Multidimensional Analytical Techniques for Studying the Thermo‐Oxidative Degradation of Impact Poly(propylene)

Abstract

Summary: Impact poly(propylene) copolymers (ICPP) are complex polymer systems containing various types of ethylene‐propylene copolymers as well as the majority poly(propylene) phase. In this study, multidimensional analytical techniques are applied to study the thermo‐oxidative degradation of these complex materials. The combination of size exclusion chromatography (SEC) and FTIR via an LC‐transform interface allows for the identification and tracking of the low molecular weight oxidized products. The degradation has a significant effect on the crystallisability of the material. DSC analysis shows that as the degradation proceeds, there is a significant decrease in the onset of the melt endotherm as well as the development of a double melt peak and peak broadening. Preparative Temperature Rising Elution Fractionation (TREF) is used to isolate the various fractions according to crystallisability during the polymer degradation. TREF‐SEC and TREF‐(SEC‐FTIR) allows for the isolation and identification of the polymer fractions undergoing oxidative degradation. It is shown that these multidimensional analytical techniques using crystallisability in the first dimensional fractionation provide more information on the mechanism and process of oxidative degradation than traditional bulk analysis methods.

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

“…The SEC results of all fractions of the copolymer 4V and selected fractions of the copolymer 3V are presented in Figure 10 and 11. Although the results for 3V have already been presented in a previous communication,17 they are included here for comparative purposes.…”

“… Changes in the molecular weight distributions of the bulk 3V samples and selected TREF fractions obtained after re‐crystallisation of samples degraded for 40, 65 and 90 h. Taken from Ref 17…”

“…The process of degradation was monitored on the bulk samples by SEC, FTIR, SEC/FTIR, crystallization analysis fractionation (CRYSTAF) and DSC. To obtain information on the degradation of the individual components of ICPP, a degraded sample was fractionated by prep TREF and the fractions analysed regarding molar mass and chemical composition 16, 17…”

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 complex molecular characteristics of IPCs have been investigated in many studies . However, the effect of the peroxide in the vis‐breaking process makes these materials even more complex in terms of molar mass distribution (MMD) and chemical composition distribution (CCD) . 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.…”