Pure Polyvinyl Alcohol Research Articles

Impact of Mn-Ni spinal ferrite nanoparticles on the structural, morphological, surface roughness, and optical parameters of polyvinyl alcohol for optoelectronic applications.

Herein, polyvinyl alcohol (PVA) acts as a host matrix for manganese-nickel ferrite (Mn0.4Ni0.6Fe2O4) nanoparticles (NPs). Oxalate precursors and a solution-cast method were used to produce a Mn0.4Ni0.6Fe2O4 spinel structure and PVA-Mn0.4Ni0.6Fe2O4 films, respectively. X-ray diffraction (XRD), scanning electron microscopy, optical microscopy (OM), a surface roughness tester, and FT-IR spectroscopy were used to identify the structure and morphology of the PVA-Mn0.4Ni0.6Fe2O4 films. XRD confirmed the formation of Mn0.4Ni0.6Fe2O4 spinel, and its additive into the PVA matrix causes an increase in the PVA amorphousity. The PVA-Mn0.4Ni0.6Fe2O4 film's transmission and absorption spectra were recorded with the help of a UV-visible spectrophotometer. The addition of 4%Mn0.4Ni0.6Fe2O4 to PVA resulted in a decrease in the optical bandgap from 5.53 eV to 4.83 eV. The Urbach energy increases from 0.46 eV for pure PVA to 2.14 eV for PVA-4%Mn0.4Ni0.6Fe2O4, indicating a rise in the defect density. In addition, the refractive index and extinction coefficient were calculated theoretically and were found to increase as the Mn0.4Ni0.6Fe2O4 content increases in the PVA matrix.

Structural, Optical, Electrical and Discharge Characteristics of PVA-ZnS Nanocomposite Polymer Electrolyte−Zn2+ Ion Conduction for Solid State Battery Applications

Polyvinyl alcohol (PVA) based Zn2+ ion conducting solid polymer electrolyte was prepared using a solution-cast method. Measurements were taken utilizing X-ray diffraction (XRD) and Fourier transform infrared analysis (FT-IR) to investigate the structure. The optical absorption spectra were investigated in the 200-800 nm range in order to acquire information about the optical properties of the material. This data comprised the direct energy gap, indirect energy gap and optical absorption edge of the material. The direct optical energy gap for pure PVA lies at 6.08 eV, while PVA doped with zinc sulphide ranges from 5.28 to 5.68 eV for the different compositions. It was evident that the energy gaps and band edge values transferred to lower energies on doping with ZnS up to a dopant concentration of 92 wt.% of PVA and 8 wt.% of ZnS. For this study, the ionic conductivity and transference number of PVA polymer electrolytes were measured in order to know more about the conductivity order and charge transport in these materials. The charge transport in PVA polymer electrolyte was measured to be largely due to ions (tion = 0.97), as indicated by the transference number. Increasing the ZnS concentration and the temperature were both found to raise the ionic conductivity. The discharge properties of solid-state battery cells made with this PVA polymer electrolyte were studied while operating under a constant load of 100 kW.

Preparation of Anti-Bacterial Cellulose Nanofibrils (CNFs) from Bamboo Pulp in a Reactable Citric Acid-Choline Chloride Deep Eutectic Solvent.

In this study, bamboo pulp was simultaneously fibrillated and esterified in one-pot citric acid-choline chloride deep eutectic solvent treatment. The results indicated that increasing the temperature and time promoted esterification, yielding 0.19 to 0.35 mmol/g of the carboxyl group in CNFs. However, increasing the temperature and time resulted in decreases in yields and the diameter of CNFs from 84.5 to 66.6% and 12 to 4 nm, respectively. Analysis of the anti-bacterial activities of CNFs suggested that the high carboxyl group content corresponded to the effective inhibition of Escherichia coli and Staphylococcus aureus Taking yield, size, carboxyl group content, and anti-bacterial activate into consideration, treatment at 120 °C for 24 h was the optimal condition, yielding 76.0% CNF with 0.31 mmol/g carboxyl groups with a diameter of 8 nm and the inhibition fof E. coli (81.7%) and S. aureus (63.1%). In addition, effect of different CNFs on characteristics of polyvinyl alcohol (PVA) films were investigated. The results indicated that CNF obtained from the optimal condition was a favorable additive for the composite film, which enhanced (74%) the tensile strength of composite film compared with the pure PVA film due to its considerable size and carboxyl group content. However, the composite films did not show an anti-bacterial activate as CNF.

Structural, thermal and dielectric properties of glycerolized hydrogen‐bonded polyvinyl alcohol films

AbstractIn order to evaluate the influence of plasticizers on the behavior of the dielectric properties of polymers intended for the elaboration of flexible sensors, we have studied the influence of the addition of glycerol (10 wt%–40 wt%) in polyvinyl alcohol (PVA). Once processed, the PVA films were not subjected to any particular annealing and they were dried at room temperature for 24 h before being characterized. This choice allows both to take advantage of the presence of water in the bulk of the material, which will help to make the PVA more flexible (increase of plasticization effect produced by extra‐H‐bonding) and avoid a transient behavior of water absorption into the material, as we could verify. DSC and FTIR investigations confirm good intermolecular interaction between vinyl polymer chains, glycerol, and water molecules. Dielectric spectroscopy analysis, carried out in [25°C–110°C] temperature and [0.1 Hz–1 MHz] frequency ranges, reveals a significant increase in the dielectric constant when the glycerol content is higher (at 0.1 Hz: 322 for pure PVA, 1.3 × 106 with 40 wt% of glycerol). Polar hydrogen bonds introduced by the glycerol are the main reason for this increase. Ionic conductivity induced by these dipoles dominates the loss tangent response of the material. The activation energy obtained from the DC conductivity plateau obeys to a conventional Arrhenius law with a decreasing value at highest glycerol contents (1.35 eV for pure PVA against 0.46 eV with 40 wt% of glycerol).

A Polyvinyl Alcohol-Tannic Acid Gel with Exceptional Mechanical Properties and Ultraviolet Resistance.

Design and preparation of gels with excellent mechanical properties has garnered wide interest at present. In this paper, preparation of polyvinyl alcohol (PVA)-tannic acid (TA) gels with exceptional properties is documented. The crystallization zone and hydrogen bonding acted as physical crosslinkages fabricated by a combination of freeze-thaw treatment and a tannic acid compound. The effect of tannic acid on mechanical properties of prepared PVA-TA gels was investigated and analyzed. When the mass fraction of PVA was 20.0 wt% and soaking time was 12 h in tannic acid aqueous solution, tensile strength and the elongation at break of PVA-TA gel reached 5.97 MPa and 1450%, respectively. This PVA-TA gel was far superior to a pure 20.0 wt% PVA hydrogel treated only with the freeze-thaw process, as well as most previously reported PVA-TA gels. The toughness of a PVA-TA gel is about 14 times that of a pure PVA gel. In addition, transparent PVA-TA gels can effectively prevent ultraviolet-light-induced degradation. This study provides a novel strategy and reference for design and preparation of high-performance gels that are promising for practical application.

Formation of beryllium oxide nanofibers by polyvinyl alcohol/beryllium sulfate/polyethyleneimine composite precursors

Polyvinyl alcohol (PVA)/beryllium sulfate (BeSO4) precursor nanofibers are fabricated by electrospinning technique, mixing PVA aqueous solution with BeSO4 salt. The productivity is increased by adding polyethyleneimine (PEI) with PVA/BeSO4 spinning solution. The beryllium oxide (BeO) nanofibers are obtained by calcinating the PVA/BeSO4/PEI precursor nanofiber heated at 1000 °C or above. The crystallographic structure of BeO nanofibers is examined by X-ray diffraction. The thermal behaviors of the pure PVA nanofibers, BeSO4 salt, and PVA/BeSO4/PEI precursor nanofibers are studied by thermogravimetry analysis. The BeO nanofiber diameters are reduced with the increase in calcination temperatures. The specific surface area of the PVA/BeSO4/PEI precursor nanofibers is around 36.9 m2 g−1, and that of the BeO nanofibers calcined at 1200 °C is about 11.9 m2 g−1. The pore properties deteriorate due to sintering and blockage as the calcination temperature increases. This work introduces mesoporous BeO nanofibers for the very first time.

The Enhanced Moisture Absorption and Tensile Strength of PVA/Uncaria gambir Extract by Boric Acid as a Highly Moisture-Resistant, Anti-UV, and Strong Film for Food Packaging Applications

There is an increasing demand for food packaging materials that are safe for the environment and human health. Pure polyvinyl alcohol (PVA) film is non-toxic and transparent but has poor UV-light shielding, thermal and moisture resistance, and antibacterial activity. Our previous work prepared and characterized a biofilm derived from PVA and edible Uncaria gambir extract (UG). The film has antibacterial properties and is anti-UV and flexible. However, UG is hydrophilic, making this film have low moisture absorption. To improve these properties, we trialed adding boric acid (BA) and UG into the PVA. This present study aims to characterize pure PVA film and blend films resulting from mixing PVA (10%), BA (0.5%), and UG (1%). It was found that the PVA/UG/BA film presented the best performance in terms of UV light absorption, tensile properties, thermal and moisture resistance, and antibacterial activity. This blend sample absorbs about 98% of the UV light at 400 nm wavelength without significantly sacrificing transparency. These findings indicate that UG and BA could be advantageous in the preparation of moisture and thermal-resistant UV shielding films with low toxicity and high antibacterial properties based on PVA. They were also found to be strong enough for food packaging applications.

Structure–mechanics relationship of hybrid polyvinyl alcohol-collagen composite by molecular dynamics simulations

Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer that can be used to make hydrogels for biomedical applications as well as biodegradable bags and films; however, compared to other plastics currently used for containers, it lacks mechanical strength, thermal stability, and can easily absorb water from humid environments. Although mechanical improvement has been observed by blending PVA with collagen in a hybrid hydrogel, there is a lack of fundamental understanding of the molecular mechanism, and it is not clear whether the improvement is limited to a hydrated state. Here, using classical molecular dynamics simulations based on fully atomistic models, we develop the equilibrated molecular structure of PVA with collagen and characterize its mechanics. We show that by interacting with a collagen molecule, PVA is equilibrated to a more ordered structure with each residue interacting with the near neighbors by forming more hydrogen bonds locally, making the structure stiffer than pure PVA. The structure shows higher thermal stability before melting, as well as higher rigidity in water. Our results provide the mechanism of the mechanical advantages of hybrid PVA-collagen polymer. The study demonstrates that the structure and mechanics of a synthetic polymer can be tuned by a tiny amount of a natural polymer at the molecular interface. Moreover, it may shed light on identifying a way to improve the mechanics of biodegradable polymer materials without adding much cost, which is crucial for environmental safety.Impact statementBlending natural and synthetic polymers (e.g., polyvinyl alcohol [PVA] and collagen in a hybrid hydrogel) has shown advantages in polymer mechanics, but there is a lack of fundamental understanding. Using molecular dynamics (MD) simulations based on fully atomistic models, we develop the equilibrated structure of the PVA with collagen and characterize its mechanics. We show that by interacting with a collagen molecule, PVA is equilibrated to a more ordered structure with each residue interacting with the near neighbors by forming more H-bonds locally and the structure is stiffer than pure PVA. Moreover, the structure shows a higher thermal stability before the melting point of PVA, as well as higher rigidity in water. Our results demonstrate that the structure and mechanics of a synthetic polymer can be tuned by a tiny amount of a natural polymer at the molecular interface. It provides the mechanism of the mechanical advantages as experimentally observed. This study paves the way for the multiscale modeling and mechanical design of the hybrid polymer material. It sheds light on identifying a way to improve the mechanics of biodegradable materials without adding much cost for both material functionality and environmental safety.Graphical abstract

Toward efficient broad-spectrum UV absorption of carbon dots: Facile preparation, performance characterization and its application as UV absorbers

UV absorbers are sustainable substances that inhibit the ultraviolet (UV) radiative degradation of polymers. In previous reports, the as-prepared carbon dots (CDs) possess only an absorption band at UVA (320–400 nm). To achieve broad-spectrum UV absorption (200–400 nm), increasing the concentration of the CDs solution becomes common. However, a high concentration solution seriously affects the light transmittance due to its heavy yellow color. Furthermore, the promising organic UV absorbers cannot achieve broad-spectrum UV absorption. In this work, we initially synthesized three-component water-soluble carbon dots (OP–CDs), which delivers an excellent UV absorption (98 % UVA and 100 % UVB at the concentration of 1.7 × 10−2 mg/mL; 99 % transmittance in visible light). Moreover, OP–CDs exhibit outstanding stability at high temperatures and different pH. With the corporation of OP–CDs and polyvinyl alcohol (PVA), a high-performance UV-shielding film was formed, leading to enhanced broad-spectrum UV shielding performance and improved mechanical properties, resistance of photocatalytic activity and anti-UV aging ability compared with pure PVA film. Notably, the PVA film remains high transparency with the addition of OP–CDs. The study suggests that the corporation of OP–CDs and polymers is effective in anti-UV degradation.

White Ginger Nanocellulose as Effective Reinforcement and Antimicrobial Polyvinyl Alcohol/ZnO Hybrid Biocomposite Films Additive for Food Packaging Applications

Polyvinyl alcohol (PVA) has been used in packaging applications due to its biocompatibility and biodegradability. However, this non-toxic synthetic material belonging to a highly hydrophilic polymer has poor resistance to wet environments, no antibacterial activity, and low tensile and thermal properties. This study aims to prepare and characterize a PVA-based biocomposite film mixed with antimicrobial white ginger nanocellulose (GCNF) and zinc oxide (ZnO) nanoparticles. The film was processed using GCNF (0.1 g) or/and ZnO nanoparticles (0.5 g). The results confirm that the GCNF/ZnO/PVA-based film presents the strongest antimicrobial activity and the highest thermal resistance. This film also had the best value in tensile strength (19.7 MPa) and modulus (253.1 MPa); 63.9% and 117.9%, respectively higher than purce PVA. Its elongation at break was 56.6%, not statistically significantly different from the pure PVA film. Thus, this PVA-based hybrid biocomposite film reinforced by GCNF and ZnO has excellent potential for fresh food packaging in industrial applications.

A guanidine phosphate-assisted boron nitride network enabled simultaneous improvements in flame resistance and thermal conductivity of polyvinyl alcohol (PVA)

Polyvinyl alcohol (PVA) plays an important role in many fields, but its flammability in air limits its wider application. In this work, SiO2@BN, a flame-retardant and heat conductive filler, were synthesized by hydrolysis of ethyl orthosilicate, and its structure and morphology were characterized successfully. SiO2@BN and guanidine phosphate (GP) were mixed evenly in the solution and added to PVA to form PVA composites. Based on the data of thermal conductivity, limiting oxygen index (LOI) and cone calorimeter test (CCT), the thermal conductivity and flame retardancy of the composite were studied, and the flame retardancy mechanism was explained. The results showed that the thermal conductivity of the PVA composite added with 2 wt.% SiO2@BN and 8 wt.% GP was 82.4% higher than that of pure PVA, and its LOI value reached 28.4%, which was 38.5% higher than that of pure PVA. The peak heat release rate (pHRR) and total heat release (THR) of the composites was 65.2% and 44.4% lower than those of pure PVA, respectively. The main reasons were the physical barrier effect of BN and SiO2, the dilution of the noncombustible gas generated by the decomposition of GP when heated, and the dehydration and carbonization of PVA promoted by the generated phosphoric acid, metaphosphoric acid and other substances.

Sugarcane liquid-generated silver nanoparticles connected ionic polymer nanocomposite for enhanced electrical and wearable sensing signals

Metal nanoparticles (NPs) bonded ionic polymer nanocomposite (IPNC) is required in wearable sensors, structural health monitoring, actuators, fuel cells, batteries, water purifiers, and supercapacitor applications due to their high gauge factor, high conductivity, and high mechanical strength. In this study, a cost-effective IPNC was developed with the bonding of Ag NPs in polyvinyl alcohol (PVA)/sugarcane (SCN) liquid-based ionic polymer (IP). The SCN liquid was used as a reducing agent for converting AgNO3 into Ag and Ag2O NPs into the backbones of PVA and finalized IP/AgNO3-based IPNC with weight ratios of 1/0.3, 1/0.5, and 1/0.7, respectively. The proposed IPNC 1/0.3 generated high sensitivity (ΔR/R) (5.7) and highest gauge factor (G) (307) compared to the existing polyurethane/cellulose/silver nanowire, polyurethane/Ag flakes, and polytetrafluoroethylene-Ag conductors composites. The 1/0.3-based IPNC generated highest ionic conductivity among all the IPNCs and depicted 4 times and 150 times higher than that of the IP and pure PVA polymer due to the uniform distribution of NPs with diameters between 18 and 53 nm in the backbone of the 1/0.3-based IPNC. The 1/0.3-based IPNC showed higher electrical current (14 mA/cm2) and capacitance (700 mF/cm2) than that of the commercial platinum-coated Nafion, polyelectrolytes, and ionic liquid-based IPNC due to the high water uptake (1.34); low contact angle (40°); and S, O, Ag, and Ag2O NPs elements on its surface. The piezoresistive sensing signals from 1/0.3-based IPNC were observed by placing them on the finger and neck. It generated sensing signals on bending of the finger, chin up, chin down, breathing, and coughing, respectively. The cost-effective Ag-attached PVA/SCN IPNC can be utilized in industrial applications such as fuel cells, batteries, water purifiers, wearable sensors, actuators, and supercapacitors.

Infrared-light-driven self-healing MoS2/polyvinyl alcohol hydrogel with simultaneous enhancement of strength and ductility

Self-healing hydrogels exhibit special self-healing or self-recovery function like human skin after injuring, thereafter, draw lots of attention in biomedical applications. However, self-healing hydrogels with strong mechanical and rapid self-healing properties are not fully realized. MoS 2 /polyvinyl alcohol (PVA) hydrogels are developed to achieve rapid self-healing function by utilizing the excellent photothermal conversion effect of MoS 2 under near-infrared (NIR) light. Effects of microstructure and content of MoS 2 on self-healing and mechanical properties of MoS 2 /PVA hydrogels are investigated, including flower-like MoS 2 spheres by bottom-up hydrothermal reaction and MoS 2 sheets by liquid-phase stripping method. The MoS 2 /PVA hydrogels embodied with the two types of MoS 2 were produced by simple freezing/thawing method, and exhibited rapid self-healing function, together with simultaneous enhancement of strength and ductility. The MoS 2 /PVA hydrogel modified by flower-like MoS 2 spheres with a content of 0.5 wt% presents a significant self-healing function with a healing efficiency up to 90.0% within 5 min, and an enhancement of tensile strength of 9.1 MPa (190% to blank PVA) and a ductility of 162.5% (290% to blank PVA). Furthermore, the MoS 2 /PVA gel with flower-like MoS 2 spheres into the PVA networks produces a significant enhancement of fracture strength (58.4 MPa) after fully curing, characterized by an increases of 612% compared with the pure PVA. The photo-induced self-healing and strengthening effects of the MoS 2 /PVA hydrogels are discussed. • A rapid self-healing MoS 2 /PVA hydrogels is developed under near-infrared light. • Photo-thermal conversion effect of MoS 2 produces the self-healing property. • Flower-like MoS 2 spheres exhibit better healing efficiency than MoS 2 sheets. • MoS 2 /PVA hydrogels present a simultaneous increase of strength and plasticity. • 2D and 3D strengthening effects of the MoS 2 /PVA composites are discussed.

Antimicrobial food packaging composite films prepared from hemicellulose/polyvinyl alcohol/potassium cinnamate blends

Hemicellulose and its derivatives have attracted extensive attention as packaging materials and various methods have been utilized to improve its film formation properties. To make use of the byproduct in dissolving pulp production, hemicellulose collected from waste water was modified by carboxymethylation and blended with polyvinyl alcohol (PVA) to prepare composite film by solution casting method. Potassium cinnamate (PC) was further incorporated to endow the film with antibacterial activity. The properties of the composite films were characterized. Due to the good compatibility and intermolecular interactions, the composite film exhibited moderate oxygen barrier property (3.64–12.21 cm3 μm m−2 d−1 KPa−1). The flexibility of the film was improved compared with pure PVA film although tensile strength was decreased. The film had good UV barrier properties and good antibacterial properties due to the introduction of PC. GAB model could be used to predict moisture sorption of the composite films. Moreover, the obtained film showed good performance in cherry tomato preservation. This work provided a prospective route for utilization of hemicellulose recovered from waste water for high value-added products.

Structural, physicochemical and biodegradable properties of composite plastics prepared with polyvinyl alcohol (PVA), OSA potato starch and gliadin

Biodegradable plastics have become a good substitute for traditional plastics. In this study, the ternary plastics were prepared by the solvent casting method using different proportions of octenyl succinic anhydride (OSA) esterified potato starch, gliadin and polyvinyl alcohol (PVA), and their structural, physicochemical and degradable properties were characterized. The results showed that composite plastic's elastic modulus (EM), water resistance, and degradability were higher than pure PVA. When the ratio of OSA potato starch to gliadin was 1:1 and replaced PVA was 25%, the compatibility of composite plastic was the best. When PVA accounts for 75% of the total plastic composition, Tm, ΔHc and ΔHm of composite plastics were larger than pure PVA plastics. Therefore, the biodegradability of PVA plastics can be improved by adding OSA potato starch and gliadin, thus providing effective plastic properties as food packaging materials.

Study Physical Characteristics of Polyvinyl Alcohol/Carboxymethyl cellulose Blend Films

The pure polyvinyl alcohol (PVA), pure CarboxyMethyl Celleluse (CMC), and CMC/PVA blend films with different amounts (0.1, 0.2, 0.25, 0.3 and 0.4gm) of both polymers were prepared by simple solution casting method in this study. FTIR and UV-Vis spectroscopies were used to characterize the physical properties of as- prepared samples. FTIR spectroscopy revealed that the original bonds for both PVA and CMC polymers are appearing in blend polymer but there is some bonds refer to CMC polymer seemed in high amount of this polymer. Optical characteristics showed that the absorbance and absorption coefficient of PVA polymer is improved with increase amounts of CMC polymer. Direct relationship between absorbance and absorption coefficient with amounts of CMC polymer will be establish. The transmittance and energy band gap of pure CMC polymer and pure PVA polymer films are decreased from 5.24 eV and 4.74 eV to 4.38 eV for blend polymer PVA 0.1g/CMC 0.4g film, respectively. From optical properties, it will be concluded that the blend film has highest absorbance and absorption coefficient and lowest transmittance in the UV energy and low value of energy band gap.

Scalable Fabrication of Thermally Conductive Layered Nacre-like Self-Assembled 3D BN-Based PVA Aerogel Framework Nanocomposites.

In this study, three-dimensional (3D) polyvinyl alcohol (PVA)/aligned boron nitride (BN) aerogel framework nanocomposites with high performance were fabricated by a facile strategy. The boron nitride powder was initially hydrolyzed and dispersed with a chemically crosslinked plasticizer, diethyl glycol (DEG), in the PVA polymer system. The boron nitride and DEG/PVA suspensions were then mixed well with different stoichiometric ratios to attain BN/PVA nanocomposites. Scanning electron microscopy revealed that BN platelets were well dispersed and successfully aligned/oriented in one direction in the PVA matrix by using a vacuum-assisted filtration technique. The formed BN/PVA aerogel cake composite showed excellent in-plane and out-of-plane thermal conductivities of 0.76 W/mK and 0.61 W/mK with a ratio of BN/PVA of (2:1) in comparison with 0.15 W/mK for the pure PVA matrix. These high thermal conductivities of BN aerogel could be attributed to the unidirectional orientation of boron nitride nanoplatelets with the post-two days vacuum drying of the specimens at elevated temperatures. This aerogel composite is unique of its kind and displayed such high thermal conductivity of the BN/PVA framework without impregnation by any external polymer. Moreover, the composites also presented good wettability results with water and displayed high electrical resistivity of ~1014 Ω cm. These nanocomposites thus, with such exceptional characteristics, have a wide range of potential uses in packaging and electronics for thermal management applications.

Simultaneous exfoliation and functionalization of black phosphorus by sucrose-assisted ball milling with NMP intercalating and preparation of flame retardant polyvinyl alcohol film

Recently, layered black phosphorus (BP) has become a rising star in two-dimensional materials because of high thermal stability, excellent mechanical properties, and size effect. Layered BP can be used as an ideal filler for the preparation of polymer-based composites with high performance. Realizing the exfoliation and functionalization of BP has become the key to BP's application. Under the protection of N-methylpyrrolidone (NMP) and the assistance of sucrose, we completed the preparation and functionalization of layered BP by ball milling. Surface grafting of oxygen-containing functional groups can realize the uniform dispersion of BP in matrix and improve its stability in air. As expected, the nanocomposites prepared by adding sucrose grafted BP into polyvinyl alcohol (PVA) matrix have significantly improved flame retardancy and mechanical strength. When the addition amount of BP-sucrose(N) was 5 wt%, compared with pure PVA, the decrease of the peak heat release rate (PHRR) and total heat release (THR) reached 52.5% and 32.8%, and the tensile strength increased by 131.2%. Moreover, the addition of NMP can avoid the excessive destruction of the two-dimensional crystal structure of BP, which can also improve the performance of nanocomposites. Due to the encapsulation effect of sucrose, the nanocomposites have excellent air stability. The Ag1/Ag2 value only decreases from 0.52 to 0.49 even after three months of exposure to environmental conditions, which proves that the degree of oxidation is low. This work has provided an efficient way to exfoliate and functionalize BP simultaneously, and expanded the application of BP in flame retardant nanocomposites.

Rice straw cellulose microfiber reinforcing PVA composite film of ultraviolet blocking through pre-cross-linking

Rice straw cellulose microfiber (CMF) was obtained through the gentle low-temperature phase transition method. Then, NaIO4 was utilized to modify CMF by selective oxidation to prepare aldehyde CMF (a-CMF) to improve the reactivity of the CMF. Finally, the a-CMF reinforced polyvinyl alcohol (PVA) composite films were prepared through a pre-cross-linking and solvent casting approach. The cross-linking network formed by a-CMF and PVA through the aldolization reaction significantly improved the mechanical properties of the a-CMF/PVA composite film. The tensile strength of a-CMF-2/PVA was 37.54 ± 0.77 MPa, which was higher than 25.88 ± 2.97 MPa of the pure PVA. SEM results showed that the fracture surface of the a-CMF/PVA composite film with the cross-linking network was smooth. In addition, prepared a-CMF-2/PVA composite films had a transmittance of over 80 % in the visible light range, and also possessed excellent UV blocking property.

Characterization, Properties and Antimicrobial Activity of Radiation Induced Phosphorus-Containing PVA Hydrogels

Function modification of polyvinyl alcohol (PVA) having phosphorus-containing heterocyclic compounds is believed to have thermal and biological applications in the area of polymers. The synthesis of phosphorus-containing PVA (P-PVA) was performed using γ-radiation. The chemical structure of the composite polymer is confirmed by spectroscopic techniques of FT-IR, 1H, 13C, and 31P-NMR. Photosensitive properties of polymers were investigated by ultraviolet spectroscopy. Thermal studies are assigned using the Differential Scanning Calorimeter (DSC) and thermogravimetric analysis (TGA). Data display that P-PVA has more thermal stability than PVA. The surface morphology of the prepared hydrogels was performed using scanning electron microscopy (SEM). Quantitative elemental analysis of the P-PVA hydrogel was done through energy-dispersive X-ray spectroscopy (EDX). Antimicrobial activity of the prepared hydrogels using different fungi such as Aspergillus fumigatus, Geotrichum candidum, Candida albicans, and Syncephal-astrum racemosum, in addition to bacteria such as Staphylococcus aureus, Bacillis subtilis (as gram-positive bacteria), Pseudomonas aeruginosa, and Escherichia coli (as gram-negative bacteria), was studied. The phosphorus-contained PVA hydrogels were found to have antimicrobial activity against various fungi and bacteria compared to pure PVA hydrogels.