A DSC study of the polymerization of 2‐Vinylpyridine in dimethylformamide

Ekenstein, G.O.R. Alberda van; Held, B.J.; Tan, Y.Y.

doi:10.1002/apmc.1985.051310109

Cited by 11 publications

(2 citation statements)

References 10 publications

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“…Triple melting has also been observed in a that the first melting endotherm was associated with the last step of secondary crystallization number of other polymers, for example: i-polystyrene (i-PS), 12,13 nylons 14 ; i-polypropylene oxide (small branches of metastable crystalline material). The second melting endotherm was associ-( i-PPO ) , 15 i-poly ( 2-vinylpyridine ) , 16 and poly-(ethylene naphthalenate) (PEN). 17 At very low ated with secondary crystallization (mainly metastable secondary branches) and the third melting crystallization times the phenomenon seems to be also present in more rigid macromolecules such endotherm was assigned to the isothermal crystals which under linear heating would undergo as poly(aryl ether ether ketone) (PEEK).…”

mentioning

confidence: 99%

The triple melting behavior of poly(ethylene terephthalate): Molecular weight effects

Medellín‐Rodríguez

Phillips

Lin

et al. 1997

J. Polym. Sci. B Polym. Phys.

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The melting behavior of isothermally crystallized PET has been studied using linear heating in a differential scanning calorimeter (DSC). Variables such as crystallization temperature, crystallization time, heating rate, and average molecular weight are the main focus of the study. On the basis of several experimental techniques, a correlation of the melting behavior of PET with the amount of secondary crystallization was found to exist. It was observed that the triple melting of PET is a function of programmable DSC variables such as crystallization temperature, crystallization time, and heating rate. However, in testing the hypothesis that there was a correlation between melting endotherms and secondary crystallization inside spherulites, it was found necessary to use a DSC‐independent variable in order to enhance the observed effects. Therefore, on the basis of a crystallization model that involves secondary branching along the edges of parent lamellar structures, it was speculated that an increase in the average molecular weight could affect the triple melting of PET due to an increase of rejected portions of the macromolecules. It was found that the second melting endotherm increased, apparently, at the expense of the third one as the average molecular weight was increased. The second melting endotherm was also found to correlate proportionally with the amount of secondary crystallization inside spherulites. The results support a model of crystallization which basically consists of parent crystals and at least one population of secondary, probably metastable, crystals. This latter structural component must involve excluded portions of the macromolecules that did not crystallize during the isothermal crystallization period of the parent crystals. An increase of molecular weight gives rise to a higher entanglement density which in turn increases the fraction of initially rejected chain sections and therefore the amount of secondary crystallization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1757–1774, 1997

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mentioning

confidence: 99%

The triple melting behavior of poly(ethylene terephthalate): Molecular weight effects

Medellín‐Rodríguez

Phillips

Lin

et al. 1997

J. Polym. Sci. B Polym. Phys.

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“…1 . By use of the method of Kelen and Tudds (18)(19)(20) the reactivity ratios were determined at rl = 0.40, and r2 = 0.86 (styrene is monomer A).…”

Section: Temperaturesmentioning

confidence: 99%

The working domain in reactive extrusion. Part I: The effect of the polymer melt viscosity

Goot¹,

Hettema²,

Janssen³

1997

Polymer Engineering & Sci

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This article describes the radical copolymerization of styrene (St) and n‐butyl‐methacrylate (BMA) in a counter‐rotating twin‐screw extruder. In order to investigate the effect of the polymer melt viscosity on the working domain in reactive extrusion, the copolymer was crosslinked with different amounts of divinylbenzene (DVB). Crosslinking of the polymer resulted in a higher polymer melt viscosity. It was demonstrated that not only the product properties but also the process characteristics were strongly influenced by the addition of divinylbenzene to the reaction mixture. The product properties changed as expected: more crosslink agent led to a higher molecular weight or an increase in gel fraction, and a much higher melt viscosity of the polymer. Besides these effects on the product properties, the addition of DVB resulted in a more stable process, leading to an enlarged working domain.

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4‐(α,α‐dimethylbenzyl)phenyl methacrylate, 2. Polymerization in N,N‐dimethylformamide

Ekenstein

Tan

1991

Makromol. Chem.

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The polymerization rate of 4-(a,cedimethylbenzyI)phenyl methacrylate in DMF at 70 "C is of the order 1,6 in [monomer] and first order in [AIBN], which deviates from classical kinetics. This could be reconciled by a reaction scheme in which dimeric monomer associates and a spontaneous termination are postulated. The scheme is supported by the dependence of the kinetic chain length, v, on the 1,6-th power in [monomer] and zeroth power in [AIBN]. The degree of polymerization is smaller than v, which indicates some chain transfer. A remarkable feature is the constancy of the dispersion degree, &&,/a,, of the polymers of about 1,4 up to high degrees of conversion.The overall activation energy of the polymerization, E,, is 60,l k J . mol-', and the preexponential factor InA = 15,s (A in (mol . dm-3)-'2s. s-'). The polymer chains seem to have a rod-like character in THF as deduced from the Mark-Houwink exponent of 1,46. In toluene the polymer tends to form associates.

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A DSC study of the polymerization of 2‐Vinylpyridine in dimethylformamide

Cited by 11 publications

References 10 publications

The triple melting behavior of poly(ethylene terephthalate): Molecular weight effects

The triple melting behavior of poly(ethylene terephthalate): Molecular weight effects

The working domain in reactive extrusion. Part I: The effect of the polymer melt viscosity

4‐(α,α‐dimethylbenzyl)phenyl methacrylate, 2. Polymerization in N,N‐dimethylformamide

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