Effect Of Talc Research Articles

Effects of talc and gamma irradiation on mechanical properties and morphology of isotactic polypropylene/talc composites

Although isotactic polypropylene (iPP) has become one of the largest and fastest growing polymeric materials, some disadvantages in its properties, like poor stability to gamma (γ) irradiation, may impede its growth in commercial use. The popularity of γ irradiation use to sterilize iPP and iPP composites devices is increasing. The purpose of our research work was to examine the effects of talc and low dose γ irradiation on mechanical properties and the morphology of iPP and iPP/talc composites. The samples were prepared in a Brabender kneading chamber and by compression molding on a laboratory press. The iPP and iPP/talc composites were characterized by tensile testing, measurements of notched impact strength, FTIR spectroscopy, differential scanning calorimetry, optical microscopy, scanning electron microscopy and wide angle X-ray diffraction. The role of untreated talc or talc surface treated with aminosilanes as well as the influence of γ irradiation on mechanical properties and the morphology of modified iPP is discussed.

PULMONARY RESPONSES TO INHALED POORLY SOLUBLE PARTICULATE IN THE HUMAN

This review focuses on the human pulmonary effects of talc, carbon black, coal dust, diesel exhaust, and titanium dioxide as examples of poorly soluble, nonfibrous particles (PSPs). Other particulates with similar characteristics (e.g., iron oxide) are included when considering the question of whether there is a characteristic human response to this class of compounds. The overall objective is to characterize the responses to these compounds using information from epidemiology, pathology, and cell biology so that comparisons with animal responses can be made. Exposure to PSPs is associated with two broad classes of disease in the human: pneumoconiosis and chronic obstructive lung disease. The basic pathologic features and pathogenesis of the different lesions associated with exposure to PSPs are described. This is followed by a review of the evidence linking exposure to coal, carbon black, diesel exhaust, talc, and titanium dioxide with these diseases. With the exception of diesel exhaust, which contains genotoxic constituents, PSPs have not been definitely linked to human lung cancer. Some questions relevant to this review are: 1. How does the human lung respond to PSPs? Specifically, (a) what are the morphologic features, and (b) what is their pathogenesis? 2. Is there evidence for clearance overload in the human, and if so, what are the characteristics of the associated tissue response? 3. Are PSPs associated with lung cancer in the human? 4. What are the major similarities and differences between human and rodent lung cancers? 5. Do inflammation, epithelial hyperplasia, and fibrosis play a role in the development of human lung cancer?

Short-term effects of additives on sludge sedimentation characteristics

The effect of different concentrations of additives on the settling properties of two types of activated sludge were evaluated by means of a Settlometer. In addition to the evaluation of the immediate positive effect of the additive, a method consisting of consecutive cycles of resuspension and evaluation of the settling properties, is proposed to study the stability of the beneficial effect of the additive. First, a sludge from industrial origin was supplemented with talc and with a polymer. Subsequently, a sludge from domestic origin was tested. Both additives were successful in improving the sedimentation characteristics of the sludges. The effect of talc was stable over a period of at least 14 h. However, the positive effect of the polymer was transient because after 4 h the beneficial effect disappeared. The experimental results from the talc addition were analysed by means of a physical model. The latter revealed that the observed increase of the initial settling velocity is smaller than but close to the increase related to the specific weight of the floc.

The Effect of Talc on Cell Nucleation in Extrusion Foam Processing of Polypropylene with CO2 and Isopentane

The effect of talc on cell nucleation of polypropylene (PP) foam was investigated. Branched high-melt-strength PP was used to reduce bubble coalescence during extrusion foam processing. When isopentane was used as a blowing agent, bubble nucleation was dominated by the talc concentration, and the isopentane content did not affect the cell density very much. By contrast, when CO2 was used as a blowing agent, both talc and CO2 concentrations determined the cell-population density. However, the effect of talc on nucleation was significant only when the CO2 content was low. In addition, the maximum achievable cell density was not improved by talc when CO2 was used whereas the maximum cell density was dramatically improved by talc when isopentane was used. The experimental results indicate that the heterogeneous bubble nucleation mechanisms in plastic foam processing with CO2 are fundamentally different from those in the processing with a long-chain blowing agent such as isopentane.

Influence of a fine talc on the properties of composites with high density polyethylene and polyethylene/polystyrene blends

Fine talc filled high density polyethylene (HDPE) and HDPE/polystyrene (PS) blends were extruded, injection moulded and characterized. Some of the mechanical properties of the talc filled HDPE and talc filled 75/25 HDPE/PS blend were deduced from stress–strain measurements. A comparison between the effect of the talc on the properties of the filled HDPE and filled 75/25 HDPE/PS blend showed that the mineral filler had the same effect on both systems provided that its array in the organic matrix is almost the same in both cases. In fact, the rheological results proved that the dispersion of talc in the HDPE matrix was not really affected by the presence of PS. The study particularly focused on the effect of talc on the ultimate tensile strength of the filled HDPE and that of the filled blend. It has been noted that the brittle nature of PS neutralizes, to a certain extent, the degrading effect of talc on this property. Furthermore, both PS and talc have a complementary effect on the stiffness and the resilience of HDPE/PS/talc blend composites.

Effect of Talc on Properties of Corn Starch Extrudates

AbstractCommercially available 0, 25, 50 and 70% amylose corn starches were extruded with up to 5% talc {(OH)2Mg3(Si2O5)2} in a single screw Brabender laboratory extruder at 18% moisture content, 140°C barrel temperature, and 140rpm screw speed. Expansion ratio, unit density, percentages of closed and open pores, porosity and molecular degradation of extruded starches were measured.Addition of talc resulted in decreases in expansion ratio, unit density and percentage of open pores, and in increases in percentage of closed pores and porosity of extrudates. The extrudates became smaller with a greater number of round and uniformly sized cells with added talc. Gel permeation chromatographic fractionation of extrudates showed extensive degradation of fraction I with increasing talc concentrations. The talc appeared to have provided nucleation sites for water vaporization as the material exited the die of the extruder.

Effectiveness of Talc as Adsorbent for Stabilization and Expression of Pisum sativum hortense Cv. Solara Lipoxygenase−Lyase Coupled Activities

Pisum sativum hortense cv. Solara lipoxygenase differs from previously described lipoxygenases by the presence, at optimum pH, of dual activities that can convert linoleic acid into two products, 9-hydroperoxyoctadecadienoic acid by a classical lipoxygenase activity and 2,4-decadienal by lyase activity on an intermediate peroxyl radical. This enzyme is a very labile protein and can lose activity during or after the purification procedure. In order to overcome this inconvenience, we immobilized P. sativum lipoxygenase−lyase by adsorption on talc and we explored the evolution and stability of both activities after adsorption. For lipoxygenase or lyase activity, we obtained a specific immobilization on talc with an increase in long-term stability at 4 °C in comparison to free enzyme and especially for immobilized lyase activity (60% of activity after 30 days). Immobilized enzymes appeared to be less sensitive to inhibitors than free, but the increase in IC50 values for immobilized enzymes was in fact the res...

Effectiveness of Talc as Adsorbent for Purification and Immobilization of Plant Lipoxygenases

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffectiveness of Talc as Adsorbent for Purification and Immobilization of Plant LipoxygenasesSerge Battu, Helene Rabinovitch-Chable, and Jean-L. BeneytoutCite this: J. Agric. Food Chem. 1994, 42, 10, 2115–2119Publication Date (Print):October 1, 1994Publication History Published online1 May 2002Published inissue 1 October 1994https://doi.org/10.1021/jf00046a008RIGHTS & PERMISSIONSArticle Views96Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts Get e-Alerts

The inter-relation of some mechanical properties with molecular weight and crystallinity in poly(ethylene terephthalate)

Some mechanical properties of poly(ethylene terephthalate) were determined as a function of molecular weight, temperature and crystallinity. The effect of talc, a nucleating agent, on mechanical properties was also considered.

EFFECT OF A TREMOLITIC TALC IN WHITEWARE BODIES*

AbstractThis paper describes the use of a specific type of tale in wall‐tile bodies and explains the effect of various percentages on shrinkage, absorption, modulus of rupture, moisture expansion, and resistance to delayed crazing. The data indicate the effects of talc with various combinations of wall‐tile body ingredients and the compositions and heat treatment of greatest potential resistance to crazing.