Degradation of poly(L‐lactide) films under ultraviolet‐induced photografting and sterilization conditions

The degradation of polymers under ultraviolet (UV) irradiation has been a great concern for biomaterial and agricultural applications. The major objective of this research was to study the effect of UV irradiation on the representative bulk and surface properties of poly (L ‐lactide) (PLA) films. Two UV sources with different spectral outputs and intensities were chosen so that one of them could be used for surface modification and the other could be used for UV sterilization of the PLA films. The results established that the molecular weight of PLA decreased significantly during irradiation from the photografting lamp under atmospheric conditions. Irradiation through a Pyrex container was shown to minimize polymer degradation during UV exposure from the photografting lamp. The PLA films UV‐irradiated under the sterilization lamp for 12 h revealed a similar reduction in the molecular weight and no change in the surface hydrophilicity. However, significantly less photodegradation was observed under the sterilization lamp when the samples were held in a Pyrex container. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of ultraviolet irradiation treatment on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens)

The poor adhesion of bamboo coatings is a serious issue in the bamboo industry. To overcome this problem it is necessary to modify the actual surface of the bamboo before finishing. A study on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens) were investigated with various UV irradiation conditions including irradiation time and dose using different UV lamps. Two types of wood coatings, i.e., solvent‐borne nitrocellulose (NC) lacquer and waterborne polyurethane (PU) coating, were used in the study, and 180° peel strength and shear strength tests for measuring adhesion of films were conducted. The results revealed that the wettability and the carbonyl group concentration of the bamboo surface were increased. This was particularly apparent for an irradiation time less than 15 s with a mercury UV lamp (H‐lamp), rated at an intensity of 100 W/cm kept at a distance of 15 cm. In all the treatments, the greenish appearance of moso bamboo was retained and the adhesion was improved. Especially, using solvent‐borne NC lacquer finishing, the higher‐dose (under a mercury UV lamp combined with metal halide lamp; H + M‐lamps) irradiated bamboo had the best adhesion, while, for waterborne PU coating, the H‐lamp irradiated one showed the best improvement. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

GPC/LS Analysis of the Photodegradation Products of Poly(phenylmethylsilane)

The photodegradation of poly(phenylmethylsilane) (PPMS) was studied using two sources of irradiation: a commercial Hg lamp and a neodymium: yttrium aluminium garnet (Nd:YAG) laser tuned to a wavelength of 266 nm. The degradation products were studied using a coupled system: Gel Permeation Chromatography/Light Scattering (GPC/LS). We focus on the importance of having a multiangle detector on the line with the GPC to obtain information related to molecular conformation, molecular weight, polydispersity and mass during the photodegradation. The results obtained were a function of the UV source. At the beginning of the photodegradation, the PPMS was strongly affected by the Hg lamp; and, the molecular weight as a function of volume retention showed the presence of at least two different species that contained differently shaped molecules. In the photodegradation of PPMS using Nd:YAG laser, the molecular weight as a function of volume retention showed a single conformation. On the basis of the polydispersity as a function of UV exposure time, it was observed that after 10 seconds of irradiation using either the Hg lamp or the laser source, homolytic scission of silicon–silicon bonds in the termini of the polymer chain was the main depolymerization process. Finally, after 25 seconds (with Hg lamp) and 60 seconds (with laser) of exposure the polydispersity was considerably increased owing to random chain scissions.     

Sterilization system for air purifier by combining ultraviolet light emitting diodes with TiO2

BACKGROUND: Ultraviolet light emitting diodes (UV LEDs) were used as a light source in TiO₂ photocatalysis because of their many advantages, such as, long life, safety, low pollution, etc. In this experiment, a light source panel was successfully fabricated with UV LEDs, the light intensities of which were relatively uniform. RESULTS: The sterilization process comprised two steps. First, an aerosol was blocked by high efficient particulate air (HEPA) filter paper coated with TiO₂ photocatalyst. Second, Staphylococcus aureus in the aerosol decreased gradually in the photocatalysis process of UV LED/TiO₂. After 52 h irradiation all the S. aureus were killed. CONCLUSION: The UV LED light source panel had a larger surface for irradiation than a mercury lamp. Thus, its sterilization efficiency was much better than that of traditional methods. The feasibility of UV LED/TiO₂ for photocatalysis was proved. Copyright © 2009 Society of Chemical Industry     

Different photodegradation processes of PVC with different average degrees of polymerization

The influence of ultraviolet (UV)‐irradiation on the photodegradation mechanism of different average degrees of polymerization (DP ) of poly(vinyl) chloride (PVC) with UV‐irradiation time was investigated by viscosity‐average molecular weight determination, UV‐vis spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), contact angle measurement, and scanning electron microscopy (SEM). PVC films with different DP (800, 1000, 1300, 3000) were prepared by solution casting. It was carried out exposing specimens to a xenon‐arc light source with a spectral irradiance of 0.68 W/(m² ·nm) at 63°C. It was found that the photodegradation mechanism of the lower DP of PVC (DP = 1000) was different from the higher DP of PVC (DP = 3000). This was because the lower DP of PVC was a homopolymer, while the higher DP of PVC was often produced by copolymerizing with a certain quantity of crosslinking agent (e.g., DAP and DAM). UV‐vis and FTIR spectroscopy studies provided some results concerning the structure of the irradiated PVC, and the carbonyl index and C? Cl index were induced to study the process of PVC photodegradation with different DP . TGA showed that the degradation temperatures of different weight loss increased with the irradiation time. The surface morphology of the irradiated polymer films with different DP was observed by contact angle measurement and SEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface hydrophilic–hydrophobic property on transparent mesoporous silica thin films containing chromium oxide single-site photocatalyst

Using a sol–gel/spin-coating method with organic template, the transparent mesoporous silica thin films containing chromium oxide moieties can be prepared on quartz plate. The spectroscopic characterization has revealed that these thin films contain isolated and tetrahedrally coordinated chromium oxide moieties (single-site photocatalyst) in their frameworks. Even before UV light irradiation these Cr-containing mesoporous silica (CrMS) thin films have demonstrated a hydrophilic surface property more strongly than Cr-containing non-porous silica films and mesoporous silica thin films without chromium oxide. Furthermore, the Cr-containing mesoporous silica thin films showed the super-hydrophilic property not only under UV light irradiation but also even under visible light irradiation from a fluorescent lamp. In the presence of ethylene gas, the polyethylene was successfully formed on the surface of the CrMS thin film under UV light irradiation. After the formation of polyethylene the surface property of the CrMS thin film was converted into hydrophobic while keeping its transparency. The isolated and tetrahedrally coordinated chromium oxide moieties are responsible for these photo-induced surface reactions.     

Photodegradation of ethylene/propylene/polar monomers,co‐, and terpolymers. II. Prepared by Ni catalyst systems

The copolymers of ethylene/propylene as well as their terpolymers with polar monomers were prepared by Ni‐catalyst systems and their photodegradation behavior was studied by Fourier transform infrared spectroscopy. The polar monomers used to synthesize co‐ and terpolymers of ethylene/propylene/polar monomer were 5‐hexen‐1‐ol, 10‐undecen‐1‐ol, acrylamide, methylmethacrylate, acrylonitrile, and methylvinyl ketone. The morphological changes of the irradiated samples were determined by scanning electron microscopy. The photodegradation kinetics has also been studied. The surface damage caused by polychromatic irradiation (λ ≥ 290 nm) at 55 °C in atmospheric air is presented in different micrographs. The rate of photo‐oxidative degradation is very fast in terpolymers containing polar monomers as compared with copolymers and homopolymers. The morphological study of the photodegraded samples showed a very good correlation with the photodegraded results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1783–1791, 2007     

Adhesion failure of antiscratch coatings on polycarbonate under UV irradiation

The adhesion failure of antiscratch (AS) coatings on unmodified and plasma‐modified polycarbonate (PC) substrate was studied using both chemical and physical methods while considering the surface and interface changes between coatings and PC under ultraviolet (UV) irradiation. The differences in the wettability and surface elemental compositions of the PC surface (PCs) and AS coatings after UV ageing were evaluated by contact angle and Fourier transform infrared (FTIR) measurements. The nanoindentation technique was employed for the quantitative assessment of the changes in the nanomechanical properties of both PCs and AS coatings under UV irradiation. The adhesion of coating on plasma‐modified PC was found to be significantly better than that of unmodified substrates. The hydrophilicity and polarity of PCs covered by AS coatings were significantly increased because of the photodegradation of PCs, whereas silicon coatings remained invariant. Nanoindentation tests revealed an obvious enhancement in stiffness of the coating and exposed PC after ageing. Based on these experiments, we proposed that adhesion failure under UV irradiation may be caused by two reasons: first, the photodegradation that occurred at the PCs covered by AS coatings; and second, the stress induced by the changes in stiffness of both AS and PCs under UV ageing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40507.     

Effect of microstructure tuning by rapid heat cycle molding on the photodegradation behavior of isotactic polypropylene

Rapid heat cycling molding (RHCM) is an injection molding technique that improves the product quality of isotactic polypropylene (iPP) by tuning the microstructure, but its effect on the photodegradation stability remains to be investigated. In this work, the effect of RHCM tuned microstructure on the photodegradation behavior of iPP was investigated and compared with conventional injection molding (CIM). Differential scanning calorimetry (DSC), x-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), atomic force microscopy (AFM), and shore durometer (D scale) were used to examine the photodegradation behavior of iPP samples. The results showed that RHCM increased the crystallinity, crystal size, and β-crystal content of iPP samples. With the increase of photodegradation time, iPP samples injected with RHCM showed higher stability in terms of microstructure and surface quality. The relative changes in CI and R_a of RHCM90 were reduced by 48% and 40% after 800 h of UV irradiation, respectively. In addition, the combined results of dynamic mechanical analysis (DMA) and UV–visible absorption spectrum showed that RHCM promoted the development of crystalline structure and reduced the mobility of the surface chain segments as well as UV absorption coefficient. These combined effects contributed positively to its photodegradation stability.     

Ag_8 W_4 O_(16)光催化剂的微波辅助制备与光催化性能

以硝酸银和钨酸钠为原料,采用微波法制备Ag_8W_4O_(16)光催化剂。使用XRD和UV-Vis等手段对样品相组成和UV-Vis吸收特性进行表征;以高压汞灯、氙灯和太阳光为实验光源,罗丹明B为模型污染物,考察Ag_8W_4O_(16)光催化剂的光催化降解活性;探讨催化剂用量、光照时间及光源种类对罗丹明B降解率的影响。XRD结果表明,所得样品为四聚体Ag_8W_4O_(16),属四方晶系,空间群为Pn2n[34],且样品纯度较高。UV-Vis分析表明,样品在(450～600)nm有较强的吸收。光催化降解结果表明,Ag_8W_4O_(16)对罗丹明B具有较好的光催化活性,光催化反应满足一级动力学方程,且光源对活性影响显著。当罗丹明B浓度20 mg·L~(-1)、体积20 mL、催化剂用量20mg和光源为500W高压汞灯时,光催化活性最高。     

Surface modification of poly(ethylene terephthalate) fiber by excimer light

Changes in the surface topography and chemical structure on the surfaces of poly(ethylene terephthalate) (PET) fibers and films caused by the irradiation using an excimer laser beam and excimer lamp light were monitored. The SEM (scanning electron microscopy) observation suggests that a wavy shape was produced by irradiation with the excimer laser beam, while such a wavy shape was not observed when the excimer lamp light was used. The XPS (X-ray photoelectron spectroscopy) analysis of the fiber surface suggests that the O/C intensity ratio was reduced by irradiation using the laser beam, whereas this ratio gradually increased with irradiation with the lamp light. This difference is attributed to the difference in the number of photons in the laser beam, which was much higher than that in the lamp light, although the laser beam and lamp light had the same wavelength and energy. As for wettability to water, the contact angle was smallest for PET irradiated by the excimer lamp light. For adhesion studies, the PET fabric was first coated with an epoxy acrylate solution, irradiated with excimer light, dipped into RFL (resorcinol-formaldehyde-latex) adhesive, and the peel strength to rubber sheet was examined. When the irradiation by the excimer laser beam was compared with that with the excimer lamp light, the laser irradiation showed a good adhesion property even for rubber vulcanization carried out for a long time at high temperature.     

Photodegradation of polypropylene in the presence of ferric chloride

The effect of ferric chloride (FeCl₃) on photodegradation of isotactic polypropylene (PP) was investigated using mainly ESR spectrometry. PP powder, its oxidized samples, and FeCl₃-adsorbing PP samples were irradiated under a nitrogen atmosphere at 77°K with ultraviolet light from a high-pressure mercury lamp and a superhigh-pressure mercury lamp modified by various filters. Methyl, polymerci alkyl, and peroxy radicals were observed in the ESR spectra of the irradiated samples, and it was found that FeCl₃ depresses the formation of alkyl radicals and accelerates the formation of peroxy radicals catalyzing the reaction. From infrared study of UV-irradiated film samples, it was also inferred that FeCl₃ accelerates the photodegradation the hydroperoxide and carbonyl groups.     

Ozonation and photodegradation kinetics of pollutant acids in wastewaters

The kinetics of the degradation of four phenolic acids by ozonation and polychromatic UV radiation were investigated. The acids: p-hydroxyphenylacetic, homoprotocatechuic (3,4-dihydroxyphenylacetic acid), gentisic (2,5-dihydroxybenzoic acid) and 2,3-dihydroxybenzoic, have been selected because of they constitute major pollutants present in some agro-industrial wastewaters. The p-hydroxyphenylacetic acid was initially ozonated and UV irradiated alone. Its kinetic constants and reaction orders in the ozonation process were deduced by using a model based in the film theory which takes into account the mass transfer with the chemical reaction. The quantum yields in the photodegradation process were evaluated from a simple reaction mechanism with the help of an emission model to determine the radiation flow rate absorbed. Later, in the simultaneous ozonation and UV photodegradation of the mixtures of the four acids, competitive kinetic methods were developed to determine the individual rate constants between ozone and each acid in the ozonation process, and the individual quantum yields for every acid in the photodegradation process.     

A novel rapid microwave crystallization of photocatalysts for practical utility in the removal of phenol derivatives

A new concept of the microwave-assisted process was used for the crystallization of titania nanoparticles. The presented microwave crystallization can be indicated as truly environmentally friendly due to its energy efficiency and very short process time. In addition, it allows one to obtain pure materials without surface defects, which was confirmed by the EPR analysis. The physicochemical properties (such as crystallinity, morphology, and textural properties) of the synthesized TiO₂ nanomaterials are strongly dependent on the microwave crystallization temperature. In this work, for the first time, the novel and convenient LED photoreactor was compared directly with the classic high-pressure mercury lamp. Photocatalytic studies showed higher activity in the oxidation of phenol and 4-chlorophenol under UV-LED light, compare to high-pressure Hg-lamp. The reason for improving photo-oxidation performance under LED light is indicated that each of the LEDs has the same parameters, so they can be considered as many single sources of UV radiation occurring throughout the entire cross-section of the reactor. This confirms that microwave-assisted crystallization of TiO₂-photocatalysts and application of LEDs as light sources can be elements of a novel photocatalytic approach toward environmental protection. The presented results show that the simultaneous approach to the development of photocatalysts and novel light is the right route to further develop photocatalysis to enter this process into truly environmental protection.     

Photodegradation of some Oxygenated Polycyclic Aromatic Hydrocarbons

In order to obtain information about the degradability of oxygenated polycyclic aromatic hydrocarbons (oxy-PAHs) in environment, photodegradation in acetonitrile solution was studied on 9,10-phenanthrenequinone, 9-phenanthrenecarbaldehyde (phenanthrene-9-carboxaldehyde) and 1,8-naphthalenedicarboxylic anhydride (1,8-naphthalic anhydride), which are formed by fuel combustion or by photoirradiation of PAHs. A solution of the substrate was irradiated under atmospheric conditions using a xenon lamp. Photodegradation rates and information about products were obtained using HPLC with fluorescence and photodiode array detectors and GC/MS.

9,10-Phenanthrenequinone rapidly degraded by irradiation of light and yielded diphenic acid, diphenic acid anhydride, phthalic acid anhydride and some unknown compounds. Diphenic acid was a main product and it was produced at maximum upon 5-hour irradiation when degradation rate approached 100%. This reaction seems not to obey first-order equation. 9-Phenanthrenecarbaldehyde degraded slower than 9,10-phenanthrenequinone and yielded a polar unknown compound as a main product. While 1,8-naphthalenedicarboxylic anhydride showed quite stable character under irradiation of light.     

纳米TiO2薄膜对活性深蓝ST-2GLN染料的光催化降解研究

采用溶胶-凝胶（Sol—Gel）法,以钛酸正丁酯为前驱体,以不锈钢表面为基底,用提拉法镀膜,在400℃下高温煅烧2h．制备出纳米TiO,薄膜光催化剂。在以波长为254nm、8W的紫外灯为光源、光源到溶液的距离为2cm的条件下。对活性深蓝ST-2GLN模拟染料废水进行光催化降解试验。探讨了光照时间、初始质量浓度、TiO2提拉层数、初始pH值和H2O2的投加量等因素对脱色率的影响。结果表明：初始质量浓度为80mg／L、TiO2提拉层数为4层、pH值为7．0的条件下,H2O2（30％）的投加量为3．0mL,经2h的光照,脱色率达到87％。光催化降解活性深蓝ST-2GLN染料的动力学研究表明．其降解过程是一个一级反应过程,反应速率常数为0．0132min一。     

纳米TiO_2薄膜对活性深蓝ST-2GLN染料的光催化降解研究

采用溶胶-凝胶(Sol-Gel)法,以钛酸正丁酯为前驱体,以不锈钢表面为基底,用提拉法镀膜,在400℃下高温煅烧2 h,制备出纳米TiO2薄膜光催化剂。在以波长为254 nm、8 W的紫外灯为光源、光源到溶液的距离为2 cm的条件下,对活性深蓝ST-2GLN模拟染料废水进行光催化降解试验。探讨了光照时间、初始质量浓度、TiO2提拉层数、初始pH值和H2O2的投加量等因素对脱色率的影响。结果表明:初始质量浓度为80 mg/L、TiO2提拉层数为4层、pH值为7.0的条件下,H2O2(30%)的投加量为3.0 mL,经2 h的光照,脱色率达到87%。光催化降解活性深蓝ST-2GLN染料的动力学研究表明,其降解过程是一个一级反应过程,反应速率常数为0.013 2 min-1。     

微波辅助离子液体中铜掺杂TiO2光催化剂的制备及微波强化光催化活性

在[Bmim] PF6离子液体中,用微波辐射干燥的方法制备了铜掺杂纳米二氧化钛光催化剂TiO2-Cu,测试催化剂对甲基橙溶液的微波（MW）、紫外（UV）、微波-紫外（MW-UV）条件下的降解率,考察了离子液体用量、铜掺杂量、微波干燥功率、微波干燥时间、煅烧温度、煅烧时间、微波降解功率等因素对TiO2-Cu催化剂活性的影响.结果表明,掺杂物质硝酸铜与钛酸丁酯的物质的量比为n（Cu）/n（Ti）=0.025,在功率为210 W的微波条件下干燥20 min,再在高温箱式电阻炉中于500℃下煅烧2h,所制得的TiO2-Cu催化剂具有较高的光催化活性;在MW、UV和MW-UV 3种降解条件下,对甲基橙的降解率分别为3.78％,92.98％,98.39％;并且在3种降解条件下,甲基橙降解率始终是：MW-UV＞ UV＞ MW.表明在紫外光照条件下,微波辅射具有强化TiO2-Cu催化剂降解甲基橙的作用.催化剂结构分析表明,TiO2中掺入铜后制得的催化剂,具有粒径均匀,比表面积、孔容、平均孔径和半孔宽均较大等特点,这也是TiO2-Cu催化剂具有较高的光催化活性的主要原因.     

UV curing and matting of acrylate nanocomposite coatings by 172 nm excimer irradiation

For UV-curable acrylate coatings reinforced by silica nanoparticles, the effect of 172 nm excimer irradiation on the surface roughness has been studied. A dual UV lamp set-up consisting of a 172 nm excimer lamp and a mercury arc lamp allowed obtaining gloss levels down to 0.5 units (at 60°) depending on the acrylate formulation and curing conditions. Moreover, UV matt-finished sample showed enhanced surface hardness and increased chemical resistance. It is assumed that 172 nm excimer irradiation resulted in a higher network density via additional cross-linking reactions.To study the depth profile of acrylate conversion for coatings cured by the combination of a 172 nm excimer lamp (accountable for surface curing) and a mercury arc lamp (responsible for through curing), FTIR microscopy as well as (Ge)ATR-FTIR having an IR penetration depth of less than 0.5 μm have been applied. Providing the presence of a photoinitiator as well as the absence of oxygen inhibition, similar degrees of double bond conversion of about 90% were observed on the entire area of the cross-section of the coating, i.e. the wavelength of UV irradiation was found to have no significant impact on acrylate conversion.