Initiator type

The thermal decomposition of single-component initiators (such as inorganic persulfates) can be used to generate the free radicals in the aqueous drops, but in 

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Initia.tors, The initiators most commonly used in emulsion polymerization are water soluble although partially soluble and oil-soluble initiators have also been used (57). Normally only one initiator type is used for a given polymerization. In some cases a finishing initiator is used (58). At high conversion the concentration of monomer in the aqueous phase is very low, leading to much radical—radical termination. An oil-soluble initiator makes its way more readily into the polymer particles, promoting conversion of monomer to polymer more effectively. 

Although reactivity ratios indicate that VP is the more reactive monomer, reaction conditions such as solvent polarity, initiator type, percent conversion, and molecular weight of the growing radical can alter these ratios (138). Therefore, depending on polymerization conditions, copolymers produced by one manufacturer may not be identical to those of another, especially if the end use appHcation of the resin is sensitive to monomer sequence distribution and MWD. 

The polymerization of vinyl monomers on the surface of silica can be induced also by free radical initiators such as azo-bis-isobutyronitrile (AIBN), di-tert-butylperoxide, benzoyl peroxide etc. The selection of initiator type and method of its introduction in polymerizable systems are determined by the nature of monomers and tasks of investigations. Usually, the following procedures are used ... 

Chloratodimercuriacetaldehyde. OHC.C( Hg),Hg0.ClO2, mw 525.70, colorl prisms. Can be prepd by treating an excess of mercuric oxide in an aq soln of chloric acid with an ale soln of acetaldehyde. It is an extremely sensitive expl of the initiating type, exploding even when shaken under liq (Refs 1 3) Nitratodimercuriacetaldehyde. OHC.C( Hg).HgO.N02, mw 504.26, N 2.78%, colorl prisms from ale. Can be prepd by adding an ale soln of acetaldehyde to an aq soln of mercuric nitrate, acidified with nitric acid. Nearly insol in w. Puffs off on heating with evolution of a yellow cloud and Hg (Refs 1,2 3)... 

The values of k" and E are highly dependent on the initiator types and their effects on the solvent types are less overwhelming. The types of solvent used as chain transfer agent are usually fixed... 

The initiator types, however, are characterized by these parameters, and since the effect of pressure is small (, 9.) and the tubular polymerization of ethylene is undertaken within a narrow range of pressure, the descriptive constant becomes... 

Figure 6, Ejfect of solvent concentration on the molecular weight-conversion rehtionships of a tubular-addition polymerization reactor of fix size using a specified initiator type. Each point along the curves represents an optimum initiator feed concentrationr-reactor jacket temperature combination, (kinetic parameters of the initiator Ea = 24,948 Kcal/mol In k/ = 26,494 In sec f = 0.5)...

Effects of Initiator Parameters. Initiator types can best be characterized by the frequency factor (k ) and the activation energy (E ), and the effect of these parameters on the molecular weight-conversion relationship is shown in Figures 7 and 8. The curves shown are the result of choosing the jacket temperature-inlet initiator concentration combination which maximizes the reactor conversion for each initiator type investigated. 

The initiator usage can play a role in the economics of resin production. The computer simulations show the usage to be dependent on the initiator type. The effect of the initiator type on the amount of initiator required to produce a given quantity of resin at optimum reactor conditions is shown in Figures 11 and 12. 

The computer simulation study of the operation of the tubular free radical polymerization reactor has shown that the conversion and the product properties are sensitive to the operating parameters such as initiator type, jacket temperature, and heat transfer for a reactor of fixed size. The molecular weight-conversion contour map is particularly significant and it is used in this paper as a basis for a comparison of the reactor performances. 

The type of initiator used affects the molecular weight and conversion limits in a reactor of fixed size and the molecular weight distribution of the material produced at a given conversion level. The initiator type also dictates the amount of initiator which is necessary to yield a given conversion to polymer, the operating temperature range of the reactor and the sensitivity of the reactor to an unstable condition. Clearly, the initiator is the most important reaction parameter in the polymer process. 

The full utilization of improved heat transfer in a given reactor can only be made when the molecular weight-conversion relationships are carefully studied with various initiator types at different heat transfer levels. Then a particular initiator system must be selected for a maximum conversion improvement for a specified product. 

The ratio of monomer to initiator ranges from 1 1 to 10 1, and preferentially is set to 9 1 [126]. By setting initiator concentration, initiator type, residence time and temperature, the polymer molecular weight, conversion and solution viscosity are determined. The monomer is, e.g. acrylate-based with or without styrene. The pressure is regulated to be 2 x 10 -5 x 10 Pa in order to avoid solvent and monomer boiling. 

Working from your initial type diagram, sketch a pair of snapshots before and after each operation. Draw them on one diagram, using highlights to show newly created objects and links and X and for objects or links that do not exist in the after snapshot. Name the input and output parameters to the action occurrence consistently with the snapshots. 

Initial type model adopted from Business Model Links, attributes, actions are all subject to refinement at this stage. 

Figure 15.4 Initial type model derived from business model...

Adopt the business model as the initial type model. That is, the model part of the type-box defining the system. Note that this gives us two of everything the external real object and its model inside the system. To distinguish where this might be ambiguous, use LibraryManagementSystem Member and Member. Note, however, that actions from the business model do not translate into internal actions that must be implemented in the system they are candidate effects , there just to conveniently factor out parts of the system behavior specification. 

An alternate approach is to start minimalist the initial type model is not known i.e. empty, and you draw elements from the business model into the system type model as you uncover a need for them in describing the system behaviors. 

We are specifying the type of a system playing a role in a collaboration that is, the view that its collaborators have of it. We already have a initial type model. We may improve it in the light of what we need to say about this action, and iterate between specifying actions and updating the type model. 

Initiator Type Initiation Temperature (°C) Degradation Onset (°C)a Temperature of Maximum Degradation Rate. (°C)b... 

Advincula et al. used the same initiator type (DPE activated with u-BuIi) to perform LASIP from colloidal sihca [265] or clay [266, 267]. The spacer between the DPE unit and the surface active group (quatemized amine for clay and chlorodi-methylsilane for silica) was a long n-alkyl chain. In all cases, a relatively broad polydispersity for the prepared polystyrene bmsh (PDI = 1.2-2) was observed. 

Once calibrated, the NIR analyzer was used to investigate a number of factors expected to affect the polymerization kinetics, including reaction temperature, initiator type, and initiator concentration (relative to monomer concentration). These experiments, in addition to improving process understanding, also mimicked the effects of inadequate process control during a reaction. Figure 15.1 shows the effect of reaction temperature on kinetics. The reaction rate nearly doubles when the temperature is raised from 65 to 75 °C, and the concentration of unreacted monomer after 85 minutes is reduced from 1.1 to 0.5%. In-hne NIR monitoring allows unusual behavior in either reaction rates or residual monomer levels to be detected and corrected immediately. 

Effect of initiator type on copolvmer properties. Copolymer IV of p-dioxanone/glycolide at 90/10 weight composition was prepared using diethylene glycol (DEG) as the initiator. Fiber properties of the resulting copolymer were determined and compared with those of Copolymer II, which was made using 1-dodecanol as an initiator (as shown in Table IV). 

PDO/glycolide initial weight ratio Initiator Type 1- dodecanol diethylene glycol... 

The hydroxymethyl-substituted methyl esters can then be transesterified with any number of different initiator types to tailor the structure of the polyol to the end-use application, and all from a single raw material source. The stoichiometry of the polyol is adjustable, to produce polyols of any molecular weight. This synthetic strategy was developed by The Dow Chemical Company as the Renuva polyols. 

In TNT pellets the initial Type II low-order detonation does not lead immediately to the final high order but to an intermediate level, of almost normal rate but of very low shock luminosity. A luminous strip due to the collision of the shock waves of two low-ordet detonations in TNT is observed in the simple dark space in some still photographs. Initiation at slightly below the limit, in all of the expls studied, produces low-order detons that fade after traversing-a short distance and the wave fronts show a strong shock effect. In TNT pellets the intermediate-order may also fade... 

E. Grosch, Explosivst 1955, 69-78 and Picatinny Arsenal Translation No 9 (1956) by Dr G. Loehr, "Measurement of the Detonation Pressures of Initiator-Type Explosives 35a) R.W. Goranson, Classified Los Alamos Rept No 487 (1955). See Ref 31 35b) R.E. Duff E. Houston, "Measurement of Chapman-Jouguet Pressure and Reaction Length in the Detonation of High Explosives , JChemPhys 23(7), 1268-73(1955) 36) G.R. 

Bomb Nose Fuzes, AN-M146 are MT fuzes of the combined vane-armed, pin-initiated type. The impact element constitutes a self-destroying feature which operates only when the time setting exceeds the time of flight or in case the time mechanism fails to operate... 

HMTD is an explosive of the initiating type it is more powerful and brisant than MF, rather being comparable to LA and Cyanuric Triazide. It does not become dead-pressed even at pressures of 11000 psi (an advantage over MF)... 

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