1,721,129 research outputs found
Kinetics of the free radical grafting of diethyl maleate onto linear polyethylene
No full textA study of the kinetics of diethyl maleate (DEM) grafting onto linear polyethylene (HDPE) initiated by dicumyl peroxide (DCP), was performed by differential scanning calorimetry (DSC) which allows the determination of kinetic parameters such as the activation energy Ea and the order of the reaction n. The calculated kinetic parameters depend on the conditions and vary with the feed composition: in particular the values of Ea and n increase with increasing of DCP/DEM ratio because of secondary reactions such as chain extension and degradation. A mathematical model based on the kinetic equations is proposed; it can be used to select feed composition and process parameters to obtain the desired products
Gradient density grafted polymers on round tire rubber particles by atom transfer radical polymerization
No full text
Effect of structure of functionalizing molecules on the inter-macromolecular reactions and blending of poly(ethylene-co-propylene) (EPM) with poly(6-aminohexanoic acid) (PA6)
No full textPreparazione di nanoparticelle inorganiche organofile per materiali compositi attraverso grafting superficiale via polimerizzazione radicalica vivente (ATRP)
No full textMetodo per trattare sostanze organiche e per realizzare un fertilizzante
No full textUn metodo per trattare sostanze organiche fluide di scarto contenenti azoto ammoniacale, in particolare sostanze derivanti da rifiuti, scarti, decomposizioni, in particolare reflui zootecnici liquidi e/o digestati derivanti da processi di degradazione organica con microorganismi, e per realizzare un materiale fertilizzante a rilascio lento e controllato di azoto ammoniacale, comprende le fasi di:
- predisporre zeolititi, ossia rocce contenenti zeolite in concentrazione maggiore del 50%;
- addizionare a dette zeolititi dette sostanze organiche fluide di scarto e miscelare;
- agitare dette zeolititi e dette sostanze organiche fluide di scarto per un tempo di agitazione;
- lasciare sedimentare dette zeolititi con dette sostanze organiche fluide di scarto per un tempo di sedimentazione in modo tale che dette zeolititi assorbano e sottraggano per scambio cationico azoto ammoniacale da dette sostanze organiche fluide di scarto;
dette zeolititi arricchite in azoto ammoniacale costituendo un materiale fertilizzante, che, quando introdotto in un terreno agricolo, è in grado di rilasciare detto azoto ammoniacale a radici di piante solo quando queste ultime rilasciano acidi umici
Crystal chemistry of the zeolites erionite and offretite
No full textMany known occurrences of the zeolites erionite and offretite have been characterized by electron probe microanalysis, X-ray powder diffraction and optical microscopy. For the first time, a substantial amount of experimentally consistent and homogeneous chemical and crystallographic data have been evaluated for these natural zeolites. Systematic analysis of the data, performed by statistical multivariate analysis, leads to the following conclusions: (1) the two zeolites have well-defined compositional fields in the chemical space describing the extraframework cation content, best illustrated in a Mg-Ca(+Na)-K(+Sr+Ba) diagram; (2) no discrimination is possible on the basis of the framework Si/Al ratio because of the extensive compositional overlap between the two species, however the Si-Al content in the framework tetrahedra is the major control on the unit-cell volume dimensions, particularly in erionite; (3) the crystal chemistry of the Mg cations is a major factor in controlling the crystallization of the mineral species; (4) cation compositions at the boundary of the recognized compositional fields might be due to chemical averaging of two-phase intergrowths, although these mixed-phase occurrences are much less common than previously thought; (5) the sign of optical elongation is not a distinctive character of the two phases, it is related to the Si/Al ratio in the framework tetrahedra of each zeolite type and cannnot be used for identification purposes; (6) the zeolite mineral species epitaxially overgrown on levyne in all cases is identified as erionite; in a few cases offretite was found to be overgrown on chabazite; (7) erionite samples epitaxially overgrown on levyne are substantially more Al-rich and Mg-poor than the erionite samples associated with other zeolites
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