The investigation results of the influence of the reclaim additions on the properties of moulding sands with the GEOPOL geopolymer
binder developed by the SAND TEAM Company were presented. Two brands of hardeners were applied in the tested compositions, the
first one was developed by the SAND TEAM Company, marked SA72 and the new hardener offered by the KRATOS Company, marked
KR72. The main purpose of investigations was to determine the influence of reclaim fractions and the applied hardener on the basic
moulding sands properties, such as: bending and tensile strength, permeability and grindability. The unfavourable influence of the reclaim
additions into moulding sands on the tested properties as well as an increased hardening rate, were found. Moulding sands, in which the
hardener KR72 of the KRATOS Company was used, were less sensitive to the reclaim additions.
The results of investigations of moulding sands with an inorganic binder called GEOPOL, developed by the SAND TEAM Company are
presented in the paper. Hardeners of various hardening rates are used for moulding sands with this binder. The main aim of investigations
was determination of the influence of the hardening rate of moulding sands with the GEOPOL binder on technological properties of these
sands (bending strength, tensile strength, permeability and grindability). In addition, the final strength of moulding sands of the selected
compositions was determined by two methods: by splitting strength and shear strength measurements. No essential influence of the
hardening rate on such parameters as: permeability, grindability and final strength was found. However, the sand in which the slowest
hardener (SA 72) were used, after 1 hour of holding, had the tensile and bending strength practically zero. Thus, the time needed for taking
to pieces the mould made of such moulding sand will be 1.5 - 2 hours.
The paper presents the results of thermoanalytical studies by TG/DTG/DTA, FTIR and GC/MS for the oil sand used in art and precision foundry. On the basis of course of DTG and DTA curves the characteristic temperature points for thermal effects accompanying the thermal decomposition reactions were determined. This results were linked with structural changes occurred in sample. It has been shown that the highest weight loss of the sample at temperatures of about 320°C is associated with destruction of C-H bonds (FTIR). In addition, a large volume of gases and high amounts of compounds from the BTEX group are generated when liquid metal interacts with oil sand. The results show, that compared to other molding sands used in foundry, this material is characterized by the highest gaseous emissions and the highest harmfulness, because benzene emissions per kilogram of oil sand are more than 7 times higher than molding sand with furan and phenolic binders and green sand with bentonite and lustrous carbon carrier.
The paper presents possibility of using biodegradable materials as parts of moulding sands’ binders based on commonly used in foundry
practice resins. The authors focus on thermal destruction of binding materials and thermal deformation of moulding sands with tested
materials. All the research is conducted for the biodegradable material and two typical resins separately. The point of the article is to show
if tested materials are compatible from thermal destruction and thermal deformation points of view. It was proved that tested materials
characterized with similar thermal destruction but thermal deformation of moulding sands with those binders was different.
In this work, an assessment and comparison of the quality of selected bentonites and bentonite mixtures was made. The samples consisted of available foundry materials used for bonding green sands. Determining the homogeneity degree and specific surface area of the grains allowed us to compare the examined materials and determine their influence on other parameters. On the basis of a thermal analysis of the bentonites or bentonite mixtures, the changes occurring in the sample during its heating were determined. Determining the potential for ion exchange and montmorillonite content enabled us to assess the binding properties of the materials. The preparation of six green sands with different bentonites or bentonite mixtures gave us the opportunity to assess the changes in apparent density, permeability, compressive strength and friability as a function of humidity, and the impact of different materials on the mentioned parameters. Their charts were analyzed, and the molding sand with the addition of bentonite or a bentonite mixture was selected for which these parameters are favorable. On this basis, the best-presented binding material was assessed and selected.
In many foundries, the requirements placed on castings production have risen mainly over the few years. Further trends in recent years have been the ever increasing level of automation and introduction of new alloys, especially composites. On the other hand, the foundry environment has become increasingly difficult because is used many organic binders. Environmental regulations will be further tightened up. These processes are pursued at national, European and global level. Conformity with emission limits is becoming increasingly difficult. The problem is emission of aromatic hydrocarbons, phenol, odours and other harmful compounds to environment. The main purpose of many companies is reduction of this toxins. The new cold-box systems (based on phenolic resins) try to reduce the emission by introducing into the resin structure silicate modifiers. Research presented of this article evaluate the effectiveness of these methods. The results show comparison of two resins ("without" and "with" silicate modifier) for assessment of emission of harmful aromatic hydrocarbons and phenol.
The paper presents the results of an investigation of the gases emission of moulding sands with an inorganic (geopolymer) binder with a relaxation additive, whose main task is to reduce the final (residual) strength and improves knocking-out properties of moulding sand. The moulding sand without a relaxation additive was the reference point. The research was carried out using in accordance with the procedure developed at the Faculty of Foundry Engineering of AGH - University of Science and Technology, on the patented stand for determining gas emissions. Quantification of BTEX compounds was performed involving gas chromatography method (GC).The study showed that the introduction of relaxation additive has no negative impact on gas emissions - both in terms of the total amount of gases generated, as well as emissions of BTEX compounds. Among the BTEX compounds, only benzene is emitted from the tested moulding sands. Its emission is associated with the introduction a small amount of an organic hardener from the group of esters.
It was found that the addition of carbon fibers (CFs) does not affect the crosslinking process in the microwave radiation (800 W, 2.45
GHz) of the BioCo2 binder, which is a water solution of poly(acrylic acid) and dextrin (PAA/D). It has influence on BioCo2 thermal
properties. The CFs addition improves the thermostability of a binder and leads to the reduction of gas products quantity generated in the
temperature range of 300-1100°C (TG-DTG, Py-GC/MS). Moreover, it causes the emission of harmful decomposition products such as
benzene, toluene, xylene and styrene to be registered in a higher temperatures (above 700°C). BioCo2 binder without CFs addition is
characterized by the emission of these substances in the lower temperature range. This indicates the positive effect of carbon fibers
presence on the amount of released harmful products.
The selected technological tests (permeability, friability, bending strength, tensile strength) have shown that the moulding sand with the
0.3 parts by weight carbon fibers addition displays the worst properties. The addition of 0.1 parts by weight of CFs is sufficient to obtain a
beneficial effect on the analyzed moulding sands properties. The reduction of harmful substances at the higher temperatures can also be
observed.
The effects of silica additive (Poraver) on selected properties of BioCo3 binder in form of an aqueous poly(sodium acrylate) and dextrin (PAANa/D) binder were determined. Based on the results of the thermoanalytical studies (TG-DTG, FTIR, Py-GC/MS), it was found that the silica additive results in the increase of the thermostability of the BioCo3 binder and its contribution does not affect the increase in the level of emissions of organic destruction products. Compounds from group of aromatic hydrocarbons are only generated in the third set temperature range (420-838°C). The addition of silicate into the moulding sand with BioCo3 causes also the formation of a hydrogen bonds network with its share in the microwave radiation field and they are mainly responsible for maintaining the cross-linked structures in the mineral matrix system. As a consequence, the microwave curing process in the presence of Poraver leads to improved strength properties of the moulding sand (���� �� ). The addition of Poraver's silica to moulding sand did not alter the permeability of the moulding sand samples, and consequently reduced their friability. Microstructure investigations (SEM) of microwave-cured samples have confirmed that heterogeneous sand grains are bonded to one another through a binder film (bridges).
The paper presents the results of an investigation of the thermal deformation of moulding sands with an inorganic (geopolymer) binder with a relaxation additive, whose main task is to reduce the final (residual) strength and improves knocking-out properties of moulding sand. The moulding sand without a relaxation additive was the reference point. The research was carried out using the hot-distortion method (DMA apparatus from Multiserw-Morek). The results were combined with linear deformation studies with determination of the linear expansion factor (Netzsch DIL 402C dilatometer). The study showed that the introduction of relaxation additive has a positive effect on the thermal stability of moulding sand by limiting the measured deformation value, in relation to the moulding sand without additive. In addition, a relaxation additive slightly changes the course of the dilatometric curve. Change in the linear dimension of the moulding sand sample with the relaxation additive differs by only 0.05%, in comparison to the moulding sand without additive.
The intercalation into interlayer spaces of montmorillonite (MMT), obtained from natural calcium bentonite, was investigated. Modification of MMT was performed by the poly(acrylic acid-co-maleic acid) sodium salt (co-MA/AA). Efficiency of modification of MMT by sodium salt co-MA/AA was assessed by the infrared spectroscopic methods (FTIR), X-ray diffraction method (XRD) and spectrophotometry UV-Vis. It was found, that MMT can be relatively simply modified with omitting the preliminary organofilisation – by introducing hydrogel chains of maleic acid-acrylic acid copolymer in a form of sodium salt into interlayer galleries. A successful intercalation by sodium salt of the above mentioned copolymer was confirmed by the powder X-ray diffraction (shifting the reflex(001) originated from the montmorillonite phase indicating an increase of interlayer distances) as well as by the infrared spectroscopy (occurring of vibrations characteristic for the introduced organic macromolecules). The performed modification causes an increase of the ion exchange ability which allows to assume that the developed hybrid composite: MMT-/maleic acid-acrylic acid copolymer (MMT-co- MA/AA) can find the application as a binding material in the moulding sands technology. In addition, modified montmorillonites indicate an increased ability for ion exchanges at higher temperatures (TG-DTG, UV-Vis). MMT modified by sodium salt of maleic acid-acrylic acid copolymer indicates a significant shifting of the loss of the ion exchange ability in the direction of the higher temperature range (500–700°C).