The behavior of bentonite binders for the elevated and high temperatures

Bentonite binders rank among the most widespread applied systems for the production of molds. Their resistance to high temperatures (thermal stability) is mainly defined by genesis of binders, chemical composition and the content of Montmorillonite. The aim of this contribution is to compare selected bentonite binders commonly used in the foundries of the Central European region, in different ways of the thermostability determination as a result of changes of the mechanical strengths of the bentonite bonded sand mixture.Masy formierskie z bentonitem jako materiałem wiążącym stanowią najbardziej rozpowszechnioną technologię otrzymywania form odlewniczych. Ich odporność na wysokie temperatury (stabilność termiczna) jest uzależniona od pochodzenia minerologicznego, składu chemicznego oraz zawartości montmorylonitu w bentonicie. Celem tego artykułu jest porównanie stabilności termicznej wybranych bentonitów - powszechnie stosowanych w odlewniach w regionie Europy Środkowej – mierzonej różnymi metodami. Kryterium oceny tych metod jest zmiana wytrzymałości mechanicznej mas formierskich wiązanych bentonitem.Web of Science5931044104

The measurement of high-temperature expansion as the standard of estimation the knock-out properties of moulding sands with hydrated sodium silicate

The necessity of receiving high quality castings forces undertaking research to elaborate moulding and core sands ensuring obtaining the materials with relevant technological parameters and also with high environmental standards. The most important group here are moulding sands with hydrated sodium silicate. Unfortunately, their fundamental disadvantages are weak knock-out properties. The article presents the most commonly used methods of measuring the knock-out properties of moulding and core sands. The authors propose a new method for estimation this parameter. The method is based on the measurement of high-temperature expansion.Potrzeba uzyskiwania wysokiej jakości odlewów wymusza podejmowanie prac badawczych dla otrzymania mas formierskich i rdzeniowych zapewniających uzyskanie tworzyw o odpowiednich parametrach technologicznych, jednocześnie spełniających wysokie wymogi ochrony środowiska. Najważniejszą grupę stanowią tutaj masy z uwodnionym krzemianem sodu. Niestety jedną z ich podstawowych wad jest słaba wybijalność. W artykule zostały przedstawione najczęściej stosowane metody pomiaru wybijalności mas formierskich i rdzeniowych Autorzy zaproponowali nową metodę oceny wybijalności opierającą się na pomiarze ekspansji wysokotemperaturowej.Web of Science59274273

Measurement of Molding Sand Elasticity

The progressive mechanization and automation of industrial equipment is the driving force of progress, not only in the field ofproduction but also in the measuring and control equipment. In mold production, the automation of processes such as formingmolds and cores along with their assembly has led to increases in serial production, reductions in defects, and the shorteningof molding times, among others. Thanks to automation in mold and core departments and the use of all sorts of manipulators,mold production in foundries has gained momentum.Unfortunately, in addition to the mentioned advantages, there are also new challenges as to the quality and properties of themolding and core sands used in highly automated foundries.This article presents recent research on molding sand elasticity.The topic was introduced as an attempt to answer the new needs of highly mechanized foundries.The article discusses a new method of measuring the resistance of molding materials to undergoing mechanical deformation(molding sand elasticity), with an additional analysis of the bending strengths of the tested samples. Precise measurements,test sample preparation, and interpretation of the received results are presented in the article

Development tendencies of moulding and core sands

Web of Science8444643

Thermostability of montmorillonitic clays

Bentonite is one of the most widespread used clays connected with various applications. In the case of foundry technology, bentonite is primarily used as a binder for mold manufacture. Thermal stability of bentonites is a natural property of clay minerals and it depends on the genesis, source and chemical composition of the clay. This property is also closely connected to bentonite structure. According to DTA analysis if only one peak of dehydroxylation is observed (about 600 ºC), the cis- isomerism of bentonite is expected, while two peaks of de-hydroxylation (about 550 and 850 ºC) are expected in the trans- one. In this overview, the bentonite structure, the water - bentonite interaction and the swelling behavior of bentonite in connection with the general technological properties of bentonite molding mixture are summarized. Further, various types of methods for determination of bentonite thermostability are discussed, including instrumental analytical methods as well as methods that employ evaluation of various technological properties of bentonite binders and/or bentonite molding mixtures.Web of Science11320720

Diverse Regulation of Vitamin D Receptor Gene Expression by 1,25-Dihydroxyvitamin D and ATRA in Murine and Human Blood Cells at Early Stages of Their Differentiation

Vitamin D receptor (VDR) is present in multiple blood cells, and the hormonal form of vitamin D, 1,25-dihydroxyvitamin D (1,25D) is essential for the proper functioning of the immune system. The role of retinoic acid receptor α (RARα) in hematopoiesis is very important, as the fusion of RARα gene with PML gene initiates acute promyelocytic leukemia where differentiation of the myeloid lineage is blocked, followed by an uncontrolled proliferation of leukemic blasts. RARα takes part in regulation of VDR transcription, and unliganded RARα acts as a transcriptional repressor to VDR gene in acute myeloid leukemia (AML) cells. This is why we decided to examine the effects of the combination of 1,25D and all-trans-retinoic acid (ATRA) on VDR gene expression in normal human and murine blood cells at various steps of their development. We tested the expression of VDR and regulation of this gene in response to 1,25D or ATRA, as well as transcriptional activities of nuclear receptors VDR and RARs in human and murine blood cells. We discovered that regulation of VDR expression in humans is different from in mice. In human blood cells at early stages of their differentiation ATRA, but not 1,25D, upregulates the expression of VDR. In contrast, in murine blood cells 1,25D, but not ATRA, upregulates the expression of VDR. VDR and RAR receptors are present and transcriptionally active in blood cells of both species, especially at early steps of blood development