Metallocenic Isotactic Poly(propylene) and its Copolymers with 1‐Hexene and Ethylene

Abstract

A comprehensive study of the structure and properties has been performed for copolymers of propylene‐1‐hexene, CiPH, and propylene‐ethylene, CiPE, synthesized by an isotactic metallocene catalyst system. The comonomer content constitutes the most important factor affecting the structure and properties of these CiPH and CiPE copolymers, although the length of the comonomer is also very important. Thus, a considerable decrease in crystallinity is observed in the two kinds of copolymers as the comonomer content increases. The structure in the CiPH copolymers evolves, however, from the typical, monoclinic crystal lattice to mesomorphic‐like, ordered entities for the highest 1‐hexene molar fraction, whereas in the CiPE copolymers the structural evolution with molar fraction goes from a monoclinic lattice to an almost amorphous material. All of these variations in crystal structure significantly influence the viscoelastic and mechanical behavior of these CiPH and CiPE copolymers. Consequently, the location and intensity of the different relaxation mechanisms, as well as the rigidity parameters (storage and Young's moduli and microhardness) and deformation mechanism are strongly dependent upon composition.magnified image

Comonomer Length Influence on the Structure and Mechanical Response of Metallocenic Polypropylenic Materials

“…Stress-strain curves for the iPP, different CiPH, and CiPOD copolymers. lowering crystallinity here commented has also been found in some other ethylene or hexene copolymers [36,47] whereas a different response is observed for copolymers with 1-butene as a comonomeric unit, the Young's modulus being nearly constant with changing 1-butene composition [47] . Moreover, the effect of the comonomer type on mechanical response is also confirmed by microhardness, MH, values.…”

“…[20,36] Moreover, the stretching of the g polymorph in metallocene iPP also leads to the obtaining of this mesomorphic form. [37] The degree of crystallinity deduced from the diffractograms, f c WAXD , is shown in the last column of Table 1.…”

Fourier Transform Infrared Spectroscopy study of polymorphism in propylene-co-1-pentene copolymers: Trigonal form identification

“…6 and 9 for the cPPe8S sample (based on its initial X-ray diffraction profile) suggests the melting of the orthorhombic crystallites from around 50°C (starting obviously those thinner and imperfect crystals, which undergo successive recrystallization/melting processes [47] up to the main and final fusion taking place).…”

Effect of a Novel Family of N,N′-Diphenyl Bisamides on the Formation of β Crystalline Form in Isotactic Polypropylene

“…The physical properties of materials based on the iPP strongly depend upon its morphology, macromolecular structure, loading condition, etc. [1][2][3] As widely reported, iPP can form four crystalline structures: , , and smectic forms under different conditions. [4][5][6] The common -phase can be promoted with addition of nucleating agents.…”