Optimization of melting conditions for the analysis of crystallization kinetics of poly(3-hydroxybutyrate)

Abstract

Studies of kinetics of polymer crystallization are generally performed by heating the material above the melting point, in order to erase previous thermal and mechanical history, followed by rapid cooling to the desired crystallization temperature or by cooling at a constant rate. For poly(3-hydroxybutyrate) this procedure implies some degradation of the polymer chain, which starts below the onset of melting. In this article the effects of melting conditions on the subsequent crystallization kinetics are discussed. It is shown that in order to sufficiently cancel memories of previous crystalline order of the analyzed PHB, it is necessary to bring the material at a temperature higher than 192 °C. Thermal treatments conducted at lower temperatures are not sufficient to destroy all solid aggregates, and crystallization of PHB has an anticipated onset of crystallization due to nucleation occurring via self-seeding. The chain degradation attained upon exposure at high temperatures has much lesser influence on crystallization kinetics than incomplete melting, with some effects detectable on the spherulitic morphology and on the final degree of crystallinity.Brought to you by | Boston University Library Mugar Memorial Library Authenticated Download Date | 8/7/15 12:16 PM

A comparative study of three-dimensional printing directions: The degradation and toxicological profile of a PLA/PHA blend

“…Regarding [39]. Two glass transition temperatures were observed for the PLA/PHA filament and both specimens indicating that the PLA/PHA blend is immiscible and exhibits phase separation in the melt [40,41].…”

Novel approach for the preparation of a compatibilized blend of nylon 11 and polypropylene with polyhydroxybutyrate: Mechanical, thermal, and barrier properties

“…[66][67][68][69] The standard values for heat of melting-PA11 = 244 J/g 70,71 , PHB = 146 J/g, 72 and PP = 207 J/g. To understand this fact, the heat of melting was computed through DSC.…”

“…The degree of crystallinity of the blend was calculated as the ratio between the enthalpy of main melting endotherm and the theoretical enthalpy for a fully crystalline polymer. [66][67][68][69] The standard values for heat of melting-PA11 = 244 J/g 70,71 , PHB = 146 J/g, 72 and PP = 207 J/g. 73 Supporting Information Table S3 shows the % crystallinity for PA11, PP, PP-g-MA, and PHB, while crystallinity of the formed blends was shown in Table V.…”

Three-dimensional printing of PLA and PLA/PHA dumbbell-shaped specimens of crisscross and transverse patterns as promising materials in emerging application areas: Prediction study

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