Homopolymerisation kinetics

Fiowever, based on the data obtained previously on homopolymerisation kinetics of different fluoroalkylmethacryl monomers it is possible to assume that the ratio... 

Another aspect that has not been taken into account in the kinetic models discussed so far is the occurrence of ether-forming reaction through epoxide homopolymerisation or reaction with hydroxyl groups. In the system TGDDM with an initial DDM concentration less than the stoichiometric level the overall conversion of epoxide is greater than that expected for epoxide-amine addition 89, 97 98). 

In practice the epoxide-amine cure is often accelerated by the addition of catalysts such as boron trifluoride complexes, and the boron trifluoride-ethylamine adduct (BFE) is widely used for this purpose. In addition to catalysing the epoxide-amine reactions, BFE can initiate homopolymerisation of epoxide. The accelerating effect of BFE is illustrated by DSC scans for the TGDDM/DDS/BFE system in Figure 12. The multiple-peaked exotherm associated with the BFE-catalysed TGDDM/DDS cure indicates that the kinetics of this system are more complex than those for the cure with amine alone. For this system the overall heat of reaction was found to decrease with increasing BFE concentration 89). For DDS alone Q0 was about 110 kJ per mole epoxide while the value for BFE alone was 75 kJ/mole, and the DDS/BFE values were between these limits. It appears that the proportion of epoxide homo-polymerisation relative to amine or hydroxyl addition increases with increasing BFE concentration. 

Integral and differential kinetic curves for homo- and copolymerisation of 4FMA and MMA were calculated for different ratios of monomers in the initial monomeric mixtureat initiation of benzoyl, lauryl and azo-fcfs-(isobutyronitrile) peroxides with the help of known values of heat effects of MMA and 4FMA homopolymerisation and the value of heat of crossed propagation obtained from experimental dependencies of heat elimination rates on the reaction time. 

Raman fibre optics has been used to study the emulsion homopolymerisations of styrene and n-butyl acrylate (35). An IR spectroscopic technique for the examination of radical copolymerisations of acryl and vinyl monomers was developed. A comparative study of the copolymerisation of model monomer pairs was made using monofunctional and polyfunctional compounds. The data established the role of structural-physical transformations, involved in the formation of crosslinked polymers, on the copolymerisation kinetics and on the nonuniformity of distribution of crosslinks in the copolymers formed (151). Raman fibre optics of polymerisation of acrylic terpolymers was also used to monitor as well as an on-line measurement of morphology/composition (66). The high temperature (330 °C) cure reaction of 4-phenoxy-4 -phenyl-ethynylbenzophenone was monitored using a modulated fibre optic FT-Raman spectrometer (80). 

An understanding of the melt polyesterification kinetics is a must to economise on the process productivity and to improve the polymer properties. There is no published literature on the melt polyesterification kinetics of PBT, HQDA and TA. Kinetic investigation of copolymerisation between PET and 4-acetoxy benzoic acid (PET/OB) did not reveal precipitation of poly (4-oxybenzoate). Here we explore the kinetics of a three component system, wherein many parallel reactions take place simultaneously. Homopolymerisation between HQDA and TA lead to a rigid rod system. 

A special aspect of (emulsion) copolymerisation compared to (emulsion) homopolymerisation is the occurrence of composition drift. In combination with the instantaneous heterogeneity (statistical broadening around the average chemical composition), this phenomenon is responsible for the chemical heterogeneity of the copolymers formed. Composition drift is a consequence of the difference between instantaneous copolymer composition and overall monomer feed composition. This difference is determined by (a) the reactivity ratios of the monomers (kinetics) and (b) the monomer ratio in the main loci of polymerisation (viz., latex particles) that can differ from the overall monomer ratio of the feed (as added according to the recipe), which in turn is caused by monomer... 

It is obvious that the typical aspects that distinguish emulsion copolymerisation from homopolymerisation, for example, monomer partitioning, dependence of kinetics on the local monomer concentration ratio etc., become much more complex when three monomers are involved, not to mention the complications in terpolymer analysis. 

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