Mechanical Properties of UV Cured Mixture of Linear and Hyperbranched Urethane Acrylates

Ispitivane su smeše uretan akrilata na bazi linearnog poliestra i dva uretan akrilata, sa istim stepenom akrilovanja, na bazi alifatskih hiperrazgranatih poliestara (HRP). Linearni poliestar sintetisan je od neopentil glikola i adipinske kiseline. HRP treće generacije dobijen je od 2,2- bis(hidroksimetil)propionske kiseline i di-trimetilol propana. Modifikacija 60 % završnih OH grupa HRP-a izvedena je masnim kiselinama sojinog ulja ili izononskom kiselinom. Linearni uretan akrilat (LUA) i hiperrazgranati uretan akrilat (HUA) na bazi HRP modifikovanog masnim kiselinama sojinog ulja i HUA na bazi HRP modifikovanog izononskom kiselinom dobijeni su reakcijom određenog poliestra i izocijanatnog adukta, prethodno dobijenog reakcijom ekvimolarnih količina izoforon diizocijanata i 2-hidroksietil akrilata. Procena mešljivosti smeša LUA i HUA izvršena je na osnovu viskozimetrijskih merenja koristeći metodu koju je ustanovio Chee. Ovako pripremljenim smešama dodato je 20 mas. % heksandioldiakrilata i 4 mas. % fotoinicijatora, Irgacure 184, i umrežene su pod dejstvom UV zračenja. Umreženi uzorci ispitivani su u ogledima dinamičkog uvijanja i jednoosnog istezanja. Mehanička svojstva umreženih uzoraka zavise od mešljivosti komponenata smeše i od njenog sastava.The mixtures of urethane acrylate resin based on linear polyester and two urethane acrylates, with the same degree of acrylation, prepared from partially modified aliphatic hyperbranched polyesters (HBP), were examined. Linear polyester was obtained from neopentil glycol and adipic acid. HBP of the third generation was synthesized from 2,2-bis(hydroxymethyl)propionic acid and ditrimethylol propane. The modification of 60 % OH end-groups of HBP was carried out with soybean fatty acids or isononanoic acid. Linear urethane acrylate (LUA) and hyperbranched urethane acrylate (HUA) based on the HBP modified with soy been faty acid and HUA based on the HBP modified with isononanoic acid were obtained by reaction of appropriate polyester and NCO adduct, previously obtained by reaction of equimolar amount of isophorone diisocyanate and 2-hydroxyethyl acrylate. The miscibility of the prepared mixtures of LUA and HUAs was estimated according to viscosity measurements using the approach developed by Chee. UV curable formulation was obtained by adding hexanediol diacrylate (20 wt. %) and photoinitiator, Irgacure 184, (4 wt. %) to the prepared LUA and HUA mixtures. The UV cured samples were examined by dynamic torsion and uniaxial tension. It was obtained that mechanical properties of the UV cured samples depend on miscibility of mixture’s constituents and on its composition

Synthesis and characterization of a new chiral polyurea-based catalyst

A series of chiral poly(urea)s was synthesized by solution polyaddition. The polymers are characterized by NMR, FTIR, DSC, viscosimetry, and microanalysis. After deposition of the rhodium, the insoluble chiral polymers were used as catalysts in the reduction of acetophenone by hydrogen transfer. The influence of the structure of the polymers on the catalytic activity and selectivity was investigated. The enantiomeric excesses (e.e.) obtained were up to 60%, and the polymeric catalysts were reused without loss of activity and selectivity

Recent advances in homogeneous and heterogeneous asymmetric catalysis with nitrogen-containing ligands

Nitrogen-containing chiral ligands are being used more and more in asymmetric catalysis. This article is an overview of results published in 1993-1996 in this field and tries to open new perspectives for this type of ligand, more particularly with the purpose of heterogenization of the catalytic systems

Polymeric and immobilized crown compounds, material for ion separation

We describe the synthesis of ionoselective polymers bearing different pendant crown ethers. The synthesis was applied to various macrocycles. We discuss the influence of macrocyclic cavity Size and rigidity of the polymers on the extraction behavior. Accessibility of active sites can be achievied with immobilized functionalized polyurethanes chemically bound to an inorganic solid support, with no change of ionoselective properties

Template effect in caesium selective phenolic resins

Two new phenolic resins have been synthesised by alkaline polycondensation of resorcinol and acetaldehyde using template polymerisation. The extraction properties of the resins have been evaluated in competitive extraction and show a selectivity in favour of Cs+. This selectivity is enhanced for the template resins. Structural data of the resins are discussed on the basis of C-13-NMR CPMAS spectra. In particular, for caesium template resins, a structure similar to resorcinarene has been evidenced

Synthesis and evaluation of resorcinol-based ion-exchange resins for the selective removal of cesium

Control of the reaction conditions during the alkaline polycondensation of resorcinol with formaldehyde leads to polymeric resins with improved capacity toward caesium. The resins obtained are characterized by determining their moisture regain and ion-exchange capacity. The distribution coefficient (D) for alkali-metal cations are determined in a competitive extraction system at different pH. The alkali-metal cation sorption selectivity series is strongly influenced by the pH of the solution. Two kinds of mechanism can explain these selectivity series. Extraction of caesium from simulated radioactive waste was studied at different pH in the presence of a large excess of sodium. The study also includes the kinetic and the ion-exchange capacity for caesium of the sodium form of the resins

Design of ion-exchange resins selective of caesium. Synergistic effect of macrocycle in phenolic resins

The extraction of caesium by resorcinol based resins was investigated. At high hydroxide concentration ([OH-] = 0.15 M), the alkali-metal cations' sorption selectivity (determined in competitive extraction system) for resorcinol resins was found to be Cs+ gt Li+ gt Rb+ gt K+ gt Na+, whereas at pH 7 this selectivity was found to be Cs+ gt Rb+ gt K+ gt gt Na+ approximate to Li+. Different mechanisms of ion exchange occurring in these phenolic resins can explain this selectivity series. Then different macrocycles were incorporated in the resins. The ionoselective properties of these new ion-exchange resins are strongly influenced by the nature of the crosslinker. The presence of macrocycles lead to an improvement of selectivity towards caesium in relation with the size of the macrocycles introduced

Elimination of vanadium and arsenic from VKCs catalysts

Vanadium and arsenic eliminations from an alkaline leaching solution of spent VKCs catalysts were studied. To this end, several commercial resins or polymers synthesized in the laboratory were evaluated in a solid-liquid batch extraction. Conditions for an effective extraction of vanadium and arsenic were determined. An extraction process, using a glass column, is described for the recovery of the vanadium. The elimination of arsenic by precipitation is proposed

Extraction of cesium from an alkaline leaching solution of spent catalysts using an ion-exchange column

The selective extraction of cesium from an alkaline leaching solution of spent catalysts using phenolic resins was studied. The resins were synthesized by alkaline polycondensation of formaldehyde by phenol, resorcinol, catechol, and phloroglucinol. Their ionoselectivities for five alkali metals were evaluated with a solid-liquid extraction, and their ion-exchange capacities were compared. The resin with the best selectivity for cesium was tested with a real solution at different pH values. An on-column extraction is proposed to obtain cesium with high purity