Self‐nucleation and recrystallization of isotactic polypropylene (α phase) investigated by differential scanning calorimetry

Journal of Polymer Science, Part B: Polymer Physics - Tập 31 Số 10 - Trang 1383-1393 - 1993
B. Fillon1, J. C. Wittmann1, Bernard Lotz1, A. Thierry1
1Institut Charles Sadron (CRM‐EAHP) (CNRS‐ULP), 6, rue Boussingault — 67083 Strasbourg Cedex (France)

Tóm tắt

AbstractThe crystallization behavior after partial or complete melting of the α phase of iPP is examined by combined differential scanning calorimetry (DSC) and optical microscopy: calorimetric results are directly correlated with corresponding morphologies of microtome sections of DSC samples. On partial melting at various temperatures (hereafter referred to as Ts) located in a narrow range (4°C) below and near Tm, the number of nuclei increases (as in classical self‐nucleation experiments), by several orders of magnitude; on subsequent cooling, the crystallization peak is shifted by up to 25°C. After partial melting in the lower part of the Ts range and recrystallization, the polymers display a prominent morphology “memory effect” whereby a phantom pattern of the initial spherulite morphology is maintained.After partial melting in the upper part of the Ts range the initial morphology is erased and self‐nucleation affects only the total number of nuclei. The present experimental procedures make it possible to define, under “standard” conditions, the crystallization range of the polymer and in particular, the maximum crystallization temperature achievable when “ideally” nucleated. © John Wiley & Sons, Inc.

Từ khóa


Tài liệu tham khảo

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Following the recommendation of the IUPAC commission on nomenclature the term “self‐nucleation” is used throughout rather than “self‐seeding” used in the original papers.

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Normally selection of this temperature is not critical provided it is well below the crystallization range. In our experiments it is 50°C (i.e. 60–65°C below the crystallization peak) where the sample is kept fort1= 5 min (Fig. 1b). In particular cases however the ensuing self‐nucleation process is significantly affected by the actual temperature selected (cf. the companion paper on self‐nucleation of β iPP).5

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Journal of Polymer Science, Part B: Polymer Physics

Tập 31 Số 10

1383-1393

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