carbonyl group. XRD analyses, thermal analyses, morphological analyses of cryogenically fractured modified PPs and mechanical property analyses revealed successful incorporation of SA compounds into PP chains with relatively low sensitivity of the crystal structure of the modified PPs to the incorporated SA compounds. Hydrophilicity assessments revealed improved paint adhesion capabilities of the modified PP surfaces, highlighting the potential for the tailored surface modification strategies to enhance material characteristics.

A switchable dual-mode film with designed intercalated and hierarchical structures for highly efficient passive radiation cooling and solar heating

A single-mode solar heating (SH) and passive radiative cooling (PRC) have been fast developed in outdoor thermal management. However, they hardly change with the temperature fluctuations of the hot and cold seasons. Herein, a flexible and stable dual-mode film with photo responsibility was engineered by integrating heating coating and cooling coating on the opposite surfaces of a porous polypropylene (PP) membrane. Flip the surfaces of the dual-mode film-facing solar light to switch between PRC and SH. The cross-linked heating side was fabricated from reduced graphene oxide (rGO) nanosheets intercalated with carbon black (CB) particles via spraying. A thick intercalated film can enhance solar absorptivity (96.4 %) and low infrared emissivity (8.0 %) due to the multiple solar reflections and adsorption between the interlayers, leading to high solar heating. The cooling side was derived from polyvinylidene fluoride (PVDF) coating embedded micro-nano Al2O3 particles via water vapor-induced phase separation (VIPS). The hierarchical coating with a pore size of 8.4 ± 0.1 µm and roughness of 4.0 ± 0.3 µm exhibits high solar reflectivity (92.2 %) and infrared emissivity (96.9 %), resulting in excellent passive radiative cooling. The net heating power (Pheating) and net cooling power (Pcooling) of the dual-mode film are 845.9 and 96.7 W m−2. Moreover, the dual-mode film exhibits outdoor thermoregulation capacity upon covering buildings, cars, and ice. In outdoor environments under solar radiation of 611 ∼ 716 W m−2, it has a temperature increase/decrease of 17.8/5.3 °C to the ambient temperature. Owing to the scalable fabrication processes and excellent thermoregulation characteristics, the dual-mode film is promising for applications in personal thermal management, energy-efficient buildings, in-car temperature control, and food freezing-thawing.

Investigating Anti-Bacterial and Anti-COVID-19 Virus Properties and Mode of Action of Pure Mg(OH)2 and Copper-infused Mg(OH)2 Nanoparticles and Coated Polypropylene Surfaces

Robust anti-microbial surfaces that are non-toxic to users have widespread application in medical, industrial, and domestic arenas. Magnesium hydroxide has recently gained attention as an anti-microbial compound that is non-toxic, biocompatible, and environmentally friendly. Here we demonstrate melt compound and thermally embossed methods for coating polypropylene with Mg(OH)2 nanoplatelets and copper-infused Mg(OH)2 nanoplatelets. Polypropylene articles coated with Mg(OH)2 nanoplatelets and copper-infused Mg(OH)2 nanoplatelets exhibit a log 8 kill of E.coli within 24 hours. In addition, Mg(OH)2 NPs suspension, at 0.25% reduced SARSCoV-2 virus titers in the solution by 2.5 x 103 PFU/mL or 29.4%, while the Cu-infused Mg(OH)2 NPs suspension, at 0.25% reduced titers by 8.1 x 103 PFU/mL or 95.3%. Fluorescence microscopy revealed that reactive oxygen species (ROS) are produced in bacteria in response to Mg(OH)2 and Cu-infused Mg(OH)2 nanoplatelets which appears to be an important but not the sole mode of anti-microbial action of the nanoplatelets. Plastics with anti-microbial surfaces from where biocides are non-leachable are highly desirable. This work provides a general fabrication strategy for developing anti-microbial plastic surfaces.

Utilizing Rapid Hydrogen Peroxide Generation from 6-Hydroxycatechol to Design Moisture-Activated, Self-Disinfecting Coating.

A coating that can be activated by moisture found in respiratory droplets could be a convenient and effective way to control the spread of airborne pathogens and reduce fomite transmission. Here, the ability of a novel 6-hydroxycatechol-containing polymer to function as a self-disinfecting coating on the surface of polypropylene (PP) fabric was explored. Catechol is the main adhesive molecule found in mussel adhesive proteins. Molecular oxygen found in an aqueous solution can oxidize catechol and generate a known disinfectant, hydrogen peroxide (H2O2), as a byproduct. However, given the limited amount of moisture found in respiratory droplets, there is a need to enhance the rate of catechol autoxidation to generate antipathogenic levels of H2O2. 6-Hydroxycatechol contains an electron donating hydroxyl group on the 6-position of the benzene ring, which makes catechol more susceptible to autoxidation. 6-Hydroxycatechol-coated PP generated over 3000 μM of H2O2 within 1 h when hydrated with a small amount of aqueous solution (100 μL of PBS). The generated H2O2 was three orders of magnitude higher when compared to the amount generated by unmodified catechol. 6-Hydroxycatechol-containing coating demonstrated a more effective antimicrobial effect against both Gram-positive (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria when compared to unmodified catechol. Similarly, the self-disinfecting coating reduced the infectivity of both bovine viral diarrhea virus and human coronavirus 229E by as much as a 2.5 log reduction value (a 99.7% reduction in viral load). Coatings containing unmodified catechol did not generate sufficient H2O2 to demonstrate significant virucidal effects. 6-Hydroxycatechol-containing coating can potentially function as a self-disinfecting coating that can be activated by the moisture present in respiratory droplets to generate H2O2 for disinfecting a broad range of pathogens.

Impact of drops of epoxy resin and hardener, silicone and turpentine oils onto balsa wood and polypropylene substrates

Electrowetting and wettability-driven spreading of liquids on porous and nonporous substrates was investigated using impact of drops of epoxy resin, epoxy hardener, and epoxy resin and hardener, as well as silicone and turpentine oils with oil-soluble aniline dyes onto balsa wood and polypropylene surfaces. The experimental results revealed that the electric field stretched drops of epoxy resin, epoxy hardener, and epoxy resin and hardener after impact on polypropylene substrate in the long-term. The spreading of drops of epoxy resin and turpentine oil with dyes after impact onto porous balsa wood under the action of a 10 kV applied voltage was relatively weak. In addition, the measured footprint areas corresponding to drops of epoxy resin, epoxy hardener, and epoxy resin and hardener demonstrated a significant increase in the wetted areas driven by the applied voltage of 10 kV on polypropylene substrate, whereas on balsa wood, the footprint is practically unaffected by the electric field. Furthermore, it was determined that surface wettability was the main mechanism of spreading of epoxy resin, as well as silicone and turpentine oils with aniline dyes on porous balsa without the electric field applied. On the other hand, insufficient concentration of ions and counterions in silicone oil was responsible for the absence of electrohydrodynamic effects after impact of such drops onto porous balsa substrate subjected to high potentials of 7 and 10 kV. Hence, wettability-driven spreading with imbibition on balsa wood was the only reason for an increase in the wetted area in the case of silicone oil.

Identification of plastic-degrading bacteria in the human gut

Environmental pollution caused by the excessive use of plastics has resulted in the inflow of microplastics into the human body. However, the effects of microplastics on the human gut microbiota still need to be better understood. To determine whether plastic-degrading bacteria exist in the human gut, we collected the feces of six human individuals, did enrichment cultures and screened for bacterial species with a low-density polyethylene (LDPE) or polypropylene (PP)-degrading activity using a micro-spray method. We successfully isolated four bacterial species with an LDPE-degrading activity and three with a PP-degrading activity. Notably, all bacterial species identified with an LDPE or PP-degrading activity were opportunistic pathogens. We analyzed the microbial degradation of the LDPE or PP surface using scanning electron microscopy and confirmed that each bacterial species caused the physical changes. Chemical structural changes were further investigated using X-ray photoelectron spectroscopy and Fourier-transform-infrared spectroscopy, confirming the oxidation of the LDPE or PP surface with the formation of carbonyl groups (C=O), ester groups (CO), and hydroxyl groups (-OH) by each bacterial species. Finally, high temperature gel permeation chromatography (HT-GPC) analysis showed that these bacterial species performed to a limited extent depolymerization. These results indicate that, as a single species, these opportunistic pathogens in the human gut have a complete set of enzymes and other components required to initiate the oxidation of the carbon chains of LDPE or PP and to degrade them. Furthermore, these findings suggest that these bacterial species can potentially biodegrade and metabolize microplastics in the human gut.

Antibacterial Activity of Oregano (Origanum vulgare L.) Essential Oil Vapors against Microbial Contaminants of Food-Contact Surfaces.

The antimicrobial effect of eight essential oils' vapors against pathogens and spoilage bacteria was assayed. Oreganum vulgare L. essential oil (OVO) showed a broad antibacterial effect, with Minimum Inhibitory Concentration (MIC) values ranging from 94 to 754 µg cm-3 air, depending on the bacterial species. Then, gaseous OVO was used for the treatment of stainless steel, polypropylene, and glass surfaces contaminated with four bacterial pathogens at 6-7 log cfu coupon-1. No viable cells were found after OVO treatment on all food-contact surfaces contaminated with all pathogens, with the exception of Sta. aureus DSM 799 on the glass surface. The antimicrobial activity of OVO after the addition of beef extract as a soiling agent reduced the Sta. aureus DSM 799 viable cell count by more than 5 log cfu coupon-1 on polypropylene and glass, while no viable cells were found in the case of stainless steel. HS-GC-MS analysis of the headspace of the boxes used for the antibacterial assay revealed 14 different volatile compounds with α-Pinene (62-63%), and p-Cymene (21%) as the main terpenes. In conclusion, gaseous OVO could be used for the microbial decontamination of food-contact surfaces, although its efficacy needs to be evaluated since it depends on several parameters such as target microorganisms, food-contact material, temperature, time of contact, and relative humidity.

Exploring untapped bacterial communities and potential polypropylene-degrading enzymes from mangrove sediment through metagenomics analysis.

The versatility of plastic has resulted in huge amounts being consumed annually. Mismanagement of post-consumption plastic material has led to plastic waste pollution. Biodegradation of plastic by microorganisms has emerged as a potential solution to this problem. Therefore, this study aimed to investigate the microbial communities involved in the biodegradation of polypropylene (PP). Mangrove soil was enriched with virgin PP sheets or chemically pretreated PP comparing between 2 and 4 months enrichment to promote the growth of bacteria involved in PP biodegradation. The diversity of the resulting microbial communities was accessed through 16S metagenomic sequencing. The results indicated that Xanthomonadaceae, unclassified Gaiellales, and Nocardioidaceae were promoted during the enrichment. Additionally, shotgun metagenomics was used to investigate enzymes involved in plastic biodegradation. The results revealed the presence of various putative plastic-degrading enzymes in the mangrove soil, including alcohol dehydrogenase, aldehyde dehydrogenase, and alkane hydroxylase. The degradation of PP plastic was determined using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and Water Contact Angle measurements. The FTIR spectra showed a reduced peak intensity of enriched and pretreated PP compared to the control. SEM images revealed the presence of bacterial biofilms as well as cracks on the PP surface. Corresponding to the FTIR and SEM analysis, the water contact angle measurement indicated a decrease in the hydrophobicity of PP and pretreated PP surface during the enrichment.

Acid-base properties and modeling by quantum chemistry of adhesion interactions at the interface of thermoplastic-aluminum systems

Thermoplastic-aluminum systems are used in the manufacture of corrosion-resistant lightweight constructions in aerospace and automotive industries. The adhesion strength of such systems is determined by the mechanism of adhesion interaction. In this article, adhesion interactions between the surfaces of polyethylene terephthalate, poly(propylene carbonate), poly(methyl methacrylate), polystyrene, polypropylene and aluminum were studied to identify a correlation between the acid-base properties of the studied surfaces, the mechanism of adhesion interaction and energy characteristics in thermoplastic-aluminum systems using experimental and theoretical approaches. The experimental approach consisted of finding the values of the free surface energy components, the acidity parameters of thermoplastics and aluminum by the E.J. Berger and van Oss-Chaudhuery-Good methods. The theoretical approach consisted of the study of adhesion interactions in thermoplastic-aluminum systems using the quantum chemistry method B3LYP-GD3/6-31G(d,p). It was theoretically established the functional groups to be the active sites on the thermoplastics surface. At the same time, the strongest adhesion interaction is manifested in systems formed by a carbonyl oxygen atom.The experimental values of the components of the free surface energy of thermoplastics and aluminum are in good agreement with the theoretical values of the energy and force of the adhesion interaction of the systems under consideration.