Polystyrene effect

A number of N-brominated and N-chlorinated heterocycles also provide sources of electrophilic bromine. Examples include 1-chlorobenzotriazole (82JOC4895 87JOC173 88CHE36) and various HBr and Br2 adducts of pyridines, or pyridine perbromides [84SC939 85JAP(K)60/87264], Polymer-supported reagents of this type include 1-cyclohexylpyridinium perbromide linked to polystyrene, effective for the bromination of 1-methylindole, benzo[fc]furan, and benzo[6]thiophene (89T7869). 

Marie M, Ashurov N, Macosko CW (2001) Reactive blending of poly(dimethyl silox-ane) with nylon 6 and polystyrene effect of reactivity on morphology. Poly Eng Sci 41 (4) 631—642... 

Falcon Labware Catalog, Becton Dickinson and Co., 1978, p. 15. Klemperer, H.G. Knox, P. Attachment and growth of BHK and liver cells on polystyrene effect of surface groups introduced by treatment with chronic acid Lab. Pract., 1977, 26, 179-180. Hadley, M.A. Byers, S.W. Suarez-Quian, C.A. Kleinman, H.K. Dym, M. J. Cell Biol. 1984, lOi. 1511-1522 Klebe, R.J. J. Cell Biol. 1987, (In press). 

DIFFUSION OF POLYSTYRENE IN POLYSTYRENE. EFFECT OF MATRIX MOLECULAR WEIGHT. 

POLYSTYRENE. EFFECT OF SOLVENT, TEMPERATURE, AND MOLECULAR WEIGHT. 

Affi ossman, S., O Neill, S.A., Stamm, M. Topography and surface composition of thin films of blends of polystyrene with brominated polystyrenes Effects of varying the degree of bromination and annealing. Macromolecules 31(18), 6280-6288 (1998)... 

Maldas D, Kokta BV, Daneault C (1989) Thermoplastic composites of polystyrene effect of different wood species on mechanical properties. J Appl Polym Sci 38 413-439... 

Pantani, R., Sorrentino, A., Speranza, V., Titomanlio, G. Injection moldings of syndiotactic polystyrene Effect of processing conditions on morphology. IcheaP-6, the Sixth Italian Conference on Chemical and Process Engineering, Pisa, Italy, June 8-11, 2003. 

F. Bueche, Diffusion of Polystyrene in Polystyrene Effect of Matrix Molecular Weight , J. Chem. Phys., 48, 1410 (1968). 

These equations imply that A132 will exceed A12 if A33 is larger than A13 + A23. This effect, termed lyophobic bonding, occurs if the solvent-surface interaction is weaker than that between the solvent molecules. More interestingly, the dispersion interaction will be repulsive (A 132 < 0) when An and/or A23 are sufficiently large. Israelachvili [1] tabulates a number of Am values Awhw Ahwh 0-4X 10 erg, Apwp 1 x 10" erg, and Aqwq = O.SX -IO erg, where W, H, P, and Q denote water, hydrocarbon, polystyrene and quartz respectively. 

A still more intricate pattern of potential energy may be expected if the repeat units of the polymer chain carry other substituents, such as the phenyl groups in polystyrene, but these examples establish the general method for quantitatively describing the effects of steric hindrance on rotation. 

In the methacrylate homologous series, the effect of side-chain bulkiness is just the opposite. In this case, however, the pendant groups are flexible and offer less of an obstacle to free rotation than the phenyl group in polystyrene. As chain bulk increases, molecules are wedged apart by these substituents, free volume increases, and Tg decreases. 

Figure 6.8 Effect of chain transfer to solvent according to Eq. (6.89) for polystyrene at 100°C. Solvents used were ethyl benzene ( ), isopropylbenzene (o), toluene (- ), and benzene (°). [Data from R. A. Gregg and F. R. Mayo, Discuss. Faraday Soc. 2 328 (1947).]...

Figure 10.8 shows two sets of data plotted according to these conventions, after correction for the effect of interference. In Fig. 10.8a, HC2/T is plotted against C2 for three different fractions of polystyrene in methyl ethyl ketone. Figure 10.8b shows Kc2/Rg versus C2 for solutions of polystyrene in cyclohexane at five different temperatures. These results are discussed further in the following example.

Prepare a Zimm plot using the data in Table 10.2 and evaluate M, B,and for this solution of polystyrene in benzene. The effective wavelength in the medium is Xq/u = 546/1.501 = 364 nm for this experiment. 

In polymers such as polystyrene that do not readily undergo charring, phosphoms-based flame retardants tend to be less effective, and such polymers are often flame retarded by antimony—halogen combinations (see Styrene). However, even in such noncharring polymers, phosphoms additives exhibit some activity that suggests at least one other mode of action. Phosphoms compounds may produce a barrier layer of polyphosphoric acid on the burning polymer (4,5). Phosphoms-based flame retardants are more effective in styrenic polymers blended with a char-forming polymer such as polyphenylene oxide or polycarbonate. 

Physical or chemical vapor-phase mechanisms may be reasonably hypothesized in cases where a phosphoms flame retardant is found to be effective in a noncharring polymer, and especially where the flame retardant or phosphoms-containing breakdown products are capable of being vaporized at the temperature of the pyrolyzing surface. In the engineering of thermoplastic Noryl (General Electric), which consists of a blend of a charrable poly(phenylene oxide) and a poorly charrable polystyrene, experimental evidence indicates that effective flame retardants such as triphenyl phosphate act in the vapor phase to suppress the flammabiUty of the polystyrene pyrolysis products (36). 

Fig. 3. Effect of density on compressive modulus of rigid cellular polymers. A, extmded polystyrene (131) B, expanded polystyrene (150) C-1, C-2, polyether polyurethane (151) D, phenol—formaldehyde (150) E, ebonite (150) E, urea—formaldehyde (150) G, poly(vinylchloride) (152). To convert...

Solid Superacids. Most large-scale petrochemical and chemical industrial processes ate preferably done, whenever possible, over soHd catalysts. SoHd acid systems have been developed with considerably higher acidity than those of acidic oxides. Graphite-intercalated AlCl is an effective sohd Friedel-Crafts catalyst but loses catalytic activity because of partial hydrolysis and leaching of the Lewis acid halide from the graphite. Aluminum chloride can also be complexed to sulfonate polystyrene resins but again the stabiUty of the catalyst is limited. 

Fig. 3. Aging effect on thermal conductivity of cellular plastics A, extmded polystyrene B, unfaced polyurethane C, unfaced phenolic and D, polyurethane...

Arsenic Peroxides. Arsenic peroxides have not been isolated however, elemental arsenic, and a great variety of arsenic compounds, have been found to be effective catalysts ia the epoxidation of olefins by aqueous hydrogen peroxide. Transient peroxoarsenic compounds are beheved to be iavolved ia these systems. Compounds that act as effective epoxidation catalysts iaclude arsenic trioxide, arsenic pentoxide, arsenious acid, arsenic acid, arsenic trichloride, arsenic oxychloride, triphenyl arsiae, phenylarsonic acid, and the arsenates of sodium, ammonium, and bismuth (56). To avoid having to dispose of the toxic residues of these reactions, the arsenic can be immobi1i2ed on a polystyrene resia (57). 

A method for the polymerization of polysulfones in nondipolar aprotic solvents has been developed and reported (9,10). The method reUes on phase-transfer catalysis. Polysulfone is made in chlorobenzene as solvent with (2.2.2)cryptand as catalyst (9). Less reactive crown ethers require dichlorobenzene as solvent (10). High molecular weight polyphenylsulfone can also be made by this route in dichlorobenzene however, only low molecular weight PES is achievable by this method. Cross-linked polystyrene-bound (2.2.2)cryptand is found to be effective in these polymerizations which allow simple recovery and reuse of the catalyst. 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

When used alone at low temperatures, diaLkyl thiodipropionates are rather weak antioxidants. However, synergistic mixtures with hindered phenols are highly effective at elevated temperatures and are used extensively to stabilize polyolefins, ABS, impact polystyrene (IPS), and other plastics. 

The Q-e Scheme. The magnitude of and T2 can frequentiy be correlated with stmctural effects, such as polar and resonance factors. For example, in the free-radical polymerization of vinyl acetate with styrene, both styrene and vinyl acetate radicals preferentially add styrene because of the formation of the resonance stabilized polystyrene radical. 

PL can be used as a sensitive probe of oxidative photodegradation in polymers. After exposure to UV irradiation, materials such as polystyrene, polyethylene, polypropylene, and PTFE exhibit PL emission characteristic of oxidation products in these hosts. The effectiveness of stabilizer additives can be monitored by their effect on PL efficiency. 

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