Use of solvent sorption to detect structural changes in rigid PVC compounds

The effects of type of PVC and its thermal history on solvent sorption behaviour were investigated. Samples were immersed in toluene at 25°C, and the equilibrium solvent uptake and sorption half-times were measured for a variety of samples. The shape of the sorption curve was also observed. Equilibrium sorption was found to decrease with increasing amount of crystallinity in the sample. Sorption half-time increased with increased crystallinity, but minimum equilibrium sorption did not correspond with maximum half-time, possibly due to the type of crystallinity present. The shape of the sorption curve (Fickian or Case II sorption) also depended on the ype of PVC used and is thermal history. The solvent sorption technique was shown to be a sensitive method for detecting small structural changes in PVC.     

Synthesis and characterization of polymerizable bisphthalonitrile monomers

The reactions of 4-aminophthalonitrile (APN) with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BPTDA), and with 1,2,3,4-benzenetetracarboxylic dianhydride (PMDA) have been studied to optimize the conditions for the synthesis of monomeric thermosetting bisphthalonitrile compound. Suitable procedures for the synthesis of the two monomers are presented. Elemental analyses, IR spectra, dynamic thermogravimetric analyses, differential scanning calorimetry, ¹H-NMR, and mass spectral studies have been used to characterize these compounds. Preliminary observations show that these materials can be polymerized to give high-temperature-resistant materials.     

Radical intermediates in the electrochemical reduction of alizarin

Conclusions In the electroreduction of alizarin in an aprotic medium the stepwise formation of the anion-radical and subsequently of the dianion has been observed; under conditions of the prolonged process the anion-radical disproportionates and through intermediate stages of deprotonation and reduction is converted into the stable dianion-radical.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 983–988, May, 1985.     

Azo initiators for the preparation of hydroxyl-terminated polybutadienes

Azo compounds such as di(4-hydroxybutyl)-2,2′-azobisisobutyrate, di(3-hydroxybutyl)-2,2′-azobisisobutyrate, di(2-hydroxypropyl)-2,2′-azobisisobutyrate, and di(2-hydroxyethyl)-2,2′-azobisisobutyrate were prepared and used as initiators for the preparation of hydroxyl-terminated polybutadienes (HTPBs) of molecular weight (M?_n) ranging from 2000 to 7500 and functionality between 1.90 and 3.0. The polymers were prepared by free-radical solution polymerization in dioxane and toluene. The polymers obtained were characterized for their molecular weight, hydroxyl number, functionality, and instrinsic viscosity.     

Modellrechnungen zum Dendriten-Wachstum in partiell-kristallinen Hochpolymeren

Zusammenfassung Überstrukturen in partiell-kristallinen Thermoplasten liegen oft in Gestalt von Sphärolithen vor. Es wird versucht, ihre Entstehung auf behindertes Dendritenwachstum zurückzuführen. Die durch das Simulationsmodell beschriebenen Strukturen werden mit experimentell beobachteten verglichen.

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Superstructures in partial-crystalline thermoplastics often show the shape of spherulites. The reason of this can be a handicapped growth of dendrites. The structures obtained by a simulation model are compared with those obtained by experiments.