Powder polymerization

Gas phase olefin polymerizations are becoming important as manufacturing processes for high density polyethylene (HOPE) and polypropylene (PP). An understanding of the kinetics of these gas-powder polymerization reactions using a highly active TiCi s catalyst is vital to the careful operation of these processes. Well-proven models for both the hexane slurry process and the bulk process have been published. This article describes an extension of these models to gas phase polymerization in semibatch and continuous backmix reactors. 

Polyakov KK, Paima V.I., Technology and Equipment for Producing Powder Polymeric Coatings, Mashinostroyenie, Moscow (1972) - in Russian. 

Mantovani F, Grassi M, Colombo I, Lapasin R. A combination of vapor sorption and dynamic laser light scattering methods for the determination of the Flory parameter chi and the crosslink density of a powdered polymeric gel. Fluid Phase Equilib 2000 167(1) 63— 81. 

Method Bl Powdered polymeric ZnPc 31 and 32 by solution reaction of tetracarbonitriles in pentanol-1 in the presence of Li-pentanolate [97]. 

Precipitation from substance Initiator Polymer Monomer is reaction medium, see third column So in M D in M PVC, PAN from liquid LDPE or LDPE made from gaseous monomer Powder Polymerization, is possible. LDPE is precipitated from the Separation of the polymer ethylene gas by means of high-from the reaction medium pressure polymerization. PAN causes no problems, even at is nonmeltable, is dissolved in high molar mass levels. dimethyl formamide and spun into threads... 

DETERMINATION OF THE THERMOPHYSICAL CHARACTERISTICS OF A BED OF POWDERED POLYMERIC MATERIALS. 

Specifically for the PS bead suspension process, Villalobos et al. [9] reported that the end of the first stage occurred at approximately 30% monomer conversion, corresponding to a critical viscosity of about 0.1 Pa s. They also found that the second stage extended up to about a 70% monomer conversion. In the vinyl chloride monomer (VCM) powder polymerization, it has been shown that, at monomer conversions around 10-30%, a continuous polymer network is commonly formed inside the polymerizing monomer droplets that significantly reduces the drop/particle coalescence rate [10]. CeboUada etal. [11] reported that the PSD was essentially estabhshed at monomer conversions of about 35-40% (i.e., end of the second stage). 

Single-screw extruders operate normally in a flood-fed mode in which the granulate or powder polymeric material is compacted in the solid... 

Polystyrene, expandable polystyrene (containing a volatile C4-C6 hydrocarbon), high impact polystyrene, styrene copolymers with acrylonitrile (SAN) and ABS, and poly(methyl methacrylate) are the main products of the suspeusion bead polymerization. PVC is the main polymeric material produced by suspension powder polymerization. 

Bead suspension polymerization yields homogeneous particles unless the formation of a specific morphology is sought by polymerizing a second monomer on a previously formed suspension particle [124], In the suspension powder polymerization, used to produce about 90% of the PVC, a porous particle is produced because the polymer is not soluble in the monomer [112]. 

In fact, most of these so-called soluble conductive polymers are not conductive, but the authors refer only to the neutral, insulating base form of a doped conducting and insoluble form (e.g., polyalkylthiophenes). Only a few doped and really conductive polymers were reported to be soluble. On the other hand, dispersions in various solvents and polymers that look like solutions could be prepared using almost any kind of ICP powder polymerized in a proper way, in either doped or neutral form [36]. 

Table 35.3 Elemental Analysis of Polypyrrole Powders Polymerized at Room Temperature Using 0.2 mol/L of Pyrrole and a FeCb/PyrroIe Ratio of 2.4...

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