Monomer conversion, rates

PjPk = active intermediate of any length with comonomer j and k as penultimate and ultimate units, respectively R = rate function for total monomer conversion (rate of polymerization) or any rate function with appropriate subscript Rp = rate function defined in Table I Rg = gas constant... 

Figure 10. Monomer conversion rates as a function of emulsion Reynolds number for straight and helical tubular reactors...

Recently Biggs [74] has investigated the emulsion polymerisation of styrene using ultrasonic irradiation as the initiation source (i. e. in the absence of a chemical initiator). Similar to Lorimer and Mason using a thermally initiated system, Biggs found both a marked increase in monomer conversion rate as a function of time as the ultrasonic intensity was increased but remarkable constancy in the resultant latex particle... 

Furthermore, the authors noticed that the DPn increased with the monomer-conversion-rate since the initiator decomposed very quickly. The products exhibited very good thermal properties actually at 300 °C the oligtaners v/eie still stable because of the absence of double bonds obtained in traditional radical polymerization ofMMA. 

This disulfide has been used in photopolymerization of styrene in bulk or in the presence of THF and the degrees of polymerization are in the range of 20 to 130 for telogen/monomer ratio of 0.1 to 0.01 and for monomer conversion rate of 20-30%. 

Therefore, the kinetic parameters of fast polymerisation processes kp and k,) and the linear velocity of reagent flow V determine the geometric size (R, L) and optimal configuration of a reaction zone. New opportunities and methods of process control have been revealed, allowing the control of the monomer conversion rate and MW characteristics of the forming polymer products, in particular, due to the forced change (limitation) of the reaction zone geometry (R, L). The principal conclusion is the necessity to reduce the reactor dimensions to the scale of a reaction zone. 

Figure 3.35 Kinetic activities of various types of AC in isoprene polymerisation with the LnCl3-3(tributylphosphate)- A1(/-C4H9)3 catalytic system at different monomer conversion rates. Polymerisation conditions tolnene, = 1.5, C i = 4.5 X 10 mol/1, = 25 °C, and Al/Ln = 30. Ln Nd (1), Gd (2) and Pr...

A nitroxide mediated polymerization of styrene was first reported in 1985 [262]. This reaction, however, was studied extensively only since 1993. The monomer conversion rates vs. temperatures are much slower than they are in conventional st5n ene polymerization. Also, the polydispersities of... 

Using supercritical carbon dioxide (scCOi), the polymerisation of L-lactide by immobilised CALB was achieved at 65 "C in a biphasic media system, where the supercritical phase coexists with a liquid organic phase (melted monomer), and the growing poly(L-lactide) (PLLA) chains are soluble. A semicrystalline polymer with MW up to 12,900 g/mol was obtained, with a monomer conversion rate dependent on enzyme concentration and its initial water activity [90]. 

Among the seven-membered lactones, e-CL is the most extensively studied. Several lipases (PPL, PFL, CAL, PCL and lipase from Yarrowia lipolytica (YLL)) have been used in the ROP of e-CL (18, 28, 71, 75, 77, 81, 82, 84-90, 94). In recent years, a lot of work has been carried out to improve the monomer conversion rate and polymer MW. 

Since it is a chain breaking process, chain transfer leads to lower molecular weights. However, its effect on the polymerization rate depends on the values of the rate coefficients. In the case where the rate limiting step is a radical transfer to the CTA (T), there is a decrease in M but no effect on monomer conversion rate. If the radical transfer from T to monomer is much slower than the transfer to T, then inhibition can occur, which slows down the reaction and leads to formation of longer chains. 

Two different high-pressure processes using autoclave or tubular reactors are applied for LDPE production. The autoclave process was developed by ICI, whereas the tubular reactor process was developed by BASF Aktiengesellschaft (predecessor of LyondellBasell s Lupotech T process). Monomer conversion rates of the adiabatic autoclave process can reach 25% compared to values up to 40% for tubular reactors, where the heat of polymerization can be partly removed through the jacketed reactor tubes via circulating cooling water. 

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