Weathering processes

AccessScience ◽  
2015 ◽  
Keyword(s):  
Weathering Processes

scholarly journals Weathering Stability and Durability of Birch Plywood Modified with Different Molecular Weight Phenol-Formaldehyde Oligomers

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 175
Author(s):  
Juris Grinins ◽  
Vladimirs Biziks ◽  
Brendan Nicholas Marais ◽  
Janis Rizikovs ◽  
Holger Militz
Keyword(s):  
Uv Light ◽  
Phenol Formaldehyde ◽  
Wood Decay ◽  
Soft Rot ◽  
Solid Wood ◽  
Solid Content ◽  
Molecular Weights ◽  
Weathering Processes ◽  
Commercial Resin ◽  
D 20

This study investigated the effect of phenol-formaldehyde (PF) resin treatment on the weathering stability and biological durability of birch plywood. Silver birch (Betula pendula) veneers were vacuum-pressure impregnated with four different PF resins with average molecular weights (Mw) of 292 (resin A), 528 (resin B), 703 (resin C), and 884 g/mol (resin D). The aging properties of PF resin modified birch plywood were analyzed using artificial weathering with ultraviolet (UV) light, UV and water spray, and weathering under outdoor conditions. The same combinations of PF-treated plywood specimens were then tested in soil-bed tests to determine their resistance against soft-rot wood decay. It was not possible to compare weathering processes under artificial conditions to processes under outdoor conditions. However, the weathering stability of birch plywood treated with PF resins A, B, and C, scored better than plywood treated with commercial resin D (regardless of solid content concentration [%]). Results from unsterile soil bed tests showed improvements in resistance to soft-rot wood decay compared to untreated plywood and solid wood. Mass loss [%] was lowest for birch plywood specimens treated with resin of highest solid content concentration (resin D, 20%). Provisional durability ratings delivered durability class (DC) ratings of 2–3, considerably improved over untreated solid wood and untreated birch plywood (DC 5).

Uranium and thorium isotopes in the rivers of the Amazonian basin: hydrology and weathering processes

2002 ◽  
Vol 17 (1) ◽  
pp. 17-31 ◽  
Author(s):  
Aguinaldo N. Marques ◽  
Iyad Al-Gharib ◽  
Michel Bernat ◽  
Fran�ois Fernex
Keyword(s):  
Weathering Processes ◽  
Basin Hydrology ◽  
Thorium Isotopes

scholarly journals Accelerated aging of WPCs Based on Polypropylene and Birch plywood Sanding Dust

2021 ◽  
Vol 11 (1) ◽  
pp. 319-328
Author(s):  
Janis Kajaks ◽  
Karlis Kalnins ◽  
Juris Matvejs
Keyword(s):  
Accelerated Aging ◽  
Degree Of Crystallinity ◽  
Accelerated Weathering ◽  
Recrystallization Process ◽  
Surface Layers ◽  
Uv Aging ◽  
Polypropylene Composites ◽  
Weathering Processes ◽  
Melting Temperatures ◽  
Dsc Measurements

Abstract A lot of researchers are closely related with natural, lignocellulose fibre containing bio-composites production and studies. Various of polymer matrices, mainly polyolefins, combinations with natural fibres as a reinforcement are used. Our studies are focused on polypropylene based bio-composites containing birch plywood production by-product sanding dust (PSD) accelerated weathering processes. The obtained results showed the following sight. After the aging the surface of all samples had faded, the changes of the gloss (decreasing) and of the whiteness degree (increasing) also had taken place, but microhardness of the surface of specimens significantly has decreased. The tensile strength and modulus of the samples after UV aging diminished about 30–35%. That indicates to the changes not only in the surface layers of polymer but also inside of the polymer structure. The FTIR measurements showed that during UV aging process occurs significant changes of chemical structure of the weathered surface of all samples. DSC measurements showed an increase of degree of crystallinity of the weathered polypropylene composites after the first heating due to the recrystallization process in the polypropylene matrix and a small decreasing after second heating. The melting temperatures of all composites after UV aging considerably diminish up to 30°C.

Hydrochemistry of reservoirs of Damodar River basin, India: weathering processes and water quality assessment

2005 ◽  
Vol 48 (8) ◽  
pp. 1014-1028 ◽  
Author(s):  
Abhay Kumar Singh ◽  
G. C. Mondal ◽  
P. K. Singh ◽  
S. Singh ◽  
T. B. Singh ◽  
...  
Keyword(s):  
Water Quality ◽  
Quality Assessment ◽  
River Basin ◽  
Water Quality Assessment ◽  
Weathering Processes ◽  
Damodar River ◽  
Damodar River Basin

Dating of chemical weathering processes by in situ measurement of U-series disequilibria in supergene Fe-oxy/hydroxides using LA-MC-ICPMS

2006 ◽  
Vol 235 (1-2) ◽  
pp. 76-94 ◽  
Author(s):  
J.P. Bernal ◽  
S.M. Eggins ◽  
M.T. McCulloch ◽  
R. Grün ◽  
R.A. Eggleton
Keyword(s):  
Chemical Weathering ◽  
In Situ Measurement ◽  
Weathering Processes

Pseudo-morphogenesis in the shells of the Silurian brachiopods

2021 ◽  
Vol 3 ◽  
pp. 49-55
Author(s):  
V.I. Katkova ◽  
◽  
T.M. Beznosova ◽  
V.N. Filippov
Keyword(s):  
Structural Organization ◽  
Mineral Matter ◽  
Mineral Component ◽  
Early Paleozoic ◽  
Shell Material ◽  
Complete Replacement ◽  
Weathering Processes ◽  
Geological Past ◽  
Chernyshev Ridge ◽  
Crystalline Aggregates

The analysis of paleontological data, the study of mineral matter transformation involving live organisms in various rocks is important for the understanding of the events of the geological past. The aim of this work is to identify the bio-genic factor in the process of pseudo-morphogenesis in the shell sashes of the Early Silurian brachiopods from the car-bonate rocks of the Chernyshev Ridge. Structural and microscopic methods (Shimadzu XRD 6000; Fourier spectrometer InfraLum FT-02; JSM 6400 JEOL; VEGA3 TESCAN; MIN-8) were used to study quartz pseudomorphoses in the sashes of four shells of the Early Silurian brachiopods Borealis sр. of Pentamerida order from the carbonate strata of the Chernyshev Ridge. The salicification of the brachiopod shell walls resulted in the complete replacement of the original carbonate skeleton with a change in its structural organization. It is established that quartz is the main mineral component of the intra-shell material and secondary dolomite crystals and newly formed calcite aggregates. The paper discusses the participation of Early Paleozoic and modern cyanobacterial symbionts in the replacement of primary calcite with quartz and the formation of quartz crystalline aggregates on the shell walls. It is shown that quartz on the surface of shell sashes and in the intra-shell substance of brachiopods has undergone repeated transformations due to the combination of ancient and modern weathering processes.

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