Reduced Water Permeability Research Articles

Silicon-Doped Graphene Oxide Quantum Dots as Efficient Nanoconjugates for Multifunctional Nanocomposites.

Graphene oxide quantum dots (GOQDs) hold great promise as a new class of high-performance carbonaceous nanomaterials due to their numerous functional properties, such as tunable photoluminescence (PL), excellent thermal and chemical stability, and superior biocompatibility. In this study, we developed a facile, one-pot, and effective strategy to engineer the interface of GOQDs through covalent doping with silicon. The successful covalent attachment of the silane dopant with pendant vinyl groups to the edges of the GOQDs was confirmed by an in-depth investigation of the structural and morphological characteristics. The Si-GOQD nanoconjugates had an average dimension of ∼8 nm, with a graphite-structured core and amorphous carbon on their shell. We further used the infrared nanoimaging based on scattering-type scanning near-field optical microscopy to unveil the spectral near-field response of GOQD samples and to measure the nanoscale IR response of its network; we then demonstrated their distinct domains with strongly enhanced near fields. The doping of Si atoms into the sp2-hybridized graphitic framework of GOQDs also led to tailored PL emissions. We then sought to explore the potential applications of Si-GOQDs on the surface of plastic films where poly(dimethylsiloxane) (PDMS) served as a bridge to tightly anchor the Si-GOQDs to the surface. The bi-layered coated films which were built with co-assembly of Si-GOQDs and PDMS contributed to suppressing the transmission of water molecules due to the generation of compact and less accessible passing sites, achieving a nearly twofold reduction in water permeability compared to the single-layered coated films. The nanoindentation and PeakForce quantitative nanomechanical mapping showed that Si-GOQD-coated substrates were softer and more deformable than those coated only with PDMS. The co-assembly of PDMS and Si-GOQDs yielded films that were less stiff than those made from PDMS alone. Our findings provided conceptual insights into the importance of nanoscale surface engineering of GOQDs in conferring excellent dispersibility and enhancing the performance of nanocomposite films.

Covalent organic framework membrane reconstructed through intra-pore reaction having tunable performance for molecular separation

An amine-rich covalent organic framework (COF) membrane was firstly designed and fabricated through the interfacial polymerization (IP) of 3,3′-diaminobenzidine (DAB) and 1,3,5-triformylphloroglucinol (Tp) reactive monomers on polysulfone (PSf) substrate. The as-prepared TpDAB/PSf membrane displayed an ultra-high water permeability of ∼ 61 L⋅m−2⋅h−1⋅bar−1 and excellent dye/salt separation performance with 97.7% rejection of congo red and no rejection of MgCl2 or Na2SO4. And then, small molecules with acyl chloride groups including sebacyl-chloride (SBC) or 1,3,5-trimellityl-chloride (TMC) were introduced to reconstruct the nanoporous structure of COF through intra-pore reaction with amine groups of the TpDAB separation layer. Although the TpDAB-SBC/PSf and TpDAB-TMC/PSf membranes exhibited reduced water permeability of ∼ 15 L⋅m−2⋅h−1⋅bar−1, both showed high rejection or desalination performance toward small molecules, such as ≥ 95% dye rejection (Mw > 461.4 Da), ∼10% Na2SO4 rejection and nearly no rejection of MgCl2. Therefore, a facile and rapid intra-pore reaction was feasible for reconstructing the nanoporous structure of amine-rich COF membranes to achieve tunable performance for the removal, purification and desalination of small molecules.

Impact of prolonged water‐gas flow on the performance of polyacrylamide

AbstractExcessive water production from natural reservoirs is a major challenge in oil and gas industry. Relative permeability modifiers (RPM) are used to selectively reduce water production with minimum effect on the hydrocarbon production. This work examined the performance of polyacrylamide in terms of its water control efficiency at prolonged water‐gas flowing cycles. During each cycle, as the volume of injected water increased, the RPM demonstrated stronger performance in terms of reducing water permeability. This is attributed to the swelling of polymer layer adsorbed to the pore surfaces. Conversely, during each cycle, higher volume of gas injection led to less reduction in the gas effective permeability (PRg) which is due to polymer shrinkage. The reduction in water absolute permeability (PRw) of the treated micromodel in each injection cycle was significantly greater than the reduction in gas permeability. Interestingly, as water‐gas cycles progressed, a significant increase in water permeability reduction was observed. It is also found that polymer expansion and shrinkage are reversible. As such, the RPM performance depends on the injected fluid, injected fluid volumes and water‐gas injecting cycling. We thus conclude that that polymer swelling, and shrinkage and polymer‐gas interaction play a vital role in RPM performance.

Numerical modelling and in-situ experiment for self-sealing of the induced fracture network of drift into the Callovo-Oxfordian claystone during a hydration process

The excavation damage zone surrounding an underground tunnel/gallery, and in particular its evolution, is being studied for the performance assessment of a radioactive waste underground repository. This paper focuses on numerical analysis of the self-sealing of the damaged zone based on an in-situ CDZ experiment for exploring the self-sealing of excavation damage zone during a hydration process. A plastic damage model is employed to describe the mechanical behaviour of Callovo-Oxfordian claystone (COx), and an added deformation model coupled with the standard Biot’s model to simulate the significant deformation of COx claystone during the change of water content. Crack estimation and permeability evaluation of unsaturated fractured COx claystone are carried out through a post-processing method based on the fracture energy regularization and the cubic law, respectively. The validation of the proposed model is performed by numerical simulation of: (1) COx claystone swelling and triaxial compression tests, (2) self-sealing of fractured COx claystone samples during hydration process, (3) self-sealing of the damaged zone during a hydration process. Comparisons between the numerical and experimental results demonstrate the reliability of the proposed model to accurately describe the self-sealing of the fractured COx claystone, and the global water permeability reduction in hydration illustrates the accomplishment of the self-sealing of damaged zone.

Synthesis of LTA zeolite membranes from metal alkoxides and examination of the pervaporation performance

In the dehydration of ethanol, membrane separation using LTA zeolites is commonly employed in place of distillation due to its lower energy consumption. In the membrane separation process, a thin zeolite membrane is preferred to reduce the permeation resistance of water in the membrane. From the aspect of reducing the resistance, the authors successfully prepared LTA zeolite membranes from metal alkoxides. The influence of the crystal growth conditions on the separation performance was investigated by the pervaporation of an ethanol-water mixture. As a result, the thickness of the LTA zeolite membrane could be decreased to less than 3 μm by optimizing the aging time of the secondary growth solution and secondary growth time. For 90 wt% ethanol solution at 343 K, the permeation flux and separation factor of the membrane were 6.3 kg m −2 h −1 and >10,000, respectively. In this paper, the SEM observation and XRD analysis were examined to understand the structure of zeolite membrane. As a result, the change in crystallographic orientation caused by the aging was proposed as key factor of permeability of the membrane. • LTA zeolite membrane was prepared by hydrothermal treatment of seed crystals with hydrolyzed metal alkoxide. • Influence of aging of secondary growth solution of the membrane on its pervaporation performance was examined. • Water permeability of the membrane decreased as the aging proceeded. • X-ray diffraction analysis of the membrane surface revealed that orientation of the crystallites in the LTA layer changed to less (200) plane being parallel to the surface of the membrane. • Decrease of (200) oriented plane by the aging may be responsible for the reduction of water permeability of the membrane.

DEVELOPMENT OF SELECTIVE GROUTING COMPOSITIONS BASED ON BITUMINOUS EMULSIONS FOR WATER INSULATION WORKS

To increase the efficiency of water inflow isolation in oil wells, selective grouting compositions are preferred. The use of selective isolation methods provides for selective clogging of water inflow channels while maintaining the permeability of oil-saturated reservoir intervals. The mechanism of selectivity realization for different groups of grouting compositions is shown. It is noted that the selectivity of the action of these compositions is significantly affected by the permeability heterogeneity of the formation. In this case, the water primarily flows through the high-permeable interlayers, where the grouting composition will be pumped in a larger volume than in the low-permeable interlayer during water insulation works. In this paper, we continue to study selective grouting compositions that clog the pore space with a material that is subsequently soluble in oil and insoluble in water. The possibility of using bitumen emulsions, including commercially available road emulsions, is analyzed. The use of bituminous emulsions as water-insulating compositions has a number of advantages: due to the low viscosity of the direct emulsion, it easily penetrates into the porous medium. At the same time, bituminous emulsions have high thermal stability. The resulting bitumen film is impervious to water and is sufficiently resistant to aggressive media (acids and alkalis). The objects of the study were used bitumen road emulsion cationic grade EBDK B-52 and acrylic dispersions, which were intended to increase the adhesion of bitumen to the surface of rock and metal. Commercially produced reagents of the Lacroten brands (E-081, E-31, E-082, E-43), Lacryl 4443 were used as acrylic dispersions. Studies of bituminous emulsions and acrylic dispersions for adhesion to the surface of metal, carbonate and terrigenous rocks have been carried out, from which it follows that acrylic dispersions with a low pH (3.0-3.6) are an effective means of processing samples. Filtration studies indicate the selective properties of the bitumen emulsion. When injecting B-52 bitumen emulsion for both the bulk model and the ideal crack model, there is a general tendency to reduce water permeability: 32.8 % for the bulk model and 33.6 % for the ideal crack model. When conducting filtration studies with the initial injection of acrylic dispersion followed by injection of the emulsion, in all experiments, filtration attenuation is observed in both the water-saturated and oil-saturated reservoir models. According to the results of the conducted studies, for the isolation of water-saturated interlayers, it is proposed to carry out works according to the scheme of selective isolation using bituminous emulsion B-52; and when carrying out works on the elimination of behind-the-casing flows, disconnecting water-filled layers and eliminating the leakage of production columns in the coupling joints, sequential injection of acrylic dispersion and bituminous emulsion is provided.

Molecular Characterization of an Aquaporin-2 Mutation Causing Nephrogenic Diabetes Insipidus.

The aquaporin 2 (AQP2) plays a critical role in water reabsorption to maintain water homeostasis. AQP2 mutation leads to nephrogenic diabetes insipidus (NDI), characterized by polyuria, polydipsia, and hypernatremia. We previously reported that a novel AQP2 mutation (G215S) caused NDI in a boy. In this study, we aimed to elucidate the cell biological consequences of this mutation on AQP2 function and clarify the molecular pathogenic mechanism for NDI in this patient. First, we analyzed AQP2 expression in Madin-Darby canine kidney (MDCK) cells by AQP2-G215S or AQP2-WT plasmid transfection and found significantly decreased AQP2-G215S expression in cytoplasmic membrane compared with AQP2-WT, independent of forskolin treatment. Further, we found co-localization of endoplasmic reticulum (ER) marker (Calnexin) with AQP2-G215S rather than AQP2-WT in MDCK cells by immunocytochemistry. The functional analysis showed that MDCK cells transfected with AQP2-G215S displayed reduced water permeability compared with AQP2-WT. Visualization of AQP2 structure implied that AQP2-G215S mutation might interrupt the folding of the sixth transmembrane α-helix and/or the packing of α-helices, resulting in the misfolding of monomer and further impaired formation of tetramer. Taken together, these findings suggested that AQP2-G215S was misfolded and retained in the ER and could not be translocated to the apical membrane to function as a water channel, which revealed the molecular pathogenic mechanism of AQP2-G215S mutation and explained for the phenotype of NDI in this patient.

Utilization of municipal solid waste incineration bottom ash (IBA) aggregates in high-strength pervious concrete

This study presents the use of IBA for the production of eco-pervious concrete, aiming at enhancing the recycling rate of IBA in construction materials. The IBA aggregates are used to replace the natural aggregates (NA) in various percentages (0%, 25%, 50%,75% and 100% by volume). The effect of IBA replacement ratios and casting methods on the mechanical properties, water permeability, porosity, density and thermal conductivity of the pervious concrete were determined. The volume stability of the pervious concrete incorporating IBA was evaluated. The results indicated that the appropriate content of IBA could benefit the mechanical properties due to the internal curing effect of IBA. However, the excessive content of IBA in the pervious concrete led to reduced water permeability, connected porosity and mechanical properties. Even so, the pervious concrete containing 100% IBA could achieve the required permeability and compressive strength for permeable pedestrian pavers (JIS A 5371). In addition, the incorporated IBA in pervious concrete causes little volume expansion from the reaction between alkalis and components consisting of metallic aluminum and glass in IBA owing to its high connected porosity. Furthermore, the pervious concrete incorporated IBA had a low density and thermal conductivity, showing the potential to be applied in thermal insulation areas.

Anti-filtration calculations of explosion-discharge dams

In this work, for a homogeneous dam, the issues of filtration-suffusion strength of an explosive-fill dam are considered. Ways to reduce water permeability are given. By clogging with fine-grained soils, affecting the strength and stability of the blast-fill dam. The paper describes the principle of colmatage depending on. The paper presents the principle of colmatage depending on the particle size distribution. In addition, the maximum colmatage size and methods, as well as the colmatage technology and the colmatant preparation method are given here.

Development of Self-Cured Sustainable Concrete Using Local Water-Entrainment Aggregates of Vesicular Basalt

The environmental and economic concerns pertaining to the construction industry have necessitated the development of sustainable concrete. Durability and strength are the two primary properties which determine the sustainability of concrete. This study evaluated the performance of self-cured concrete produced from local vesicular basalt porous aggregates. The durability indicators, porosity, permeability and pore size of the hardened concrete, were obtained from the water sorptivity (water permeability under capillary action) test, the water permeability under pressure action test and the Brunauer–Emmett–Teller (BET) surface area test and strength was evaluated in terms of compressive strength of concrete. The concrete specimens were produced with 10% porous vesicular basalt aggregate in replacement of coarse aggregate. The concrete specimens were tested at 3, 7 and 28 days. The self-curing effect on concrete strength was evaluated against water, air and membrane cured specimens, at surface/volume ratio of 26.4/40 and w/c ratio of 0.35/0.5. A 20% decrease in sorptivity coefficient, 10% increase in solid surface area and about 10% increase in compressive strength of the self-cured concrete was observed over the conventionally cured concrete. The study concludes that the addition of water-entrainment aggregates to concrete reduces water permeability, results in a finer pore structure of concrete and increases the quality and durability of concrete.

The Deafening Importance of Aquaporin‐4: The Role of Potassium Regulation in Hearing Loss

Hearing is heavily dependent on Aquaporin 4 (AQP4), the principal protein that facilitates water transport through the cell membrane of epithelial supporting cells in the inner ear, which also house the potassium channels responsible for recycling and regulating K+ ions, thus playing a vital role in the equilibration of the cellular volume in response to transcellular K+ fluxes. When the AQP4 is unable to maintain equilibrium within the cell, it dramatically affects the potassium cycle and ultimately deafness due to a lack of potassium ions in the endolymph, and the action potential isn't enough to pass on the vibration to the brain. According to Nicchia, et. al, a study done in 2010 found a heterozygous missense mutation in the gene which causes an Asp/Glu substitution at position 184 (D184E) which leads to a change in the D-loop of the protein. The mutated D-loop is more hydrophobic, reducing water gating and thus, reducing water permeability. This upset in water equilibrium along with the mutation slowing down and reducing the swelling kinetics leads to deafness. In that study, the mutation reduced the rate of cell swelling by 34.7 percent. Similarly, when there is an AQP4 deficiency, the existing AQP4 is not enough to properly equilibrate the cellular volume, which lowers the endolymphatic K+ concentration, causing the individual to be hearing impaired. In this study, we examined the effects the mutation had on hearing loss and how that differed from the effects of simply having a deficiency in AQP4 to further understand its role in hearing loss. The Mahtomedi MSOE Center for BioMolecular Modeling MAPS Team used 3-D modeling and printing technology to examine structure-function relationships of AQP4 in the ear. The visual model will be a valuable tool in developing our story.

Effect of hydrophobic agent in cement and concrete : A Review

Hydrophobic agents have been used in cement and concrete to reduce water penetration in concrete since many years. Hydrophobic agents are the materials that are employed in cement for enhancing the contact angle between the water and the concrete surface. Fatty acids and their fractions have been introduced in the cement as either phase change materials or as an admixture to minimize water ingress into concrete. Many alkenes, oils, fats, and greasy substances come under the category of hydrophobic molecule. Due to reduction in water permeability, hydrophobic agent enhances the durability and aesthetic appearance of the concrete. Since the mid-20th century, hydrophobic concrete found much popularity in building and construction. Hydrophobic are non-polar and lipophilic substances exhibits high contact angle thereby minimizes the rate of detrimental reactions. This article presents an overview of the work that has been carried out on the application of hydrophobic agents in cement mortar and concrete.

Effect of graphene oxide quantum dots on the interfacial polymerization of a thin-film nanocomposite forward osmosis membrane: An experimental and molecular dynamics study

We report an ultra-low loading of graphene oxide quantum dots (GQDs) into the polyamide (PA) layer of an outer-selective hollow fiber (OSHF) thin-film composite (TFC) membrane using the vacuum-assisted interfacial polymerization (VAIP) technique to improve the water permeability of OSHF TFC membranes without sacrificing membrane selectivity. Experimental results showed that GQD loading in the PA layer influenced membrane performance. The membrane with a GQD loading of 5 mg L−1 (TFN5) demonstrated an optimal water flux of 30.9 L m−2 h−1 and a specific reverse solute flux (SRSF) of 0.12 g L−1. To investigate the effect of GQDs on the interfacial polymerization (IP) reaction and membrane performance, molecular dynamics (MD) simulation was employed at the water-hexane and water-PA interfaces. The simulation results showed that GQDs decreased the reaction rate during the IP process by reducing the diffusivities of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). Additionally, GQDs reduced water permeability by acting as barriers to water molecules when present at a high concentration near the PA layer surface. At a very high loading, GQDs aggregated at the water-hexane interface and reduced the membrane selectivity by forming non-selective voids at the interface between the PA layer and GQDs. Together with the experimental findings, the MD simulation results delivered a good insight into the GQDs' effect on the TFC membrane's surface and transport properties at both macroscopic and microscopic levels.

Mathematical modeling of in-depth gel treatment for water control in a heterogeneous oil reservoir: gel kinetics coupled by flow transport model

ABSSTRACT This paper studies the performance of in-depth gel treatment in a heterogeneous oil reservoir. A two-dimensional numerical model considering the disproportionate permeability reduction mechanism is developed to study the effects of gel on water permeability reduction and water viscosity enhancement. To describe the in situ gel formation, kinetic equation is provided to address polymer-crosslinker reaction. We investigate the impacts of gel treatment on oil and water production rates, water cut and oil recovery in both homogenous and heterogeneous reservoirs. Results reveal a proper water-control in both reservoirs. The presented approach is considered useful in designing gel injection techniques to control water production.

Performance-Guided Design of Permeable Asphalt Concrete with Modified Asphalt Binder Using Crumb Rubber and SBS Modifier for Sponge Cities.

The construction of sponge city is a major green innovation to implement the concept of sustainable development. In this study, the road performance of permeable asphalt concrete (PAC), which displays pronounced water permeability and noise reduction that are favorable for sponge cities, has been improved with a two-fold modification using styrene–butadiene–styrene (SBS) and crumb rubber (CR). Four percent SBS and three different ratios (10%, 15%, and 20%) of CR have been used to modify the virgin asphalt binder. The Marshall design has been followed to produce PAC samples. To evaluate the asphalt binder performance, multiple-stress creep-recovery (MSCR) test, linear amplitude sweep (LAS) test, and engineering property test programs including softening point test, penetration test, and rotational viscosity test have been conducted. Freeze–thaw splitting test, Hamburg wheel-tracking test, resilient modulus test, and permeability coefficient test have been performed to evaluate the asphalt mixture performance. The test results show that the addition of SBS and CR reduces the permeability coefficient, but significantly improves the high temperature performance, fatigue performance, and rutting resistance as well as the resilient modulus. However, the optimum rubber content should not exceed 15%. Meanwhile, after adding CR and SBS modifier, the indirect tensile strength (ITS) and tensile strength ratio (TSR) increase. It indicates that the moisture stability and crack resistance have been improved by the composite modification effect.

Sugarcane juice concentration using a novel aquaporin hollow fiber forward osmosis membrane

In this work, the performance of a commercially available aquaporin HFFO membrane was studied for concentrating the sugarcane juice by adopting appropriate UF pretreatment technique. The influences of draw and feed solution flowrates, draw concentration and its direction of flow such as co-current or counter-current on water and reverse solute flux was evaluated in batch mode. The specific reverse solute flux for counter-current mode was found to be less compared to co-current mode of operation. Improved draw solution (NaCl) flowrate increased the water flux with reduced specific reverse solute flux. The FS concentration ratio was 1.65 within 12 min of batch FO operation by using 100 g L−1 draw solution. Membrane fouling was studied systematically with appropriate membrane cleaning strategy. The effect of UF clarified and raw sugarcane juice on FO membrane fouling was calculated and it was found that raw sugarcane juice led to severe membrane fouling that reduced water permeability after 60 min of operation. The membrane fouled by UF clarified juice was able to regenerate by DI water wash for 30 min, however in the case of membrane fouled by raw juice, an additional 0.1 M NaOH wash was required.

Reuse potential of spent RO membrane for NF and UF process

With the increasing demand on reverse osmosis (RO) membranes for water purification worldwide, the number of disposed membrane elements is expected to increase accordingly. Thus, recycling and reuse of end-of-life RO membranes should be a global environmental action. In this work, we aim to reuse the spent RO membrane for nanofiltration (NF) and ultrafiltration (UF) process by subjecting the spent membrane to solvent and oxidizing solution treatment, respectively. Our results showed that solvent-treated RO membrane could perform as good as commercial NF membrane by achieving similar separation efficiencies, but with reduced water permeability due to membrane surface fouling. By degrading the polyamide layer of RO membrane, the transformed membrane could achieve high water permeability (85.6 L/m2.h.bar) and excellent rejection against macromolecules (at least 87.4%), suggesting its reuse potential as UF membrane. More importantly, our findings showed that in-situ transformation on the spent RO membrane using solvent and oxidizing solution could be safely conducted as the properties of the entire spiral wound element did not show significant changes upon prolonged exposure of these two solutions. Our findings are important to open up new possibilities for the discarded RO membranes for reuse in NF and UF process, prolonging the lifespan of spent membranes and promoting the sustainability of the membrane process.

On the formation of a waterproofing shell around the underground structure lining in watered ground

To prevent the filtration of groundwater into the used underground structure in operation through its lining, it is proposed to make two waterproofing shells by the underground method around the outer surface of the lining of an underground structure; the upper one is made of the soil mass compacted by cementation with reduced water permeability and the lower one is made of the silicate cement. To make the upper shell, boreholes are drilled from an underground structure through its lining and the cement mortar is alternately injected through them into the watered ground providing its hydraulic fracturing; and to make the lower shell, injection pipes with a diameter of 102-152 mm are installed between the boreholes in the lining flush with its outer surface, the silicate cement mortar is alternately injected into the injection pipes, an incipient crack is created between the outer surface of the lining and the ground under the action of the mortar injection pressure on the ground opposite the injection pipe, an incipient crack is hydraulically extended along the contact of the lining with the ground and filled with the silicate cement mortar until refusal to absorb it. To determine the optimal parameters of the hydraulic separation process, tests were carried out on the laboratory table simulator.

Influence of drop irrigation and ways of primary tillage on yield and quality of fruits of sweet pepper in the conditions of the Republic of Dagestan

Relevance. In the conditions of the dry-steppe zone of lowland Dagestan, the beneficial effect of drip irrigation in combination with dump cultivation on the yield and quality of sweet pepper fruits from Moldova proved. Results. It experimentally established that maintaining moisture in the active 0.5 m soil layer during the growing season within 80- 100% of LMC against the background of dump processing to a depth of 0.23-0.25 m led to an increase in yield and biochemical composition of sweet pepper fruits. Differences in the influence of dump and small (0.10-0.12 m) tillage on agrophysical and phytosanitary indicators of fertility of meadow medium loamy soil were revealed. The data showing the inappropriateness of using small-scale cultivation under conditions of irrigated vegetable growing, which leads to a deterioration in the agrophysical indicators of fertility: increase in soil density by 0.05-0.08 t/m3, decrease in the number of water-resistant units by 7,0%, water permeability reduction by 22.0% and water resistance coefficient by 12.9%, 2.1 times increase in planting weed and 212.6% potential soil weed. Of the three studied thresholds of soil moisture (70, 80 and 90% LMC), it was established that the best conditions for plant growth and development, optimization of their photosynthetic activity are created at a humidity threshold of 80% LMC, at which the most efficient use of irrigation water is noted. Drip irrigation with maintaining the pre-irrigation threshold for soil moisture not lower than 80% of against the background of dump processing leads to an increase in the number of fruits on 1 plant, an increase in the mass of 1 fruit, which contributed to an increase in yield to 62 t/ha.

Biodegradable PLA/PBSA Multinanolayer Nanocomposites: Effect of Nanoclays Incorporation in Multinanolayered Structure on Mechanical and Water Barrier Properties.

Biodegradable PLA/PBSA multinanolayer nanocomposites were obtained from semi-crystalline poly(butylene succinate-co-butylene adipate) (PBSA) nanolayers filled with nanoclays and confined against amorphous poly(lactic acid) (PLA) nanolayers in a continuous manner by applying an innovative coextrusion technology. The cloisite 30B (C30B) filler incorporation in nanolayers was considered to be an improvement of barrier properties of the multilayer films additional to the confinement effect resulting to forced assembly during the multilayer coextrusion process. 2049-layer films of ~300 µm thick were processed containing loaded PBSA nanolayers of ~200 nm, which presented certain homogeneity and were mostly continuous for the 80/20 wt% PLA/PBSA composition. The nanocomposite PBSA films (monolayer) were also processed for comparison. The presence of exfoliated and intercalated clay structure and some aggregates were observed within the PBSA nanolayers depending on the C30B content. A greater reduction of macromolecular chain segment mobility was measured due to combined effects of confinement effect and clays constraints. The absence of both polymer and clays interdiffusions was highlighted since the PLA glass transition was unchanged. Besides, a larger increase in local chain rigidification was evidenced through RAF values due to geometrical constraints initiated by close nanoclay contact without changing the crystallinity of PBSA. Tortuosity effects into the filled PBSA layers adding to confinement effects induced by PLA layers have caused a significant improvement of water barrier properties through a reduction of water permeability, water vapor solubility and water vapor diffusivity. The obtaining barrier properties were successfully correlated to microstructure, thermal properties and mobility of PBSA amorphous phase.