The thermal properties of polypropylene

Abstract

The thermodynamic properties of isotactic polypropylene in the fully crystalline, glassy, and molten state are established from 0 to 500 K based on data bank heat capacities and the vibrational frequency spectrum. The seven skeletal vibrations are described by θ3 and θ1 of 91 and 714 K for crystalline polypropylene. For the calculation of Cp − Cv, a Lindemann A0 value of 1.5 × 10−3 K mol/J was found. Calculated and experimental heat capacity data show agreement within an average error of −0.3 ± 1.6%. Glassy polypropylene was similarly treated up to the glass transition temperature at 260 K (θ3 = 78 K, θ1 = 633 K, average heat capacity error −0.6 ± 2.8%). The residual 0 K entropy of glassy polypropylene is 1.9 J/K mol. Partially crystalline polypropylene is shown through high‐sensitivity DSC measurements to have a glass transition range from 260 to 380 K. Similarly, high‐sensitivity DSC has been used to characterize the condis phase of polypropylene (conformationally disordered polypropylene) which was prior called “smectic mesophase” or “paracrystalline.” Its heat of transformation to the stable crystal phase is 600 J/mol.

Crystallization of isotactic polypropylene from mesomorphic phase: a constant heating rate study

“…The case when x = 0.75 reproduces the experimental DSC well. This value is significantly smaller than the previously reported values (= 0.97 [8] and 0.93 [9]). It is essential to consider the balance among the fractions of alpha-crystal, mesomorphic phase and amorphous phase to obtain the reliable value, otherwise we end up overestimation of the value.…”

“…Although rough estimation of the energy level of mesomorphic phase is possible by assuming the original fraction of mesomorphic phase transforms into the same fraction of alpha-crystal [8,9], in reality the balance among the fractions of alpha-crystal, mesomorphic phase and amorphous phase as a function of temperature should be taken into consideration for the more precise estimation.…”

Metallocenic Copolymers of Isotactic Propylene and 1‐Octadecene: Crystalline Structure and Mechanical Behavior

“…The mesomorphic modification of ZieglerNatta iPP is described in literature as a structure with an intermediate order between the crystal and the amorphous phases, being constituted by a paracrystalline, microcrystalline, nanocrystalline or a conformationally disordered structure. [38][39][40][41][42][43] Therefore, variation of the different mechanical parameters and of the shape of the stress-strain curves in these two copolymers with the highest 1-octadecene contents (CiPOD5.3 and CiPOD7.6) should be also related, additionally to the decrease in number of ordered entities and their size. Thus, the size, perfection, amount and morphological details of ordered crystallites are key parameters in determining the mechanical response in these CiPPOD copolymers and they become softer as comonomer content increases, irrespective of the lattice being monoclinic or mesomorphic.…”

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

“…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].…”