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Propagation, frontal polymerization

A. Tredigi, R. Pegghini, A. Sliepgevigh, and M. Morbidelli, Polymer blends by self-propagating frontal polymerization, J. Appl. Polym. Sci., 70 (1998), pp. 2695-2702. [Pg.244]

Arrhenius kinetics and is highly exothermic can support localized polymerizations that propagate. Frontal polymerization has been studied with many different polymerization mechanisms but free-radical polymerization is the most studied. Most of the work has focused on the dynamics of the process, but recently applications have been studied. Hydrogels have been prepared frontally, which have superior properties to those prepared by conventional methods. [Pg.977]

DBTDL was used as a catalyst in the frontal polymerization of 1,6-hexanediisocyanate with ethylene glycol. In frontal polymerization the polymerization is locally initiated and the exotherm of the reaction propagates the polymerization throughout the system. Pyrocatechol was used to avoid spontaneous polymerization. Pyrocatechol chelates tin and depresses the catalytic activity at room temperature without affecting catalysis at the higher temperature. To achieve a uniform advancing reactive front, and to avoid fingering, the viscosity of the blend was increased with colloidal silica. [Pg.694]

In recent decades, production of uniform polymers and cross-linked networks has been achieved by frontal polymerization (FP). FP is a method in which a monomer is converted into a polymer via a localized reaction zone that propagates through the... [Pg.467]

We now return to the base model (2,17)-(2.21) of frontal polymerization. We want to find uiuformly propagating FP waves and perform linear and nonlinear stability analyses, as we did in the case of the gasless combustion model. Before we study the model, we would like to reformulate it using the reaction front approximation. [Pg.230]

Mathematical models of the frontal copolymerization process were developed, studied and compared with experimental data in [67, 90]. An interesting observation was that the propagation speed of the copolymerization wave was not necessarily related to the propagation speeds in the two homopolymerization processes, in which the same two monomers were polymerized separately. For example, the propagation speeds in the homopolymerization processes could be 1 cm/min in each, but in the copolymerization process, the speed could be 0.5 cm/min. Mathematical models of free-radical binary frontal polymerization were presented and studied in [66, 91]. Another model in which two different monomers were present in the system (thiol-ene polymerization) was discussed in [21]. A mathematical model that describes both free-radical binary frontal polymerization and frontal copolymerization was presented in [65]. The paper was devoted to the linear stability analysis of polymerization waves in two monomer systems. It turned out that the dispersion relation for two monomer systems was the same as the dispersion relation for homopolymerization. In fact, this dispersion relation held true for W-monomer systems provided that there is only one reaction front, and the final concentrations of the monomers could be written as a function of the reaction front temperature. [Pg.238]

Some other works that we would like to mention studied the kinetics effects in FP [85], the influence of the gel effect on the propagation of thermal frontal polymerization waves [28], the use of complex initiators as a means to increase the degree of conversion of the monomer [30], and FP of metal-containing monomers [3]. [Pg.239]

Frontal polymerization, the process of propagation of a polymerization wave, is important from both fundamental and applied viewpoints. In this chapter, we reviewed theoretical results on the base model of free-radical frontal polymerization. Based on the analogy of the gasless combustion model and using the methods developed in combustion theory, we determined uniformly propagating polymerization waves and discussed their linear and nonlinear stability. [Pg.239]

Self-propagating free-radical binary frontal polymerization. Journal of Engi-... [Pg.243]

One of the most promising applications of nonlinear dynamics to polymer science is the phenomenon of frontal polymerization (Section III). Frontal pol)mierization is a process of converting monomer into polymer via a localized reaction zone that propagates through the monomer. There are two modes of frontal polymerization. [Pg.13]

Isothermal Frontal Polymerization (IFP), also called Interfacial Gel Polymerization, is a slow process in which polymerization occurs at a constant temperature and a localized reaction zone propagates because of the gel effect (64,65). Using IFP (27), one can control the gradient of an added material like a dye, to generate materials useful, for example, in optical applications (66,67). Lewis et al. provide experimental and theoretical results in chapter 14. [Pg.14]

Thermal frontal polymerization is a mode of converting monomer into polymer via a localized exothermic reaction zone that propagates through the coupling of thermal diffusion and the Arrhenius reaction kinetics of an exothermic polymerization. We review the range of nonlinear phenomena that have been observed in frontal polymerization systems and report new results on the role of gravity in spin modes and the development of spherically-propagating fronts. [Pg.106]

The most commonly observed case with frontal polymerization is the spin mode in which a hot spot propagates around the front. A helical pattern is often observed in the sample. The first case was with the frontal polymerization... [Pg.111]

Spontaneous Frontal Polymerization Propagating Front Spontaneously Generated by Locally Autoaccelerated Free-Radical Polymerization... [Pg.135]

Frontal polymerization discovered in 1972 (5) could be realized in free-radical polymerization because of its nonlinear behavior. If the top of a mixture of monomer and initiator in a tube is attached to an external heat source, die initiators are locally decomposed to generate radicals. The polymerization locally initiated is autoaccelerated by the c(xnbinatithermal autocatalysis exclusively at the top of the reaction systmn. An interface between reacted and unreacted regions, called propagating front, is thus formed. Pojman et al. extensively studied the dynamics of frontal polymerization (d-P) and its applicatim in matoials syndiesis (I -I3). [Pg.136]

Isothermal frontal polymerization (IFP) is a self-sustaining, directional polymerization that can be used to produce gradient refractive index materials. Accurate detection of frontal properties has been difficult due to the concentration gradient that forms from the diffusion and subsequent polymerization of the monomer solution into the polymer seed. A laser technique that detects tiny differences in refractive indices has been modified to detect the various regions in propagating fronts. Propagation distances and gradient profiles have been determined both mathematically and experimentally at various initiator concentrations and cure temperatures for IFP systems of methyl methacrylate with poly(methyl methacrylate) seeds and wilh the thermal initiator 2,2 -azobisisobutryonitrile. [Pg.169]

Frontal polymerization (propagating fronts of polymerization) was first developed by Davtyan and colleagues, who published an excellent review of the pioneering work done in the former Soviet Union up to 1984 (Davtyan et al., 1984). Since 1990, much work in this field has been performed in Hattiesbimg, Mississippi (Khan and Pojman, 1996 Pojman et al., 1996b). [Pg.237]

Pojman, J. A. Ilyashenko, V. M. Khan, A. M. 1996b. Free-Radical Frontal Polymerization Self-Propagating Thermal Reaction Waves, J. Chem. Soc. Faraday Trans. 92, 2825-2837. [Pg.378]

Pojman discusses thermal frontal polymerization in Chapter 4. He focuses on thermal frontal polymerization in which a locahzed reaction zone propagates through the coupling of thermal diffusion and the Arrhenius dependence of the kinetics of an exothermic polymerization. Frontal polymerization is close to commercial apphcation for cure-on-demand appHcations and is also showing value as a way to make some materials that are superior to those prepared by traditional methods. It also manifests many types of instabihties, including buoyancy-driven convection, surface-tension-driven convection, and spin modes. [Pg.2]

Frontal polymerization can be used to study interesting modes not observable in other systems. For example, spherically propagating fronts can be studied. [Pg.3]

Lewis and Volpert continue the discussion of the isothermal form of frontal polymerization in Chapter 5. Isothermal frontal polymerization is also a localized reaction zone that propagates but because of the autoacceleration of the rate of free-radical polymerization with conversion. A seed of poly(methyl methacrylate) is placed in contact with a solution of a peroxide or nitrile initiator, and a front propagates from the seed. The monomer diffuses into the seed, creating a viscous zone in which the rate of polymerization is faster than in the bulk solution. The result is a front that propagates but not with a constant velocity because the reaction is proceeding in the bulk solution at a slower rate. This process is used to create gradient refractive index materials by adding the appropriate dopant. [Pg.3]

Figure 4.20 Image of a frontally polymerized triacrylate with 40% kaolin clay with 5 phr Luperox 231. The arrow indicates the direction of propagation. Figure 4.20 Image of a frontally polymerized triacrylate with 40% kaolin clay with 5 phr Luperox 231. The arrow indicates the direction of propagation.
Pojman, J.A., llyashenko, V.M., and Khan, A.M. (1996) Free-radical frontal polymerization self-propagating thermal reaction waves. J. Chem. Soc., Faraday Trans., 92, 2825-2837. [Pg.64]

Huh, D.S. and Kim, H.S. (2003) Bistability of propagating front with spin-mode in a frontal polymerization of trimethylolpropane triacrylate. Polym. Int., 52, 1900-1904. [Pg.67]


See other pages where Propagation, frontal polymerization is mentioned: [Pg.195]    [Pg.196]    [Pg.197]    [Pg.198]    [Pg.239]    [Pg.341]    [Pg.128]    [Pg.130]    [Pg.121]    [Pg.122]    [Pg.135]    [Pg.137]    [Pg.147]    [Pg.170]    [Pg.237]    [Pg.240]    [Pg.242]    [Pg.309]   
See also in sourсe #XX -- [ Pg.231 , Pg.232 ]




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