Polymers swelling capacity

This equation may be used for the estimation of the swelling capacity of the activated seed particles with the monomer. A typical graph sketched based on Eq. (11) is given in Fig. 18. This graph shows the variation of the swelling capacity of the seed polymer particles VmIVp) with the ratio of interfacial tension-initial particle radius... 

Cross-hnked polyacrylamides are a group of hydrophihc solid supports introduced primarily for preparation of biopolymers (Fig. 4). Unhke PS resins, polyacrylamides have excellent swelling capacity in both protic (water, alcohols) and aprotic (dichloromethane, dimethylformamide) solvents [88]. These beads are stable towards bases, acids, and weak reducing and oxidizing agents [89]. Predictably, conditions under which amide bonds are cleaved (i.e., sodium in liquid ammonia) [90] lead to rapid decomposition of the polymer. 

The general requirements for a support are mechanical stability and chemical inertness under the reaction conditions to be used. Mechanical stability is required to avoid the breaking down of the polymer into smaller particles, which could lead to the clogging of filters. Supports also need to be chemically functionalized, so that the synthetic intermediates can be covalently attached to the support via a suitable linker. Moreover, if the intermediates are located within the support (and not only on the surface), diffusion of reagents into the support particles will be necessary, and materials with sufficient permeability or swelling capacity need to be chosen. 

In addition to forming the chains of polyacrylate, the chains are cross-linked. This is a process in which two or more chains are held together by other compounds in a network. Typical cross-linkers for this polymer include di- and tri-acrylate esters. The swelling and elasticity of the polyacrylate polymer depends on the structure of this network and the number of cross-links. The swelling capacity of the polymer decreases with increased cross-link density. After formation, the polyacrylate is dried and formed into microparticles of irregular shape that can be stored for a long time. 

The early stages of graft polymerization appear to be particularly affected by the structure and surface area of the initial cellulose material. In subsequent stages, the nature of the polymer being grafted and its swelling capacity in the reaction medium or in its own monomer are more important. 

Fig. 2. Swelling capacity of po mer-oligomer particles versus for different vatum of Vi. To = radius of polymer-oligomer particles prior to swelling with Z,. =...

Direct copolymerization of VFA can be carried out either with BVU, in the presence of silica particles, or with VTS, which must be pre-grafted onto silica surfaces. Both reactions can be used to immobilize large amounts of PVFA-co-PVAm on silica surfaces. The second described direct co-polymer-ization procedure is exhibited by the covalently bonded polyelectrolyte layer on the inorganic substrate. The swelling capacity of the PVFA/silica hydrogels can be controlled by the degree of hydrolysis of the PVFA. 

A prescribed amount of superabsorbent polymer is mixed with a prescribed amount of the desired aqueous solution, which is stirred by means of a magnetic stirring bar in a small beaker. As the water absorption proceeds, the viscosity of the suspension increases until the stirring vortex disappears at the sorption time, ty. The swelling capacity at equilibrium (Qmax) is calculated by using Eq. (2) ... 

As a result of the nucleation in the HD containing monomer droplets, HD inside the polymer particles promotes the swelling capacity of polymer particles, as shown in the post-polymerization swelling experiments. 

The presence of hydrophobe in the resultant polymer particles increases their swelling capacity. 

The "gas-phase" (fluidized-bed) process is much like the slurry process in that polymer particles are formed at similar temperatures, but a liquid hydrocarbon diluent is not used. A bed of catalyst/polymer is stirred either by mechanical means, or, more often, by fluidization, while ethylene, N2, and other hydrocarbons that act as a coolant are circulated [718-722], Although the "gas phase" process offers many advantages, including the lack of a diluent that can cause polymer swelling, its weak point is poor heat removal from the polymer particles, because of the low heat capacity of a gas. Thus, reactor fouling still occurs,... 

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