Preparation of UV reactive montmorillonite and characterization of its nanocomposites with poly(vinyl alcohol)

A cation‐exchanged montmorillonite clay is prepared as filler material with high dispersibility, that should act as Fe³⁺‐donor for photochemical crosslinking of PVA/Fe³⁺‐MMT materials with filler contents of up to 50 wt % with regard to the polymer matrix. Hence, no organic photoinitiators and hazardous compounds are utilized. This material may be considered environmentally benign and could be applied in the field of food packaging or for biomedical applications. Upon UV exposure of liquid PVA/Fe³⁺‐MMT dispersion samples, a significant change of the refractive index is determined and the absorption at 360 nm decreased. This indicates the transition of Fe³⁺ to Fe²⁺, which initiates a radical crosslinking mechanism. A homogenous distribution and parallel orientation of the modified clay particles is revealed by SEM measurements. The solubility behavior of the PVA/Fe³⁺‐MMT composite materials in deionized water, changes considerably due to the high filler content and UV‐induced crosslinking, resulting in gel contents exceeding 90 wt %. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dual xanthan gum/poly(vinyl acetate) or alkyl‐functionalized poly(vinyl alcohol) films as models for advanced coatings

Double‐layer films, prepared by casting films of xanthan gum (XG), and subsequently poly(vinyl acetate) (PVAc) onto the former, are reported. The resulting XG/PVAc films provide high protection as coatings to a bleaching agent, 6‐(phthalimido)peroxyhexanoic acid, in liquid detergents, due to the combined roles of the outer PVAc layer as water‐barrier and the inner XG layer as water‐sink. PVAc films cast from either homogeneous solutions in acetone or aqueous dispersions were used; the stabilities exerted by the former were markedly superior. For comparison, poly(vinyl alcohol) (PVA) was also used as outer wall material, resulting in much lower protection due to its hydrophilicity. Functionalization (silylation or acetalyzation) of PVA films is also suggested as a means to decrease the surface hydrophilicity of the material. The dual hydrophilic–hydrophobic films presented herein serve as models for advanced coatings in (micro)encapsulation processes, owing to the straightforward study of their morphology and transport phenomena. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40870.     

Antimicrobial activity of water resistant surface coating from catechol conjugated polyquaternary amine on versatile substrates

Water resistant polymer with adhesive behavior is reported to exhibit long‐term antimicrobial activities under diverse conditions. To obtain highly adhesive polymer with prolonged antimicrobial activities and catechol moiety, 2‐chloro‐3′,4′‐dihydroxyacetophenone (CCDP) has been quaternized to poly(dimethylaminoethyl methacrylate) (PDMA). Later, for gaining the antimicrobial effects, the polymer (CCDP‐q‐PDMA) was quaternized with 1‐bromododecane (C12) [CCDP/C12‐q‐PDMA]. X‐ray photoelectron spectroscopy rectified the quaternization and adhesion of the polymer onto different substrates. The CCDP/C12‐q‐PDMA coated substrates exhibited remarkable bacterial killing efficiency against both Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli, after incubation for 24 h. The remarkable antimicrobial activities exhibited in aqueous medium at 60°C for up to 60 days indicate the strong adhesiveness of CCDP/C12‐q‐PDMA on the substrate. Therefore, the synthesized polymer offers merit as a potential coating material, to protect a broad range of material from microbial contamination, for a prolonged period of time, under a highly stressed water environment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40708.     

Effects of a silane coupling agent on the tensile adhesive strength between resin and titanium

Adhesion of a cured dental opaquer, which masks metallic appearance and color, to sandblasted Ti aided by 3‐methacryloyloxypropyltrimethoxysilane (MPTS) is investigated. The tensile bond strengths of Ti and the opaquer are 43.3 and 45.9 MPa, respectively, when MPTS dissolved in ethanol (6 wt %) and premixed with the opaquer (3 wt %) are applied to the sandblasted Ti surface. Mirror finishing alone and sandblasting alone result in the bond strengths of 1.8 and 21.3 MPa, respectively. After thermal cycling (4 and 60°C for 5000 cycles), the bond strengths of the Ti with sandblasting and the MPTS treatment remain higher than that of the Ti with sandblasting only. Sandblasting and the MPTS treatment effectively promote the adhesion of the opaquer to Ti that rapidly forms an oxide surface layer. The silane‐aided adhesion of the opaquer to the sandblasted Ni? Cr, Co? Cr, and Au? Ag? Pd alloys attain adhesive strengths of 33.2, 31.9, and 31.6 MPa, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of different porous fillers on interfacial properties of poly (vinyl alcohol) hybrid films

Poly(vinyl alcohol) (PVA)-based hybrids have demonstrated broad liquid separation applications but separation performances are constrained by the compatibility between fillers and polymer, and thus it is essential to study the interfacial properties of these hybrids. In this work, PVA hybrids with four different porous fillers have been fabricated and characterized with Fourier transform infrared, X-ray diffraction, Scanning electron microscope, swelling and contact angle tests. Swelling results show that PVA has a degree of swelling (DS) of 79% in water but the swelling is compressed after adding fillers and the DS for PVA hybrids has decreased by 19%, 17%, 15%, and 9% for 30 wt% loading of ZIF-8, UiO-66, Hβ and ZSM-5, respectively. For methanol and its 10 wt% aqueous solution, similar swelling results are obtained due to mutual interactions among the filler, polymer and test liquids. Based on water and glycerol contact angle results, the surface energy of PVA is estimated to be 40.56 Nm⁻¹ and it drops to 27.39 Nm⁻¹ after adding less hydrophilic ZIF-8 or rise to 48.56 Nm⁻¹ after introducing more hydrophilic ZSM-5. The high-film hydrophilicity and then large surface energy have rendered methanol/water sorption selectivity of PVA hybrids decrease to some extent or vice versa.     

Effect of interfacial pretreatment on the properties of montmorillonite/poly(vinyl alcohol) nanocomposites

This work explores the factors that control the dispersion of exfoliated montmorillonite (MMT) in poly(vinyl alcohol) (PVOH) during solution blending and solvent evaporation. Nanocomposite films were prepared by solution blending of aqueous PVOH solutions with dilute suspensions of fully exfoliated MMT platelets (as confirmed by AFM). Dynamic light scattering (DLS) indicates that addition of MMT suspensions to PVOH solutions results in undesired particle aggregation and thus poor MMT dispersion in cast films (as evidenced by transmission electron microscopic images and gas permeation measurements). We believe that PVOH bridging induces MMT platelet aggregation. To counteract bridging aggregation, we explore the novel idea of pretreating the MMT surface with a small amount of compatible polymer prior to solution blending with PVOH. We hypothesize that “pretreating” the MMT platelet surfaces with adsorbed polymer in dilute suspensions will protect the platelets from bridging aggregation during solution blending and solvent evaporation. MMT/PVOH composite films have been prepared using low‐molecular‐weight PVOH as the pretreatment polymer; and low‐, medium‐, and high‐molecular‐weight PVOH as the matrix polymer. A PEO‐PPO‐PEO triblock copolymer (F108 from the Pluronics^® family) was also evaluated as the pretreatment polymer. DLS shows that pretreated MMT platelets are less susceptible to aggregation during blending with PVOH solutions. Results compare the crystalline structure, thermal properties, dynamic mechanical properties, gas permeability, and dissolution behavior of MMT/PVOH films incorporating untreated versus pretreated MMT. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41867.     

Influence of the dispersion of nano titanium dioxide on the tribological performance of fabric self‐lubricating liner

Nanoparticles with unique properties have been widely used in various fields. The tribological performance of the fabric self‐lubricating liner, which is used as the main component of spherical plain bearings, directly affects the bearing service life. The purpose of this study was to prepare a self‐lubricating liner enhanced with nano titanium dioxide (nano‐TiO₂) by dispersion technology. The effects of several factors on the dispersion of nano‐TiO₂ were studied in detail. The effects of the dispersion of nano‐TiO₂ on the tribological properties of a self‐lubricating liner were analyzed comparatively. The best dispersing conditions were determined through experiments and statistical characterization. From the results of the tribological tests, the fabric self‐lubricating liner reinforced with nano‐TiO₂ showed better antifriction and wear‐resistant properties than that without nanoparticles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2100–2105, 2013     

Hydrogen-bonding assembly of heteropolyacid and poly(vinyl alcohol) for strong,flexible, and transparent UV-protective films

Although many preparation approaches have been developed, it remains a huge challenge to achieve ultraviolet (UV)-protection films that combine high transparency, excellent UV-shielding, and mechanical properties. Herein, we demonstrate a facile and eco-friendly process for fabricating strong, flexible, and transparent UV-protective poly(vinyl alcohol) (PVA) films by exploiting silicomolybdic acid (SiMoA) as UV absorber and reinforcing phase. Fourier-transform infrared analysis confirms the formation of strong hydrogen-bonding interactions between PVA and SiMoA. The glass-transition temperature, mechanical properties, and UV-shielding stability of the UV-protective PVA composite films obviously increase with increasing the content of SiMoA. By incorporation of only 2 wt % SiMoA, the UV-protective PVA composite film can block more than 90% of UV light in the entire UV regions and retain high visible light transparency (up to 95%). Simultaneously, the UV-protective PVA composite film presents excellent mechanical properties with a tensile strength of 65.2 MPa and an elongation at break of 172.6%, which are 72.0 and 69.5% higher than that of pristine PVA films. This work provides a simple but effective approach for creating strong, flexible, and transparent UV-blocking polymeric materials via hydrogen-bonding assembly, which are expected to have wide application prospects in UV-protection field. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48813.     

Interfacial modification mechanism of nanocellulose as a compatibilizer for immiscible binary poly(vinyl alcohol)/poly(ethylene oxide) blends

We undertook this study to understand reinforcement mechanism of short cellulose nanocrystals (CNCs) and long cellulose nanofibrils (CNFs) as compatibility agents for improving the interfacial miscibility of poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO) blends. The effects of the two cellulose nanofibers on the morphological, mechanical, and thermal properties of the polymer blends were compared systematically. The light transparency, scanning electron microscopy, and Fourier transform infrared results show that nanocellulose between PVA and PEO eliminated the negative effects generated by the immiscible interface through increased hydrogen bonding. Thermogravimetric analysis and differential scanning calorimetry results show that crystalline region reorganization around the interface facilitated the shift of the polymer blends from multiple phases to a homogeneous phase. According to the Halpin‐Kardos and Quali models, we assumed that the potential for repairing the immiscible interface would have a larger effect than the potential of reinforcement. At the same concentration, polymer blends with CNCs showed greater light transparency, strength, modulus, and crystal structure than with those with CNFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45896.     

Effect of clay type on dispersion and barrier properties of hydrophobically modified poly(vinyl alcohol)–bentonite nanocomposites

The oxygen and water vapor permeability at high relative humidity was studied for composite films formed by incorporation of three different bentonites (MMT) into an ethylene‐modified, water‐soluble poly(vinyl alcohol), EPVOH. The oxygen permeability decreased linearly with an increased addition of hydrophilic MMTs. X‐ray diffraction and Fourier transform infrared spectroscopy suggested a homogeneous distribution in the thickness direction with disordered and probably exfoliated structures for hydrophilic MMTs. In contrast, organophilic modified clay showed an intercalated structure with the clay preferentially located at the lower film surface, a combination which was however efficient in reducing the water vapor‐ and oxygen permeabilities at low addition levels. Composite films of EPVOH and Na⁺‐exchanged MMT resulted in high resistance to dissolution in water, which was ascribed to strong interactions between the components resulting from matching polarities. Annealing the films at 120°C resulted in enhanced resistance to water dissolution and a further reduction in oxygen permeability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42229.     

Oil- and water-resistant paper substrate using blends of chitosan-graft-polydimethylsiloxane and poly(vinyl alcohol)

Reported herein is an economical, plastic- and fluorine-free coating approach for oil and water repellent paper substrates using blends of poly(vinyl alcohol) and chitosan-graft-polydimethylsiloxane copolymer. The obtained coated paper showed good water-resistance, as evidenced by its low Cobb60 values of ~20 ± 2.1 g/m² and high water contact angles of 119 ± 6.3 °. The kit rating of the coated paper was 7.6/12, indicating decent grease-resistant properties as compared to the kit value of 0/12 for the uncoated paper. The coated paper is also repulpable as demonstrated by the complete washing off the coating from the coated paper. Giving the cost-effective nature of the coating materials and good water and oil-resistant properties of the coated paper, the approach developed here is commercially viable, and will offer a multitude of environmental benefits such as the elimination of microplastic- and PFAS problems associated with existing paper coatings.     

Shear strain and microscopic characterization of a bamboo bonding interface with poly(vinyl alcohol) modified phenol–formaldehyde resin

The study of the shear strain distribution at the bonding interface helped us to understand the bamboo bonding interface response mechanisms to solve problems of ply bamboo deformation or bonding failure. The shear strain distribution across a two‐ply bamboo sheet bonded with a ductile phenol–formaldehyde resin (PF) modified by poly(vinyl alcohol) (PVA) was measured by means of electronic speckle pattern interferometry, along with tensile strength measurements to prove the shear stain distribution on a macroscopic scale. This research effectively combined macroscopic mechanical properties with microcosmic interfacial mechanical properties. The shear strength and shear strain results showed that PF modified with 20% PVA performed better than common PF and PF modified with 5 and 10% PVA. Microscopic fluorescent characterization of the bonding interface also provided evidence that a new bonding mechanism was adequate for bamboo bonding under the ductile PF modified with 20% PVA. Moreover, we suppose that the results of this study will help in the choice of bamboo‐specific adhesives under different strain conditions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1345‐1350, 2013     

Mechanical clamp stress on poly(vinyl chloride) infusion tubing: Impact on the surface degradation

Several commercial infusion tubes made of plasticized poly(vinyl chloride) were shown to present a layer of bloomed species on their internal wall (lubricants and stabilizers), which are poorly soluble in water. During infusion, tubes are crushed and pinched to regulate the flow. The impact of mechanical stress on these layers infusion was studied. Device inner surfaces were characterized by atomic force microscopy in order to put into evidence surface degradations before and after infusion. This was correlated with a global and local infrared analysis. Because of the clamp stress, the deposits were damaged. Thus, injecting water into the damaged tubing increased the layer degradation. Roller clamp and pinch clamp may have very different effects on the inner layer morphology and degradation and this may be modulated by the initial layer morphology. Injecting water into clamp stressed tubing may increase the risk of detaching parts of the internal layer and be a supplementary factor of particulate contamination for the patient.     

Reusable dry adhesives based on ethylene vinyl acetate copolymer with strong adhesion

This work proposed the design and fabrication method for T-shaped dry adhesives based on stretchable ethylene-vinyl acetate (EVA) copolymer, with strong normal adhesion strength up to 70 N cm⁻². As fabricated adhesives based on the inexpensive soft replication process have comprehensive advantages including easy demolding applicable for various curable materials; self-cleaning characteristic based on excellent nonwetting characteristics to both water and oil; reversible adhere/detach cycling for reusability. The flexible and transparent EVA dry adhesive films were readily fabricated to be novel dry-adhesive coatings decorated on various substrates and shapes. We also explored the adhere and detach mechanism for the significantly enhanced adhesion of T-shaped EVA microstructures, which indicated the increased contact area and the friction dissipation between the undercut and the substrate contribute to the adhesion enhancement, while the excellent elastic deformation of EVA may play an important role for adhesion enhance during the pulling-off process. These results showed the great potential of high-performance T-shaped EVA-based polymer dry adhesives for practical applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47296.     

Development of antifouling poly(vinyl chloride) blend membranes by atom transfer radical polymerization

In this study, antifouling poly(vinyl chloride) (PVC) blend membranes were prepared by blending the PVC based amphiphilic copolymer PVC‐g‐poly(hydroxyethyl methacrylate) (PVC‐g‐PHEMA), synthesized by atom transfer radical polymerization (ATRP), into the hydrophobic PVC matrix via the nonsolvent‐induced phase separation method. The in situ ATRP reaction solutions were also used as the blend additives to improve membrane performance. Attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that the blend membranes based on the two blend routes exhibited similar surface chemical compositions. The membrane morphology and surface wettability were determined by scanning electronic microscopy and water contact angle measurement, respectively. The blend membranes showed improved water permeability, comparable rejections and enhanced antifouling properties compared with the pure PVC membrane. The PVC blend membranes also had excellent long‐term stability in terms of chemical compositions and fouling resistance. The results demonstrated that ATRP was a promising technique to synthesize amphiphilic copolymer and prepare stable blend antifouling membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45832.     

Enhanced dielectric and ferroelectric properties induced by Ag @ Pb(Zr,Ti)O3 in poly(vinyl alcohol) matrix composites: A solution casting approach

The present research work focused on the dielectric and electrical properties of silver (Ag) doped Pb(Zr,Ti)O₃ (PZT) particles embedded in a matrix of poly(vinyl alcohol) (PVA) via solution casting technique. The structural analysis confirmed the presence of Ag particles and the microstructural study revealed that both Ag and PZT particles were successfully homogenized over the polymer matrix. The Ag–PZT–PVA composites showed enhanced dielectric properties over a wide range of frequency and the dielectric constant value of such composites was significantly increased to 366 (100 Hz) at 1.1 wt % filler loading. The percolation threshold of the Ag–PZT–PVA composites was found to be 0.9 wt %. The experimental result well fitted to the percolation theory. The enhancement of dielectric constant of the resulting composite systems might be attributed to the increment of conductivity of the interlayer between PZT and PVA due to the presence of Ag particles, which improved the space charge polarization and Maxwell–Wagner–Sillars (MWS) polarization effects. Furthermore, the remnant polarization of the unpoled Ag–PZT–PVA composites (2P_r ～1.48 µC/cm² for 1.1.wt % of Ag–PZT) has also improved, which is favorable for enhanced ferroelectric properties of the composites. The present findings of the composites might be exploited in the potential application of high performance energy storage devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45583.     

Dual‐bonding structured ternary composite film of poly(vinyl alcohol)–boric acid–nanodiamond

Ternary composite films of poly(vinyl alcohol) (PVA), boric acid (BA), and detonation nanodiamond (DND) were prepared by aqueous solution method. Because of its excellent mechanical/thermal properties and low friction coefficient, DND is expected to offer PVA film superior performance if the puzzles of particle agglomeration in polymer matrix and fragile interface reaction between DND and PVA can be settled. BA was used as a crosslinking agent to form a strong network structure between DND and PVA. Investigation on microstructure of PVA/BA/DND films and bonding mechanisms therein shows that BA, DND, and PVA may crosslink by oxo‐bridges owing to the interaction of hydroxyl groups. The Young's modulus (E) of composite films was enhanced by nearly 3.3 times with only 0.8 wt % DND loading, and the antiwear, thermal stability, and waterproof properties can be significantly improved after the crosslinking. Meanwhile, the transparency of composite films can be well preserved even with large DND content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45449.     

Ferroelectric nanodot formation from spin‐coated poly(vinylidene fluoride‐co‐trifluoroethylene) films and their application to organic solar cells

We demonstrated a facile route to the preparation of self‐assembled poly(vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)] nanodots from spin‐coated thin films. We found that the initial film thickness would play an important role in the formation of such P(VDF‐TrFE) nanodots. Interestingly, the electric dipoles of such nanodots were self‐aligned toward the bottom electrode and their ferroelectric properties were determined by using piezoresponse force microscopy. In addition, the self‐polarized ferroelectric nanostructures were introduced to small molecular organic photovoltaic devices and allowed for enhancing the short circuit current density (J_sc) from 9.4 mA/cm² to 10.2 mA/cm² and the power conversion efficiency from 2.37% to 2.65%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41230.     

Synthesis and optimization of dopamine hydrochloride functionalized palygorskite and their application in protective coatings on water saturated surface of concrete

The synthesis process of dopamine hydrochloride functionalized palygorskite (Pal) nanoparticles (Pal@PDA) is optimized by adjusting the mass ratio of them. The optimal preparation technology of the Pal@PDA is determined by scanning electron microscopy and comparing the adhesive strength between the biomimetic protective coatings and dry and water saturated concrete surface. When the mass ratio of dopamine hydrochloride to Pal is 1:4, the prepared Pal@PDA does not contain excess polydopamine (PDA) nanoparticles and the coatings incorporating the Pal@PDA have the highest adhesive strength on dry and water saturated concrete surface at the same conditions. Compared with the pure epoxy primer, the adhesive strength between the epoxy primer incorporating 5 wt% Pal@PDA and the water saturated concrete surface increases by 25.69% (from 3.282 to 4.125 MPa). Furthermore, the Pal@PDA is embedded into pure epoxy resin to prepare the biomimetic resin composites, the tensile strength and compressive strength of the composites incorporating 5 wt% Pal@PDA are 91.20% and 34.77% higher than that of pure epoxy resin, respectively. Further studies confirm that the active groups on the Pal@PDA surface form the stable covalent and non-covalent bonds with epoxy primer and the water saturated concrete surface, which is the major mechanism of improving interfacial adhesion.