FRP initiation

FRP (initiator type peroxide/azo compound) CRP NMRP, ATRP RAFT... 

Technical Aspects The reaction mechanism in the synthesis of HIPS involves the basic reactions present in any FRP initiation (thermal and chemical), propagation, transfer to monomer, and termination, mainly by combination (see Chapter 4 for the basic FRP mechanism). In addition... 

Input parameters used for the kinetic modeiiing of the RAFT mediated aciyiate FRP initiated with AIBN. ... 

The initial evaluation showed that utilizing fiber-reinforced polymer (FRP) for pipelines is a feasible alternative to steel pipelines with regard to performance and cost [35]. From the cost analysis, an FRP pipe is quite attractive, especially in the regional or distributed service. Currently, spoolable piping manufacturers could install a composite pipeline for serving a 100,000 population for a cost of 250,000-500,000/mi. (does not include the cost for right-of-way), which is well below the DOE s capital cost target in 2017 of 800,000/mi. [35]. From this estimate and cost analyses, it is seen that FRP pipe economics is very attractive, especially for the distribution service. 

Also, Kerep and Ritter reported a radical chain transfer agent as a dual initiator, FRP-1 [45]. The first step builds on the fact that hydroxyl groups are much better nucleophiles in enzymatic ROP than thiols. Due to the chemoselectivity of the enzyme, PCLs with predominantly thiol endgroups were obtained, which were subsequently used as macroinitiator for styrene. The authors report that the reaction yield can be further increased by microwave irradiation. Although thiols provide less control over the radical polymerization than RAFT agents, the subsequent radical polymerization successfully leads to the synthesis of PCL-Z -PS. 

Friction Detonators. The following types of devices intended for initiating demolition charges, land mines and some underwater charges are described in Vol 4 of Encycl Friction Detonator, 8-Second Delay, M2 (p D804-R Fig 67) and Friction Detonator, 15 Second Delay, Ml (p D805-R Fig 68) French Friction Detonators are in Ref Ref Soci 6 Alsasienne d Explosifs, FrP 102355 CA 52, 3346(1958)... 

In living polymerization processes it is in fact possible to adjust the final degree of polymerization by simply tuning the initiator amount while keeping narrow the chain length distribution (CLD), i.e. with polydispersity values lower than 1.3 (this quantity reflects the broadness of the final CLD typical minimum values in FRP range from 1.5 to 2). Also, by suitable selection of chemistry and structure... 

Substrates used included fiber-reinforced epoxy base polymer [FRP], nylon 66, polytetrafluoroethylene [Teflon], poly(ethylene terephthalate) [PET], phenolic resin, and thermoplastic polyimide [ULTEM, GE]. FRPs were the primary substrates used. Initially, they were cleaned with detergent in an ultrasonic bath followed by rinsing with deionized water and alcohol. For further cleaning, they were treated with oxygen plasma (1.33 seem, 60 W, 5 min) followed by a hydrogen plasma treatment (3 seem, 60 W, 5 min). 

When shrinkage stops, further evaporation drives the meniscus into the body and the rate of evaporation falls (i.e., the FRP begins). The point at which the rate starts to fall is the critical moisture content. In the initial part of the FRP (sometimes referred to as the first FRP), most of the evaporaation occurs at the exterior surface. Contiguous pathways exist along which liquid can flow to the surface. At the same time, some liquid evaporates in the pores and the vapour diffuses to the surface. Eventually, a stage is reached when the liquid near the outside of the body becomes isolated into pockets. Flow to the surface stops, and the liquid is removed (predominantly by diffusion of the vapor). This stage is sometimes referred to as the second FRP. 

Table IV. Gel fraction and mechanical properties of PDMAEMA-/-PCL APCNs obtained by ATRP or FRP in THF at 60°C using a PCLDMA crosslinker of 1700 g.mol (initial molar fraction 3%).

The crucial feature of an FRP is an adjustable radical source, which is commonly materialized by a thermolabile substance—or initiator—that splits apart under heating to form free radicals, that is, highly reactive species with an... 

The most conventional kinetic scheme of FRP includes initiation, propagation, and bimolecular termination reaction steps. Additional reactions such as chain transfer are introduced to improve the process description. Free radicals are highly reactive chemical species produced by the homolytic dissociation of covalent bonds. Such species are produced through physical (thermoexcitation, radiation) or chemical methods (oxidation-reduction, addition, etc.). Generally, their survival time is less than a second, except for those radicals highly stabilized by specific chemical groups the hybridization state is sp. ... 

In its simplest and essential form, the mechanism of FRP involves the steps of initiation (radical generation), propagation, and bimolecular termination. The corresponding reaction rates for the three steps are denoted by R, R, and R, respectively. To derive a rate expression, for the sake of generality, the simplified mechanism and expressions in columns 2 and 3 of Table 4.5 are considered first later a more detailed mechanism (column 4 of Table 4.5), specific for chemical initiation and involving termination by disproportionation and combination, is analyzed. 

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