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Microstructural changes of expansive clays during dehydration caused by suction pressure - a case study of Miocene to Pliocene clays from Warsaw (Poland)

Wójcik Emilia, Trzciński Jerzy, Łądkiewicz-Krochmal Katarzyna

Acta Geologica Polonica

2019

Vol. 69, no. 3

465--488

This paper presents the qualitative and quantitative characteristics of microstructures of Neogene clays from Warsaw, Poland. Scanning Electron Microscope (SEM) studies were used for the microstructural analysis of natural clays and clay pastes. Qualitative microstructural changes were observed: from a honeycomb microstructure for the initial clay paste to a turbulent microstructure for the dried paste. It was also noticed that water loss caused by the increase of the suction pressure had a significant impact on the microstructural transformations. Significant changes in the quantitative values of the pore space parameters were also observed. Increase of suction pressure and water loss caused a decrease in porosity and changes in the values of morphometric parameters, such as pore distribution; for example, a significant increase of the number of pores of 0−10 μm size and changes in the geometric parameters of the pore space were noticed with the increase of suction pressure. The pore space with larger isometric pores was modified into a pore space with the dominance of small anisometric and fissure-like pores. The increased degree of anisotropy from a poorly-oriented to a highly-oriented microstructure was also observed. After rapid shrinkage the reduction in the number of pores, maximum pore diameter, and total pore perimeter was recorded. The process of rapid water loss induced the closure of very small pores. A similar effect was observed during the increase of the suction pressure, where the closure of pore space of the clay pastes was observed very clearly.

Supermolecular structure, morphology and physical properties of urea-urethane elastomers

Ryszkowska J.

Polimery

2012

T. 57, nr 11-12

775-785

Urea-urethane elastomers from polyesterdiol, 4,4'-diphenylmethane diisocyanate (MDI) and dicyandiamide were examined. Their structure was analysed using atomic force microscopy, and the obtained images underwent quantitative analysis. FT-IR spectroscopic analyses were performed, and the phase separation degree was calculated using the results. The structure was also estimated via indirect methods with the use of thermal analysis DSC and TGA. Mechanical and abrasive wear properties were also tested. As a result of the analyses, a linear dependence was found between the size of the hard domain agglomerates and the analysed properties of PUR materials, such as the glass transition temperature of the soft phase, the temperature of the maximum speed of the hard phase's degradation, density, hardness, tensile strength and strain.

Badano elastomery uretanowo-mocznikowe wytworzone z poliestrodiolu, 4,4'-difenylometanodiizocyjanianu (MDI) i dicyjanodiamidu. Z zastosowaniem mikroskopii sił atomowych oceniano ich struktury nadcząsteczkowe a otrzymane obrazy poddano analizie ilościowej. Zarejestrowano widma FT-IR, a na ich podstawie obliczono stopień separacji fazowej. Strukturę oceniano też metodami pośrednimi wykorzystując analizę termiczną DSC i TGA. Określono właściwości wytrzymałościowe i zużycie ścierne otrzymywanych elastomerów. Stwierdzono liniową zależność pomiędzy rozmiarem aglomeratów domen twardych a temperaturą zeszklenia fazy miękkiej, temperaturą maksymalnej szybkości degradacji fazy twardej, gęstością, twardością, wytrzymałością na rozciąganie i odkształceniem trwałym.