Preparation of graphene oxide/poly(vinyl alcohol) composite membrane and pervaporation performance for ethanol dehydration

Although poly(vinyl alcohol) (PVA) membranes are widely used in solvent dehydration by pervaporation, the separation factor is rather limited. Considering this, novel PVA mixed matrix membranes with graphene oxide (GO) nanosheets were prepared. poly(acrylonitrile) ultrafiltration (PAN) membrane was used as support layer. The PVA/GO composite membranes were characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, thermogravimetric analysis and water contact angle. We also explored the pervaporation performance of the membrane for ethanol dehydration. GO slightly improves the thermal stability and crystallinity of the composite membranes. In addition, the hydrophilicity of the composite membranes is weakened after GO addition, but the crosslinking degree is increased, resulting a significant increase in the separation factor and a certain decrease in the total flux. With the amount of GO addition increases, the total flux of the PVA/GO composite membrane decreases, while the separation factor increases first and then decreases, and the preferred amount of GO addition is 2.0 wt%. Especially, the separation factor of the composite membranes with 2.0 wt% GO addition could reach 3 059, which is 16 times higher than PVA membranes, with the corresponding permeability flux is 145 g m⁻² h⁻¹.

The separation factor of the composite GOP-2.0 membranes could reach 3 059, which is 16 times higher than PVA membranes.     

Charged ultrafiltration membranes based on TEMPO-oxidized cellulose nanofibrils/poly(vinyl alcohol) antifouling coating

This study reports the potential of TEMPO-oxidized cellulose nanofibrils (T-CNF)/poly(vinyl alcohol) (PVA) coatings to develop functionalized membranes in the ultrafiltration regime with outstanding antifouling performance and dimensional/pH stability. PVA acts as an anchoring phase interacting with the polyethersulfone (PES) substrate and stabilizing for the hygroscopic T-CNF via crosslinking. The T-CNF/PVA coated PES membranes showed a nano-textured surface, a change in the surface charge, and improved mechanical properties compared to the original PES substrate. A low reduction (4%) in permeance was observed for the coated membranes, attributable to the nanometric coating thickness, surface charge, and hydrophilic nature of the coated layer. The coated membranes exhibited charge specific adsorption driven by electrostatic interaction combined with rejection due to size exclusion (MWCO 530 kDa that correspond to a size of ∼35–40 nm). Furthermore, a significant reduction in organic fouling and biofouling was found for T-CNF/PVA coated membranes when exposed to BSA and E. coli. The results demonstrate the potential of simple modifications using nanocellulose to manipulate the pore structure and surface chemistry of commercially available membranes without compromising on permeability and mechanical stability.

Crosslinked cellulose nanofiber-polyvinyl alcohol antifouling membrane.     

Boronate sol–gel method for one-step fabrication of polyvinyl alcohol hydrogel coatings by simple cast- and dip-coating techniques

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities. A mixture of PVA and DBA in aqueous ethanol is prepared as a coating agent. The long pot life of the mixture allows for the coating of a wide range of materials with hydrogel films by simple cast- and dip-coating techniques. The resultant films show negligible dissolution in water and the intrinsic hydrophilicity of PVA provides the films with functional properties, such as improved antifogging property and resistance to protein and cell fouling. The self-assembling process shows adaptive inclusion properties toward nanoscale materials, such as metal–organic coordination polymers and inorganic nanoparticles, affording composite films. Furthermore, the coating film exhibits a unique secondary functionalization reactivity toward boronic acid-appended fluorescent dyes, through which a variety of materials are converted into fluorescent materials.

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities.     

Preparation of ultra-high mechanical strength wear-resistant carbon fiber textiles with a PVA/PEG coating

Polyvinyl alcohol (PVA) is an organic polymer that is non-toxic, harmless to the human body, and has good biocompatibility. Polyethylene glycol (PEG) is a polymer that has good lubricity and compatibility. The unique graphite structure of carbon fibers can promote the potential application of carbon–fiber composites in tribology. This study explores the relationship between two kinds of organic polymer compounds and carbon fiber cloth (CFC), specifically a PVA/PEG composite coating that is impregnated on the CFC surface. The CFC is synthesized by chemical cross-linking, and the CFC composites (PVA/PEG/CFC) were synthesized. The tribological properties of PVA/PEG/CFC were tested under different concentrations, loads, and velocities. The effects of the different lubricants, surface morphologies, and tensile strengths on the mechanical and tribological properties of PVA/PEG/CFC were studied. In comparison to the original CFC, the friction coefficient and wear morphology of the composite material were reduced and the friction coefficient trend was stable. The addition of PVA/PEG improved the surface lubrication performance of the composite material and reduced the average friction coefficient. In addition, under the different lubrication mechanisms, oil as a lubricant can significantly reduce the friction coefficient and surface wear. In summary, the biocompatible coating process that is proposed in this study can effectively improve the tribological properties of the surface of the CFC.

Polyvinyl alcohol (PVA) is an organic polymer that is non-toxic, harmless to the human body, and has good biocompatibility. Polyethylene glycol (PEG) is a polymer that has good lubricity and compatibility. As a new coating material, PVA/PEG has good mechanical properties.     

Photocurable acrylate epoxy/ZnO–Ag nanocomposite coating: fabrication,mechanical and antibacterial properties

In this study, a UV-curable acrylate epoxy nanocomposite coating has been prepared by incorporation of ZnO–Ag hybrid nanoparticles. For this purpose, firstly ZnO–Ag hybrid nanoparticles were fabricated by a seed-mediated growth method. Then, these ZnO–Ag hybrid nanoparticles (2 wt%) were added into the UV-curable acrylate resin matrices. The photocuring process of nanocomposite was evaluated by various factors, such as the conversion of acrylate double bonds, pendulum hardness and gel fraction. Under the 4.8 s UV-exposure time for full crosslinking, the obtained data indicated that incorporation of ZnO–Ag nanohybrids into the coating matrix changed the crosslinking process of coating significantly. A mechanical teat indicated that the presence of nanohybrids in photocurable coating matrix enhanced its abrasion resistance from 98.7 to 131.6 L per mil (33.3%). The antibacterial test against E. coli over 7 h indicated that E. coli bacteria were killed totally by nanocomposite coating, whereas it was 2.6 × 10⁴ CFU mL⁻¹ for the neat coating without nanoparticles.

ZnO-Ag hybrid nanoparticles were fabricated by seed-mediated growth method and incorporated into the UV-curable acrylate resin matrice to form a composite. This improved the mechanical property of UV-cured coating and exhibited high antibacterial activity against E. coli.     

Novel cross-linked poly(vinyl alcohol)-based electrolyte membranes for fuel cell applications

Herein, a new series of polymer electrolyte membranes was prepared by chemically cross-linked poly(vinyl alcohol) (PVA) and sulfonated poly(ether sulfone) (SPES). A typical polymerization reaction was conducted using three different monomers i.e. bisphenol A, phenolphthalein, and 4,4′-dichlorodiphenyl sulfone. The SPES polymer was obtained by the post-sulfonation technique using chlorosulfonic acid as a sulfonating agent. The resultant SPES polymer at different concentrations was blended with cross-linked poly(vinyl alcohol). Structural analysis of the samples was conducted by FTIR, SEM, and XRD. Among the prepared PEM materials, PVA–SPES-20 blend membranes exhibited higher ion-exchange capacity and % water uptake values than those of the other membranes. In addition, the PVA–SPES-20 membrane exhibits the proton conductivity of 0.0367 S cm⁻¹ at 30 °C, whereas pristine PVA shows the proton conductivity of 0.0259 S cm⁻¹. The overall experimental results revealed that the PVA–SPES blend membranes are promising candidates for fuel cell applications.

A series of cross-linked poly(vinyl alcohol)-sulfonated poly(ether sulfone) blend membranes were prepared. The studies of physico-chemical properties revealed that the reported membranes are promising candidate for PEMFC applications.     

Synthesis and evaluation of eco-friendly carboxymethyl cellulose/polyvinyl alcohol/CuO bionanocomposites and their use in coating processed cheese

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese. Copper oxide nanoparticles (CuO-NPs) were prepared and added to a mixed solution of carboxymethyl cellulose (CMC)/polyvinyl alcohol (PVA) using compositions of 0.3, 0.6 and 0.9% (w/v). The CMC/PVA/CuO bionanocomposites were prepared by a solution casting method and used for coating processed cheese. The fabricated bionanocomposite films and CuO-NPs were characterized by TEM, SEM, EDEX, XRD, DLS, and FT-IR analysis. Inclusion of CuO-NPs decreased the gas transmission rate (GTR) and water vapor transmission rate (WVTR) of the prepared film. Also, the bionanocomposite suspensions exhibited high but variable inhibitory effects against several pathogenic bacteria and fungi. The impact of coating of processed cheese surfaces with the prepared bionanocomposite films on microbiological, physicochemical, textural and sensory properties of the processed cheese were assessed during 6 months of cold storage. Coating cheese with film containing CuO-NPs eliminated mould growth on the cheese surface and decreased significantly (P < 0.05) the total bacterial count of the cheese. Furthermore, coating of cheese decreased the moisture losses and retarded the increase in the cheese hardness during storage. The highest acceptability at the end of the storage period was given for processed cheese coated with the bionanocomposite containing 0.9% CuO-NPs. Thus, the obtained CMC/PVA/CuO bionanocomposite films could be a promising candidate for cheese packaging applications.

In the present study, we formulated and characterized CMC/PVA/CuO bionanocomposites to evaluate their use in coating processed cheese.     

Characterizing the interaction between methyl ferulate and human serum albumin by saturation transfer difference NMR

Methyl ferulate (MF) is an alkyl ferulate ester that widely exists in edible plants and has application value in the food and medicine industries. Thus, its effect on biological macromolecules should be considered. In this study, we exploit saturation transfer difference NMR (STD-NMR) to characterize the interaction of all protons of MF with human serum albumin (HSA) at the molecular level. STD-NMR and K_a (1.298 × 10³ M⁻¹) revealed that protons H1–6 and H8 bound to HSA with a medium affinity. Binding epitope mapping further showed that the aromatic ring played a key role in the HSA–MF interaction. STD-NMR site-marker-displacement experiments and circular dichroism spectroscopy revealed that MF prefered to bind to site II of HSA without changing the basic skeleton of HSA. Computer simulations confirmed these experimental results. Overall, this work elucidates the molecular level interaction of MF with HSA and provides new insights into the possibility of the potential applications of MF in the food and medicine industries.

STD-NMR technique characterized the recognition mechanism of methyl ferulate and human serum albumin qualitatively and quantitatively.     

Preparation of high-permeance ceramic microfiltration membranes using a pore-sealing method

A pore-sealing method for preparation of high-permeance alumina microfiltration (MF) membranes free of any intermediate layers is presented. It involves sequential coating of a polyvinyl butyral (PVB) layer and an alumina membrane precursor on the surface of the macroporous alumina support. An alumina MF membrane with no intermediate layers can be obtained on the support after pyrolysis of the PVB interlayer. The interlayer-free membrane prepared by this method has an average pore diameter of 0.26 μm and a water permeance of 1468 ± 81 L m⁻² h⁻¹ bar⁻¹ which is prominently higher than that of the ceramic membranes prepared with other techniques. The conspicuous increase of water permeance is speculated mainly due to the filtration resistance decrease of the interlayer-free ceramic membrane.

A pore-sealing method for preparation of high-permeance alumina microfiltration (MF) membranes free of any intermediate layers is presented.     

Enhanced desalination using a three-layer OTMS based superhydrophobic membrane for a membrane distillation process

Superhydrophobic membranes are essential for improved seawater desalination. This study presents the successful casting of a three-layered membrane composed of a top superhydrophobic coating onto a polypropylene (PP) mat through simple sol–gel processing of octadecyltrimethoxysilane (OTMS), and the bottom layer was casted with hydrophilic poly(vinyl alcohol) (PVA) by using a knife casting technique; this membrane represents a novel class of improved-performance membranes consisting of a top superhydrophobic coating onto a hydrophobic PP mat and a hydrophilic layer (PVA) at the bottom. OTMSs are well known low-surface-energy materials that enhance superhydrophobicity, and they were observed to be the ideal chemical group for increasing the hydrophobicity of the PP mat. The PVA layer acted as base layer absorbing the condensed vapor and thus enhancing the vapor flux across the membrane. The hybrid three-layered membrane exhibited superhydrophobicity, with an average contact angle of more than 160°, and demonstrated high performance in terms of rejection and water flux. This study also examined the pore size distribution, surface roughness, surface area, tensile strength, water flux, and salt rejection of the fabricated membrane. The salt rejection level was calculated to be 99.7%, and a high permeate flux of approximately 6.7 LMH was maintained for 16 h.

Superhydrophobic membranes are essential for enhanced desalination by utilizing MD.     

Formation and characterization of polytetrafluoroethylene nanofiber membranes for high-efficiency fine particulate filtration

Polytetrafluoroethylene (PTFE) porous membranes are widely used for high-temperature filtration. The polytetrafluoroethylene nanofiber membranes for fine particulate filtration were prepared by sintering the precursor electrospun polytetrafluoroethylene/polyvinyl/boric acid alcohol composite membranes. The effects of PTFE/PVA mass ratio and sintering temperature on the morphology and properties of the prepared membranes were investigated to obtain the PTFE nanofibers with different diameters, and the film has been characterized by SEM, TG, XRD, FT-IR, and EDS, and the mechanical and hydrophobic properties of the membranes were also investigated. The PTFE nanofiber membranes after sintering had nanofiber and nanowire structures. Moreover, the membranes were tested in air filtration. The filtration efficiency and pressure drop were tested to evaluate the membrane permeability and separation properties. The results showed a high filtration efficiency (98%) and a low pressure drop (90 Pa) for 300 nm sodium chloride aerosol particles at a 30 L min⁻¹ airflow velocity and the hydrophobic membranes showed durable self-cleaning properties, which suggested that the PTFE nanofiber membranes were a promising candidate for high temperature filtration applications.

Polytetrafluoroethylene (PTFE) porous membranes are widely used for high-temperature filtration.     

Synthesis and characterization of polyaniline–hydrotalcite–graphene oxide composite and application in polyurethane coating

In this paper, a composite from polyaniline and graphene oxide-hydrotalcite hybrid (PAN–HG) was fabricated by direct polymerization of aniline using ammonium persulphate as an oxidant in the presence of a HG hybrid. The structure and morphological properties of synthesized PAN–HG composites were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectra, and scanning electron microscopy (SEM) techniques. The electrochemical properties of the composite particles were also analyzed by potentiodynamic polarization curves to evaluate the corrosion inhabitation. The results were calculated by Tafel fitting and showed that the effective corrosion protection values were 73.11%, 88.46%, and 95.49%, corresponding to HG, 1PAN–HG, and 2PAN–HG. The influence of PAN–HG on the corrosion protection of the polyurethane coating applied on the CT3 steel was investigated. As a result, the PU containing 0.5% of 2PAN–HG showed the most effective protection of the CT3 steel substrate. The R_C of the coating was about 1.61 × 10⁷ Ω cm², and after immersion for 30 days, the R_C value was 0.17 × 10⁶ Ω cm². From all the analyzed results, PAN–HG has enhanced the corrosion protection and a complicated protection mechanism was also concluded and explained.

Corrosion protection: PAN–HG performed effect of 95.49% protection of CT3-steel in NaCl 3.5%. PU(PAN–HG) coating provides good corrosion protection with complex mechanism of high barrier, ion-exchange and e⁻ trapping to HG structure.     

Mechanical properties of an interpenetrating network poly(vinyl alcohol)/alginate hydrogel with hierarchical fibrous structures

Bioinspired hierarchical fibrous structures were constructed in an interpenetrating poly(vinyl alcohol, PVA)/alginate hydrogel network to improve its mechanical properties. The interpenetrating hydrogel network with hierarchical fibrous structures was prepared by combining the confined drying method and freeze–thaw method. First, Ca²⁺ cross-linked alginate formed a nano–micro hierarchical fibrous structure via the confined drying method. Then, PVA that was uniformly distributed among the Ca²⁺–alginate chains was cross-linked by hydrogen bonding via the freeze–thaw method, further dividing the hierarchical fibers into finer fibers. The results of a tensile test demonstrated that both the tensile stress and fracture energy improved by more than double after the introduction of 2 wt% PVA, achieving a combination of high strength (∼12.9 MPa), high toughness (∼13.2 MJ m⁻³) and large strain (∼161.4%). Cyclic tensile tests showed that a hysteresis loop existed on the loading–unloading curves of the hydrogel along the fibrous directions, and a good self-recovery property emerged after resting for a period of time. The hydrogel with hierarchical fibrous structures constructed by alginate and PVA can be employed in biomedical applications in the future.

The mechanical properties both along and perpendicular to the fibrous directions were improved more than double after the construction of hierarchically arranged fibrous structures in the interpenetrating network PVA/alginate hydrogel.     

Development of active and intelligent films based on cassava starch and Chinese bayberry (Myrica rubra Sieb. et Zucc.) anthocyanins

Chinese bayberry (Myrica rubra Sieb. et Zucc.) fruit is a functional food rich in anthocyanins. In this study, anthocyanin-rich bayberry extract (BBE) was added into cassava starch to develop food packaging films with antioxidant and pH-sensitive properties. Results showed the main anthocyanin in BBE was cyanidin-3-O-glucoside (95.6%). The addition of 1 wt% of BBE into the film matrix resulted in a dense and compact internal microstructure, which greatly improved the water vapor permeability and tensile strength of the film. However, the addition of 2, 3 and 4 wt% of BBE into film matrix produced heterogeneous inner microstructures due to the formation of agglomerated BBE. The intermolecular interactions between BBE and the starch film matrix were through hydrogen binding. As compared with the starch film, starch–BBE films exhibited higher thicknesses, tensile strength, UV-vis light barrier and antioxidant properties. Moreover, starch–BBE films presented significant color changes when exposed to hydrogen chloride and ammonia gases. The pH-sensitive starch–BBE films were able to monitor the freshness of pork. Our results suggested that starch–BBE films could be used as smart and active packaging materials in the food industry.

In this study, anthocyanin-rich Chinese bayberry extract (BBE) was added into cassava starch to develop food packaging films with antioxidant and pH-sensitive properties.     

Sodium alginate/collagen composite multiscale porous scaffolds containing poly(ε-caprolactone) microspheres fabricated based on additive manufacturing technology

Biocompatible porous scaffolds with adjustable pore structures, appropriate mechanical properties and drug loading properties are important components of bone tissue engineering. In this work, biocompatible sodium alginate (SA)/collagen (Col) multiscale porous scaffolds containing poly(ε-caprolactone) microspheres (Ms-PCL) have been facilely fabricated based on 3D extrusion printing of the pre-crosslinked composite hydrogels. The prepared composite hydrogels can be 3D extrusion printed into porous scaffolds with different designed shapes and adjustable pore structures. The hydroxyapatite (HAP) nanoparticles have been added into the SA/Col hydrogels to achieve stress dispersion and form double crosslinking networks. SA-Ca²⁺ crosslinking networks and Col–genipin (GP) crosslinking networks have been constructed to improve the mechanical properties of the scaffolds (about 2557 kPa of compressive stress at 70% strain), and reduce the swelling rate and degradation rate of SA/Col scaffolds. Moreover, the SA/Col hydrogels contain hydrophobic antibacterial drug enrofloxacin loaded Ms-PCL, and in vitro drug release research shows a sustained-release function of porous scaffolds, indicating the potential application of SA/Col porous scaffolds as drug carriers. In addition, the antibacterial experiments show that the composite scaffolds display a distinguished and long-term antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, mouse bone mesenchymal stem cells (mBMSCs) are seeded on the SA/Col composite scaffolds, and an in vitro biocompatibility experiment shows that the mBMSCs can adhere well on the composite scaffolds, which indicate that the fabricated composite scaffolds are biocompatible. In short, all of the above results suggest that the biocompatible SA/Col composite porous scaffolds have enormous application and potential in bone tissue engineering.

Biocompatible porous scaffolds with adjustable pore structures, appropriate mechanical properties and drug loading properties are important components of bone tissue engineering.     

Upcycling green carbon black as a reinforcing agent for styrene–butadiene rubber materials

This study reports the effects of recovered carbon black (produced in a clean and sustainable way) as a reinforcing agent on the physicochemical properties of a styrene–butadiene rubber (SBR) matrix. SBR-based composite materials are prepared with recovered green carbon black (GCB), and these are thoroughly compared to the composite materials containing conventional virgin carbon black (VCB) (produced by the incomplete combustion of petroleum products). The GCB–SBR composite materials generally show detectably inferior properties compared to the VCB–SBR composite under the same preparation conditions due to the limited functionality of the GCB filler. However, the introduction of a small amount of crosslinker, acrylate-functionalized POSS (polyhedral oligomeric silsesquioxane), into the GCB–SBR composite materials effectively enhances the overall physical properties, including the tensile strength, fracture elongation, and thermal stability. The degree of the crosslinking efficiency, thermal stability, and mechanical properties of the composite materials are optimized and thoroughly examined to demonstrate the possibility of replacing typical VCB with GCB, which can allow for upcycling the inexpensive and ecofriendly carbon black materials as effective reinforcing fillers.

Green carbon black (GCB) could be upcyclable as an eco-friendly filler for styrene butadiene rubber (SBR)-based composite materials to replace conventional virgin carbon black (VCB) upon properly utilizing POSS.     

Sulfonated graphene oxide/Nafion composite membranes for high temperature and low humidity proton exchange membrane fuel cells

Iron oxide (Fe₃O₄) nanoparticles anchored over sulfonated graphene oxide (SGO) and Nafion/Fe₃O₄–SGO composites were fabricated and applied as potential proton exchange membranes in proton exchange membrane fuel cells (PEMFCs) operated at high temperature and low humidity. Fe₃O₄ nanoparticles bridge SGO and Nafion through electrostatic interaction/hydrogen bonding and increased the intrinsic thermal and mechanical stabilities of Nafion/Fe₃O₄–SGO composite membranes. Nafion/Fe₃O₄–SGO composite membranes increased the compactness of ionic domains and enhanced the water absorption and proton conductivity while restricting hydrogen permeability across the membranes. The proton conductivity of Nafion/Fe₃O₄–SGO (3 wt%) composite membrane at 120 °C under 20% relative humidity (RH) was 11.62 mS cm⁻¹, which is 4.74 fold higher than that of a pristine recast Nafion membrane. PEMFC containing the Nafion/Fe₃O₄–SGO composite membrane delivered a peak power density of 258.82 mW cm⁻² at a load current density of 640.73 mA cm⁻² while operating at 120 °C under 25% RH and ambient pressure. In contrast, under identical operating conditions, a peak power density of only 144.89 mW cm⁻² was achieved with the pristine recast Nafion membrane at a load current density of 431.36 mA cm⁻². Thus, Nafion/Fe₃O₄–SGO composite membranes can be used to address various critical problems associated with commercial Nafion membranes in PEMFC applications.

Preparation process of Nafion/Fe₃O₄–SGO composite membranes.     

Modified melamine-formaldehyde resins improve tensile strength along with antifouling and flame retardancy in impregnation of cellulose paper

In this study, polyvinyl alcohol (PVA) and benzoguanamine (BG) modified melamine-formaldehyde (MF) resins were used to prepare two high-pressure laminates (HPLs) as well as a pure cellulose paper laminate and core sandwich laminates with the core material of aramid paper (AP) or polypropylene non-woven fabric (PPNF). The tensile strength, flame retardancy and antifouling properties of the modified MF resin laminates were studied and compared with the MF resin laminate. The tensile test results showed that the MF resins modified with BG and PVA improved the tensile strength of the impregnated paper. In comparison with pure kraft cellulose paper laminates, the aramid paper core laminates displayed comparatively higher tensile strength. Antifouling test results indicated that modified MF resin laminates had no obvious change while the MF resin laminate was stained. Thermal stability of the modified resins was investigated by thermogravimetric (TG) analysis and the results showed that the char yield of modified MF resin was higher than that of the unmodified MF resin due to the addition of BG. The modified MF resin laminates exhibited better flame retardancy properties through the analysis of limiting oxygen index (LOI), vertical burning and cone calorimetry (CONE) compared to the MF resin laminate. In addition, the flame retardancy of laminates was further enhanced when prepared with core materials of aramid paper. Scanning electron microscopy analysis of residue char after CONE tests showed that the AP-core laminate formed a dense and stable char layer compared with the loose char layer of the PPNF-core laminate. This study shows a new direction to develop sustainable high-performance flame retardant laminates for commercial decoration application.

Polyvinyl alcohol (PVA) and benzoguanamine (BG) modified melamine-formaldehyde (MF) resins were used to prepare high-pressure laminates (HPLs) and the improved tensile strength, flame retardancy and antifouling properties were investigated.     

Ultralight aerogel based on molecular-modified poly(m-phenylenediamine) crosslinking with polyvinyl alcohol/graphene oxide for flow adsorption

Poly(m-phenylenediamine) is an excellent adsorbent material. Nevertheless, it is difficult to recover and can even generate secondary pollution due to its powder-like form. Aerogels, monolithic three-dimensional structured materials, that are ultralight and have porous properties are efficient at adsorbing contaminants from water and can solve these problems. Here, we synthesized an aerogel based on molecular-modified poly(m-phenylenediamine) (mPmPD) crosslinking with polyvinyl alcohol (PVA) and graphene oxide (GO) (GO/mPmPD/PVA). Of note is that 3-aminophenylboronic acid was introduced into the polymer structure to induce a crosslinking reaction between boric acid units and PVA to constrain poly(m-phenylenediamine) in the aerogel. The GO/mPmPD/PVA aerogel shows stable mechanical properties in aqueous solution and an effective adsorption capacity for Ag(i); the maximum Ag(i) adsorption capacity is 917.41 mg g⁻¹. The mechanism of Ag(i) adsorption and reduction was clarified in that Ag(i) chelated with imine units, and a redox reaction occured between Ag(i) and the benzenoid amine units. Furthermore, the GO/mPmPD/PVA aerogel also shows excellent adsorption ability toward methyl orange and Congo red dyes. This GO/mPmPD/PVA aerogel shows enormous potential for application to silver recovery and dye removal due to its low cost, effective adsorption capacity and facile separation with aqueous solution.

An aerogel composed of molecular-modified poly(m-phenylenediamine), polyvinyl alcohol and graphene oxide for Ag(i) recovery and dye removal is demonstrated.     

Structure and properties of chitosan/sodium dodecyl sulfate composite films

In this study, we investigated the effect of sodium dodecyl sulfate (SDS) content on the structure and properties of chitosan films. It is found that the binding of SDS to chitosan was realized through the interactions between –SO₄⁻ and –NH₃⁺, forming an ionically cross-linked film. Structural analysis revealed that the crystallization was greatly hindered by introducing SDS. With an increase of SDS content, the glass transition temperatures (T_g) of chitosan films increased due to the formation of crosslinks. Compared to pure chitosan film, the composite films had lower content of moisture and possessed better thermal stability. In addition, the mechanical properties of the as-obtained composite films were closely related to the content of SDS, and were significantly improved in the biopolymer films with moderate SDS content. These results indicate that the microstructure as well as properties of the chitosan films can be regulated by adding SDS.

SDS binds strongly to chitosan through electrostatic interactions, and it has a remarkable effect on the structure and properties of chitosan films.