Polyamide Research Articles

Screening of the biphenyl polyamides nanofilms appropriate for molecular separation in organic solution feed

Developing polymeric separation membranes that combine excellent solvent stability, high permeability, and customizable molecular weight interception remains a challenge. Herein, thin-film composite (TFC) polyamide (PA) membranes with poly(ether ether ketone) (PEEK) support and biphenyl-centered polyamides active layer were fabricated through interfacial polymerization technique for the first time. Enhanced solvent stability was exhibited by the fabricated membranes due to the intrinsic resistance to organic solvents possessed by PEEK and biphenyl polyamides. The separation performance of the obtained membranes was systematically studied by relating to the properties of PA nanofilms in terms of nano-mechanical strength, morphologies, and microporosity. The organic solvent nanofiltration (OSN) performance of the resultant membranes in terms of permeability and molecular weight cut-off (MWCO) could be regulated. The optimized membrane exhibited a pure solvent permeability as high as 21.6 L m−2 h−1 bar−1 for acetonitrile and 14.0 L m−2 h−1 bar−1 for methanol. It also showed excellent long-term durability with almost unchanged permeability as well as solute retention remained above 97.8 % after a cumulative OSN operation of N, N-Dimethylformamide (DMF) based feed for 240 h. In particular, OSN membrane with targeted MWCOs covering the range of 170–370 g·mol−1 could be fabricated by selecting appropriate biphenyl acyl chlorides as building blocks. This approach offers a scalable and versatile platform for the development of solvent-stable, highly permeable, and customizable MWCO membranes for process-oriented OSN.

Turing structured nanofiltration membrane fabricated by sulfonated cellulose nanocrystals mediated interfacial polymerization for enhanced permeability separation performance

Preparing Turing structure nanofiltration (NF) membrane is a representative strategy to obtain high permeability and selectivity. However, getting a tailored Turing structure by adjusting the interfacial polymerization (IP) process remains a significant challenge. Herein, sulfonated cellulose nanocrystals (S-CNC) with excellent hydrophilicity and negative surface charges were selected as aqueous phase additives to explore their influence on the morphology and composition of polyamide (PA) layer as well as its NF performance. It was found the surface morphology of the PA layer was effectively changed by adjusting the content of S-CNC in the aqueous phase. As the content of S-CNC increased, the Turing structure underwent a series of evolutions, from an “octopus leg structure” to a densely packed ridge-valley structure to a large ridge-valley structure filled with dense nodular particles. Finally, it changed back to the typical PA morphology of densely distributed nodular particles. By exploring the interaction between S-CNC and piperazine (PIP), it was demonstrated that the hydrogen bond and electrostatic interaction between S-CNC and PIP synergistically inhibited the diffusion of PIP, thus resulting in various Turing structures. Benefiting from the unique Turing structure, the prepared SCNF-10 NF membranes showed excellent permeability and separation properties with pure water permeability (PWP) of 16.9 LMH bar−1 and Na2SO4 rejection rate of 98.0 %. SCNF-10 NF membranes also exhibited good selectivity with a separation factor of 34.6 for mono-bivalent salts and long-term permeation stability. It is anticipated that this regulation strategy for various Turing structures preparation can provide a deeper understanding of the application of cellulose nanocrystals to NF membranes in the later stage, which will also promote the development of the high performance of NF membranes.

Self-assembled nanoflower-mediated interfacial polymerization through tunable intra- and inter-layer channels to boost total heat exchange performance

Total heat exchange membranes (THEMs) are vital for minimizing energy consumption and enhancing indoor air quality in energy recovery ventilation (ERV) systems. Manipulating the surface morphology of polyamide (PA) membranes via nanofiller-mediated interfacial polymerization is key to advancing total heat recovery performance. This study presented the fabrication of PA thin-film nanocomposite (TFN) membranes by integrating self-assembled poly(amic acid-imide) nanoflowers (P(AA-I)-NFs) with intertwined nanosheets into the organic phase. This facile approach effectively eliminated nonselective interphase voids and defects, owing to the superior polymer affinity of the organic nanoflowers. The finely tuned intra- and inter-layer channels within P(AA-I)-NFs significantly impacted monomer mass transfer, facilitated the shuttle effect, expanded the interfacial polymerization zone, and led to the formation of a rougher, thicker PA layer with enhanced surface area. The optimized P(AA-I)-NFs/PA TFN membranes exhibited outstanding performance, including CO₂ permeability of 0.51 GPU, water vapor permeability of 656.59 GPU, and an enthalpy exchange efficiency of 71.47 %, surpassing the trade-off limitations typically observed in commercial and other advanced THEMs. These findings underscored the potential of P(AA-I)-NFs-mediated TFN membranes as highly competitive candidates for next-generation ERV systems.

A novel TFNi pervaporation membrane with g-C3N4 quantum dots for high-efficiency IPA dehydration

Pervaporation (PV) shows significant potential for the highly selective isopropanol (IPA). The pursuit of developing PV membranes with outstanding separation effect and enduring high purity permeation is an indispensable goal. Based on polyamide (PA) separation layers, a polydopamine (PDA) mixed g-C3N4 quantum dots (gCNQDs) coating as the interlayer was deposited onto a porous ceramic hollow fiber substrate to fabricate thin-film nanocomposite membranes with an interlayer (TFNi). The nanocomposite interlayer enabled the formation of a smoother and highly separated selective polyamide layer. The separation factor exhibited a 31-fold enhancement with the augmentation of the blending fraction of gCNQDs during the PDA coating process. The resulting TFNi membrane attained an exceedingly high separation factor of 10270 ± 90 with a permeate water concentration of 99.9% and demonstrated a satisfactory flux of 1.40 ± 0.08 kg⋅m-2⋅h-1 during the PV process of 90 wt% IPA dehydration at 60 °C. This study presents a fresh perspective on the implementation of nanocomposite interlayers, which is expected to expand the application of high-performance TFNi membranes in PV dehydration processes.

Construction of sub-10nm ultra-thin polyamide layer using porous GOQDs-AGQDs interlayer

The application of high-performance polyamide nanofiltration membranes with controllable structures shows promising prospects in fields such as seawater desalination and wastewater treatment. In this study, a high-performance polyamide composite nanofiltration membrane with sub-10nm ultra-thin separation layer was designed and fabricated using a hydrophilic porous GOQDs-AGQDs (graphene oxide quantum dots-amino graphene quantum dots) interlayer to reconstruct the substrate architecture. The GOQDs-AGQDs interlayer not only improved the uniformity and smoothness of the microporous substrate, but also could form hydrogen bond with amine monomers to effectively inhibit its diffusion, thereby effectively slowing down the interfacial polymerization process and facilitating the formation of an ultra-thin, smooth and dense polyamide (PA) layer. The results demonstrate that the optimized PA/GOQDs-AGQDs/PES membrane achieved a PA separation layer thickness as low as 9.4 nm, with a permeation flux of 27.2 L·m−2 ·h−1·bar−1, nearly three times that of the original PA/PES membrane. Simultaneously, it enhanced the Na2SO4 rejection rate to 97.1 %, achieving synchronous improvements in permeability and selectivity. Additionally, the PA/GOQDs-AGQDs/PES composite membrane exhibited relatively low surface roughness and demonstrated excellent long-term stability. This work presents a novel strategy for the controllable fabrication of high-performance nanofiltration membranes.

Enhanced anti-fouling and selective performance of GO-modified nanofiltration membranes for lithium extraction from salt lake brine

Nanofiltration (NF) is a promising method in lithium extraction from salt lake brine with a high Mg2+/Li+ mass ratio. However, membrane fouling challenges its applicability and productivity. This study incorporated graphene oxide (GO) into the polyamide (PA) selective layer of NF membranes to enhance anti-fouling properties and improve lithium extraction from brine. Membrane structure analyses revealed that 0.002 wt% and 0.01 wt% GO facilitated the interfacial polymerization reaction. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results indicated that the PA selective layers in the GO-0.002 % and GO-0.01 % membranes were denser, smoother, and thinner. In contrast, the addition of 0.05 wt% GO resulted in the Turing structures on the membrane surface. Adsorption kinetics indicated pollutant adhesion in the following order: GO-0.05 % > GO-0 % > GO-0.002 % > GO-0.01 %, which was attributed to calcium-carboxyl complexation, as directly measured by AFM and consistent with carboxyl density. The GO-0.002 % and GO-0.01 % NF membranes demonstrated excellent anti-fouling properties in brines, with lower initial fouling rates and higher flux recovery after cleaning, underscoring the significant role of calcium-carboxyl complexation in membrane fouling. The retention of Mg2+ increased to 95 %, while that of Li+ decreased to below −28 % for GO-0.002 % and GO-0.01 % membranes, indicating promising potential for Mg and Li separation. This study provides valuable insights into developing NF membranes with high Mg/Li selectivity and anti-fouling capabilities for lithium extraction from salt lake brine.

Laboratory Investigation of the Strength Degradation against Ultraviolet Radiation of Geonets for Slope Protection.

Sufficient light and high UV intensity pose significant challenges to the long-term performance of polymeric geonet materials for slope-protection structures. This study investigates strength degradation under the effect of UV radiation; five different types of geonets were selected, which can be categorized as polyamide (PA), polypropylene (PP), and polyethylene (PE) materials. A comprehensive experimental investigation was performed, including tension strength, peer strength, artificially accelerated aging, and SEM tests, to further establish a service life prediction method used for slope-protection design. The results showed that the tension strength, percentage of breaking elongation, and peer strength all depict a descending trend with aging-elapsed time, especially in the early 600 h. The decreasing tendency of these mechanical properties' magnitude differed in the diversity of direction and material type. Significant changes have been generated on the geonet surface after aging; materials with smooth surfaces exhibit a strong ability against strength degradation. Fitting results affirmed the predictive technique as a useful engineering tool for tension strength assessments, offering guidelines for using and designing of geonets for slope-protection structures.

Investigation of new analysis methods for simultaneous and rapid identification of five different microplastics using ATR-FTIR spectroscopy and chemometrics

Microplastic (MP) pollution in water has become one of the most important global problems of our time. The development of appropriate and rapid analysis techniques is of great importance at the beginning of the studies aimed at solving this problem. In the presented study, in order to perform the qualitative and quantitative analysis of MP forms of polyamide (PA), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET), which are known to be most abundant in water, in a fast and easy way, new Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy methods were tried to be developed by utilizing chemometric methods. While principal component analysis (PCA) was applied for qualitative analyses, partial least squares (PLS) models were created for quantitative analyses. Raw, 1st, and 2nd order derivatives of all spectra and their spectra with different levels of smoothing points were taken and 24 different chemometric models were created for each MP. In interpreting the statistical performances of the developed PCA and PLS models, different parameters were used. According to the obtained results, the qualitative discrimination of all polymer types was successfully achieved. It was determined that the PLS models developed for the quantitative determination of mixtures consisting of different concentrations of MP types could not be at the desired level. However, it was determined that the PLS models developed for PA, PE, PP, and PET, where the normal spectrum was used, could give quantitatively accurate results, albeit partially.

Studies on mechanical, thermal, rheological and impact properties of polyamide 6 and thermoplastic copoly(ether-ester) elastomer blends

A series of blends of polyamide 6 (PA-6) (nylon-6) and a copoly(ether-ester) (HYTREL) were prepared by the melt-mixing method using a twin-screw extruder. The HYTREL content was varied from 0% to 25% by weight of the blends. Thermal and rheological studies on the blends using differential scanning calorimetry, dynamic mechanical analysis (DMA) and capillary rheometer showed that the blends are semi-compatible in nature. A two-phase globular morphology of the blends was established by scanning electron microscope (SEM) analysis. The matrix ligament thickness (interparticle distance) in each blend composition was measured from SEM images and compared with those calculated using Wu’s equation. The impact strength of the blends as measured by the Izod impact test was found to be substantially improved as a result of the incorporation of HYTREL. The toughness determined by loss area calculation from the DMA spectrum showed similar trends. The toughness was found to be optimal in a blend having 15 wt.% HYTREL with an average dispersed particle size of around 450 nm. The yield stress of the blend decreased in comparison to PA-6 on addition of HYTREL, while the thermal stability of PA-6 remained unaffected.

Optimizing Surface Characteristics of Stainless Steel (SUS) for Enhanced Adhesion in Heterojunction Bilayer SUS/Polyamide 66 Composites.

The increasing environmental concerns and stringent regulations targeting emissions and energy efficiency necessitate innovative material solutions that not only comply with these standards but also enhance performance and sustainability. This study investigates the potential of heterojunction bilayer composites comprising stainless steel (SUS) and polyamide 66 (PA66), aiming to improve fuel efficiency and reduce harmful emissions by achieving lightweight materials. Joining a polymer to SUS is challenging due to the differing physical and chemical properties of each material. To address this, various surface treatment techniques such as blasting, plasma, annealing, and etching were systematically studied to determine their effects on the microstructural, chemical, and mechanical properties of the SUS surface, thereby identifying mechanisms that improve adhesion. Chemical etching using HNO3/HCl and CuSO4/HCl increased surface roughness and mechanical properties, but these properties decreased after annealing. In contrast, K3Fe(CN)6/NaOH treatment increased the lap shear strength after annealing. Blasting increased surface roughness and toughness with increasing spray pressure and further enhanced these properties after annealing. Contact angle measurements indicated that the hydrophilicity of the SUS surface improved with surface treatment and further improved due to microstructure formation after annealing. This study demonstrates that customized surface treatments can significantly enhance the interfacial adhesion and mechanical properties of SUS/polymer heterojunction bilayer composites, and further research is recommended to explore the long-term stability and durability of these treatments under various environmental conditions.

Investigation on the creep mechanism of PA6 films based on quasi point defect theory

Polyamide 6 (PA6) films with significant α relaxation process was selected as the model system. The creep behavior and rheological mechanism during deformation in the amorphous regions of semi-crystalline polymers are systematically investigated by carrying out creep experiments. Based on the quasi point defect (QPD) theory, the complete physical process of PA6 film creep behavior from elasticity to viscoelasticity and viscoplasticity was analyzed and modeled from the perspective of structural heterogeneity. The results demonstrate that the creep deformation of PA6 film is a typical thermo-mechanical coupling and nonlinear mechanics process, and potential creep mechanisms corresponds to stress-induced local shear deformation enhancement and thermal activation-induced particle flow diffusion. The elastic-plastic transition involved in the creep deformation process of semi-crystalline polymer originates from the activation of quasi-point defective sites in the amorphous region, the expansion of sheared micro-domains and irreversible fusion. The generalized fractional Kelvin (GFK) model is proposed, and the physical meaning of parameters is explained by combining the quasi point defect theory and creep delay spectrum(L(τ)). Finally, the effectiveness of the GFK model and the QPD theory in studying the deformation behavior of PA6 films was validated by comparing experimental data with theoretical results, which theoretically reveals the structural evolution of PA6 film during creep process.

Monitoring the process of interfacial polymerization for fabrication of polyamide reverse osmosis membrane via molecular simulation based on π-π interaction between surfactant and monomer

Accurate regulation of the interfacial polymerization (IP) process is prerequisite for preparation of thin film composite reverse osmosis (RO) membranes with ideal polyamide (PA) layers, and surfactant assembly-regulated IP (SARIP) is proved to be an effective approach. However, mechanism in molecular level for modulation of IP based on surfactants is still inadequate. Here, sodium dodecylbenzene sulphonate (SDBS) and sodium dodecyl sulfate (SDS) have been chosen as surfactants to make comparison of the IP process based on π-π interaction between surfactant and monomer via molecular simulation. As illustrated by Molecular Dynamics (MD) simulations, surfactants enlarge the width of the miscible zone, increase the diffusion rate together with the relative concentration of MPD in the miscible zone, as well as regulate the position of IP reaction towards the aqueous phase. Compared to SDS, SDBS makes the diffusion of MPD in good order, thus avoiding the severe variation in structure and morphology on PA layer. As calculated by DFT, higher interaction energy between the phenyl group of MPD and SDBS based on the π-π interaction is achieved, leading to uniform distribution of MPD close to the phenyl group of SDBS instead of escaping violently into miscible zone. Thus, strong consistency between the position of IP reaction and the height of the phenyl group in SDBS is emerged, which further explains the intrinsic reason for the variation of the IP position and the modulation of the PA microstructure. The mechanism for IP regulation based on SARIP at molecular level is finally proposed via molecular simulation, providing new idea for the preparation of high-performance RO membranes.

Characteristics of soil microplastics and ecological risks in the Qilian Mountains region, Northeast Tibetan Plateau

Microplastics (MPs) pollution has become a vital global environmental issue. However, comprehensive understanding of the ecological risks of MPs in soils of Northeast Tibetan Plateau still requires further study. In this study, we used the Agilent 8700 Laser Direct Infrared (LDIR) spectroscopy to analyze the characteristics of 10–1000 μm MPs in soils of different vegetation types throughout the Qilian Mountains basin, and to comprehensively explore the ecological risks of MPs in various ecological environments. The results indicate that MPs abundance is highest in soil of shrub areas (26,369 ± 32,147 items kg−1-dry weight (dw)), followed by woodland (22,215 ± 22,544 items kg−1-dw), desert (17,769 ± 9,040 items kg−1-dw), grassland (16,462 ± 12,872 items kg−1-dw), and forest (15,662 ± 13,857 items kg−1-dw). MPs in soils of different vegetation types show similar physical and chemical characteristics, with the shape dominated by fragments (93%–96%), followed by fibers and a few beads, with dominant sizes of 10–30 μm (63%–76%), and polymers dominated by polyamide (PA) and polyethylene terephthalate (PET). Additionally, the environmental risks posed by the fundamental characteristics of MPs have been quantified through the Pollution Load Index (PLI), Pollution Hazard Index (PHI), and Potential Ecological Risk Index (PERI) models. According to the PLI assessment, the current levels of MPs in the environment have not yet imposed significant burdens on the ecosystem. However, the results of PHI and PERI indicate a higher risk of MPs pollution in the Qilian Mountains. This study offers vital information for MPs pollution in the whole Qilian Mountains regions and their potential environmental risks in remote areas’ soil.

Sustainable preparation of nano monodispered ATP based color master batch and its application in PA6

AbstractAs a representative of dope‐dye, the color masterbatch method has been widely applied in modern dyeing processes, while it has difficulties in solving the dispersibility of inorganic pigments color master batch in the polymer matrix. In this work, attapulgite (ATP) was used as the adsorption carrier of inorganic pigments to prepare color‐dyed attapulgite (CD‐ATP). The selected environmentally friendly inorganic pigments were well adsorbed by ATP in KOH aqueous solution, and could stably be monodispersed in KOH aqueous solution for more than 168 h. Moreover, the KOH aqueous solution could be reused repeatedly, thereby, a sustainable method to prepare novel CD‐ATP was realized. By blending the as‐prepared CD‐ATP with polyamide‐6 (PA6), a series of dope‐dyed colorful PA6 composites was prepared. Scanning electron microscope (SEM) results indicated that the CD‐ATP was still monodispersed in the PA6 matrix, and endowed PA6 with a vivid color. Further studies show that the adding of CD‐ATP had little influence on the properties of PA6, but significantly reduced the water adsorption. This novel color‐dyed ATP has potential implications in making paper‐making blankets and is highly expected to have more extensive applications in many fields of life.

Elaboration and Experimental Characterizations of Copper-Filled Polyamide Micro-Composites for Tribological Applications

Polyamide 66 (PA66) has been used for dynamic bearing applications due to its good wear and abrasion resistance, hardness, and rigidity. PA66/copper micro-composites were studied with respect to micro-mechanical, tribological, and structural properties. A mixing step followed by injection molding was used to develop the different composites: PA66+5 wt.% Cu, PA66+10 wt.% Cu, and PA66+15 wt.% Cu. The morphological aspects of the composites were studied using scanning electron microscopy and microtomography. Good dispersion and adhesion of Cu particles across the matrix were also seen. DSC analysis showed a slight improvement in the % of crystallinity and thermal characteristics of the composites, particularly with 5 wt.% filler. Additional crystallization enhanced the tensile performance of the composites, including the modulus, elongation at break, and tensile strength. Nanoindentation tests also indicated an increase in indentation hardness and elastic modulus as a function of the filler fraction. A pin-on-disk tribometer was used to study the friction and wear properties of neat PA66 and copper-filled PA66 composites. It was found that the composite with 5 weight percent copper had the best wear resistance. A progressive decrease in the friction coefficient was also seen. Copper filler increases hardness and may effectively reduce the temperature at contact interfaces during rotating cycles.

Three-Dimensionally Printed Ternary Composites of Polyamide: Effect of Gradient Structure on Dimensional Stability and Mechanical Properties

Fused deposition modeling (FDM) 3D printing has the advantages of a simple molding principle, convenient operation, and low cost, making it suitable for the production and fabrication of complex structural parts. Moving forward to mass production using 3D printing, the major hurdle to overcome is the achievement of high dimensional stability and adequate mechanical properties. In particular, engineering plastics require precise dimensional accuracy. In this study, we overcame the issues of FDM 3D printing in terms of ternary material compounds for polyamides with gradient structures. Using multi-walled carbon nanotubes (MWCNTs) and boron nitride (BN) as fillers, polyamide 6 (PA6)-based 3D-printed parts with high dimensional stability were prepared using a single-nozzle, two-component composite fused deposition modeling (FDM) 3D printing technology to construct a gradient structure. The ternary composites were characterized via DSC and XRD to determine the optimal crystallinity. The warpage and shrinkage of the printed samples were measured to ensure the dimensional properties. The mechanical properties were analyzed to determine the influence of the gradient structures on the composites. The experimental results show that the warpage of pure polymer 3D-printed parts is as high as 72.64%, and the introduction of a gradient structure can reduce the warpage to 3.40% by offsetting the shrinkage internal stress between layers. In addition, the tensile strength of the gradient material reaches up to 42.91 MPa, and the increasing filler content improves the interlayer bonding of the composites, with the bending strength reaching up to 60.91 MPa and the interlayer shear strength reaching up to 10.23 MPa. Therefore, gradient structure design can be used to produce PA6 3D-printed composites with high dimensional stability without sacrificing the mechanical properties of PA6 composites.

Translaminar fracture toughness characterisation for a glass fibre/polyamide 6 laminated composite by a novel approach based on fictitious material concept

This paper proposes a novel approach for the characterisation of the material fracture toughness associated with translaminar tensile failure, consisting in the application of the Fictitious Material Concept (FMC) by using the testing configuration of the Modified Two Parameter Model (MTPM). The main advantage of such an approach is to avoid the use of nonlinear fracture mechanics for material fracture toughness characterisation. The novel approach is applied to compute the translaminar fracture toughness of a unidirectional glass fibre (GF)/polyamide 6 (PA6) laminated composite. Moreover, the experimental campaign carried out is numerically simulated by means of a micromechanical finite element model, and the fracture toughness is computed by employing two different approaches, that is, the novel one and the MTPM. The present study proves, for the first time, that the Fictitious Material Concept can be applied by considering both experimental and numerical structural responses since it provides, in both cases, quite satisfactory accuracy in term of laminated composite fracture toughness. Therefore, the great advantage is that, when a validated numerical model is available, experimental campaigns may be avoided, saving time and money. Moreover, it is proved that the FMC can be used to investigate specimen size effect on fracture toughness.

Thermomechanical Assessment of Recovered PA12 Powders with Basalt Filler for Automotive Components

Additive manufacturing processes allow for precise and efficient production, but it is estimated that one-third of the materials used results in waste. Further improvement in a sustainable perspective could come from the ability to manage these scraps and from the exploration of different routes for recovery and reuse. The Selective Laser Sintering process is particularly sensitive to this issue due to the waste ratio which can reach a very high quantity of not-sintered virgin powders. In this research study, recovered PA12 powders, preliminarily characterized through thermal and mechanical analysis, were mixed with 15% basalt powder to improve their aspect and thermomechanical resistance. The influence of basalt powder (BP) on mechanical properties as well as on the thermal stability of polyamide12 (PA12) powder composites was investigated. A study conducted on mechanical properties showed that polymeric composites’ stiffness and hardness were influenced by adding filler, thus improving mechanical parameters. On the other hand, the application of thermogravimetric analysis allowed us to determine the composite’s thermal stability. The objective is to obtain a recovered fully biobased material that could be used to substitute the petroleum-derived polymeric ones currently employed in the production of interiors and shells in the automotive sector.

Selective hydrophilization based on alkaline-catalyzed alcoholysis: An approach to enhance the flotation of waste polyesters

Polyester plastics, constituting a substantial segment of the global plastic market, offer considerable potential market for the polyesters recycling. This study proposed an efficient separation technology for waste polyesters through flotation assisted by alkaline-catalyzed alcoholysis modification. The alkaline-catalyzed alcoholysis modification facilitates the selective hydrophilization of waste polyesters, regulating their float-sink behavior in flotation. According to the polyester floatability, the hydrophilicity of the modified polyesters is in order of PA6 > PET ≈ PU > PC > PMMA. Due to the different C–O and C–N bond strength, the modification selectively induced alcoholysis on the polyesters surface, enhancing their hydrophilicity by increasing the number of rough structure and hydrophilic functional groups on surfaces rather than introducing heteroatoms. The sinking products in flotation, including polyamide 6 (PA6), polyethylene terephthalate (PET), and polyurethane (PU), could be separated from the floating products, such as polycarbonate (PC), and polymethyl methacrylate (PMMA). The binary separation was achieved under optimum conditions. The recovery and purity of PA6, PET, and PU could reach 100.0 % and 100.0 %, 100.0 % and 85.7 %, 79.9 % and 83.1 %, respectively. Consequently, the heterogeneous alcoholysis reactivity contributes to the selective hydrophilization of waste polyesters. This study established a hydrophilicity order of modified polyesters, and promoted flotation separation of waste polyesters.

Microplastic-contamination in the flesh and gastrointestinal tract of nile tilapia (Oreochromis niloticus) reared in floating net cages at lake Ranu Grati, Pasuruan, East Java, Indonesia

In recent years, microplastics (MPs) have emerged as a prominent environmental problem in waters and environments, including lake waters. Microplastics in freshwater, such as those in floating net cages (FNC), can be consumed by Nile tilapia (Oreochromis niloticus), one of the commercially available cultivated fish in Indonesia. This study aims to determine the prevalence of microplastics and compare their characteristics in the surface water, flesh, and gastrointestinal tract (GIT) of Nile Tilapia (O. niloticus) at Lake Ranu Grati, Pasuruan, East Java, Indonesia. Visual characteristics of MPs were observed using a stereo microscope, and polymers were analysed by ATR-FTIR (Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy). The abundance of MPs from water sample locations in Lake Ranu Grati reached 1116 MPs particles. In the water samples, the inner and outer sides of the FNC are dominated by the MPs with a size range of 251–500 µm and 1001-2000 µm in the milieu of Ranu Grati Lake. The most common MPs' types and colours are fibre and black, dominated by Polyethylene (PE). In 25 O. niloticus samples, 576 particles of MPs were found in the flesh and 724 particles in the gastrointestinal tract (GIT). This study found no significant variation in microplastic abundance between flesh and GIT samples (p>0.05; Mann-Whitney U test). Microplastics in Nile Tilapia flesh samples were dominated by blue fibres with a size range of 101–250 µm, and the polymer found was PA (polyamide). Meanwhile, in the GIT samples, microplastics were dominated by black fibre, with a size range of 251–500 µm, and the polymer found was PA (polyamide).