Investigation of Miscibility between iPP and Propylene−Butene Random Copolymer by Small-Angle Neutron Scattering

Abstract

The degree of miscibilityof (iPP)/atactic propylene-butene random copolymer (a(P/B)) blends has been evaluated by using χ parameters obtained from a series of SANS experiments. It was found that the observed χ value decreased with increasing the butene content in a(P/B) from approximately zero in iPP/aPP. It showed a relatively larger negative value when the butane content was high. The temperature dependence of χ for this blend system was also measured. The sign of the slope of χ vs 1/T plot was apparently affected by butene content. It changed from positive to negative with an increase of butene content in a(P/B), indicating switching of the phase behavior from a UCST to an LCST system. SANS results were analyzed with the lattice cluster (LC) theory. It is estimated that the enthalpic interaction between a propylene and a butene monomer unit is negative. The value of trans-gauche exchange energy obtained from the LC theory is found to be associated with the segment length evaluated from SANS.

Effect of melt miscibility, polymorphism, and crystal morphology on tensile deformation of blends of isotactic polypropylene and propylene‐1‐hexene random copolymers

“…This effect was attributed to a negative enthalpy interaction between propylene and 1‐butene monomer units and to attractive entropic contributions. Based on such results, it was hypothesized that the branches longer than ethyl, such as the butyl branch of propylene 1‐hexene copolymers (PH) or the hexyl of propylene 1‐octene (PO), would contribute to a more effective interaction with the iPP chain . Furthermore, in our recent work on melt miscibility of iPP and PH copolymers we estimated a critical value of difference in 1‐hexene content for miscibility of propylene 1‐hexene copolymers of about 11 mol%.…”

“…Mixtures of iPP and propylene‐1‐alkene thermoplastic elastomers, form both miscible, and immiscible (but compatible) blends . In binary blends of random atactic propylene‐butene (PB) copolymers analyzed by SANS, the melt‐miscibility increased with increasing difference in content of 1‐butene . This effect was attributed to a negative enthalpy interaction between propylene and 1‐butene monomer units and to attractive entropic contributions.…”

Polypropylene and Polyethylene−Copolymer Blend Miscibility: Slow Chain Dynamics in Individual Blend Components near the Glass Transition

“…In order to determine whether PP and PE copolymers can form miscible, intimately mixed chain-level blends and, more importantly, understand why they do or do not exhibit such behavior, one must first narrow the field of all possible choices reported in the recent literature. ,,– In this investigation, we limit our investigations to amorphous systems, since phase separation in amorphous binary blends typically implies phase separation in their crystalline counterparts. 129 Xe NMR diffusion/equilibration experiments can indicate which blends are intimately mixed, albeit with a minimum length scale much longer than constituent radii of gyration, as we previously demonstrated for PIB/PEB blends .…”

Effect of chain blockiness on the phase behavior of ethylene‐octene copolymer blends

“…A primary difficulty in experimentally assessing the phase behavior of polyolefin blends, especially at melt process temperatures, is the similarity in chemical structure of the blend constituents. The most rigorous studies have relied on extrapolation of results with model copolymers to predict the phase behavior of real polymers 4–8. However, in a recent review of binary blends of high‐density polyethylene with low‐density polyethylenes of different chain microstructure, Zhao and Choi9 noted that the effects of branch content, molecular weight averages, molecular weight distribution, and branch length are still controversial.…”