Polymerisation pressure

The pressure effects on molecular associations are usually small and considerably smaller than the effects of temperature and solvent [108,109]. The response of inter-molecular associations in solution to pressure depends on the change in free volume (dF ) upon association according to equation (14)  

Comparing the materials prepared at the two pressures, no pronounced difference was seen using ATR (p/fa = 1.7) as template, whereas when using the more basic AME (pATa = 4.1) as template and isopropanol as diluent, a significant effect of the pressure applied during polymerisation on the affinity and selectivity for AME was seen (Table 5.8). The capacity factor for AME was ca. 30% higher on the polymer prepared at 1000 bar than on the one prepared at normal pressure at a sample load of 100 nmol and ca. 40% higher when the same comparison was done 

CHROMATOGRAPHIC RETENTION OF TRIAZINES (10 NMOLE INJECTED SEPARATELY) ON AME IMPRINTED POLYMERS PREPARED AT DIFFERENT PRESSURES [110] 

The chromatographic evaluation was done using acetonitrile as mobile phase. The polymers were prepared at 60°C, using isopropanol as diluent and at the pressures given in the table. 

EFFECT OF DILUENT AND THERMAL TREATMENT ON POLYMER MORPHOLOGY, THERMAL STABILITY AND CHROMATOGRAPHIC PERFORMANCE OF MIPs USING L-PA AS TEMPLATE 

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Phenylethylene boils at 145-146° at atmospheric pressure, but the high temperature causes a considerable loss by polymerisation. It has been stated that the addition of about 0-1 per cent, by weight of hydroquinone considerably reduces the extent of polymerisation at atmospheric pressure. 

Fig. 2. Emulsion polymerisation plant. A, Emulsion feed tank B, polymerisation reactor C, dmmming tank E, filter M, meter P, pressure gauge T,...

The synthesis of the high molecular weight polymer from chlorotrifluoroethylene [79-38-9] has been carried out in bulk (2 >—21 solution (28—30), suspension (31—36), and emulsion (37—41) polymerisation systems using free-radical initiators, uv, and gamma radiation. Emulsion and suspension polymers are more thermally stable than bulk-produced polymers. Polymerisations can be carried out in glass or stainless steel agitated reactors under conditions (pressure 0.34—1.03 MPa (50—150 psi) and temperature 21—53°C) that require no unique equipment. 

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

The chemical iadustry manufactures a large variety of semicrystalline ethylene copolymers containing small amounts of a-olefins. These copolymers are produced ia catalytic polymerisation reactions and have densities lower than those of ethylene homopolymers known as high density polyethylene (HDPE). Ethylene copolymers produced ia catalytic polymerisation reactions are usually described as linear ethylene polymers, to distiaguish them from ethylene polymers containing long branches which are produced ia radical polymerisation reactions at high pressures (see Olefin POLYMERS, LOWDENSITY polyethylene). 

The technologies suitable for LLDPE manufacture include gas-phase fluidised-bed polymerisation, polymerisation in solution, polymerisation in a polymer melt under high ethylene pressure, and slurry polymerisation. Most catalysts are fine-tuned for each particular process. 

Fig. 4. Typical nylon-6,6 autoclave polymerisation cycle showing the changes in pressure (—) and temperature (---). To convert MPa to psi, multiply by...

The low vinyl acetate ethylene—vinyl acetate copolymers, ie, those containing 10—40 wt % vinyl acetate, are made by processes similar to those used to make low density polyethylene for which pressures are usually > 103 MPa (15,000 psi). A medium, ie, 45 wt % vinyl acetate copolymer with mbber-like properties is made by solution polymerisation in /-butyl alcohol at 34.5 MPa (5000 psi). The 70—95 wt % vinyl acetate emulsion copolymers are made in emulsion processes under ethylene pressures of 2.07—10.4 MPa (300—1500 psi). 

Fischer-Tropsch Waxes. Polymethylene wax [8002-74-2] production is based on the Fischer-Tropsch synthesis, which is basicaHy the polymerisation of carbon monoxide under high pressure and over special catalysts to produce hydrocarbons (see Fuels, synthetic-liquid fuels). 

Except for the solvent process above, the cmde product obtained is a mixture of chloroprene, residual dichlorobutene, dimers, and minor by-products. Depending on the variant employed, this stream can be distiUed either before or after decantation of water to separate chloroprene from the higher boiling impurities. When the concentration of 1-chloro-1,3-butadiene [627-22-5] is in excess of that allowed for polymerisation, more efficient distillation is required siace the isomers differ by only about seven degrees ia boiling poiat. The latter step may be combiaed with repurifying monomer recovered from polymerisation. Reduced pressure is used for final purification of the monomer. All streams except final polymerisation-grade monomer are inhibited to prevent polymerisation. 

Because chloroprene is a flammable, polymerisable Hquid with significant toxicity, it must be handled with care even in the laboratory. In commercial quantities, precaution must be taken against temperature rise from dimerisation and polymerisation and possible accumulation of explosive vapor concentrations. Storage vessels for inhibited monomer require adequate cooling capacity and vessel pressure rehef faciUties, with care that the latter are free of polymer deposits. When transportation of monomer is required, it is loaded cold (< — 10° C) into sealed, insulated vessels with careful monitoring of loading and arrival temperature and duration of transit. 

The reactivity of ethylene is high, whereas that of propylene is low and the various dienes have different polymerisation reactivities. The viscous mbber solution contains some unpolymerised ethylene, propylene, unpolymerised diene, and about 10% EPDM, all in homogeneous solution. This solution is passed continuously into a flash tank, where reduced pressure causes most of the unpolymerised monomers to escape as gases, which are collected and recycled. 

Trimetbyl vinyl silane [754-05-2] M 100.2, b 54.4 /744mm, 55.5 /767mm, d S(25,4) 0.6865, n D 1.3880. If the H NMR spectrum shows impurities then dissolve in Et20, wash with aq NH4CI soln, dry over CaCl2, filter, evaporate and distil at atmospheric pressure in an inert atmosphere. It is used as a copolymer and may polymerise in the presence of free radicals. It is soluble in CH2CI2. [J Org Chem 17 1379 7952.]... 

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