Effect of Crosslinking on Block and Random Copolymers of Styrene and Butadiene

Mohammady, Sayed Z.; Mansour, Ahmed S.; Soden, W. v.

doi:10.1002/1521-3935(20010901)202:13<2732::aid-macp2732>3.0.co;2-c

Cited by 16 publications

(19 citation statements)

References 14 publications

(48 reference statements)

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“…Temperature scans were made for each of the block copolymer samples at fixed frequency values (0.1, 1, and 10 Hz). The crosslinking of SBS and SSBS was achieved with 1 phr dicumylperoxide (DCUP) at 150 °C for 1 h37 (1 phr = 1 g of DCUP/100 g of the polymer).…”

Section: Methodsmentioning

confidence: 99%

Dynamic mechanical relaxation behavior of block copolymers at high temperatures

Mohammady

Mansour

Stoll

2001

J Polym Sci B Polym Phys

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We carried out dynamic mechanical measurements to investigate three different examples of block copolymers: styrene–isoprene diblock copolymers and styrene–butadiene–styrene and styrene–(styrene butadiene)–styrene triblock copolymers. Isochronal and isothermal measurements of the real and imaginary parts of the complex shear modulus were performed over wide ranges of temperature and frequency. The measurements showed the presence of an additional relaxation process appearing at temperatures higher than those of the glass relaxation of the polystyrene phase, which has been misinterpreted by some authors as an order–disorder transition. The frequency dependence revealed that this process was a relaxation process and did not belong to a first‐order transition. Moreover, the influence of crosslinking via dicumylperoxide was measured, and we constructed complete master curves to confirm the presence of two relaxation processes. The high‐temperature relaxation process was strongly suppressed by crosslinking. Therefore, it was possible to detect the glass relaxation process of the polystyrene phase in a precise manner. The results were compared with those of homopolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2198–2206, 2001

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Section: Methodsmentioning

confidence: 99%

Dynamic mechanical relaxation behavior of block copolymers at high temperatures

Mohammady

Mansour

Stoll

2001

J Polym Sci B Polym Phys

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“…The terpolymers investigated have relatively different molecular weight distributions (2.22, 2.56 and 3.17 for AN‐1, AN‐2 and AN‐3, respectively). The effect of molecular weight distribution on the molecular dynamics of the glass process of polymer fractions, and mixtures of homopolymers, has been discussed in the literature 11, 15–18. Those authors showed that the molecular dynamics of the glass process (the target to be investigated in the present work) is independent of the values of polydispersity.…”

Section: Resultsmentioning

confidence: 99%

“…A great deal of research effort has been expended over the years in quantitatively describing the cooperative nature of the glass process 15–23. It is well established now that there is a domain in which cooperative particle motion can take place and its size decreases as the temperature increases.…”

Section: Resultsmentioning

confidence: 99%

“…This domain is named the cooperative rearranging region (CRR) 17, 19, 23. Based on the literature, the CRR can take values between 2 and 25 nm, depending on the method of data treatment 15–23…”

Section: Resultsmentioning

confidence: 99%

“…5 can be fitted by means of the well‐known William–Landel–Ferry (WLF) equation (Eqn (2)) or its mathematical equivalent, the Vogel–Fulcher–Tammann (VFT) equation:11 where C 1 and C 2 are fitting parameters and T 0 is a constant value normally taken at the vicinity of T g . In fact, these equations cannot give any idea about CRR values, but researchers15, 16, 18, 21–23 have suggested a ‘dislocation concept’ for bundles of polymer chain molecules, where the smallest isotropic arrangements of such bundles (so‐called meander cubes) may be taken as cooperatively rearranging units 15, 16. The authors were able to calculate the diameter ( r ) of the molecular bundles by thermodynamic treatments.…”

Section: Resultsmentioning

confidence: 99%

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Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Mohammady¹,

Elkholy²,

Elsabeé³

2006

Polymer International

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Terpolymer samples were prepared by free radical polymerization of methyl methacrylate (MMA), indene (In) and acrylonitrile (AN) in bulk. The samples were chosen so that the molar ratio of AN to MMA varied from 1.00:4.39 to 1.00:0.83, while the molar ratio of In was kept almost unchanged. The glass transition temperatures (T g ) of the samples were determined using differential scanning calorimetry. Moreover, isochronal dynamic mechanical measurements of the complex bending modulus as well as the complex dielectric permittivity were carried out over wide temperature ranges, namely from 50 to 190• C, depending on the material investigated. All samples exhibited a single common T g value, which increased to higher temperature upon increasing the content of AN. In addition, the results were investigated quantitatively in the framework of a molecular model.

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Fourier transform near‐infrared and electron spin resonance studies on the crosslinking reaction of liquid carboxylated poly(acrylonitrile‐co‐butadiene) rubber with dicumyl peroxide in dioxane

Masaki

Ohkawara

Hirano

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:The crosslinking reaction of liquid carboxylated poly(acrylonitrile-co-butadiene) [or nitrile rubber (NBR); acrylonitrile ϭ 10 wt %] with dicumyl peroxide (DCPO) was studied in dioxane by means of Fourier transform near-infrared spectroscopy (FT-NIR) and electron spin resonance spectroscopy (ESR). Among the three butadiene units (1,2, cis-1,4, and trans-1,4 units) of NBR, only the pendant vinyl group of the 1,2 unit showed an absorption at 6110 cm Ϫ1 from the FT-NIR examination of dioxane solutions of NBR, 1-octene, 3,3-dimethyl-1-butene, trans-2-octene, cis-5-octen-1-ol, poly-cis-1,4-butadiene, and poly-1,2-butadiene. The crosslinking reaction was followed in situ in dioxane by the monitoring of the disappearance of the pendant vinyl double bond with FT-NIR. The initial disappearance rate (R 0 ) of the vinyl group was expressed by R 0 ϭ k [DCPO] 0.9 [NBR] Ϫ0.2 (120°C). The overall activation energy of the reaction was calculated to be 20.7 kcal/mol. This unusual rate equation suggests unimolecular termination due to degradative chain transfer and depressed reactivity of the vinyl group caused by crosslinking. ESR study of the reaction mixture revealed that an allyl-type polymer radical was formed in the reaction, and its concentration increased with time and was then saturated.

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Effect of Crosslinking on Block and Random Copolymers of Styrene and Butadiene

Cited by 16 publications

References 14 publications

Dynamic mechanical relaxation behavior of block copolymers at high temperatures

Dynamic mechanical relaxation behavior of block copolymers at high temperatures

Investigation of the relaxation behavior of novel terpolymers of acrylonitrile, methyl methacylate and indene

Fourier transform near‐infrared and electron spin resonance studies on the crosslinking reaction of liquid carboxylated poly(acrylonitrile‐co‐butadiene) rubber with dicumyl peroxide in dioxane

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