PVA Degradation Research Articles

Cost-effective degradation of ultra-high concentration polyvinyl alcohol through peroxymonosulfate based oxidation using nano spinel CoFe2O4 deposited acidified diatomite as the catalyst

To degrade the ultra-high concentration polyvinyl alcohol present in the disposable nuclear protective clothing, nano spinel CoFe2O4 was successfully deposited on acidified diatomite, serving as a catalyst to activate peroxymonosulfate. CF@Dt consists of a base layer with high mechanical strength, which was wrapped by a dense catalytic layer. CF@Dt/PMS reduced the molecular weight of PVA from over 100,000–1380 Da in 300 min, with a total organic carbon removal of 76.3 %. This proves the superiority of CF@Dt/PMS system in degrading ultra-high concentrations of PVA. The performance of CF@Dt/PMS process in PVA degradation was well maintained under a wide range of pH conditions. Although CoFe2O4/PMS process also achieved decent degradation of PVA, CF@Dt exhibited better stability and longer reusability than CoFe2O4. The low metal dissolution rate of CF@Dt was attributed to the chemical interaction between the hydroxyl groups of diatomite and CoFe2O4, as well as the pore confinement effect of diatomite. •OH was found to be crucial in the degradation of PVA by CF@Dt/PMS, with minimal impact from the electron transfer mechanism. The mechanisms of PMS activation by CoFe2O4 and CF@Dt were investigated by density functional theory. Furthermore, an economic evaluation of various PVA degradation processes revealed that the CF@Dt/PMS system is the most cost-effective option.

Radiation-Induced Degradation of PVA 26 by UV Radiation in the Presence of Zno Nanocatalyst

This research work evaluates the degradation of PVA-26 by UV radiation dose between different time intervals from 15-60 minutes under a UV chamber with the intensity of 144W by nanocatalyst ZnO, in the presence of H2O2. We investigated the effect of radiation, acidic medium, sample initial and final concentration, H2O2 concentration, and catalyst dose on the degradation process under these conditions. Different solutions of PVA-26, i.e., 50 ppm, 100 ppm, 150 ppm, and 200 ppm irradiated by the UV lamp at a wavelength of 290 nm. The efficiency of degradation of PVA-26 was checked using different parameters such as (UV/H2O2, UV/ H2O2 + ZnO, UV/ H2O2 + ZnO acidic medium, UV/ZnO H2O2/ZnO, and H2O2/ZnO + acidic medium). The experimental results showed that the rate of degradation increased by increasing radiation time, the concentration of H2O2, and the catalyst. The maximum degradation was observed up to 82 % under optimum conditions (60 minutes radiation time, 0.3 ml H2O2, and 0.1 g/L ZnO in HNO3) after that degradation rate decreased dramatically due to coagulation of HOo radicals. The characterization of the maximum degraded product was analyzed and examined by UV-spectrophotometer and FTIR.

Electrocatalytic activation of peroxomonosulfate (PMS) under aerobic condition for the remediation of oil sands process water: Insight into one-pot synergistic coupling of PMS electro-activation and heterogeneous electro-Fenton processes

Alkaline industrial effluents possess a different challenge during treatment by advanced oxidation processes due to the reduction in redox potential of hydroxyl radical (•OH) in basic media. Herein, electrocatalytic peroxomonosulfate activation (EC-PMS), which synergistically couples an early-stage PMS electro-activation (E-PMS) with subsequent heterogeneous electro-Fenton oxidation (HEF) catalyzed by Fe-modified biochar (BC-Fe) was investigated for enhanced degradation and mineralization of organics in oil sands process water (OSPW). The EC-PMS was first studied for the degradation of surrogate naphthenic acids (NAs) (5-phenylvalveric acid, (PVA)) as a synthetic process water and complete degradation of 50 mg L−1 PVA solution was achieved within very short treatment time (0.5 h) with excellent mineralization (>70 % TOC removal) in 6 h. The efficiency of EC-PMS for PVA degradation was affected by the applied current density, PMS, and catalyst dosage. The organic degradation, electroparamagnetic resonance spectrometry, quenching and chemical probe experiments showed that sulfate radical (SO4•−) generated by E-PMS was the dominant radical oxidant for the degradation of PVA, contributing over 93 %, whereas •OH produced from BC-Fe decomposition of electrogenerated H2O2 in HEF was responsible for the mineralization of the organic solution at the later stage of the coupled process. The EC-PMS showed excellent reusability and was effective for the treatment of real OSPW, achieving complete degradation of real NAs in OSPW and relatively good mineralization of the water. Analysis of the EC-PMS treated OSPW did not simulate any response during the bioactivity assay test using a macrophage cell line, indicating the complete detoxification of the water.

Synergetic PVA degradation and H2 evolution in photocatalytic fuel cells using Ag@Fe2O3 cathode

Synergetic PVA degradation and H2 evolution in photocatalytic fuel cells using Ag@Fe2O3 cathode

Augmented Catalytic Performance of PVA- Assisted Fe2O3 Nano Catalyst for Water Treatment Synthesized via Green Route

Abstract Metal oxides (MO) are widely preferred for removing various effluents from water and air; however due to poor utilization of visible light, the application of MO nanoparticles for water treatments is hindered. This work reports the synthesis of ring-structured PVA-assisted Fe2O3 (P-Fe2O3) nanocomposite through a green route synthesis, for the elimination of methylene blue via sunlight triggered photocatalyst. FTIR spectroscopy confirmed the presence of desired functional groups in novel ring-structured Fe2O3 and PVA-assisted Fe2O3 (P-Fe2O3) nanocomposite. The crystallinity of Fe2O3 was also studied through XRD. Surface topography of Fe2O3 was examined through FE-SEM, that reveals a central hole with extended surface area of Fe2O3. UV-vis-spectroscopy is used to evaluate photocatalytic efficiency which shows, pristine Fe2O3 exhibited 37% degradation in stipulated time intervals of 30~120 mins. The photocatalytic efficiency of augmented P-Fe2O3 nanocomposite expelled 82% of the methylene blue in span of just 02 hours. The stability of the developed nanocomposite in the effluent medium was investigated through FTIR by observing the change in carboxyl adsorption band produced during degradation of PVA, that manifests the fact that no degradation was witnessed for PVA even after 120 min, that makes P-Fe2O3 a promising material for the degradation of AZO dyes.

Rapid seawater‐degradable PBSG/PVA blends: Easy water solubility and easy hydrolysis dual‐promoting degradation

AbstractIn order to shorten the degradation incubation period of existing seawater‐degradable materials and achieve “disappearance” in seawater as soon as possible, based on the successful introduction of hydrolyzed sites GA into the PBS main chain to obtain the PBSG copolymer matrix, water‐soluble PVA is introduced to finally obtain a series of PBSG/PVA blends, aiming to promote the hydrolysis process of polyester matrix by the dual action of water‐soluble PVA and easily hydrolyzed site GA. Compared with pure polyester, PBSG/PVA blends exhibt rapid loss of mechanical properties, weight loss and molecular weight drop in seawater. Among them, PBSG50/PVA0588 = 50/50 with the fastest degradation rate completely loses its mechanical properties within 1 week, and its molecular weight decreases by about 97% after 417 days. In the first 51 days of degradation, the swelling and dissolution of PVA can effectively accelerate the decrease of the molecular weight of polyester matrix, and the Mn decreases by about 50%–80%, which is much higher than that of pure polyester (about 40%). After 417 days in the late stage of degradation, compared with PBS/PVA blends, the easy hydrolysis of GA promots the obvious degradation of the matrix, and the weight loss of matrix can reach 20%.

Degradation of surrogate and real naphthenic acids from simulated and real oil sands process water using electrochemically activated peroxymonosulfate (EO-PMS) process

The remediation of dissolved organics in oil sands process water (OSPW), specifically, naphthenic acids (NAs) is considered a major challenge facing the oil sands industry due to recalcitrant and persistent nature of this class of organics in the environment. Herein, the degradation of 5-Phenylvaleric Acid (PVA) as a NA surrogate compound and real NAs in a simulated OSPW and real OSPW was investigated by coupling electro-oxidation and electrochemically activated peroxymonosulfate (EO-PMS) process. The combined EO-PMS process showed high removal efficiency of PVA, in which EO was enhanced by the successful electrochemical activation of PMS at different electrode surfaces. The effects of different cathode and anode materials, initial PMS concentration, and applied current intensity on the PVA degradation were investigated. The PVA degradation efficiencies increased with the increase in the PMS concentration and applied current, however, decreased at higher levels. Carbon felt cathode and BDD anode showed the highest improvement during EO-PMS process. Both sulfate radicals (SO4•‾) and hydroxyl radicals (•OH) were found to be the primary reactive oxidants identified for the PVA degradation by both radical scavenger and spin-trapped techniques. A complete degradation of 50 mg/L PVA solution and significant reduction of the classical and oxidized NAs as well as aromatics in real OSPW were achieved by EO-PMS compared to EO alone. The results confirmed that the combination of electrochemical oxidation and electro-activated PMS process (EO-PMS) could be a promising and efficient technology for the treatment of recalcitrant NA compounds in OSPW.

Modifying Anti-Compression Property and Water-Soluble Ability of Polyglycolic Acid via Melt Blending with Polyvinyl Alcohol.

Biodegradable polymeric materials have become the most attractive research interest in recent years and are gradually widely used in various fields in the case of environmental pollution. In this paper, binary blends, mainly including varying contents of polyglycolic acid (PGA) and poly(vinyl alcohol) (PVA), were prepared via a melt compounding strategy. The ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA) was employed as the compatibilizer to improve the compatibility between the PGA and PVA and the polyolefin elastomer (POE) was used as toughening agent. The anti-compression property and water-soluble ability of the blends were particularly studied to explore their potential application in an oil/gas exploitation field. Special attentions were paid to the evolution of the water-soluble ability of PGAX with the PVA concentration. Furthermore, isothermal shear measurement and thermogravimetric analysis were performed to evaluate the thermal stability of PGA and PGA blends (PGAX) during melt processing. The results showed that the incompatibility between PGA and PVA largely deteriorated the mechanical property, i.e., anti-compression strength, leading to fragile characteristics under a lower compressive load for the PGAX samples with varied contents of PVA. The presence of PVA and EMA-GMA greatly enhanced the viscoelasticity of the PGA melt, showing an increased storage modulus and viscosity at a low shear frequency; however, the thermal instability of PGAX was intensified owing to the greater ease of thermal degradation of PVA than that of PGA. Meanwhile, the water-soluble ability of PGAX was improved due to the high water dissolution of PVA, which played the role as a sacrificial material. The purpose of this work is to pursue an effective modification for PGA processing and application via melt blending.

Swellable PVA/PVP hydrogel microneedle patches for the extraction of interstitial skin fluid toward minimally invasive monitoring of blood glucose level.

Interstitial skin fluid (ISF) is an emerging alternative source of blood samples that has attracted great interest from researchers. It is a very promising way to use microneedle patches for extracting ISF. However, the recovery of ISF still faces great challenges, such as long extraction time and low extraction volume, which may affect the analysis of biomarkers. Traditional centrifugation methods cannot completely recover ISF, which leads to inaccuracy in ISF detection. In this paper, the prepared polyvinyl alcohol/polyvinylpyrrolidone (PVA/PVP) microneedle patches had the ability to insert into the skin in a dry state; at the same time, the microneedle patches had good swelling properties and could extract ISF in a short time without any additional devices. Due to the thermal degradation of PVA, the way of gentle heating was used to recover ISF, which could greatly improve the accuracy of detection. By comparing the D-glucose content assay kit with the blood glucose concentration of rats detected using a commercial glucometer, the detection accuracy of the microneedle patches was verified. The microneedle patches can be used to sample ISF and analyze the level of biomarkers in ISF, and are expected to provide a basis for the prevention and diagnosis of clinical diseases in the future.

Ultraviolet light exposure degradation effect on the properties of nanocrystalline cellulose-reinforced polyvinyl alcohol composite film

PVA used in packaging applications has been faced with a UV light degradation challenge, which often reduces its durability while in use. The UV light stability enhancement effect of nanocrystalline cellulose (NCC) reinforcement in PVA was studied. Polyvinyl alcohol composite film was reinforced with NCC from palm oil waste (PVA-NCC film) and exposed to UV light (22 W, SUV-16 254 nm) for different time duration to study the material durability enhancement. The percentage weight loss of the samples was measured to observe the UV light degradation effect. Furthermore, the samples’ structural, morphological, and tensile properties were studied before and after exposure to UV light with FT-IR, scanning electron microscopy (SEM), and tensile test. The results showed physical degradation, morphological and tensile properties enhancement of PVA with NCC’s addition. The addition of NCC to the PVA matrix reduced the degradation rate under UV light significantly. Also, the percentage of weight loss was observed to change with the exposure time to UV light.

Spin-trapping analysis for thermal degradation of poly(vinyl alcohol)

Spin-trapping electron spin resonance (ESR) and gel permeation chromatography (GPC) were applied to analyze the thermal degradation mechanisms of poly(vinyl alcohol) (PVA). The lifetime of the short-lived radical intermediate produced by thermal degradation at up to 200 °C was extended via the spin-trapping method for the purpose of investigating its molecular structure. Under the addition of the spin-trapping reagents dimethyl-1-pyrroline-N-oxide (DMPO) or 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), into the PVA, the production of some radical intermediates, including hydroxyl (•OH) and some main chain radicals (–CH=CH–•CH– and •CH(OH)–CH2–), was confirmed via simulation analysis of the observed ESR spectra. The GPC measurement revealed that the cross-linking reaction occurred more often at temperatures above 100 °C and that the main chain scission also occurs significantly at around 200 °C. The elimination of •OH is therefore a key reaction in PVA degradation, and •CH(OH)–CH2– is produced by the β-scission from the main chain radical –CH2–•C(OH)–CH2–. This last radical was not observed in the present study; however, it should be produced through a hydrogen abstraction by •OH.

Nonlinear System Identification for Aqueous PVA Degradation in a Continuous UV/H2O2 Tubular Photoreactor

In this study, the performance of three black-box identification techniques using linear autoregressive with exogenous input (ARX), nonlinear ARX (NARX), and Hammerstein–Wiener (HW) algorithm to model the dynamics of UV/H₂O₂ continuous tubular photochemical reactor for the treatment of poly(vinyl alcohol) (PVA) based on experimental data is investigated. In addition, the inherent nonlinearity of the reaction process is assessed. The reactor dynamics in the NARX model is estimated by wavelet, sigmoid, and tree partition networks along with the assessment of the performance of each model. Although a sigmoid network describes the nature of chemical processes better, the results show that tree partition network-based NARX is the most suitable estimator for the studied process as represented by its highest quality of fit (91.59% for training data set and 88.17% for validation of data set), lowest loss function (mean-squared error, MSE) (0.0004279), model realizability, open-loop stability, model whiteness, and model independence.

Catalytic Degradation of Poly(Vinyl Alcohol) by FexMnyCuzOw/γ-Al2O3 Nano-particles Catalyst Using Box-Behnken Design

FexMnyCuzOw/γ-Al2O3 nanoparticles were prepared by a wet impregnation -calcination method and characterized by means of XRD, BET, SEM-EDS. Box-Behnken design was used to investigate the degradation of PVA in aqueous solution. Besides, the effect of different calcination temperature, FexMnyCuzOw/γ-Al2O3 dosage, H2O2 dosage, initial P VA concentration and initial solution pH on the removal of P VA were also studied. Results showed that P VA can be efficiently removed and oxidized by the heterogeneous Fenton-like process with appropriate amount of FexMnyCuzOw/γ-Al2O3 and H2O2. In this paper, the efficiency of P VA was above 90 % by FexMnyCuzOw/γ-Al2O3 nanoparticles at an initial P VA concentration below 25 g/l, temperature at 60 oC, initial pH from 1.0 to 6.0, H2O2 and catalyst dose of 60 ml/l and 0.5 g/l, respectively. In addition, chromatography (GPC) was applied to further analyze the degradation of P VA under different experimental conditions, which revealed that the backbone chain of P VA could be effectively broken and oxidized. Several unsaturated degradation products, including butanones, benzaldehydes, hexanals and acetic acids were also detected and identified by gas chromatography-mass spectrometry (GC-MS). Besides, the nano catalyst maintained favorable catalytic ability during the five-times utilization, which means it could be recycled by filtration and calcination.

Accelerated degradation of polyvinyl alcohol via a novel and cost effective heterogeneous system based on Na2S2O8 activated by Fe complex functionalized waste PAN fiber and visible LED irradiation

To realize the low cost and highly effective removal of PVA from wastewater, waste polyacrylonitrile (PAN) fiber was modified and reacted with Fe3+ ions to fabricate the amidoximated PAN fiber Fe complex (Fe-AO-PAN), which then was characterized and employed to activate Na2S2O8 for PVA degradation. Fe-AO-PAN was found to effectively activate Na2S2O8 in the dark, and LED visible irradiation enhanced its activation effect on Na2S2O8, thus accelerating the PVA degradation. Increasing irradiation or high Fe content of Fe-AO-PAN could significantly promote the PVA degradation. Fe-AO-PAN also showed better activation performance for Na2S2O8 in a wide pH range. Electron Spin Resonance (ESR) studies suggested that hydroxyl radicals were the main reactive oxygen species generated in Na2S2O8/Fe-AO-PAN system, which was primarily responsible for PVA degradation. By increasing LED visible irradiation, Na2S2O8/Fe-AO-PAN system exhibited the similar degradation and detoxicity efficiency of PVA solution to H2O2/Fe-AO-PAN system with high pressure Hg lamp irradiation. These findings presented a novel method of waste control by waste in environmental remediation.

Properties of Poly(Vinyl Alcohol)/Chitosan Nanocomposite Films Reinforced with Oil Palm Empty Fruit Bunch Amorphous Lignocellulose Nanofibers

The objective of this study was to investigate the properties of poly(vinyl alcohol)/chitosan nanocomposite films reinforced with different concentration of amorphous LCNFs. The properties analyzed were morphological, physical, chemical, thermal, biological, and mechanical characteristics. Oil palm empty fruit bunch LCNFs obtained from multi-mechanical stages were more dominated by amorphous region than crystalline part. Varied film thickness, swelling degree, and transparency of PVA/chitosan nanocomposite films reinforced with amorphous part were produced. Aggregated LCNFs, which reinforced PVA/chitosan polymer blends, resulted in irregular, rough, and uneven external surfaces as well as protrusions. Based on XRD analysis, there were two or three imperative peaks that indicated the presence of crystalline states. The increase in LCNFs concentration above 0.5% to PVA/chitosan polymer blends led to the decrease in crystallinity index of the films. A noticeable alteration of FTIR spectra, which included wavenumber and intensity, was obviously observed along with the inclusion of amorphous LCNFs. That indicated that a good miscibility between amorphous LCNFs and PVA/chitosan polymer blend generated chemical interaction of those polymers during physical blending. Reinforcement of PVA/chitosan polymer blends with amorphous LCNFs influenced the changes of Tg (glass transition temperature), Tm (melting point temperature), and Tmax (maximum degradation temperature). Three thermal phases of PVA/chitosan/LCNFs nanocomposite films were also observed, including absorbed moisture evaporation, PVA and chitosan polymer backbone structural degradation and LCNFs pyrolysis, and by-products degradation of these polymers. The addition of LCNFs 0.5% had the highest tensile strength and the addition of LCNFs above 0.5% decreased the strength. The incorporation of OPEFB LCNFs did not show anti-microbial and anti-fungal properties of the films. The addition of amorphous LCNFs 0.5% into PVA/chitosan polymer blends resulted in regular and smooth external surfaces, enhanced tensile strength, increased crystallinity index, and enhanced thermal stability of the films.

Bioinformatics Analysis and Characterization of Highly Efficient Polyvinyl Alcohol (PVA)-Degrading Enzymes from the Novel PVA Degrader Stenotrophomonas rhizophila QL-P4.

Polyvinyl alcohol (PVA) is used widely in industry, and associated environmental pollution is a serious problem. Herein, we report a novel, efficient PVA degrader, Stenotrophomonas rhizophila QL-P4, isolated from fallen leaves from a virgin forest in the Qinling Mountains. The complete genome was obtained using single-molecule real-time (SMRT) technology and corrected using Illumina sequencing. Bioinformatics analysis revealed eight PVA/vinyl alcohol oligomer (OVA)-degrading genes. Of these, seven genes were predicted to be involved in the classic intracellular PVA/OVA degradation pathway, and one (BAY15_3292) was identified as a novel PVA oxidase. Five PVA/OVA-degrading enzymes were purified and characterized. One of these, BAY15_1712, a PVA dehydrogenase (PVADH), displayed high catalytic efficiency toward PVA and OVA substrate. All reported PVADHs only have PVA-degrading ability. Most importantly, we discovered a novel PVA oxidase (BAY15_3292) that exhibited higher PVA-degrading efficiency than the reported PVADHs. Further investigation indicated that BAY15_3292 plays a crucial role in PVA degradation in S. rhizophila QL-P4. Knocking out BAY15_3292 resulted in a significant decline in PVA-degrading activity in S. rhizophila QL-P4. Interestingly, we found that BAY15_3292 possesses exocrine activity, which distinguishes it from classic PVADHs. Transparent circle experiments further proved that BAY15_3292 greatly affects extracellular PVA degradation in S. rhizophila QL-P4. The exocrine characteristics of BAY15_3292 facilitate its potential application to PVA bioremediation. In addition, we report three new efficient secondary alcohol dehydrogenases (SADHs) with OVA-degrading ability in S. rhizophila QL-P4; in contrast, only one OVA-degrading SADH was reported previously.IMPORTANCE With the widespread application of PVA in industry, PVA-related environmental pollution is an increasingly serious issue. Because PVA is difficult to degrade, it accumulates in aquatic environments and causes chronic toxicity to aquatic organisms. Biodegradation of PVA, as an economical and environment-friendly method, has attracted much interest. To date, effective and applicable PVA-degrading bacteria/enzymes have not been reported. Herein, we report a new efficient PVA degrader (S. rhizophila QL-P4) that has five PVA/OVA-degrading enzymes with high catalytic efficiency, among which BAY15_1712 is the only reported PVADH with both PVA- and OVA-degrading abilities. Importantly, we discovered a novel PVA oxidase (BAY15_3292) that is not only more efficient than other reported PVA-degrading PVADHs but also has exocrine activity. Overall, our findings provide new insight into PVA-degrading pathways in microorganisms and suggest S. rhizophila QL-P4 and its enzymes have the potential for application to PVA bioremediation to reduce or eliminate PVA-related environmental pollution.

An Effect of Salt Concentration and Inoculum Size on Poly(Vinyl Alcohol) Utilization by Two Sphingomonas Strains

Due to its widespread use and water solubility, poly(vinyl alcohol) (PVA) has the potential to find its way into various water or soil ecosystems. Despite the fact that many bacterial species with the capacity of utilizing PVA have been found and described, the influences of some environmental factors on their capabilities to biodegrade PVA have not been adequately studied. Therefore, study was made of the effects of two environmental factors on PVA degradation exhibited by two Sphingomonas strains. Both strains originated from common wastewater treatment plants, and proved to be considerably sensitive to increased inorganic salt concentrations; in brief, 13.3 mmol/l either of phosphate or chloride ions significantly delayed the degradation process or inhibited it entirely. In contrast to such halosensitivity, both strains were able to rapidly utilize PVA under suitable conditions, even when low inoculum sizes were applied. Initial cell densities, ranging from 100 to 107 cells/ml, were used in two series of degradation trials and PVA degradation occurred in all cases; merely delays extending over several days in the degradation process were noted when inoculum sizes of 100–103 cells/ml were applied.

Determination of degradation kinetics of polyvinyl alcohol/X-zeolite nanocomposite

Poly(vinyl alcohol) (PVA) containing Ag-modified X-zeolite (PVA/X-zeolite) nanocomposite was successfully fabricated using solution casting technique. Morphology, structural and thermal properties of the pure PVA and its nanocomposite were characterized by FE-scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX), X-ray diffraction, and differential scanning calorimetry (DSC), respectively. Results from DSC traces showed that the X-zeolite acts as efficient nucleating agent toward PVA crystallization. Photographs of FE-SEM demonstrate the nanosize and homogenous dispersion of the X-zeolite in PVA matrix. Moreover, EDX analysis confirmed the presence of constituent elements of the X-zeolite in the nanocomposite as well. Thermal degradation of PVA and PVA/X-zeolite nanocomposite was addressed in details by thermogravimetry analysis under non-isothermal conditions. Similar to pure PVA, the PVA/X-zeolite nanocomposite thermally degraded in two steps ranged from 400 to 690 K and 700 to 780 K, respectively. Values of the apparent activation energies were estimated using Friedman’s isoconversional method. A strong dependence of the Ea on conversion (α) was observed. To confirm the anticipated reaction models, differential master plot analysis was applied to the experimental data. Results showed that the degradation of PVA and its nanocomposite could be described by the reaction-order (A type) kinetic model.

Study on thermal properties of poly(vinyl alcohol) and polyurethane composites with multiwalled carbon nanotubes/silica nanohybrids

Two kinds of multiwalled carbon nanotubes/silica nanohybrids (CNTs/SiO2) were synthesized via a sol–gel method by coating SiO2 on the surfaces of CNTs that had been functionalized with poly(sodium- p-styrenesulfonate) (PSS). The influence of the nanohybrids on the thermal properties of poly(vinyl alcohol) (PVA) and polyurethane (PU) composites was investigated. Characterization of CNTs/SiO2 nanohybrids, elucidated with scanning electron microscopy and X-ray diffraction, showed that PSS played a key role in the final morphology and resulted in a “core/shell” and “candied haws on a stick”-like structure. The thermal degradation and thermo-oxidation of PVA and PU composites evaluated by thermogravimetic analyses suggested that the thermal properties of PVA/(CNTs/SiO2) composites were improved at relative high temperature range when compared with pure PVA, and the improvement mainly depended on the loading fraction of the nanohybrids, while for PU/(CNTs/SiO2) composites, a small fraction of the nanohybrids increased the materials thermal properties, but the improvements were influenced by the type of CNTs/SiO2 nanohybrids.

Simultaneous Enhancements of UV-Shielding Properties and Photostability of Poly(vinyl alcohol) via Incorporation of Sepia Eumelanin

Sepia eumelanin (SE), a biomacromolecule, was developed to prepare the excellent UV-shielding polymer material with better photostability. UV–vis transmittance spectra showed that poly(vinyl alcohol) PVA/SE film blocked most ultraviolet light below 300 nm even with a low concentration of SE (0.5 wt %), which still kept its high transparency in the visible spectrum. Rhodamine B photodegradation measurement further confirmed the excellent UV-shielding properties of PVA/SE film. FTIR indicated that the carbonyl absorption bands resulting from phtodegradation for PVA/SE film did not change after UV exposure for 2700 h. The tensile properties of neat PVA were deceased intensely after UV irradiation; however, those of PVA/SE film were reduced a little. Moreover, AFM indicated that the surface roughness of PVA/SE film was much lower than that of a neat PVA one. It could be concluded that SE reduced the PVA degradation rate dramatically, revealing enhanced photostability of PVA/SE film. The mechanism for outstand...