Using Crystallisation Fractionation to Monitor Thermo‐Oxidative Degradation of Impact Poly(propylene) Copolymers

Abstract

ICPPs are complex materials that contain various ethylene/propylene copolymers in addition to the majority poly(propylene) phase. To understand their molecular structure, multiple fractionation and analysis techniques are used. In this study, TREF and CRYSTAF are used to study the difference in the thermo‐oxidative degradation of two grades of ICPPs with different ethylene contents. Direct correlations are drawn between the carbonyl index, molecular weight and crystallisability at various stages of degradation. The higher ethylene content sample shows increased thermal stability. This is due to the fact that the ethylene/propylene fraction is more stable due to the higher comonomer content and lower isotacticity as well as due to the higher amount of this fraction in the material.magnified image

Advanced Separation Techniques for Polyolefins

“…Recently, the use of a graphitic stationary phase (Hypercarb) for the separation of PP according to tacticity was reported [38]. This technique enables the generation of 2D characterization data for virtually any polyolefin over a wide compositional range regardless of crystallinity [46][47][48][49]. The fast and efficient separation of polyolefins and olefin copolymers with respect to chemical composition in a short time can only be achieved by the above method [39][40][41][42][43][44].…”

“…For the present LLDPE Expanded IR spectra of linear PE (a) and eicosane (b) with peak deconvolutions for the methylene and methyl absorption bands, the shoulder at 2,900 cm À1 is a CH 2 combination absorption (reprinted from [46] with permission of Wiley-VCH) samples, a cooling rate of 0.20 C/min was used; the heating rate was 0.25 C/min. These parameters must, therefore, be selected very carefully.…”

“…46 Schematic diagram of instrument combining TREF, dynamic crystallization and CEF (reprinted from[113] with permission of Wiley-VCH)Fig. 2.47 CEF analysis of Elite TM resin: top diagram shows the IR concentration reading, bottom diagram shows the crystallization and elution temperature profiles (reprinted from [113] with permission of Wiley-VCH)Fig.…”

Exploring the Compositional Heterogeneity of Vis‐Broken Impact Poly(propylene) Copolymers by Advanced Fractionation Methods

“…Numerous studies have shown that the vis‐breaking process can be applied to IPCs to decrease the average molar mass and to reduce the molar mass dispersity. Longer polymer chains are broken down to shorter chains with the help of peroxides . The vis‐broken IPC materials have higher MFRs, hence, e.g., filling of the narrow cavity molds in injection molding applications is facilitated …”

“…The need to understand how the peroxide affects the microstructure of these complex copolymers is critical in determining the final applicability and properties of the vis‐broken materials. Several studies have been conducted using high temperature size exclusion chromatography (HT‐SEC) to prove that the vis‐broken IPCs exhibit reduced molar masses and MMDs . Swart and van Reenen studied vis‐broken IPC bulk materials and their temperature rising elution fractionation (TREF) fractions using 13 C NMR and SEC coupled to Fourier transform infrared spectroscopy (FTIR) spectroscopy.…”