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Cationic system

As pointed out in Section 4.2.2, cationic polymerization processes are initiated by photoinitiators, which are essentially precursors generating Lewis and Bronsted acids. The mechanism of the process is ionic, and this chemistry does not function with the type of double bonds and unsaturation found in fhe monomers and oligomers reacting via free radical mechanism. [Pg.78]

Cafionic photoinitiation is based on the ring opening of the oxirane group. The photoinitiators of practical importance belong to three main classes of compounds diazonium salts, onium (e.g., iodonium and sulfonium) salts, and organometallic complexes, which upon irradiation by UV light decompose and yield an acid catalyst. [Pg.78]

Epoxy-functional polydimethylsiloxane oligomers are another group that can be cured by UV radiation. Epoxysilicone block copolymers exhibit a good photoinitiator miscibility, high cure rate, and compatibility with epoxy and vinyl ether monomers. These block copolymers form flexible films with excellent release properties and are therefore used as release coatings.  [Pg.78]

Example of a General-Purpose Cationic UV Curable Formulation [Pg.79]

Source Cyracure Cycloaliphatic Epoxies, Cationic UV Cure, Form 321-00013-0901 AMS, Dow Chemical Company (2001). [Pg.79]

In principle, cationic systems should be the most versatile UV systems because of the wide range of monomers and oligomers that are theoretically available. In practice, there are a limited number of commercially available monomers and oligomers and even fewer photoinitiators. Cationic systems are very fast-curing and often cure to completion after irradiation is ceased. The major chemical limitations to photocationic systems are inhibition by atmospheric moisture and by small quantities of basic or alkaline materials. [Pg.33]

The epoxy monomers used in UV systems are called cycloaliphatic epoxies and are quite different from the monomers used in conventional epoxy resins. Typical examples are 3,4-Epoxycyclohexylmethyl-3,4-Epoxy-cyclohexane-carboxylate and Bis(3,4Epoxycyclohexyl) adipate. These monomers are good for producing thin, clear coatings but suffer from strong odours, and post-heating is often necessary to produce optimum properties. [Pg.33]

Scientists in basic cationic polymerisation chemistry have studied vinyl ethers for many years but, until recently, few monomers were available which gave products with useful properties e.g., triethylene glycol divinyl ether and cyclohexyl vinyl ether. Morflex has a range [Pg.33]

Toagosei in Japan have developed oxetane monomers. These four-membered cyclic ether monomers are claimed to give superior properties to cycloaliphatic epoxies. [Pg.34]

Few photoinitiators are available for cationic systems. The most widely used are diaryl iodonium salts such as diaryliodonium hexafluoro-antimonate, triaryl salts such as triphenyl sulfonium hexafluoro-phosphate, and mixed triphenyl sulfonium salts. These photoinitiators are decomposed by UV light by a homolytic cleavage to produce a radical anion and a radical cation. The latter abstracts hydrogen from surrounding molecules and generates a proton, which is the initiating species  [Pg.34]


Chain transfer is far more important than in the anionic case, so we do not encounter living polymers in cationic systems. [Pg.411]

Since the discovery of living cationic systems, cationic polymerization has progressed to a new stage where the synthesis of designed materials is now possible. The rapid advances in this field will lead to useful new polymeric materials and processes that will greatiy increase the economic impact of cationic initiation. [Pg.246]

With appropriately substituted oxetanes, aluminum-based initiators (321) impose a degree of microstmctural control on the substituted polyoxetane stmcture that is not obtainable with a pure cationic system. A polymer having largely the stmcture of poly(3-hydroxyoxetane) has been obtained from an anionic rearrangement polymerisation of glycidol or its trimethylsilyl ether, both oxirane monomers (322). Polymerisation-induced epitaxy can produce ultrathin films of highly oriented POX molecules on, for instance, graphite (323). Theoretical studies on the cationic polymerisation mechanism of oxetanes have been made (324—326). [Pg.369]

An example of preferred conrotatory cyclization of four-7c-electron pentadienyl cation systems can be found in the acid-catalyzed cyclization of the dienone 12, which proceeds through the 3-hydroxypentadienyl cation 13. The stereochemistry is that expected for a conrotatory process. [Pg.618]

Cationic polymerization in hot melts has been applied to epoxidized polymers [38,39]. No hot melts based on vinyl ether or other cation-sensitive functionalized polymers have been described in the literature. With cationic systems, it is important that the other ingredients in the adhesive be of low basicity to avoid scavenging the initiating acid generated by the photoinitiator. [Pg.736]

After the feed solution is processed to the extent that the resin becomes exhausted and caimot accomplish any further ion exchange, the resin must be regenerated. In normal column operation, for a cation system being converted first to the hydrogen then to the sodium form, regeneration employs the following basic steps ... [Pg.398]

Figure 12-50A. Centrifugai compressor auxiiiiaries—forced feed iubri-cation system. (Used by permission A C Compressor Corporation.)... Figure 12-50A. Centrifugai compressor auxiiiiaries—forced feed iubri-cation system. (Used by permission A C Compressor Corporation.)...
These terms were coined by Otsu and Yoshida24 based on the similar terminology introduced by Kennedy25 to cover analogous cationic systems. Except for the case of the dithiuram disulfides and related species (Section 9.3.2.1), these expressions have now fallen from favor and are no longer used as a generic terminology. In this chapter, wc use the term initiator to denote alkoxyamincs in NMP and halo-compounds in ATRP despite the confusion this can create, especially when the process also involves added conventional initiators. [Pg.458]

In an electrochemical study of the behavior of the counterions in the mixed cation systems sodium and silver, sodium and calcium, and silver and calcium containing the dodecyl sulfate anion, Corkill and Goodman [102] determined the CMC of sodium, calcium, and silver dodecyl sulfates in water and in solutions of sodium and silver nitrate. [Pg.250]

The difference in behaviour between pentyl and butyl cation systems (Figs. 3 and 4) has also been encountered in trapping experiments with carbonium ions, primarily formed from alkanes and SbFs, by CO (Hogeveen and Roobeek, 1972). In the case of n-butane the secondary butyloxocarbonium ion is the main product, whereas in the case of n-pentane only the tertiary pentyloxocarbonium ion is found. [Pg.41]

Pattern of the Isotherms in Binary Monovalent Cation Systems... [Pg.127]

Multivalent cation mixtures have not been studied as extensively as monovalent cation mixtures. The following systems have been studied so far (Ca, Ba),/2C1, (Y, La)i/3Cl,6i and (Y, Dy)i/3C1.6i The isotherms of (Y, La)i/3C1 are shown in Fig. 14. In these three systems the mobility decreases with increasing molar volume. This trend is similar to that in monovalent cation systems. An equation such as Eq. (12) seems to hold. The larger cation is more mobile than the smaller one in the former two... [Pg.143]

Fig. 4.3a. The change in the energy of LU, ezv and in the total energy, E, of ethylene-chlorine cation system... Fig. 4.3a. The change in the energy of LU, ezv and in the total energy, E, of ethylene-chlorine cation system...
Fig. 4.3 b. The changes in the LU partial population of pt orbital at -carbon ethylene-chlorine cation system... [Pg.33]

In the cationic systems, the positive charges are delocalized over almost all atoms, even if the individual structures may be described by the Zintl concept that assigns localized positive charges to tricoordinate E atoms. It appears that the Zintl concept is better suited, yet not sufficient, to describe the structures of the heavier chalcogen elements. [Pg.411]

The cyclobutyl/cyclopropylmethyl cation system (C4II7 ) has probably been the focus of more studies than any other carbocation system except the 2-norbornyl cation. Bridged cyclobutyl cations 16 are called bicyclobutonium ions. Bicyclobutonium... [Pg.145]


See other pages where Cationic system is mentioned: [Pg.327]    [Pg.358]    [Pg.293]    [Pg.448]    [Pg.355]    [Pg.82]    [Pg.282]    [Pg.47]    [Pg.48]    [Pg.58]    [Pg.72]    [Pg.4]    [Pg.14]    [Pg.36]    [Pg.218]    [Pg.36]    [Pg.107]    [Pg.90]    [Pg.35]    [Pg.636]    [Pg.66]    [Pg.67]    [Pg.194]    [Pg.130]    [Pg.131]    [Pg.71]    [Pg.433]    [Pg.464]    [Pg.269]    [Pg.354]    [Pg.797]   
See also in sourсe #XX -- [ Pg.189 , Pg.190 , Pg.191 , Pg.192 , Pg.193 , Pg.194 , Pg.195 , Pg.196 , Pg.197 , Pg.198 , Pg.199 , Pg.200 , Pg.201 , Pg.202 , Pg.203 , Pg.204 , Pg.205 ]

See also in sourсe #XX -- [ Pg.199 ]

See also in sourсe #XX -- [ Pg.63 ]




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2-Heptyl cation systems

2-Heptyl cation systems cations

Acyclic cationic systems

Adamantyl system cation

Allyl system cation

Allylic systems, cations

Anionic-cationic surfactant systems

Anionic-cationic surfactant systems precipitation

Biological systems, cation-anion

Cation efflux system

Cation systems

Cation systems, monovalent

Cation-coupled transport systems

Cation-pool Initiated Polymerization of Vinyl Ethers Using a Microflow System

Cation-pool method system

Cation-sensing systems

Cationic Peptide Delivery Systems in Combination with Other Adjuvants

Cationic catalytic system

Cationic curable systems

Cationic epoxy systems

Cationic liposomal system

Cationic photocurable systems

Cationic polymerization microflow-system

Cationic polymerization practical systems

Cationic starches systems

Cationic systems, studies

Cationic transfer hydrogenation systems

Cationic-anionic surfactant systems examined

Cationically cured systems

Cations aromatic systems

Cations cationic alkyl model system

Cations common in biological systems

Cations with three atom allyl system

Cations, operational system

Cations, operational system analysis

Conjugated systems allylic cations

Conjugated unsaturated systems allyl cation

Cyclopropyl-allyl cation system

Dehydrocyclization 2-heptyl cation systems

Dehydrocyclization cation systems

Delocalized systems cations

Drug delivery system cationic polymers

Dual cation systems

Endo systems, 2-norbomyl cation

Energy diagram cation system

Gene delivery system cationic polymers

Gene delivery systems cationic liposomes

General Considerations on the Photoinitiated Cationic Polymerization Employed in Negative Resist Systems

Living polymerization systems cationic

Lumophore-spacer-receptor systems cations

Membrane chromatographic system cation-exchange membranes

Mixed-cation systems

Model system, cationic alkyl

Novel Vaccine Adjuvants Based on Cationic Peptide Delivery Systems

Octyl cation systems

Octyl cation systems dehydrocyclization

Octyl cation systems intermediates

Octyl cation systems optimized structure for cis- and

Organic cations in constrained systems

Pentadienyl system cation

Polar Cycloadditions in Which Cationic Aromatic Systems Act as Electrophiles

Radical cation polymerization phase system

Radical cation polymerization system

Radical cations of cyclopropane systems

Recognition Based on Cation Control of Photoinduced Electron Transfer in Nonconjugated Donor-Acceptor Systems

Specific Living Cationic Polymerization Systems

Suppressor Systems in Cation Exchange Chromatography

Systems containing divalent cations

Systems containing hexavalent cations

Systems containing tetravalent cations

Systems containing trivalent cations

Transition state cation system

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