Polystyrene yielding

The covalent bonding of photosensitizer moieties such as benzophenone, rose bengal, and eosin to polystyrene yields polymeric photosensitizers that can be used to bring about excitation and subsequent chemical reaction in low-molecular-weight substrates [Neckers, 1986 Nishikubo et al., 1989]. 

The polimerization of the latter monomers can be initiated by a strong base. Hence, their addition to living polystyrene yields corresponding... 

Identifying of individual compounds in liquid products, especially branched molecules from polypropylene, is rather difficult, because of the cracking of polypropylene yields a great number of isomer compounds. The liquid product obtained by cracking of polyethylene consisted mostly of n-alkenes and n-aUcanes, which were evenly distributed by carbon number, whereas the cracking of polystyrene yielded blends of aromatic compounds, styrene, ethylbenzene, benzene, toluene [45, 54],... 

Conrad Industries (Chehahs, Washington) have demonstrated the pyrolysis of post-use plastics into petrochemical feedstocks. The plastic most studied was a mixture of 60% high-density polyethylene, 20% polypropylene, and 20% polystyrene. Yields of liquid products were in the range 65-75% at 482-510°C. Other studies examined the effects of PET and PVC on the liquid yields. The liquid products were determined to be suitable feedstocks for further refining, but the economics were not competitive with conventional petroleum refining in 1994 [36]. 

Because of the difference in form between Eqs. (2) and (3), the mechanisms of deformation and fracture change with the state of stress. For example, polystyrene yields by shear band formation under ccm ression, but crazes and frachues in a brittle matmer under tensile loading. Chants in failure nwchanian with state of stress are e cially important in particulate conqx tes, since the second phase can alter the local state of stress in the surrounding matrix. 

Hodge s group has also used linear phosphinated polystyrene to form haloolefins from carbon tetrabromide and aromatic aldehydes (27). Using 2 mol equiv of phosphine, 1 mol equiv of CBr and 1 mol equiv of -tolualdehyde at 50 C for 16 h formed a 54% yield of the dibrominated alkene. Substitution of 1% or 8% DVB cross-linked polystyrene for linear polystyrene yielded 67% and 12% of dibrominated alkene under the same conditions (Table II). 

There is experimental evidence, for many rubber-toughened polymers, that the rubber particles cavitate early in the deformation. The degree of cross-linking is kept relatively low in the polybutadiene phase of ABS to aid cavitation, and sometimes silicone oil is added for the same reason. Figure 4.12 shows both the conventional stress-strain curve and the volumetric strain versus tensile strain for rubber-modified polystyrene. When the polystyrene yields, the volume strain increases at a higher rate. Majority of the dilatational strain is due to cavitation in the rubber phase. 

The reaction is accompanied by a loss of molecular weight. Nitration of isotactic polystyrene yields a more crystalline product (about 1.6 N02/ring) than the parent compound. Here too, however, a loss in molecular weight accompanies the reaction. Polystyrene can be nitrated under mild conditions using acetyl nitrate. The product contains approximately 0.6 nitro groups per each benzene ring. ... 

The reactivity of the initiating radicals toward the backbones can vary and this can also change the efficiency of grafting. Benzoyl peroxide initiated polymerizations of methyl methacrylate monomer, for instance, in the presence of polystyrene yield appreciable quantities of graft copolymers. Very little graft copolymers, however, form when di-r-butyl peroxide initiates the same reactions. Azobisisobutyronitrile also fails to yield appreciable quantities of graft copolymers. This is due to very inefficient chain transferring to the polymer backbones by r-butoxy and isobutyronitrile radicals. 

Polystyrene yields benzene (I = 660) as the major photolysis product, smaller amounts of toluene, ethylbenzene and styrene are produced. Quantitation of the last three materials is complicated by variable amounts of residual monomer in the samples available and a small amount of thermal decomposition occurring in the injection port. 

It is interesting to note that the conversion of electronic to vibrational energy results in scission of the more stable pendant C—H bond rather than the main chain C—C bond. The observed results are consistent with this process because of the glassy nature of the polymer at room temperature. Almost certainly the main-chain bonds break and make . This proposal is supported by the observation that p-halogenated polystyrenes yield the halogen hydride, hydrogen and a cross-linked polymer on photolysis. 

The thermal degradation of synthetic polymers has proven to be an extremely important analytical technique for revealing composition, structure, and stability profiles. It actually causes unzipping of the polymer chain to yield sequential monomer units. Thus, thermal depolymerization of rubber (at 700°C and atmospheric pressure) yielded isoprene and dipentene, whereas polystyrene yielded a series of monomeric and dimeric hydrocarbons. 

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