Modified polystyrenes

In these mbber-modified polystyrene polymers, the mbbers should have low T, large particle sizes (0.5—5 J.m), graftable and cross-linkable sites, and should be compatible with styrene monomer (93). Polybutadiene, with a T of —SS C, meets all of these requirements and is used most frequently. These mbber-modified systems exhibit excellent low temperature impact strength, a required attribute for use in refrigerators. 

A new process to develop interface vulcanization is grafting of selective accelerators onto a polymer chain, which in the subsequent process of vulcanization acts as an effective cure accelerator for the second polymer component in the blend. Beniska et al. [6] prepared SERFS blends where the polystyrene phase was grafted with the accelerator for curing SBR. Improved hardness, tensile strength, and abrasion resistance were obtained. Blends containing modified polystyrene and rw-1,4-polybutadiene showed similar characteristics as SBS triblock copolymers. 

NBR - acrylonitrile-co-butadiene rubber NR - natural rubber OPS - oxazoline modified polystyrene PA - polyamide... 

General Considerations. Continuous mass processes for polystyrene have been in commercial use since the 1930 s, and for rubber-modified polystyrene (HIPS) since the 1950 s. Much of the information on equipment design, process configuration and operating parameters connected with continuous processes is found in the patent literature. There are inherent limitations to such sources. Recognizing this, we will provide... 

Soto, A.M., Justicia, H., and Wray, J.W. et al. (1991). Para-nonyl-phenol an estrogenic xen-obiotic released from modified polystyrene. Environmental Health Perspectives 92, 167-173. 

More recently 233) it has been reported that cross-linked polystyrene containing imidazole ligands did not provide a support rigid enough to prevent dimerization, and that the p-oxo dimer was benzene extracted from oxygenated tetraphenyl porphyrin iron(ll), Fe(TPP), which had been attached to the modified polystyrene. A discussion of model synthetic porphyrins, from which definitive structural and other physical data are obtained, is given in section V.C. 

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-... 

Dopamine, a neurotransmitter, was covalently coupled, via an amide bond, to a modified polystyrene having A-(2-(3,4-dihydroxyphenyl)ethyl) isonicotinamide units. The dopamine-coupled polymer was coated onto glassy carbon electrodes. In aqueous electrolyte solutions (pH 7), cathodic current caused cleavage of the amide linkage and release of dopamine at potentials more negative than 0.9 V [41]. The chemical scheme for the amide bond cleavage is presented in Figure 18. 

For the hydrosilylation reaction various rhodium, platinum, and cobalt catalysts were employed. For the further chain extension the OH-functionalities were deprotected by KCN in methanol. The final step involved the enzymatic polymerization from the maltoheptaose-modified polystyrene using a-D-glucose-l-phosphalc dipotassium salt dihydrate in a citrate buffer (pH = 6.2) and potato phosphorylase (Scheme 59). The characterization of the block copolymers was problematic in the case of high amylose contents, due to the insolubility of the copolymers in THF. 

Soto AM, Justicia H, Wray JW, Sonnenschein C (1991) p-Nonyl-phenol an estrogenic xenobiotic released from modified polystyrene. Environ Health Perspect 92 167-173... 

The effect of heat ageing on a polyolefin, as on modified polystyrene, is considerably influenced by particular pigment lakes. Heavy metal ions, especially copper,... 

Soto and co-workers first reported the estrogenicity of NP released from modified polystyrene tubes in 1991 [1], Soto also proved that... 

The preferred morphology of these rubber modified amorphous thermoplastics is the distribution of distinct rubber particles unfilled or filled in an isotropic matrix of the basic polymer. This was shown to be the case for rubber modified polystyrene and for ABS-type polymers. 

ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

SB for butadiene rubber-modified polystyrene or HIPS (high-impact polystyrene)... 

Figure 4.40 shows an example of impact strength versus low temperatures for a given impact-modified polystyrene. 

ISO 2897-1 1997 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 2897-2 2003 Plastics - Impact-resistant polystyrene (PS-I) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 14631 1999 Extruded sheets of impact-modified polystyrene (PS-I) - Requirements and test methods... 

The selective electrophilic aromatic substitution carried out by displacement of a metallic substituent (Hg, Sn) ( F-fluorodemetallation) using [ F]p2 or [ F]AcOF remains a method of choice to introduce a fluorine atom on a specific position. In the early preparations of [6- F]fluoro-L-DOPA, the reaction of a 6-substituted mercuric derivative with [ F]acetyl hypofluorite yielded the expected compound in 11 % yield [73,74]. Reaction of a mercuric precursor, free or on a modified polystyrene support P-CH2-COOHg(DOPA precursor) allows the preparation of [ F]fluoro-L-DOPA in an overall yield up to 23 %. The polymer supports are easily prepared, require no special treatment for storage and are convenient to use in automated production [75]. 

For the SPE of the more polar aromatic sulfonates, IPs with tetralkylammonium are previously formed [85,93,94]. The combination of the formation of IP with cetyltrimethylammonium and SPE is efficacious in the extraction of benzene and naphthalene sulfonates from an aqueous environment. Good recoveries are also obtained with octylammonium acetate as the IP agent, both when it is added to the aqueous sample prior to the extraction and when it saturates the solid phase to produce an anion-exchange column [95,96]. An alternative approach is based on the use of deactivated charcoal (Carbonpack B) [96] or of chemically modified polystyrene-divinylbenzene resins [85]. Often graphitized carbon black (GCB) is used for the clean-up process of the sample [96]. 

A number of approaches may be adopted to achieve chemical synthesis of a peptide. The Merrifield solid phase synthesis method is perhaps the most widely used. This entails sequential addition of amino acids to a growing peptide chain anchored to the surface of modified polystyrene beads. The modified beads contain reactive chloromethyl (—CH2CI) groups. 

Protein adsorption is the first event that takes place on material surfaces when blood or other body fluids are brought into contact with any material. Therefore, cell - material interactions must be discussed by taking into consideration the species and the nature of the protein adsorbed on the material surfaces. For instance, a series of cell-attachment and spreading experiments [11] of fibroblasts on the surface of modified polystyrene (TCP and Primaria) carried out in the presence of fetal calf serum (FCS) showed that FCS contains components which tend to decrease the attachment and spreading of fibroblast cells. The effect of these nonadhesive components was only evident when the FCS was depleted of vitronectin, showing that vitronectin overcomes the effect of these nonadhesive components and promotes cell-attachment and spreading on the polystyrene surface. Fibronectin, on the other hand, does not play a principal role in this fibroroblast adhesive process (Fig. 2). 

Straight and modified polystyrenes have little or no effect on explosives and propellants. However, modified polystyrenes show greater susceptibility than straight polystyrenes to attack by explosives and propellants that contain NG/TNT. 

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