Styrene polymerisation temperatures

This is styrene-butadiene rubber polymerised at a temperature of 5 °C (41 °F) in contrast to the original polymerisation temperature of 50 °C (122 °F). It is also known as Low Temperature Polymer (LTP). Nitrile rubber can also be made by a low temperature process. Such polymers are characterised by improved processibility. 

As regards a comparison of the relative effectiveness of titanium-and analogous zirconium-based catalysts in syndiospecific styrene polymerisation, the latter in general are less active than the former. Usually, polymer yields are lower, and a higher polymerisation temperature and reaction time as well as higher [Al(Me)01/transition metal compound ratios are required. Among the few zirconium compounds examined, only tetrabenzylzirconium activated with methylaluminoxane has relatively higher syndiospecific activity [10,48,56],... 

CTC decreases as polymerisation temperatures increase, furthermore, for the styrene-MA pair the charge-transfer complex should be non-existent above 130° C. However, alternating styrene-co-MA and other MA copolymers have been grafted on a variety of other polymeric materials (39,40,41). Our own results further confirm the contribution of CTC to general activation of the grafting reaction. It is important to note that the grafting efficiency... 

An alternative method of initiating styrene polymerisation depends on the addition of free radical generators. Various eatalysts are used at different temperatures depending on their rates of decomposition, but only peroxides are used extensively in industrial production processes. Other classes of initiators are usually either not readily available or not stable enough imder the conditions of st5rene polymerisation. 

Free radical initiators are used to either improve line productivity, by creation of radicals at a lower temperature than thermal initiation and/or to improve the quality of HIPS. During styrene polymerisation, organic peroxides are usually used at less than 1000 ppm of concentration. 

Georges and co-workers [41] reported the first controlled polymerisation using the NMP technique. The stable free radical 2,2,6,6-tetramethyl-l-piperidynyl-N-oxy (TEMPO) was initially used, with a thermal radical initiator, for the polymerisation of styrene. NMP polymerisations usnally require higher polymerisation temperatures, and it was not possible to polymerise acrylates in the presence of excess TEMPO in the early systems, due to the very low propagation rate. The radical polymerisation... 

Styrene. Styrene is readily polymerised to a glass-clear resin, polystyrene, but the exact nature of the polymer is influenced by the nature of the catalyst, the temperature, solvent, etc. 

Figure 2.20. Rates of catalysed and uncatalysed polymerisation of styrene at different temperatures. Catalysts used (all at 0.0133 moleA). A, bis-(2,4-dichlorobenzoyl) peroxide B, lauroyl peroxide C, benzoyl peroxide D, bis-(/)-chlorobenzoyl) peroxide E, none. (After Boundy and Boyer )...

The dehydrogenation reaction produces crude styrene which consists of approximately 37.0% styrene, 61% ethylbenzene and about 2% of aromatic hydrocarbon such as benzene and toluene with some tarry matter. The purification of the styrene is made rather difficult by the fact that the boiling point of styrene (145.2°C) is only 9°C higher than that of ethylbenzene and because of the strong tendency of styrene to polymerise at elevated temperatures. To achieve a successful distillation it is therefore necessary to provide suitable inhibitors for the styrene, to distil under a partial vacuum and to make use of specially designed distillation columns. 

In one process the crude styrene is first passed through a pot containing elemental sulphur, enough of which dissolves to become a polymerisation inhibitor. The benzene and toluene are then removed by distillation. The elthylbenzene is then separated from the styrene and tar by passing this through two distillation columns, each with top temperatures of about 50°C and bottom temperatures of 90°C under a vacuum of about 35 mmHg. The tar and sulphur are... 

A large number of accidents due to the polymerisation of styrene in storage containers are caused by a temperature which is too high. It is recommended not to store styrene at a temperature greater than 32°C. However, the presence of polymerisation primers, which are placed deliberately or accidentally, is the most frequent cause of violent polymerisations of styrene. 

So styrene, which is not stabilised by an inhibitor at ambient temperature, can, especially from 40°C onwards and in the presence of oxygen or air, give rise to polymerisation as well as oxidation, which leads to a polyperoxide. If this polyperoxide is isolated, it detonates spontaneously. However, its solubility in monomer limits the risks. This property probably caused a detonation that... 

Bulk Polymerisation In bulk polymerisation no initiator is required. Styrene gets partially polymerised batch-wise by heating the monomer in large vessels at 80°C for two days until there occurs about 35 per cent conversion. Then the syrupy mixture is allowed to fed continuously into the top of the tower which is twenty-five feet high. The top of the tower is kept at a temperature of about 100°C, the centre at 150° C and the bottom at 180°C. 

Chain-Transfer with anisole. The phenomenon of chain-transfer, especially with aromatic compounds, has been extensively investigated for the polymerisation of styrene, but there is only one such study with isobutene [13]. Isobutene (0.1 mole/l) was polymerised by titanium tetrachloride (3 x 10 3 mole/l) in methylene dichloride with a constant, low, but unknown concentration of water in the presence of anisole (0.02 to 0.15 mole/l) over the temperature range -9° to -90°. The reactions were stopped at 10-20 per cent conversion by the addition of methanol. 

As Skinner has pointed out [7], there is no evidence for the existence of BFyH20 in the gas phase at ordinary temperatures, and the solid monohydrate of BF3 owes its stability to the lattice energy thus D(BF3 - OH2) must be very small. The calculation of AH2 shows that even if BFyH20 could exist in solution as isolated molecules at low temperatures, reaction (3) would not take place. We conclude therefore that proton transfer to the complex anion cannot occur in this system and that there is probably no true termination except by impurities. The only termination reactions which have been definitely established in cationic polymerisations have been described before [2, 8], and cannot at present be discussed profitably in terms of their energetics. It should be noted, however, that in systems such as styrene-S C/4 the smaller proton affinity of the dead (unsaturated or cyclised) polymer, coupled, with the greater size of the anion and smaller size of the cation may make AHX much less positive so that reaction (2) may then be possible because AG° 0. This would mean that the equilibrium between initiation and termination is in an intermediate position. 

H20, temperature -30 °C to -95 °C) the initial rate of polymerisation of isobutene is proportional to the concentration of monomer, that of styrene proportional to the square of the monomer concentration [13], so that the same mechanism cannot apply to both monomers. Further, in the very system in which the Gantmakher and Medvedev mechanism would be most plausible styrene + SnCl4 + nitrobenzene [10] - the polymerisation is found to be of first order in monomer and not, as Gantmakher and Medvedev predict, of second order, and moreover depended on the presence of water. 

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