scholarly journals Assessment of Paint Layers Quality by FTIR and DSC Techniques

2019 ◽  
Vol 56 (1) ◽  
pp. 87-91
Author(s):  
Eduard-Marius Lungulescu ◽  
Iosif Lingvay ◽  
Adriana-Mariana Bors ◽  
Laszlo Fortuna ◽  
Nicoleta-Oana Nicula (Butoi)
Keyword(s):  
Ageing Time ◽  
Oxidative Degradation ◽  
Activation Energies ◽  
Natural Weathering ◽  
Temperate Climate ◽  
Railway Bridge ◽  
Natural Lighting ◽  
Laboratory Conditions ◽  
Painting Layer

In order to identify the causes that led to microbiological degradation by biofouling increases a top coat painting layer applied to a railway bridge was analyzed by both FTIR and the DSC methods; the analysed painting material was that used to paint the bridge in 2013.The determinations were performed comparatively on samples of a similar painting material after 10 days of curing in a natural atmosphere at 25 � 5 �C, after 60 days of storage under laboratory conditions (22 � 5 �C, RH 60 � 10 %, natural lighting), and on samples from the painting material of a certain railway bridge after approx. 4.5 years (exposed natural weathering of temperate climate with Mediterranean influences). From FTIR determinations, the amount of oxygen containing groups (C = O, C-O, C-O-C, -HO) resulted from ageing under various conditions of the painting material.From DSC determinations, the resistance of the paint to the oxidative degradation decreases with the ageing time as resulted from oxidation onset temperatures and oxidation activation energies values - which decreases with 4 kJ / mole (about 2.2 %) in only 60 days of storage in the laboratory and with 7 kJ/mole (about 3.9 %) following exposure to 100 w/m2 for only 15 h and 29 kJ / mole (over 16 %) after exposure to 4.5 years of natural weathering.

Polymer durability estimates based on apparent activation energies for thermal oxidative degradation

2001 ◽  
Vol 367-368 ◽  
pp. 107-112 ◽  
Author(s):  
Samuel Ding ◽  
Atul Khare ◽  
Michael T.K. Ling ◽  
Craig Sandford ◽  
Lecon Woo
Keyword(s):  
Oxidative Degradation ◽  
Activation Energies ◽  
Thermal Oxidative Degradation ◽  
Apparent Activation Energies

scholarly journals Alkaline oxidative degradation of diphenylmethane structures — Activation energy and computational analysis of the reaction mechanism

2001 ◽  
Vol 79 (9) ◽  
pp. 1394-1401
Author(s):  
Lubo Jurasek ◽  
Lívia Krištofová ◽  
Yujun Sun ◽  
Dimitris S Argyropoulos
Keyword(s):  
Activation Energy ◽  
Reaction Mechanism ◽  
Computational Analysis ◽  
Model Compound ◽  
Degradation Products ◽  
Oxidative Degradation ◽  
Semiempirical Method ◽  
Activation Energies ◽  
Ring Cleavage ◽  
Residual Lignin

A diphenylmethane model compound (2,2'-methylenebis[6-methoxy-4-methylphenol]) and residual kraft lignin were treated with alkaline hydrogen peroxide. Kinetic data for the disappearance of the model and the diphenylmethane structures in the residual lignin was collected. The activation energies for the degradation were found to be similar (54 ± 11 kJ mol–1 for the model and 58 ± 5 kJ mol–1 for the residual lignin). A comparison of the activation energies with the data of a previous study on a biphenyl model compound (3,3'-dimethoxy-5,5'-dimethyl-[1,1'-biphenyl]-2,2'-diol) showed a substantially higher activation energy for the degradation of the latter. Pathways for the degradation of 2,2'-methylenebis[6-methoxy-4-methylphenol] were proposed and the intermediates subjected to computational analysis using a semiempirical method (PM3). The results suggest that initially a common pathway exists, resulting in 2-[2-hydroxy-3-methoxy-5-methyl-phenylmethyl]-4-methyl-2,4-hexadienedioic acid. Then the pathway branches into three, resulting in three major degradation products. The main driving force of the reactions is the formation of radical sites after reaction with hydroxyl radicals and subsequent radical coupling with perhydroxyl radicals to form peroxides. All the reactions on the pathways are exothermic except for the transformations of peroxides into dioxetanes. The dioxetanes cleave exothermically resulting in ring cleavage and fragmentation. The computed data permitted for the rationalization as to why the diphenylmethane structures appear to be more labile than biphenyl structures under alkaline oxidative conditions.Key words: activation energy, alkaline oxidative degradation, computational chemistry, lignin, reaction mechanism.

The Thermal and Oxidative Stability of Chlorosulfonated Polyethylene Vulcanizates as Measured by Stress Relaxation

1971 ◽  
Vol 44 (5) ◽  
pp. 1410-1420
Author(s):  
F. Haaf ◽  
P. R. Johnson
Keyword(s):  
Stress Relaxation ◽  
Elevated Temperatures ◽  
Oxidative Degradation ◽  
Activation Energies ◽  
Polymer Chains ◽  
Chlorosulfonated Polyethylene ◽  
Thermal And Oxidative Stability ◽  
Relaxation Measurements ◽  
Accelerator System ◽  
Interchange Reactions

Abstract Stress relaxation measurements of chlorosulfonated polyethylene vulcanizates show that curing with m-phenylene-bis-maleimide gives thermally more stable crosslinks than the conventional metal oxide/sulfur accelerator system. The superior thermal stability of the bis-maleimide cure is based on the covalent nature of the crosslinks. In conventionally cured vulcanizates interchange reactions of the metal sulfonate and polysulfide crosslinks occur at elevated temperatures. The interchange reactions of the crosslinks cause a rapid stress decline at the beginning of the stress relaxation process. Over longer aging periods stress relaxation due to oxidative degradation becomes apparent in vulcanizates of both types. The activation energies of oxidative stress relaxations are very similar for the bis-maleimide and the conventional cure. The similarity of the activation energies indicates that oxidative degradation follows the same path. The site of the oxidative attack is established for bis-maleimide cured vulcanizates. Oxidative degradation is found to occur in the polymer chains rather than in the crosslinks. The effects of fillers and stabilizers are investigated and their mode of action is explained on the basis of the stress relaxation results.

Chemiluminescence of isotactic polypropylene induced by photo-oxidative degradation and natural weathering

2006 ◽  
Vol 102 (5) ◽  
pp. 4623-4629 ◽  
Author(s):  
Silviu Jipa ◽  
Radu Setnescu ◽  
Traian Zaharescu ◽  
Tanta Setnescu ◽  
Mustapha Kaci ◽  
...  
Keyword(s):  
Isotactic Polypropylene ◽  
Oxidative Degradation ◽  
Natural Weathering

Human drug taking under controlled laboratory conditions.

1988 ◽  
Author(s):  
Marian W. Fischman ◽  
Richard W. Foltin ◽  
Joseph V. Brady
Keyword(s):  
Laboratory Conditions

A Chinese Railway Bridge

1913 ◽  
Vol 75 (1942supp) ◽  
pp. 181-181
Author(s):  
F. C. Coleman
Keyword(s):  
Railway Bridge

Multiple recycling of paperboard: Paperboard characteristics and maximum number of recycling cycles— Part I: Multiple recycling of corrugated base paper

TAPPI Journal ◽  
2019 ◽  
Vol 18 (11) ◽  
pp. 631-638
Author(s):  
FREDERIC KREPLIN ◽  
HANS-JOACHIM PUTZ ◽  
SAMUEL SCHABEL
Keyword(s):  
Compression Test ◽  
Production Capacity ◽  
Strength Properties ◽  
Paper Properties ◽  
Corrugated Board ◽  
Laboratory Conditions ◽  
Base Paper ◽  
Study Results ◽  
Short Span ◽  
Multiple Recycling

Paper for recycling is an important fiber source for the production of corrugated base paper. The change in production capacity toward more and more packaging papers affects the composition of paper for recycling and influences the paper quality. This research project investigated the influence of the multiple recycling of five different corrugated base papers (kraftliner, neutral sulfite semichemical [NSSC] fluting, corrugating medium, testliner 2, and testliner 3) on suspension and strength properties under laboratory conditions. The corrugated board base papers were repulped in a low consistency pulper and processed into Rapid-Köthen laboratory sheets. The sheets were then recycled up to 15 times in the same process. In each cycle, the suspension and the paper properties were recorded. In particular, the focus was on corrugated board-specific parameters, such as short-span compression test, ring crush test, corrugating medium test, and burst. The study results indicate how multiple recycling under laboratory conditions affects fiber and paper properties.

Daylight in Underground Spaces

2018 ◽  
pp. 156-161
Author(s):  
Alexei K. Solovyov
Keyword(s):  
Light Guide ◽  
Heat Losses ◽  
Internal Environment ◽  
Method Of Calculation ◽  
Natural Lighting ◽  
Different Depths ◽  
The Common ◽  
Different Diameters

Underground spaces in town centres present a big attraction for investors. However, they put special requirements to the internal environment. Those requirements can be fulfilled by means of daylighting. Examples of lighting of underground spaces are discussed. It is shown that the common systems of natural lighting are not always possible to use and cause big heat losses. Hollow light guide pipes allow avoid the shortcomings of common daylight systems. Method of calculation of daylight factors from hollow light guide pipes is shown. The results of calculation of daylight factors under the light guide pipes of different diameters in the different depths are presented.

Review of the Current State and Future Development in Standardizing Natural Lighting in Interiors

2018 ◽  
pp. 5-26 ◽  
Author(s):  
Stanislav Darula
Keyword(s):  
Human Life ◽  
Natural Light ◽  
Artificial Lighting ◽  
Computer Tools ◽  
Natural Lighting ◽  
Current State ◽  
Minimum Requirements ◽  
Life On Earth ◽  
Window Design

Three elements mainly wind, water and sun seemed to determine in ancient ages the basic phenomena of life on Earth. Architectural history documented the importance of sun influence on urban and building construction already in layouts of Mesopotamian and Greek houses. Not only sun radiation but especially daylight played a significant role in the creation of indoor environment. Later, in the 20th century, a search of interaction between human life in buildings and natural conditions were studied considering well­being and energy conscious design recently using computer tools in complex research and more detail interdisciplinary solutions. At the same time the restricted daytime availability of natural light was supplemented by more efficient and continually cheaper artificial lighting of interiors. There are two main approaches to standardize the design and evaluation of indoor visual environment. The first is based on the determination of the minimum requirements respecting human health and visibility needs in all activities while the second emphasizes the behaviour and comfort of occupants in buildings considering year­around natural changes of physical quantities like light, temperature, noise and energy consumption. The new current standardization basis for daylight evaluation and window design criteria stimulate the study of methodology principles that historically were based on the overcast type of sky luminance pattern avoiding yearly availability of sky illuminance levels. New trends to base the daylight standardization on yearly or long­term availability of daylight are using the averages or median sky illuminance levels to characterise local climatological conditions. This paper offers the review and discussion about the principles of the natural light standardization with a short introduction to the history and current state, with a trial to focus on the possible development of lighting engineering and its standards in future.

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