Bulk polymerization, description

Model Description of the Bulk Polymerization of MMA with Chain Transfer to Monomer... 

Description Catalyst components are mixed and fed directly to prepolymerization (1) with a light inert hydrocarbon, where a first bulk polymerization occurs under mild controlled conditions. This step exploits the catalyst system potential in terms of morphology, mileage and complete reliability in the following gas-phase reaction sections. 

Treatment of solid wood over the years for increased utility included many chemical systems that affected the cell wall and filled the void spaces in the wood. Some of these treatments found commercial applications, while some remain laboratory curiosities. A brief description of the earlier treatments is given for heat-stabilized wood, phenol-formaldehyde-treated veneers, bulking of the cell wall with polyethylene glycol, ozone gas-phase treatment, ammonia liquid- and gas-phase treatment, and p- and y-radiation. Many of these treatments led to commercial products, such as Staybwood, Staypak, Im-preg, and Compreg. This chapter is concerned primarily with wood-polymer composites using vinyl monomers. Generally, wood-polymers imply bulk polymerization of a vinyl-type monomer in the void spaces of solid wood. 

An early published example of reactive processing was a description of bulk polymerization of caprolactam in an extruder to give nylon-6.Intense activity in recent years, mostly in industrial laboratories and at extruder companies, has produced more than 600 patents and 60 published papers on the subject of... 

Auto-acceleration of free-radical polymerizations occurs in O Driscoll s model when polymeric radicals beyond a certain chain length are restricted in their segmental mobility by the development of a gel-like medium. Detailed descriptions have been given of the application of the model to the bulk polymerization of methyl... 

As has been explained in Sect. 2.2, a complete description of the kinetics of the bulk photopolymerization of diacrylates cannot be given at the present time, however. In this section, we will describe a few typical side reactions during the bulk polymerization of diacrylates as well as a preliminary approach for the treatment of the kinetics during vitrification of the system. 

Different descriptions of general procedures for the bulk polymerization of acrylates (sheets, molding material) are given in Refs. [12] and [19]. The bulk polymerization of y-alkoxy-p-hydroxypropylacrylates is described in Ref. [32]. Bulk atom transfer radical polymerization is reviewed in Ref [33]. 

Bulk polymerizations in sealed tubes are described in references 45 and 75-78. The description in Sorenson and CampbelFs book [75,76] is reasonably detailed. In this procedure a Pyrex tube is cooled with Dry Ice-acetone, flushed with nitrogen, charged with initiator and monomer, again flushed with nitrogen, and carefully sealed, keeping in mind that considerable pressure may develop during the process. The tube is placed in a protective jacket and then heated. Table IX outlines some of the polymerizations carried out by similar procedures. 

Beside centre-of-mass diffusion and segmental reorientation, the description of the diffusion behaviour of propagating polymer coils can be further complicated by other modes of diffusion, such as reaction diffusion [41], which is the diffusive motion of the polymer-chain-end radical as a result of propagation, and reptation [42-45]. All these different modes of diffusion are, however, not equally important over the entire range of conversion and the discussion of free-radical termination is therefore normally divided into three conversion regimes [15]. In the low conversion regime (approx. 0-10% conversion in a bulk polymerization), prior to the onset of the gel-effect, polymer chains may overlap but are... 

Since process and properties are so closely linked in the production of emulsion polymers, a variety of processes have been devised as efforts to design and control the microstructure of latex particles have intensified. The central issue is whether, as a general rule, particle growth is better represented in terms of a surface growth model or of a bulk polymerization model. Results obtained by a variety of methods developed to study particle and film morphology will be reviewed, and the special case of water-soluble monomers will be considered along with descriptions of process techniques designed to control particle structure. 

The main process control challenges in solution and bulk polymerizations are the control of molecular weight averages [103], molecular weight distribution (MWD) [104], monomer conversion [105], and copolymer composition and copolymer composition distribution (CCD) [106, 107]. The development of mathematical models for solution and bulk processes is relatively easy, as it is not necessary to take into account mass transfer between different phases. The main challenge in this field is the proper description of the glass and gel effects, which is usually performed with the help of anpirical models [108]. Therefore, reliable process models are usually available for solution and bulk processes. 

The final goal of all attempts is a description, and hopefully also a reliable prediction, of the macromolecular properties in bulk and in moderately concentrated solutions. It may be useful to recall that even the polymerization processes are conducted either in the melt or in fairly concentrated solutions. Under such conditions a complex interplay between the structures of the individual macro-molecules with strong mutual interactions takes place. In order to disentangle the complexity it will be helpful to derive at first a precise picture of the structure of individual macromolecules. Their properties can most adequately be studied... 

The complications for fhe fheoretical description of proton fransporf in the interfacial region befween polymer and water are caused by the flexibility of fhe side chains, fheir random distributions at polymeric aggregates, and their partial penetration into the bulk of water-filled pores. The importance of an appropriate flexibilify of hydrated side chains has been explored recently in extensive molecular modeling studies. Continuum dielectric approaches and molecular dynamics simulations have been utilized to explore the effects of sfafic inferfacial charge distributions on proton mobility in single-pore environments of Molecular level simulations were employed... 

The above discussion of the polymerization rate vs. time curves of the different systems is descriptive rather than explanatory. Almost every system exhibits a characteristic behavior, and the authors feel that it is no longer possible to press the various systems into one scheme. In earlier times when just conversion-time curves were determined, the bulk of these curves was referred to as sigmoidal in shape, and only large deviations from the normal behavior could be observed. Consequently an equally generalized scheme has been used to explain this general... 

Description The process involves continuous, bulk-phase polymerization of styrene using a combination of thermal and chemical initiation. A typical unit design consists of separate reaction trains for GPPS and HIPS grades, which have been optimized for each resin... 

The authors considered their description of a series of bulk and suspension polymerizations of vinyl chloride with various initiators as very satisfactory [17] with Q St 15. In spite of that, their approach has been criticized by Ugelstad who considers termination of growing radicals exclusively by mutual collisions to be very improbable [19], A large number of primary particles are formed in a short time interval, and many of these are then easily absorbed by the already solid flakes. Desorption of sorbed radicals has also to be considered. Radical distribution among the two phases should be controlled by these processes, especially at low conversion. 

The science of polymeric adhesion is concerned with the description of two distinct steps the formation of the adhesive bond ( adhesive bond making ) and the physical strength of the adhesive bond ( adhesive bond breaking ). The bulk of this chapter is associated with the latter topic, that is, the strength of joints made with adhesives. For this first section, we deal primarily with the former topic. 

We propose the following kinetic equation, which allows us a quantitative description of the 3-D polymerization of the polyfunctional oligomers in bulk in the entire interval of transformation level [8-10] ... 

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