Polystyrene. producers

Polystyrene produced by free-radical polymerisation techniques is part syndio-tactic and part atactic in structure and therefore amorphous. In 1955 Natta and his co-workers reported the preparation of substantially isotactic polystyrene using aluminium alkyl-titanium halide catalyst complexes. Similar systems were also patented by Ziegler at about the same time. The use of n-butyl-lithium as a catalyst has been described. Whereas at room temperature atactic polymers are produced, polymerisation at -30°C leads to isotactic polymer, with a narrow molecular weight distribution. 

The quantum yield of polymerization is 6.72 and for photoinitiation < / = 2.85 x 10 . The polystyrene produced with this initiator shows photosensitivity when irradiated with UV light (A = 280 nm). This polymer, which carries two photosensitive end groups of - SC(S) N(CH3)2, behaves as a telechelic polymer and it is useful for production of ABA block copolymer. 

Figure 15 High-surface area silica treated with aqueous solution of 1 wt% vinyltrimethoxy silane. A silica was polymerized with styrene and washed with CS2 three times. Polystyrene produced in experiment A was deposited with B silica and the silica washed with CS2 three times. (From Ref. 77.)...

Polystyrene (PS) The volume of expanded polystyrene produced probably exceeds the volume production of all other plastics (excluding the polyurethanes) put together. At least half the weight of polystyrene produced is in the form of high impact polystyrene (HIPS)—a complex blend containing styrene-butadiene rubber or polybutadiene. 

The majority of polymers formed by living radical polymerization (NMP, ATRP, RAFT) will possess labile functionality at chain ends. Recent studies have examined the thermal stability of polystyrene produced by NMP with TEMPO (Scheme 8.3),2021 ATRP and RAFT (Scheme 8.4).22 In each case, the end groups... 

For simplicity it will be assumed the plant will be located in the United States. The 1969 American sources of styrene are given in Table 2E-1 The 1969 uses for this styrene are given in Table 2E-2. It should be noted that over 50% of the styrene produced is used to make straight and rubber-modified polystyrene. The capacities and locations of the main polystyrene producers are given in Table 2E-3. With the exception of Midland, Mich. Kobuta, Pa. Torrence, Calif. and Penuelas, Puerto Rico, all the styrene is produced in the Gulf Coast states of Louisiana and Texas. At Midland, Dow Chemical uses nearly all the styrene internally. The same is true of Sinclair-Koppers at Kobuta. The capacity of the Shell plant in California is pres-... 

The amounts of each stream can be related to the rate of polystyrene produced by multiplying by the numbers in the unit ratio material balance (Figs. 4E-l,4E-2, and 4E-3). 

In the polystyrenes produced by cationic initiators most of the chain-ends are terminal indanyl groups, and olefinic groups are rare. As this terminal indanyl group cannot be aluminated like a double bond, the amount of tritium incorporated comes only from the initial AlBr2CH2CHPh-groups and the few residual terminal double bonds and it, therefore, represents (approximately) the total number of initiated chains. 

The polyester reaction rate is nil at this temperature.) In polymerizing the styrene component within the polyester prepolymer mixture, the first amounts of polystyrene produced early in the reaction remains dissolved until some critical concentration is reached, followed by phase separation, see Figs. 2 and 3. 

In the use of polystyrene, the polymerization reaction is exothermic to the extent of 17 Kcal/mol or 200 BTU/lb (heat of polymerization). The polystyrene produced has a broad molecular weight distribution and poor mechanical properties. The residual monomer in the ground polymers can be removed using efficient devolatilization equipment. Several reviews are worthwhile consulting [42-44],... 

In each case it appears that the same end product can be obtained by several routes. However, the end products are not exactly identical because the reactivities of the various reagents with the polymer differ so that the number and distribution of the phosphine groups differ. The chloromethylated polystyrene produced in the first stage of the reaction,... 

Meyerhoff and Cantow (118) compared the relationships between [ /] and MW for polystyrenes prepared in various ways they found that for given Mw isotactic polystyrenes produced with Ziegler catalysts had the highest [ij], followed by low-conversion free-radical polymers both high-conversion (80%) and anionic (Szwarc) polymers had lower [ij]. These differences were all attributed to differences in LCB, though in principle differences in tacticity such as those between Ziegler and free-radical or anionic polymers could produce differences in the coil size in solution and hence in [iy]. 

From the data in Table 3.9 it can be seen that all three copolymers contain a slightly higher concentration of the azo component than that of the monomer mixtures. The molar masses of the products are essentially unaffected by the presence of the azo monomers and were identical with that of a polystyrene produced under identical conditions. That the azo monomers did not undergo thermolysis under these conditions is confirmed by the independence of the molar mass from the conversion since thermolysis would lead to an increase in the molar mass at higher conversion. 

Such a copolymer could be easily degraded at the ester linkages the size and frequency of the side chains may then be determined from the polystyrene produced on hydrolysis, when the transfer constant is known. 

The low solubility of sodium naphthalene at —78° C is responsible for a higher viscosity of the polystyrene produced under these conditions (47). Actually, the results of Dr. Rembaum reported in our paper (26) seem to be erroneous whereas the results of Dr. Waack, reported in the same paper, are correct. Taken together they gave the impression of scatter of experimental results and led to the wrong conclusion that theviscosity of the polymers obtained at 0° C and at —78° C is the same if the ratio of monomer to catalyst was kept constant. This point is finally clarified by experiments performed by Dr. Frank Brower of Dow Chemical Co. His results are summarized in Table 2 which is self-explanatory. 

Piirma and co-workers (14, 15) have performed careful studies on the polystyrene produced by emulsion polymerization using gel... 

It may be of interest that isotactic polystyrene formed by styrene polymerisation with Ziegler Natta catalysts [13] did not appear to be a polymer that could exhibit significantly better usable properties compared with atactic polystyrene produced in free radical styrene polymerisation processes. 

Styrene polymerisation with heterogeneous Ziegler Natta catalysts activated by alkylaluminium compounds generally produces a mixture of isotactic and non-stereoregular polymer. For example, polystyrene produced with the... 

Unsubstituted polymer chains cannot form different stereo isomers, while substituted polymers can have a large number of different possible isomeric forms. As a result it is possible to have various configurations for substituted polymers. For example polystyrene produced by radical polymerization is atactic which means the phenyl groups bound to every second C-atom are randomly distributed on both sides of the polymer chain. Polymers produced using Ziegler catalysts, made from monomers like styrene, propene and others are isotactic (Figure 2-2) ... 

The polystyrene produced by catalyst 25 is most likely produced by the titanium center, as shown by the results of fhe confrol experiments carried out with Ti(NMe2)4 as a catalyst—which was found to exhibit a styrene polymerization activity comparable to that observed for 25 under identical conditions. 

It is interesting that the polystyrene produced by suspension polymerization, particularly the Koppers material, had a heat distortion temperature superior to that of the Dow polystyrene [6]. This was attributed to the measurable levels of residual dimers and trimers in the Dow product due to its thermal initiation and which were absent in the peroxide-initiated suspension process. 

The first constraint that the engineer faces when the task is to develop a commercial process, is that a large amount of heat is generated when one converts styrene to polystyrene. The heat of polymerization is approximately 300 BTU/lb (700 J/g) at 100 °C and decreases with increasing temperature. This leads to a temperature increase of approximately 350 °C for pure styrene if it is polymerized to completion and no heat is removed from the process. This alone does not rule out an adiabatic process however, polystyrene degrades rapidly at temperatures above 250 °C and the molecular weight of the polystyrene produced decreases rapidly with temperature (see Figure 3.1). Therefore, no practical products could be produced with an adiabatic process without at least 50% diluent to limit the temperature rise to 175°C. 

Another type of initiator that has been evaluated for increasing polystyrene production rates are the multifunctional peroxides. Examples include 2,2-bis [4,4-bis(tert-butylperoxy)cyclohexyl]propane (I) [9], peroxyfumaric acid, 0,0-te/Y-butyl O-butyl ester (II) [10], ter t-butyl peritaconate (III) [11], and poly (monopercarbonates) (IV) (Figure 7.4) [12]. Although all of these initiators indeed show extremely fast production rates of high MW polystyrene, they all suffer from a flaw, i.e. the polystyrene produced is branched and special precautions must be taken to keep the continuous bulk polymerization reactors from fouling [13]. This is likely why none are currently used commercially for polystyrene manufacture. 

Figure 7.10 GPC curves of BMWD polystyrene produced at 140 °C in the presence of 100 ppm SEM and 1000 ppm BPO...

High -cis polybutadiene has relatively high heat resistance, which is advantageous in the processing of HIPS. On the other hand, this type of polybutadiene crystallizes at about 0 °C, owing to its stereoregular structure, with the consequence that the low-temperature toughness of polystyrene, produced in this way, is reduced. 

Figure 18.2 13C NMR of syndiotactic polystyrene produced by highly stereocon-trolled catalyst system. Apparatus JEOL Lambda 500 (13C 125.65 MHz). Frequency 25000 Hz. pulse 9.0 xs (45° pulse). Repetition time 4 s. Scans 10000...

Pyrolysis of polystyrene produces an oil very high in concentration of the monomer, styrene and also other aromatic compounds. Eigure 11.15 shows a typical gas chromatogram for the pyrolysis oil produced from the pyrolysis of polystyrene, showing... 

The styrene/methyl methacrylate pair contains monomers with different relative reactivity levels in Table 9-1. Polystyryl anion will initiate the polymerization of methyl methacrylate, but the anion of the latter monomer is not sufficiently nucleophilic to cross-initiate the polymerization of styrene. Thus the anionic polymerization of a mixture of the two monomers yields polyfmethyl methacrylate) while addition of methyl methacrylate to living polystyrene produces a block copolymer of the two monomers. 

Commerically available samples of biaxially oriented polystyrene and SMA copolymer sheet material, having a thickness of 0.0381cm, were used in this investigation. It is generally recognized that crystallization under stress can enhance the tensile properties of a semi-crystalline polymer through a special arrangement of the crystalline portion ( 23). Therefore, the physical properties of the styrene-maleic anhydride copolymers chosen were compared to those of polystyrene produced in the same manner and are shown in Table I (24). 

V Polystyrene produced exclusively fiom the polymmzatimi of styrene X ... 

This is reflected in the rj, T2 values (see Table 8.3). For example, the styrene/MMA pair has rj = 0.02, V2 = 20.0 when initiated by QHsMgBr in ether at —78°C. Thus the polymerization of the mixture in this case will cause homopolymerization of MMA followed by that of styrene. However, excess MMA will add to living polystyrene producing a block copolymer of the two monomers. 

The apparent propagation rate constant for polymerization of styrene in THF at 25°C using sodium naphthalene as initiator is 550 L mol s . If the initial concentration of styrene is 156 g/L and that of sodium naphthalene is 0.03 g/L, calculate the initial rate of polymerization and, for complete conversion of the styrene, the number average molecular weight of the polystyrene formed. Comment upon the expected value of the polydispersity index (M /M ) and the stereoregularity of the polystyrene produced. 

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