Cellulose degradation in newsprint paper ageing

The degradation of cellulose is an important factor influencing its physical, mechanical, optical and chemical properties and the longevity of paper in the electrical industry and in stored paper and books. A study of the accelerated ageing of newsprint paper has been performed at 98 °C during 0, 1, 2, 3, 5, 7, 10, 15, 20, 30 and 60 days. Degradation has been studied by viscometry, gel permeation chromatography (GPC) and saccharides determination. In the first stages of the accelerated ageing the cellulose depolymerisation takes place homogeneously (mainly due to the hydrolysis), later other reactions (oxidation, crosslinking) take place. The saccharides content in the paper decreases and the hemicelluloses are degraded faster.     

Studies on paper chromatography

Conclusion A study with filter paper strips partially impregnated with the precipitating agent with or without colloid as the fixing agent reveals that in the case of spotted strips run in aqueous alcoholic mixture as the solvent, uniform bands of the precipitate are formed. In these cases, chromatographic observations such as measurement of S and R_f values is possible. Rhythmic structures can also be obtained with these strips when the reactant solution is used as the solvent. In the absence of colloids rhythmic structures are obtained at a high concentration and the bands obtained have to be washed and repeatedly dipped in hot water in order to clear the structure of rings present underneath. In the presence of colloid, rhythmic vertical bands are obtained at a much lower concentration and the clear interspaces are visible even without washing. Thus an independent method for obtaining rhythmic structures on filter paper with a technique very similar to chromatography has been developed.Part I see Z. analyt. Chem. 149, 339 (1956).     

Studies on paper chromatography

Zusammenfassung In Gegenwart von Komplexon tritt durch Bildung eines gefärbten Komplexes zwischen Zirkonium und dem Reagens Brenzcatechinviolett eine tiefblaue Färbung auf. Nahezu alle störenden Ionen werden durch Komplexon maskiert. Nur Sb^III und Sn^IV sind abzutrennen, was in Gegenwart von Komplexon mit Ammoniak leicht vor sich geht. Die Empfindlichkeit wird durch die meisten Kationen bis zu Grenzkonzentrationen l1000 nicht beeinflußt und beträgt 0,6 [A] 0,03, pD=4,7. Komplexbildende Anionen stören. Die Störung durch Fluorid-Ion kann jedoch mittels Berylliumzugabe ausgeschaltet werden.Den Firmen Riedel-de Haën, Seelze/Hann., und B. Siegfried, Zofingen, Schweiz, danken wir herzlichst für die Überlassung von Chemikalien.     

Stabilizing effect of 1,1,5-trihydroperfluoropentanol on photochemical degradation of polycaproamide

The effect of fluorinated alcohols on the photochemical degradation of polycaproamide was studied. It was shown that, even when a small amount (0.035 wt %) of 1,1,5-trihydroperfluoropentanol is added, the rate of photodegradation of polyamide fibers decreases. Electron microscopic examination showed that, in the presence of the fluorinated alcohol, the test fibers are characterized by a reduced number of defects. The simultaneous introduction of microquantities of 1,1,5-trihydroperfluoropentanol and N,N-bis(2,2,6,6-tetramethyl-4-piperidinyl) 1,3-benzenedicarbamide is responsible for the synergistic photostabilizing effect.     

The effects of ageing by ultraviolet degradation of recycled polyolefin blends

Products manufactured from recycled polyolefin blends were subjected to accelerate weathering conditions and subsequent tests. Field-aged products were also tested.Samples were analysed for changes in mechanical, rheological and chemical properties. Data obtained in this study, by means of tensile, impact, and melt flow tests, GPC, gloss and colour analyses showed that the effect of UV exposure, whether in the field or artificial environments, was not significant as far as the mechanical properties of the materials were concerned. There was some change in the surface characteristics but such surface effects would not compromise the mechanical integrity of the product when recycled. During reprocessing of the materials, it is likely that stabilizer is redistributed at the surface of any new moulding, thus renewing the surface characteristics. Hence damaged or end-of-life products need not be discounted from recycling.     

光电催化降解模拟工业染色废水的研究

印染废水毒性大、组分比较复杂、可生化性差,大部分有机物质多具有致癌、致畸、致突变的作用[1-5],常规的处理方法对印染废水的处理效果并不理想[6].     

一类新型光化学振荡体系的研究

三个三苯甲烷类、九个变色酸双偶氮类共十二个水溶液体系中, 用HP-8451型快速扫描光度计, 在体系不搅拌、控制浓度和温度情况下, 可以记录到衰减式规整的周期振荡波。辐射开抬后出现1000s以上的振荡前置期, 振荡主期的周期为112±5s,最大振幅约为0.06A。搅拌时光化学反应为零级。本文还研究了浓度、温度和搅拌对形成光化学振荡影响, 讨论了它们的可能机制。此十二个振荡体系末见文献报道。     

Thermal and photochemical ageing of epoxy resin - Influence of curing agents

The thermal and photochemical ageing of epoxy resin was studied using photoacoustic-FTIR spectroscopy. This technique was satisfactory for both unfilled resin and glass fibre filled epoxy composite. The influence of the curing agent (anhydride or amine) was significant for ageing. The durability of anhydride-epoxy system was the best for both thermal and photoageing.     

Studies on the thermal ageing of organic coatings

The ageing of organic protective coatings depends on environmental impacts and is associated with a variety of ichemical and physical processes. The results of former thermal ageing studies indicate that evaporation and polymer degradation are the decisive processes for changes in coating properties. For the verification of these assumptions the impact of - the thermal exposure temperature T_L and - the length of the exposure time t_L on properties of clear lacquer coatings was determined by further studies. The gradation of T_L was aimed at creating conditions where on the one hand only evaporation processes occur, while on the other hand evaporation and polymer degradation reactions occur in parallel. The objective was to find the time t_L and the temperature T_L at which degradation starts to prevail.     

Self-sensitization of tetracycline degradation with simulated solar light catalyzed by ZnO@montmorillonite

Zinc oxide (ZnO) nano-particles were chemically deposited onto montmorillonite (MONT) clay particles. The composite ZnO@MONT was then characterized and used as a catalyst for photo-degradation of aqueous tetracycline. Unlike earlier studies, solar simulated light can be effectively used in this work. The composite shows high efficiency as adsorbent and as a photo-degradation catalyst. Both adsorbed and dissolved tetracycline molecules undergo mineralization under the photo-catalytic conditions, and up to 94% of the contaminant gross amount is completely mineralized. Other forms of ZnO particles, commercial ZnO and synthetic ZnO particles were examined in separate experiments. The ZnO@MONT is superior to both pristine counterparts. The ability of tetracycline to sensitize the supported ZnO particles, to solar simulated light, before being photo-degraded itself, is discussed here for the first time. In addition to enhanced catalytic activity of the ZnO@MONT, the composite can be efficiently recovered and reused with no significant loss of efficiency.     

有机硅反应活性中间体的研究I:光化学方法产生含呋喃环硅烯

2-(α-呋喃基)-2-苯基六甲基三硅烷在光照下可产生新型的有机硅活性中间体-α-呋喃基苯基硅烯.它与2,3-二甲基-1,3-丁二烯反应后,得到了相应的加成与插入反应产物;与环己烯反应后,再用甲醇分解所得硅杂环丙烷中间物得到了α-呋喃基环己基苯基甲氧基硅烷.     

Anion mediation of aluminium-catalysed degradation of paper

The use of aluminium salts in papermaking has been linked well for over a century with causing degradation of paper. This is because the typical salts used in papermaking hydrolyse to release acid, which is a known catalyst that promotes degradation of cellulose, reducing both its degree of polymerisation and intrinsic strength. However, data reported here show that simplistic statements about the acidity of aluminium salts hide an interesting and complicated chemistry. In particular the presence of anions capable of coordinating with aluminium in solution is shown to exert an overwhelming influence on degradation reactions catalysed by the metal. Furthermore, the work highlights potential ways of pacifying aluminium cations contained in paper, effectively reducing or eliminating the degradation reactions they promote.     

Studies on thermal degradation of epoxy resins by high-resolution pyrolysis-gas chromatography

The optimum pyrolytic conditions for thermosetting epoxy resin samples were first empirically studied. On the basis of the optimized pyrolytic conditions, epoxy prepolymers and epoxy resin samples cured with and without curing agents, such as diamine and dicarboxylic acid anhydride, were studied using high-resolution pyrolysis-gas chromatography. In addition to some intact prepolymer molecules, various degradation products characteristic of the prepolymers, up to diglycidyl ether of bisphenol A, were detected on the pyrograms of the prepolymers. On the other hand, various phenols characteristic of the prepolymers and a variety of pyrolyzates characteristic of the reacted curing agents, including intact dicarboxylic acid anhydride, were observed on the programs of the cured resin samples. The potential of this technique for studying the curing process of the epoxy resins is discussed.     

Studies on thermal degradation of aliphatic polyamides by pyrolysis-glass capillary chromatography

A series of aliphatic polyamides samples (five kinds of α-aminocarboxyclic acid-type nylons and seven kinds of diamine-dicarboxyclic acid-type nylons) were pyrolysed in a vertical microfurnace-type pyrolyser at 550°C, and their high-resolution pyrograms were obtained by a glass capillary gas chromatograph directly attached to the pyrolyser. The characteristic peaks on the resulting pyrograms were identified using a mass spectrometer, which was also attached to the gas chromatograph. On the basis of the various characteristic degradation products identified, such as hydrocarbons, mononitriles, lactams, cyclopentanone hydrocarbons containing one amide group and mononitriles containing one amide group, general mechanisms for the degradation of the aliphatic polyamides were formulated.     

The impact of volatile compounds released by paper on cellulose degradation in ambient hygrothermal conditions

The reactivity towards cellulose of various volatile compounds commonly released by paper was studied. Sheets of Whatman No. 1 (W1) and No. 40 (W40) were exposed to various concentrations of these compounds in vapour phase ranging from 20 to 80 ppm in closed vessels for 52 days in controlled ambient conditions, after which they were hygrothermally aged. The measured properties of the paper were copper number, degree of polymerization, zero-span breaking length, pH and yellowness index. The results showed that hydrogen peroxide was the most aggressive among the volatile compounds tested as it severely degraded W1 cellulose. The exposure of W1 to formic acid led to significant degradation, designating this volatile organic compound (VOC) as the most reactive toward cellulose among the carboxyl and carbonyl functionalized VOCs tested. On the other hand, acetic acid was found comparatively less reactive. Nitrogen oxides, which were produced up to 3 ppm from a side-reaction of the carboxylic acids with the magnesium nitrate used to control the relative humidity in the closed vessels, appeared to contribute significantly to the degradation despite their low concentration. Antagonistic effects were evidenced in binary vapour mixtures where the presence of aldehydes (formaldehyde and acetaldehyde) counteracted substantially the degradation induced by the most reactive compounds. It was also shown that acetaldehyde, hexanal and furfural in individual exposures had little to no reactivity. Upon exposure to formaldehyde, the rate of glycosidic bond cleavage of cellulose induced by the ageing of W1 was significantly reduced.     

The effect of volatile organic compounds and hypoxia on paper degradation

The possible effects of volatile organic compounds (VOCs) and of hypoxic conditions on the durability of library and archival collections have been investigated. There is growing evidence that particularly in micro-environments, there may be an important contribution of these indoor-generated pollutants to the degradation of paper. However, since the principal source of VOCs in repositories is the collections themselves, there are also significant possibilities for less stable papers, which are net VOC emitters, to promote the degradation of more stable papers, which may be net VOC absorbers.Using a range of model and real historic papers, the influence of acetic acid, formic acid, furfural, toluene, 1,4-diethylbenzene, iso-butylbenzol, 2-pentylfuran, paraformaldehyde, hexanal and vanillin was evaluated by adding them to samples degraded in closed vessels at elevated temperature. Possible protective effects of the use of activated charcoal cloth, oxygen removal, and of various chemisorbents were also investigated.The results strongly suggest that particularly VOCs with acidic or oxidisable functions can have a strong effect on degradation of cellulose. This is less pronounced in lignin-containing and acidic papers and more pronounced in papers with a small alkaline reserve. The removal of VOCs from the immediate environment can have a pronounced beneficial effect on papers emitting VOCs more intensively, in fact, the lifetime expectancy can be doubled.The results have immediate implications for storage of paper-based heritage in enclosures, but also for initiation of long-term VOC monitoring programmes in libraries and archives, where significant development is still needed.     

In vitro degradation and swelling behaviour of rubbery thermoplastic starch in simulated body and simulated saliva fluid and effects of the degradation products on cells

Degradation in vitro is of importance in implanted biological industry. This research investigated the swelling and degradation behaviours of glycerol plasticized thermoplastic starch (GTPS) in simulated body fluid (SBF) and simulated saliva fluid (SSF), respectively. The weight loss, swelling degree and linear extensibility as a function of time were measured. Changes in the morphology (SEM), chemical structure (FT-IR), crystal property (XRD) and thermogravimetic property (TG) during degradation were also investigated. Results show that the degradation in SSF was much quicker than that in SBF. About 1 h was needed for the swelling equilibrium in SBF, which was a little quicker than that in SSF. In alkaline solution the swelling speed and the swelling degree were larger than those in neutral and acidic solutions. The degradation in SBF was typical bulk degradation. In SSF the surface and bulk degradation took place synchronously, but the surface degradation played an important role in the first 2 h. Results from FT-IR and XRD suggest that the glycosidic linkages in starch chains were broken and the crystal structure in GTPS was destructed during degradation. Cytotoxicity test was used to investigate the effects of the short-term extracted dilutions and long-term degradation products on the cells, which illustrates that the degradation products not only had non-toxicity but also accelerated the cells' growth.     

Studies on thermal degradation of benzylidene malononitriles

Thermal decomposition studies have been carried out using flash vacuum thermolysis (FVT) to find out the decomposition temperature for benzylidene malononitriles (BMNs) including 2-chlorobenzylidene malononitrile (cs), a widely used riot control agent. The FVT studies have been carried out in a specially designed all glass assembly at various temperatures ranging from 300 to 600°C. A number of rearranged products along with hydrogen cyanide were obtained as major decomposition products. The products were analysed and the structures were confirmed by GC/MS. the thermal behaviour of BMNs has also been investigated by TG under nitrogen atmosphere. These studies show that the pyrotechnic mixture for tear gas munitions should not have burst temperature above 300°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Kinetics and mechanism of photocatalytic degradation of metobromuron by TiO2 in simulated sunlight

The kinetics of photocatalytic degradation of metobromuron in aqueous solution, with TiO₂ as photocatalyst under simulated sunlight irradiation, have been systematically investigated. The single-variable-at-a-time method and the central composite design based on response surface methodology were used to study the individual and synergistic effects of several classical conditions on the efficiency of photocatalysis. Three different conditions, TiO₂ concentration, pH, and initial concentration of metobromuron, were found to independently determine the efficiency of degradation. The optimum degradation conditions were: TiO₂ concentration 3.00 g/L, pH 7.88, and initial concentration of metobromuron 60.23 μM. In addition, a mechanism of degradation of metobromuron is tentatively proposed on the basis of the experimental results and theoretical calculation of frontier electron densities and point charges. The results suggest that substitution of the Br atom, addition of ·OH radicals, and the cleavage of urea side chain are the predominant degradation pathways during the initial stage of photocatalytic degradation.     

Studies on the photochemical oxidation of N,N-diacyl-1,4-dihydropyrazine derivatives

The photochemical oxidation of N,N-diacyl-1,4-dihydropyrazines was investigated by irradiation from a medium-pressure mercury lamp. The main products of the photooxygenation were isolated and unambiguously confirmed by ¹H NMR spectra, ¹³C NMR spectra, H-H, C-H correlation spectra, high-resolution mass spectrometry, and single-crystal x-ray diffraction analysis. The complicated NMR spectra of main products were studied by variable-temperature NMR experiments. The mechanism of the photooxygenation of N,N-diacyl-1,4-dihydropyrazines is suggested to be a [2 + 2] cycloaddition of oxygen to the double bond.