Structure and properties of polypropylene crystallized from the glassy state

Abstract

SynopsisGlassy isotactic propylene (PP) films of thickness up to 0.3 mm were obtained by an ultraquenching technique. The structure and properties of the as-quenched and subsequently crystallized samples were characterized*by various techniques. Electron microscopy indicates the glass has no structure larger than 25 A. X-ray diffraction shows PP crystallizes from the glass into a smectic structure at ca. -20°$ and then transforms to monoclinic microcrystals at ca. 40OC; a nodular structure (80 to 100 A in diameter) was observed on the surface. The transformation temperature increases with the f i l m thickness. Annealing above the a-relaxation temperature results in an increase in the nodule size. A correspondence was found between the diameter of the nodules observed on the surface and long spacings obtained by small-angle X-ray scattering from the bulk. Dynamic mechanical spectra show the presence of two relaxation-like peaks at ca. -10°C and 10°C for the as-ultraquenched samples. X-ray scattering, differential scanning calorimetry (DSC), and torsion pendulum measurements show PP crystallizes from the glass at a temperature, depending on the rate of heating, that corresponds to the lower relaxation peak temperature.

Influence of annealing on microstructure & molecular orientation, thermal behaviour, mechanical properties and their correlations of uniaxially drawn iPP thin film

“…It can be seen that the WAXD patterns of unannealed drawn iPP film (UA) in both equatorial (EQ) and meridional (ME) scans consist of two intense broad peaks at 2θ equal 15.4 and 21.4°, and a shoulder peak at 28.8°. This pattern has been well known as the 'smectic phase' of iPP as first observed by Natta and Coradini [26] and by the latter researchers [27][28][29][30][31][32][33][34][35][36][37][38]. In general, the smectic phase of iPP can transform to the more stable crystalline phase (α-form) through annealing at appropriate temperature, i.e.…”

“…This intermediate state is between ordered and amorphous phases, and widely known by various names such as "quenched" [19], "mesomorphic" [20,21], "paracrystalline" [22], nano-crystallites [23], condis crystal [24] and a well known "smectic" phase [25][26][27]. Later, it was also found that the smectic phase could be obtained by cold drawing of iPP film at room temperature [28][29][30].…”

Effect of Film Formation Method and Annealing on Morphology and Crystal Structure of Poly(L-Lactic Acid) Films

“…As annealing time and/or temperature increase, the nodules enlarge, and may develop into larger needle-like crystals [8]. It is also observed that nodules develop into lath-like lamellae through merging or lateral aggregation [9,10]. At larger scale, the sheaf-like structures can be observed [12,13], and category 2 spherulites, in which lamellae grow unidirectionally in the central region and the spherical symmetry does not extend to the center [6], are developed [14].…”

“…Annealing such films from the glassy state can generates crystal structures different from those developed in as cast films. One common feature is the nodular structure [8][9][10]; the nodule is the nanometer-sized crystalline particle developed during annealing from the glassy state [11]. As annealing time and/or temperature increase, the nodules enlarge, and may develop into larger needle-like crystals [8].…”

correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP

“…The applications of PP may extend by addition of fillers/nanoparticles [12,13] and/or blending with TPs [14,15] or LCP [1][2][3][4][5][6][7][8], in order to improve its mechanical properties. Besides, PP can also crystallize to four different forms depending on the crystallization conditions [16][17][18][19][20][21][22]: monoclinic α-phase, hexagonal β-phase, orthorhombic γ-phase and the so-called smectic phase. The α-phase is the stable crystalline form and is the most commonly observed under the usual crystallization conditions.…”