Effects of UV‐irradiation on the nonisothermal crystallization kinetics of polypropylene

The influences of UV‐induced photodegradation on the nonisothermal crystallization kinetics of polypropylene (PP) were investigated by differential scanning calorimetry. The Avrami analysis modified by Jeziorny, Ozawa method, and a method modified by Liu were employed to describe the nonisothermal crystallization process of unexposed and photodegraded PP samples. Kinetics studies reveal that the rates of nucleation and growth may be affected differently by photodegradation. A short‐term UV‐irradiation may accelerate the overall nonisothermal crystallization process of PP, but a long‐term UV‐irradiation should impede it. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Kinetic behavior of photo‐polymerization of UV‐curable resins with carboxylic acid and amino groups

Photo‐polymerization behaviors of bisphenol‐A epoxy diacrylate (EPA) and six kinds of EPA‐derived resins containing different amounts of carboxylic acid, urethane, amide, and imide groups were studied by a photo differential scanning calorimetry. The dark polymerization was performed and pseudo‐steady state assumption of growing radicals was made to obtain the kinetic constants for propagation, bimolecular termination, monomolecular termination, and the concentration of growing radicals of different resins as a function of extent of reaction. Compared with EPA, it was found that the rate of polymerization and kinetic constants of the six resins were relatively small because the mobility of reacting species in resins was restricted by carboxylic acid, urethane, amide, and imide groups. Finally, three different photo‐initiators were used to initiate the polymerization, and their kinetic behaviors were compared. The effect of tertiary amine group of photo‐initiator on the rate of polymerization of resins having carboxylic acid group and the initiator efficiency were discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Photo‐oxidation of polystyrene/clay nanocomposites under accelerated UV exposure: Effect on the structure and molecular weight

The present work investigates the effects of photo‐oxidation under accelerated UV conditions on the structure, the molecular weight and the morphology of polystyrene (PS)/organophilic montmorillonite (OMMT) at various clay contents: 2.5, 5, and 7 wt %. Fourier transform infrared spectroscopy, viscosimetry and scanning electron microscopy were used to evaluate the extent of degradation of nanocomposite samples in comparison with neat PS, up to 216 h of exposure. The study has shown that the formation rates of both carbonyl and hydroperoxide groups increase with exposure time, being much higher for PS/OMMT nanocomposites. Moreover, it is also observed that all samples exhibit a large increase in the scission index, however less pronounced for neat PS. These results clearly indicate the formation of low molecular weight products that could arise from chain scission. Further, the photo‐oxidation rate seems to be more affected by the presence of clay, which acts as a catalyst, rather than by the variation of clay contents. Finally, the degraded materials exhibit eroded surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Review and evaluation of color spaces for image/video compression

A color space plays an important role in color image processing and color vision applications. While compressing images/videos, properties of the human visual system are used to remove image details unperceivable by the human eye, appropriately called psychovisual redundancies. This is where the effect of the color spaces' properties on compression efficiency is introduced. In this work, we study the suitability of various color spaces for compression of images and videos. This review work is undertaken in two stages. Initially, a comprehensive review of the published color spaces is done. These color spaces are classified and their advantages, limitations, and applications are also highlighted. Next, the color spaces are quantitatively analyzed and benchmarked in the perspective of image and video compression algorithms, to identify and evaluate crucial color space parameters for image and video compression algorithms.     

Effect of pre‐treatments based on UV photocatalysis and photo‐oxidation on toluene biofiltration performance

BACKGROUND: The integration of UV photocatalysis and biofiltration seems to be a promising combination of technologies for the removal of hydrophobic and poorly biodegradable air pollutants. The influence of pre‐treatments based on UV_{254 nm} photocatalysis and photo‐oxidation on the biofiltration of toluene as a target compound was evaluated in a controlled long‐term experimental study using different system configurations: a standalone biofilter, a combined UV photocatalytic reactor‐biofilter, and a combined UV photo‐oxidation reactor (without catalyst)‐biofilter. RESULTS: Under the operational conditions used (residence time of 2.7 s and toluene concentrations 600–1200 mg C m^?3), relatively low removal efficiencies (6–3%) were reached in the photocatalytic reactor and no degradation of toluene was found when the photo‐oxidation reactor was operated without catalyst. A noticeable improvement in the performance of the biofilter combined with a photocatalytic reactor was observed, and the elimination capacity of the biological process increased by more than 12 g C h^?1 m^?3 at the inlet loads studied of 50–100 g C h^?1 m^?3. No positive effect on toluene removal was observed for the combination of UV photoreactor and biofilter. CONCLUSIONS: Biofilter pre‐treatment based on UV_{254 nm} photocatalysis showed promising results for the removal of hydrophobic and recalcitrant air pollutants, providing synergistic improvement in the removal of toluene. Copyright © 2011 Society of Chemical Industry     

Photo‐oxidation of cyanide in aqueous solution by the UV/H2O2 process

Photo‐oxidation of cyanide was studied in aqueous solution using a low‐pressure ultra‐violet (UV) lamp along with H₂O₂ as an oxidant. It was observed that by UV alone, cyanide degradation was slow but when H₂O₂ was used with UV, the degradation rate became faster and complete degradation occurred in 40 min. The rate of degradation increased as the lamp wattage was increased. It was also observed that cyanide oxidation is dependent on initial H₂O₂ concentration and the optimum dose of H₂O₂ was found to be 35.3 mmol dm^?3. Photo‐oxidation reactions were carried out at alkaline pH values (10–11) as at acidic pH values, cyanide ions form highly toxic HCN gas which is volatile and difficult to oxidise. By the UV/H₂O₂ process, using a 25 W low‐pressure UV lamp and at alkaline pH of 10.5 with an H₂O₂ dose of 35.3 mmol dm^?3, cyanide (100 mg dm^?3) was completely degraded in 40 min when air was bubbled through the reactor, but when pure oxygen was bubbled the time reduced to 25 min. The cyanide degradation reaction pathway has been established. It was found that cyanide was first oxidised to cyanate and later the cyanate was oxidised to carbon dioxide and nitrogen. The kinetics of cyanide oxidation were found to be pseudo‐first order and the rate constant estimated to be 9.9 × 10^?2min^?1 at 40 °C. The power required for complete degradation of 1 kg of cyanide was found to be 167 kWh (kilowatt hour). Copyright © 2004 Society of Chemical Industry     

Development of a photoresponsive cell culture surface: Regional enhancement of living‐cell adhesion induced by local light irradiation

Using a functional polymer containing nitrospirobenzopyran residues and poly(ethylene glycol), we developed a photoresponsive cell culture surface (PRCS), at which the cell adhesion can be enhanced locally by UV light irradiation (350–400 nm, 35 mW/cm², 5 min) even on the region where living cells exist. Cell adhesion was evaluated by observing BALB/3T3 fibroblasts, which had been seeded on PRCS and then irradiated with UV light regionally, after 12 h incubation and subsequent washing to remove scarcely adhering cells. As a result, it was confirmed that the number of remaining cells in irradiated region was at most 2.5 times greater than that in nonirradiated regions, suggesting the implementation of a novel scheme to manipulate living cells individually by light irradiation in a parallel and simultaneous manner. Influence of the composition of the polymer material consisting the substrate surface was also investigated systematically. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 495–499, 2006     

Surface‐initiated atom transfer radical polymerization (ATRP) of styrene from silica nanoparticles under UV irradiation

Diethyldithiocarbamyl‐modified silica nanoparticles were prepared and used as macroinitiator for the surface‐initiated atom transfer radical polymerization (SI‐ATRP) of styrene under UV irradiation. Well‐defined polymer chains were grown from the nanoparticle surfaces to yield particles composed of a silica core and a well‐defined, densely grafted outer PS layer with a mass ratio of styrene to silica, or percentage grafting, of 276.3% after an UV irradiation time of 5 h. Copyright © 2004 Society of Chemical Industry     

Effects of sunshine UV irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene fiber

This study investigated sunlight‐simulated ultraviolet (UV) beam irradiation on the tensile properties and structure of ultrahigh molecular weight polyethylene (UHMWPE) fibers. The tensile results showed that after 300 h sunlight UV irradiation, the tensile properties of the UHMWPE fibers were obviously degraded. Investigation of morphology revealed that the crystallinity was slightly increased, whereas the overall orientation and molecular weight of the fibers were decreased. SEM observations indicated that the degradation process was nonuniform throughout the fiber and a change from a ductile to a brittle fracture mechanism was found after UV irradiation. DMA results showed two β‐relaxations and one α‐relaxation in the original single filament, and UV irradiation led to the increased intensity of the high‐temperature β‐relaxation and the lowered position of the low‐temperature β‐relaxation. This indicated that irradiation‐induced molecular scission and branching were located primarily in the amorphous and the interface areas of the fiber. Changes in the thermal behavior were also examined by DSC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2757–2763, 2003     

Performance of natural‐fiber–plastic composites under stress for outdoor applications: Effect of moisture,temperature, and ultraviolet light exposure

The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural‐fiber–plastic composites (NFPC) were assessed. We conducted short‐term tests in the laboratory and long‐term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X‐ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short‐ and the long‐term tests. The X‐ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006     

Effect of gamma‐irradiation on the electret properties of poly(L‐lactide)

Electret stability of poly(L ‐lactide) (PLA) films, gamma‐irradiated up to 100 kGy has been investigated by measuring the surface potential during the storage period. PLA samples—40‐μm thick films—were prepared by the casting method and then irradiated in a ⁶⁰Co radiation facility at a dose rate of 0.25 kGy/h. The structural changes during the irradiation were estimated by viscometric, differential scanning calorimetry and scanning electron microscope measurements. Random chain scission and appearance of end radicals are the most probable results of the irradiation process. After irradiation, the samples were charged in a corona discharge system and surface potential was measured by the method of the vibrating electrode with compensation. The values of the surface potential of the irradiated samples were higher in comparison with the non‐irradiated samples. This effect could be related to the degradation of the macromolecules and changes in the crystal state of PLA during the irradiation. Both of the mentioned factors lead to structural defects that increase the number of discrete trapping levels. The effect of low pressure on the surface potential drop was also investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rapid living free‐radical polymerization of methyl acrylate under 60Co γ‐ray irradiation at room temperature

Rapid living free‐radical polymerization of methyl acrylate under ⁶⁰Co γ‐ray irradiation in the presence of benzyl 1H‐imidazole‐1‐carbodithioate at room temperature is reported. The results showed that the polymerization is a fast living process, and that the molecular weight of the polymer is as high as 39 600 g mol^?1 at 68 % conversion with M_w/M_n = 1.09 within 68 min. The polymerization rate was markedly influenced by the structures of thiocarbonylthio compounds. Copyright © 2004 Society of Chemical Industry     

Preparation of melting‐free poly(lactic acid) by amorphous and crystal crosslinking under UV irradiation

The poly(lactic acid) (PLA) with 3.6% mol of benzophenone (BP) per repeat unit of PLA can be crosslinked to a gel fraction of 98.5% at UV energy of 160 J/cm². From NMR analysis, the photocrosslinking of PLA was attributed to the recombination of primary and tertiary carbon radicals in the repeating units which were generated by the hydrogen abstraction of BP. With increasing crosslinking, melting peak disappeared and glass transition temperature elevated with loss of crystallinity, indicating that the crosslinking occurred in the crystalline region as well as in the amorphous region. The thermal stability of the crosslinked PLA also improved as shown by higher onset temperature as much as 56°C and higher maximum decomposition temperature compared with the pristine PLA. The higher toughness of the crosslinked PLA film was obtained together with the improvement in tensile strength and modulus with increasing crosslinking density. In addition to photocrosslinking of amorphous region, the crosslinking of crystalline region can have significant influence in the improvement of thermal and mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and photo‐ and biodegradabilities of poly[(hydroxybutyrate‐co‐hydroxyvalerate)‐ g‐phenyl vinyl ketone]

The graft copolymer, poly[(hydroxybutyrate‐co‐hydroxyvalerate)‐g‐phenyl vinyl ketone] [P(HBV‐g‐PVK)], was synthesized by graft polymerization of phenyl vinyl ketone (PVK) onto poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) under nitrogen atmosphere using benzoyl peroxide. The structure of P(HBV‐g‐PVK) was identified by Fourier transform IR and ¹H‐NMR spectra. The effects of weight ratio of PVK to PHBV in feed, initiator concentration, reaction time, and reaction temperature on the grafting ratio and grafting efficiency were investigated. The thermal decomposition temperature of P(HBV‐g‐PVK) was 272°C. The tensile strengths of P(HBV‐g‐PVK) after photo‐ or biodegradation were significantly decreased due to degradation by UV irradiation or Aspergillus niger. The value of color difference (ΔE) of P(HBV‐g‐PVK) was greater than that of PHBV. The film surfaces of P(HBV‐g‐PVK) treated with UV irradiation and Aspergillus niger showed many pits as compared with the untreated P(HBV‐g‐PVK). It has been found that the photo‐ and biodegradabilities of P(HBV‐g‐PVK) was excellent. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1432–1439, 1999     

A practical parametrical characterization of the Fenton and the photo‐Fenton sulfamethazine treatment using semi‐empirical modeling

BACKGROUND: Sulfamethazine (SMT) has received little attention in the water treatment literature. Yet, SMT is among the non‐biodegradable substances increasingly found in aqueous media and affecting both public health and wastewater treatments. For a long time, advanced oxidation processes (AOPs) were studied via pure empirical modeling, although the surface response models resulting from lumped information (TOC, COD, etc.) present limitations regarding extrapolation and optimization. Conversely, detailed first‐principles modeling may not be affordable due to the computational burden and the chemical analysis needs. Thus, a balanced approach may be practical in many cases. RESULTS: Experiments on SMT solutions (500 mL, 50 mg L^?1) were performed under conditions set by an experimental design. A set of replicated degradation time‐profiles (TOC and SMT concentrations) was obtained and a semi‐empirical kinetic model was fitted to these data to determine maximum conversion and kinetic rate. CONCLUSIONS: SMT can be completely degraded from water via photo‐Fenton treatment. Conditions for this treatment were investigated and its outcomes were systematically characterized by a simple kinetic model and two lumped parameters, conversion and kinetic rate. Both, the model and the corresponding parametrical characterization are introduced as a means to discriminate the most efficient treatment conditions in a practical and efficient way. Copyright © 2011 Society of Chemical Industry     

Combustion properties and transference behavior of ultrafine microencapsulated ammonium polyphosphate in ramie fabric‐reinforced poly(L‐lactic acid) biocomposites

Flame‐retardant biocomposites have attracted much attention in past decades. They can provide many advantages, such as total biodegradability and their abundant renewable sources. In the work reported, biocomposites based on poly(L ‐lactic acid) (PLLA), ramie fabric (FAB) and microencapsulated ammonium polyphosphate (MCAPP) were synthesized via hot press molding using the powder‐stacking procedure. The effects of transference behavior of the flame retardant on sustaining flame retardancy of the biocomposites were investigated. Thermogravimetric analysis shows that the improved flame retardancy is due to an increased char residue at high temperature. Field emission scanning electron microscopy images and wide‐angle X‐ray diffraction data were used to investigate the hydrolysis reaction and transference behavior of ammonium polyphosphate in the biocomposites. UL‐94 testing and limiting oxygen index measurements show that the PLLA/FAB/MCAPP biocomposites retain their flame retardancy even after 21 days in UV‐irradiation hydrothermal aging tests. The good sustained flame retardancy of the PLLA/FAB/MCAPP biocomposites is attributed to the docking interactions and good distribution of MCAPP in the biocomposites. Copyright © 2010 Society of Chemical Industry     

Synthesis of new optically active poly(amide‐imide)s containing EPICLON and L‐phenylalanine in the main chain by microwave irradiation and classical heating

EPICLON [3a,4,5,7a‐Tetrahydro‐7‐methyl‐5‐(tetrahydro‐2,5‐dioxo‐3‐furanyl)‐1,3‐isobenzofurandione] or [5‐(2,5‐dioxotetrahydrofurfuryl)‐3‐methyl‐3‐cyclohexyl‐1,2‐dicarboxylic acid anhydride] ( 1 ) was reacted with L ‐phenylalanine ( 2 ) in acetic acid, and the resulting amic acid was refluxed under a Dean‐Stark system with benzene, which produced diacid ( 3 ) in high yield. Compound ( 3 ) was converted to the diacid chloride ( 4 ) by reaction with oxalyl chloride in dry carbon tetrachloride. The polycondensation reaction of this diacid chloride ( 4 ) with several aromatic diamines such as 4,4′‐sulfonyldianiline ( 5a ), 4,4′‐diaminodiphenylmethane ( 5b ), 4,4′‐diaminodiphenylether ( 5c ), 1,4‐phenylenediamine ( 5d ), 1,3‐phenylenediamine ( 5e ), 2,4‐diaminotoluene ( 5f ), and 1,5‐diaminonaphthalene ( 5g ) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as N‐methylpyrrolidone ( NMP ). The polymerization reactions were also performed under two different classical heating methods: low temperature solution polycondensation in the presence of trimethylsilyl chloride, and high temperature polymerization. A series of optically active poly(amide‐imide)s with moderate yield and inherent viscosity of 0.14–0.22 dL/g were obtained. All of the above polymers were fully characterized by IR, elemental analyses, and specific rotation. Some structural characterization and physical properties of this optically active poly(amide‐imide)s are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3281–3291, 2004     

Potential of microbial growth control in water hydraulic systems by UV‐irradiation and filtration

Water hydraulic systems use water as a pressure medium and, thus, do not pose such adverse environmental impacts as oil hydraulics. Microbial deterioration of the pressure medium and biofouling of the surfaces restrict the applicability of the water‐based technology. The potential of microbial growth control by UV‐irradiation and filtration was studied in a pilot‐scale water hydraulic system. The UV‐irradiation (25 m Ws cm^?2) of the pressure medium reduced the total viable counts of bacteria by 1–2 log₁₀ cfu cm^?3, whereas the total microbial cell numbers and the numbers of surface‐attached microorganisms remained unaffected. Prefiltration (1.2 µm, absolute) of the pressure medium decreased the total microbial cell number in the water phase and retarded the attachment of bacteria. The filtration during the operation (2 µm, absolute) decreased the total numbers of microbial cells and the total viable counts in the pressure medium, and microbial attachment on the surfaces. Microbial attachment was not prevented by filtration. The microbial water quality obtained by pre‐ and on‐line filtration of the pressure medium was sufficient to ensure the long‐term operation of the water hydraulic system assuming that clean work practices are complied with in assembly and during the operation. © 2002 Society of Chemical Industry     

Degradation of benzene,toluene ethylbenzene and p‐xylene (BTEX) in aqueous solutions using UV/H2O2 system

The homogeneous degradation of benzene (B), toluene (T), ethylbenzene (E) and p‐xylene (X) (BTEX) was studied in aqueous solutions, at pH 3.0, of hydrogen peroxide (5.8 mM ) under UV irradiation in a photoreactor equipped with a 300 nm lamp of light intensity 3.5 × 10^?5 Ein L^?1 min^?1. BTEX was substantially degraded by the H₂O₂/UV system, with >90% disappearing in 10 min of irradiation. The decomposition of BTEX was studied either as single or as multi‐component systems. The effects of irradiation time, amounts of H₂O₂ in molar ratios, rate of degradation and competition between components were thoroughly examined. It can be stated that the rate of BTEX degradation in mixture was higher than those for the individual components due to external effects of the absorption of UV light by the mixture, and their effects on enhancing the formation of OH^? radicals. The appropriate figure of merit, the electrical energy per mass (EE/M), was estimated at various molar ratios and it was confirmed that the best value was the one depicted for p‐xylene (0.065 kWh kg^?1). A theoretical model for the degradation pathway was proposed. Copyright © 2004 Society of Chemical Industry