The content of styrene units in nonhydrogenated and hydrogenated styrene‐butadiene‐styrene and styrene‐isoprene‐styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene‐butadiene‐styrene and styrene‐isoprene‐styrene triblock copolymers (r = 0.974 for styrene contents of 19.3–46.3% for nonhydrogenated ones and r = 0.970 for the styrene contents of 23–58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene‐isoprene‐styrene or hydrogenated styrene‐butadiene‐styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene‐butadiene‐styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene‐containing polymers in blends such as poly(acrylonitrile‐butadiene styrene). 相似文献
Solubilization of hydrophilic saccharide chains into organic solvents has been attempted by incorporating saccharide-substituted styrene unit into polystyrene main chain. Lactose-, maltopentaose, and amylose-substituted styrene monomers were copolymerized with styrene. Resulting chloroform-soluble copolymers were characterized, and structural formation was investigated. Copolymers of lactose-substituted styrene and maltopentaose-substituted styrene with styrene were dissolved into chloroform. The chloroform-soluble polymers contained about 12 disaccharide lactose chains or 1.7 maltopentaose chains as the pendant groups in one polystyrene molecule. Chloroform-insoluble methyl orange was dissolved into chloroform with the help of chloroform-soluble polystyrene having some saccharide chains. On the other hand, when an amylose-substituted styrene unit was inserted in a polystyrene chain, the resulting polymer became insoluble into chloroform. Amylose polysaccharide of DPn = ∼24 was not dissolved into chloroform by this method. 相似文献
The graft-copolymerization of styrene on PP in the solid phase has been studied under various reaction conditions using a radical initiator. Polymerization kinetics were investigated by DSC experiments and reactions in glass ampoules. The conversion rate and grafting efficiency of styrene appeared to be strongly influenced by the presence of the PP matrix and the styrene/PP ratio. From reactions in a lab scale reactor the concentrations of styrene and initiator, the dosing rate and the temperature were investigated to be critical parameters determining the grafting efficiency and the average length and number of grafts. The phenomena observed were explained by describing the process in relative rates of diffusion and polymerization, including swelling of the polymer by styrene monomer and diffusion limitations (Trommsdorff effect). 相似文献
Summary: Radical homopolymerizations and copolymerizations of styrene were performed in toluene and N,N‐dimethylformamide (DMF) as solvents using different initiators with and without microwave irradiation. Only the homopolymerization of styrene under microwave irradiation in DMF with DtBP showed significantly enhanced styrene conversion whereas other initiators resulted in no or only slight increase of styrene conversion under microwave irradiation. In any case, DMF was required to gain in styrene conversion under microwave irradiation. Significantly higher monomer conversions were observed under otherwise comparable conditions in the copolymerization of styrene and methyl methacrylate (MMA) in DMF. Microwave‐induced selectivity of monomers was not observed in copolymerizations.
Yield of styrene polymerizations under varying reaction conditions initiated by DtBP. 相似文献
The macro-kinetics and pathway of styrene oxidation catalyzed by Co2+-exchanged X, using O2 as oxidant, were investigated. The effects of external diffusion, internal diffusion, the styrene concentration, O2 pressure, the catalyst concentration and the reaction temperature on the styrene oxidation reaction rate were examined. The
results showed that the reaction rate of styrene oxidation was 0.19 order with respect to the styrene concentration, 0.64
order with respect to O2 pressure, and zero to first order with respect to the different catalyst concentration. The calculated activation energy
for this reaction was 13.79 kJ/mol. On the other hand, the three products in the styrene oxidation reaction were, respectively,
used as the reactant to examine the reaction pathway of styrene oxidation. The results revealed that styrene oxidation reaction
occurred as two parallel reactions. One was the production of styrene oxide and the other was the production of benzaldehyde
and formaldehyde with former partially oxidized to benzoic acid and the latter mostly oxidized to O2 and H2O.
Published in Russian in Kinetika i Kataliz, 2009, vol. 50, No. 2, pp. 212–217.
The article is published in the original. 相似文献
Samples of styrene–acrylonitrile (SAN) copolymer of different compositions, molecular weights, block copolymers, and a blend of styrene and acrylonitrile homopolymers were prepared and characterized by the method of pyrolysis gas chromatography. On decomposition of SAN copolymer samples at 645°C, eleven components were identified, the most important of them being styrene, acrylonitrile, and propionitrile. By examination of the pyrolyzate composition during pyrolysis of the SAN copolymer of different compositions, it was established that the propionitrile yield was definitely decreased when the acrylonitrile concentration in copolymer was about 60 mole-%. Further, from the propionitrile yield, we could distinguish random SAN copolymer from the styrene-acrylonitrile homopolymer blend, and on the basis of propionitrile yield some information on the molecular structure of the copolymer could be obtained. The styrene yield depends linearly on the copolymer composition. This permits determination of copolymer composition on the basis of the styrene yield. Furthermore, the effects of decomposition temperature and of molecular weight on the yields of styrene and acrylonitrile were examined. 相似文献
