Formation of Halloysite from Feldspar: Low Temperature, Artificial Weathering Versus Natural Weathering

1969 ◽  
Vol 17 (1) ◽  
pp. 13-22 ◽  
Author(s):  
Walter E. Parham
Keyword(s):  
Low Temperature ◽  
Natural Weathering ◽  
Artificial Weathering

scholarly journals Influence of Natural and Artificial Weathering on the Colour Change of Different Wood and Wood-Based Materials

Forests ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 488 ◽  
Author(s):  
Davor Kržišnik ◽  
Boštjan Lesar ◽  
Nejc Thaler ◽  
Miha Humar
Keyword(s):  
Laboratory Test ◽  
Colour Change ◽  
Natural Weathering ◽  
Blue Staining ◽  
Artificial Weathering ◽  
Blue Stain Fungi ◽  
Colour Changes ◽  
Blue Stain ◽  
Positive Correlations ◽  
The Aesthetic

The importance of the aesthetic performance of wood is increasing and the colour is one of the most important parameters of aesthetics, hence the colour stability of twelve different wood-based materials was evaluated by several in-service and laboratory tests. The wood used for wooden façades and decking belongs to a group of severely exposed surfaces. Discolouration of wood in such applications is a long-known phenomenon, which is a result of different biotic and abiotic causes. The ongoing in-service trial started in October 2013, whilst a laboratory test mimicking seasonal exposure was performed in parallel. Samples were exposed to blue stain fungi (Aureobasidium pullulans and Dothichiza pithyophila) in a laboratory test according to the EN 152 procedure. Afterwards, the same samples were artificially weathered and re-exposed to the same blue stain fungi for the second time. The purpose of this experiment was to investigate the synergistic effect of weathering and staining. The broader aim of the study was to determine the correlation factors between artificial and natural weathering and to compare laboratory and field test data of fungal disfigurement of various bio-based materials. During the four years of exposure, the most prominent colour changes were determined on decking. Respective changes on the façade elements were significantly less prominent, being the lest evident on the south and east façade. The results showed that there are positive correlations between natural weathering and the combination of artificial weathering and blue staining. Hence, the artificial weathering of wood-based materials in the laboratory should consist of two steps, blue staining and artificial weathering, in order to simulate colour changes.

scholarly journals Mechanical performance of wood under artificial and natural weathering treatments

BioResources ◽  
2019 ◽  
Vol 14 (3) ◽  
pp. 6267-6277
Keyword(s):  
Exposure Time ◽  
Modulus Of Elasticity ◽  
Elastic Limit ◽  
Bending Strength ◽  
Mechanical Performance ◽  
General Information ◽  
Bending Test ◽  
Natural Weathering ◽  
Linear Regression Models ◽  
Artificial Weathering

Natural and artificial weathering treatments were studied to determine the change of wood properties as a function of exposure time. This paper aimed to provide general information about the mechanical performance of wood under natural and artificial weathering treatments and define a relationship between them. The eight strength classes of ABNT NBR 7190 (1997) were considered, in addition to a paired sampling approach. The modulus of elasticity and conventional strength value in static bending, strength in compression parallel to the grain, hardness perpendicular to the grain, and the elastic limit in the static bending test were investigated. Linear regression models for mechanical performances under artificial and natural aging treatments of the exposure time were made and tested using an analysis of variance. According to the results, 360 days of natural weathering provoked a change in mechanical performance of 15.72% that included a decrease in strength and modulus of elasticity and an increase in elastic limit. Twelve hours of the artificial weathering treatment provided the effect of 6.22 days of natural weathering exposure.

scholarly journals A durable coating to prevent stress corrosion effects on the surface strength of annealed glass

2021 ◽  
Author(s):  
Gregorio Mariggiò ◽  
Sara Dalle Vacche ◽  
Roberta Bongiovanni ◽  
Christian Louter ◽  
Mauro Corrado
Keyword(s):  
Cyclic Loading ◽  
Stress Corrosion ◽  
Bending Strength ◽  
Natural Weathering ◽  
Ring Test ◽  
Polymeric Coating ◽  
Surface Strength ◽  
Artificial Weathering ◽  
Double Ring ◽  
Annealed Glass

AbstractThe durability of an innovative polymeric coating recently developed by the authors to prevent stress corrosion in annealed glass is herein examined. The coating, having functional graded properties through the thickness, is optimised to provide a very good adhesion with glass and an excellent hydrophobic behavior on the side exposed to the environment, thus creating a good barrier to humidity, which is the triggering agent for stress corrosion. Three scenarios are analysed in terms of ageing: (i) cyclic loading, accomplished by subjecting coated samples to repetitive loading; (ii) natural weathering, performed by exposing coated samples to atmospheric agents; (iii) artificial weathering, carried out by exposing coated specimens to fluorescent UV lamps, heat and water. The durability of the coating is assessed indirectly, on the base of its residual effectiveness in preventing stress corrosion, by comparing the bending strength, obtained with the coaxial double ring test, of aged coated glass specimens with that of un-coated and freshly coated specimens. The obtained results prove that the proposed formulation is almost insensitive to cyclic loading, maintains a very good performance in case of natural weathering, whereas is slightly more sensitive to artificial weathering.

Low-temperature thermal effects in natural volcanic glasses due to strain

1962 ◽  
Vol 33 (258) ◽  
pp. 237-246 ◽  
Author(s):  
A. Ewart ◽  
M. Fieldes
Keyword(s):  
Surface Water ◽  
Low Temperature ◽  
Thermal Effects ◽  
Surface Strain ◽  
Systematic Variation ◽  
Natural Weathering ◽  
Volcanic Glasses ◽  
External Strain

SummarySharp exothermic peaks occurring at about 90° C during D.T.A. treatment of natural volcanic glasses are described and are shown to be due to release of external strain. This is probably triggered by loss of surface water. No systematic variation in strain could be found in glass of different geological histories, but strain is found to decrease during natural weathering of volcanic glasses. Differences in weatherability of natural glasses may be related to degree of surface strain.

scholarly journals Comparison of Exterior Coatings Applied to Oak Wood as a Function of Natural and Artificial Weathering Exposure

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 864
Author(s):  
Eliška Oberhofnerová ◽  
Kristýna Šimůnková ◽  
Ondřej Dvořák ◽  
Irena Štěrbová ◽  
Salim Hiziroglu ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Surface Wettability ◽  
Natural Weathering ◽  
Testing Time ◽  
Artificial Weathering ◽  
Oak Wood ◽  
Microscopic Evaluation ◽  
Colour Changes ◽  
Coating Durability ◽  
Pigmented Coatings

Artificial weathering can significantly reduce the testing time needed for proving coating durability, nevertheless its reliability is still not thoroughly proven. In this study, eight different transparent and pigmented coating systems, namely oil, acrylate, alkyd and urethane alkyd were evaluated through natural and artificial weathering tests on oak samples by measuring colour, gloss and surface wettability and by macroscopic and microscopic evaluation. The oil coatings performed well in wood colour stability evaluations, while the best gloss and wettability change results were noted for acrylate coatings. Pigmented coatings were characterized by significantly lower colour changes than transparent ones. The gloss and wettability changes were more sensitive to coating disruption than to total colour changes of coated wood associated with chemical changes in wood. The findings in this work showed that values of gloss changes and surface wettability for all types of coatings exposed to artificial and natural weathering resulted in significant differences from each other. The data obtained by artificial weathering method provide basic results of coatings durability and, ideally, natural weathering should be performed at the same time to support the results from laboratory tests by exposing wood under real conditions.

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