Mitigating gels

Retardation is sometimes observed in RAFT polymerizations when high concentrations of RAFT agent are used and/or with inappropriate choice of RAFT agent. Some decrease in polymerization rate is clearly attributable to a mitigation of the gel (or Norrish-Trommsdorf) effect.384" 94 However, it is also clear that other effects are important. 

The partitioning of electrically neutral species (assumption 5) and electrically charged species (assumption 6) between the gel and the sample affects the algebraic part of the model. It is a serious problem for both electrically neutral species (e.g., oxygen) and charged (ionic) species. However, it can, to some extent, be mitigated by the choice of the gel matrix. 

Fouling (e.g., microbial adhesion, gel layer formation, and solute adhesion) at the membrane surface is a more complex phenomenon involving polarization, irreversible adsorption of macrosolutes or colloid particulates to, and/or gradual buildup of an adherent and coherent layer of solid material on, the membrane surface. It is amenable to mitigation by appropriate selection or surface treatment of the membrane surface (to minimize adsorption) by suitable fluid management or by employment of other forces to transport fouhng solutes. 

This multi-reactor system used for copolymerization of C2 with higher a-olefins comprises a CSTR connected in series to a tubular reactor (TR). The latter receives a polymer solution from the CSTR. Polymerization in TR improves efficiency, by reducing the amount of energy required to recover the polymer and residual comonomer from the solution. The use of preheated C2 in TR mitigates the contaminating gel problems (fouling TR and creating fish eyes on film) and reduces hexane extractables... 

Possibility of fouling mitigation due to enhanced hydrophilicity of the TiOj-modified membrane Possibility of fouling mitigation due to decomposition of organic contaminants forming the gel layer or filtration cake Contaminants could be decomposed either in feed or in permeate Higher decomposition rate in case of the gas-phase reactions compared to conventional photoreactors with photocatalyst immobilized on a non-porous support... 

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