Para-Methylstyrene

Among the many unusual properties that the arborescent architecture leads to, most notable is the discovery that block copolymers with a high MW dendritic (arborescent) polyisobutylene core and poly(para-methylstyrene) end blocks can manifest themselves either as a rubber, or as a plastic, depending on their environment (Figures 7.16 and 7.17). The behavior is thermally irreversible. 

The most prevalent approach to achieve long-lasting and nonstaining ozone protection of rubber compounds is to use an inherently ozone-resistant, saturated backbone polymer in blends with a diene rubber. The ozone-resistant polymer must be used in sufficient concentration (minimum 25 phr) and must also be sufficiently dispersed to form domains that effectively block the continuous propagation of an ozone-initiated crack through the diene rubber phase within the compound. Elastomers such as ethylene-propylene-diene terpolymers, halogenated butyl mbbers, or brominated isobutylene-co-para-methylstyrene elastomers have been proposed in combination with NR and/or butadiene rubber. 

Polymer Preparation. Poly-para-methylstyrene (P-p-MS) was prepared by anionic polymerization in benzene at 50"C initiated by n-butyllithium (9) or in THF at 25°C initiated by sodium naphthalene (10). Polymerizations in benzene allowed preparation of more monodisperse materials than those prepared in THF since the propagation rate is slower relative to the initiation rate in the nonpolar solvent (11). Two different molecular weight materials were chlorinated (P-p-MS 1 and P-p-MS2). 

Equation 2 illustrates another route to prepare graft copolymers, involving the preparation of polyolefin containing para-methylstyrene groups (I1). 

Potential Uses. Because much toluene is demethylated for use as benzene, considerable effort has been expended on developing processes in which toluene can be used in place of benzene to make directly from toluene the same products that arc derived from benzene. Such processes both save the cost of demethylation and utilize the methyl group already on toluene. Most of this effort has been directed toward manufacture of styrene. A11 alternative approach is the manufacture of para-methylstyrene by selective ethylation of toluene, followed by dehydrogenation. Resins from this monomer are expected to displace polystyrene because of price and performance advantages. 

Baer, K.N., Boeri, R.L., Ward, T.J. and Dixon, D.W. (2002) Aquatic toxicity evaluation of para-methylstyrene, Ecotoxicology and Environmental Safety 53 (3), 432438. 

Another good example of using Raman spectroscopy in the polymer industry is to investigate polymer blends. Raman microimages have been used to investigate the spatial distributions of the components in a blend of brominated poly(isobutylene-co-para-methylstyrene (BIMS) and cis-1-4-polybutadiene (BR) containing silica, zinc stearate, thiate, and other additives (21). A Raman spectrum of a blend is shown in Fig. 7-33. Specific bands can be assigned to BIMS, BR, silica, and zinc stearate. A 10 x 10 xm contour... 

Processing with the styrene monomer requires that precautions have to be taken to ensure the proper removal and handling of this toxic material. Legal limits in the workplace have been set up by regulations. Other monomers used include diallyl phthlate (DAP), para-methylstyrene (PMS), vinyl acetate (VA), vinyl toluene (VT), adding paraffin wax, and styrene suppressant additive. Suppliers and fabricators continue to target in the reduction of styrene monomer quickly, effectively, and economically. A wide variation in properties can be obtained by changes in polyester formulation. 

Dehydrogenation of para-ethyltoluene (PET) gives para-methylstyrene, a very useful polymer precursor molecule yielding polymers which have improved properties, such as higher flash-point and glass transition temperature, than those obtained via styrene polymerization. Early work in this area conducted at Mobil has demonstrated that modified HZSM-5 zeolite can result in an improved selectivity to the desired para-isomer. Characterization studies on these modified materials... 

Ethenyl-4-methylbenzene HSDB 6503 4-Methylstyrene 1-Methyl-4-vinylbenzene p-Methyl styrene para-Methylstyrene Styrene, p-methyl- 1-p-Tolylethene p-Vinyltoluene 4-Vinyltoluene. Liquid mp = -34,1" bp = 172.8 = 0.9173 Xm = 210, 216, 251, 284, 294... 

Kseding, W. W, Brewster Young. L, Prapot, A. G, Para-methylstyrene CHEMTECH, 556-562 (Sept. 1982)... 

Polyoxymethylene, polyformaldehyde Propylene oxide rubber Polypropylene Poly(phenylene ether) Poly(para-methylstyrene) Poly(phenylene oxide)... 

PARA-METHYLSTYRENE A NEW COMMERCIAL MONOMER FOR THE STYRENICS INDUSTRY... 

Mobil PMS is a new styrenlc monomer which is composed of 97% para-methylstyrene and 3% meta isomer (0% ortho). It is a different mixture of methylstyrene Isomers than commercially available vlnyltoluene, which contains approximately 35% para and 65% meta Isomers. It is important to compare the processes and properties for PMS and vlnyltoluene in order to understand the significance of the new material. A summary of the typical properties of styrene, vlnyltoluene and PMS is shown in Table 1. PMS and vlnyltoluene have higher boiling points and significantly lower vapor pressure than styrene, which reduces the inhalation exposure in the work environment and decreases the potential fire hazard. 

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