On the form IV of syndiotactic polypropylene

Auriemma, Finizia; Rosa, Claudio De; Ballesteros, Odda Ruiz de; Vinti, Valeria; Corradini, Paolo

doi:10.1002/(sici)1099-0488(199802)36:3<395::aid-polb1>3.0.co;2-r

Cited by 65 publications

(92 citation statements)

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“…To date, four limit-ordered crystalline modifications of s-PP were proposed and described in the literature. [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] Of the four crystalline forms, only the molecular chain packing models of the limitordered form I 56 -59,64,66 and the limit-disordered form I 59,63,66 (after the most recent nomenclature given by De Rosa et al 70 ) are appropriate for characterizing s-PP samples that are crystallized under quiescent conditions from the melt state (or from solution).…”

Section: Dependence Of Subsequent Melting Endotherms On Crystallizatimentioning

confidence: 99%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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ABSTRACT:The melting behavior of syndiotactic polypropylene (s-PP) after isothermal crystallization from the melt state was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques. Three melting endotherms were observed for isothermal crystallization at high degrees of undercooling. The minor endotherm, located closed to the corresponding crystallization temperature, was postulated to be the melting of the secondary crystallites formed at the crystallization temperature. The low-temperature melting peak was found to be the melting of the primary crystallites formed, and the high-temperature melting peak was a result of the melting of the crystallites recrystallized during a heating scan. The triple-melting behavior observed in subsequent melting endotherms of s-PP was therefore described as contributions from melting of the secondary crystallites and their recrystallization, partial melting of the less stable fraction of the primary crystallites and their recrystallization, melting of the primary crystallites, and remelting of the recrystallized crystallites formed during the heating scan. In addition, determination of the equilibrium melting temperature for this s-PP resin according to the linear and nonlinear Hoffman-Weeks extrapolations provided values of 143.1 and 185.6°C, respectively.

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Section: Dependence Of Subsequent Melting Endotherms On Crystallizatimentioning

confidence: 99%

Crystallization and melting behavior in syndiotactic polypropylene: Origin of multiple melting phenomenon

Supaphol

2001

J of Applied Polymer Sci

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“…Form III is characterized by chains in trans planar conformation packed in an orthorhombic unit cell with axes a ¼ 5. [18].…”

Section: Introductionmentioning

confidence: 99%

Diffusion and morphological properties of syndiotactic polypropylene (sPP) films

Yamashita

Fujiwara

Fujikawa

et al. 2009

Polymer Engineering & Sci

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Four different fabrication procedures were used for casting thin films of syndiotactic polypropylene (sPP). A hot press system operated at 200°C and 30 MPa pressure was used to melt polypropylene powder and make the cast films. Different cooling procedures were used to anneal the films, including cooling in liquid nitrogen (LN), ice water, and air at room temperature (RT). The morphological and mass transfer properties of the films were studied with XRD, polarized optical microscopy, bulk flow, and diffusion experiments. All sPP films contained amorphous and crystalline phases. The crystalline phase was determined to be disordered Form I. The sPP films annealed with LN had the lowest crystallinity whereas the sPP films cooled in air at RT had the highest crystallinity. Diffusion of toluene in the films and comparison with Maxwell's equation indicated that the crystalline phase mass permeability is much lower than the amorphous phase, which causes films with low crystallinity to have a higher effective diffusion constant and permeability compared with high crystallinity films. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

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“…Variations in tacticity have profound effects on thermal and physical properties. This is especially true for sPP, which has a rich variety of crystalline morphologies [2][3][4][5][6][7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Form III has been obtained by drawing melt quenched, melt crystallized, and melt spun fibers to high tensile strains (O400%) [12]. Form IV consists of chains in the (t 6 g 2 t 2 g 2 ) n conformation, which is intermediate between the helical (ttgg) n and the trans-planar conformation [13,14]. It is obtained by the exposure of sPP fibers originally rich in form III to suitable solvent vapors at temperatures below 50 8C [14].…”

Section: Introductionmentioning

confidence: 99%