Structure and properties of impact copolymer polypropylene. II. Phase structure and crystalline morphology

Abstract

In this work, an impact copolymer polypropylene (ICPP) was separated into 4 fractions, A, B, C, and D. The phase structure, thermal behavior, and crystalline morphology of the ICPP and its 4 fractions were studied thoroughly using scanning electron microscopy (SEM). Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and polarized light microscopy (PLM). Results of SEM and DMA show that ethylene-propylene rubber (EPR) and part of the ethylene-propylene segmented copolymer disperse as toughening particles in the ICPP. The size and size distribution of these particles are determined by chain structure of the fractions of ICPP. From fraction A to fraction D, the morphology changes from noncrystalline to semicrystalline gradually, as shown by DSC. DSC results also indicate that thermal behavior of the ICPP agrees greatly with its chain structure. PLM demonstrates that it is difficult for the ICPP to grow perfect spherulites, that is, partially, because the matrix of ICPP, fraction D, has defects in its macromolecular chain. Another cause is that there is a good compatible structure in the ICPP and so the noncrystalline component (including all fractions) hinders the growth of the spherulite.

The effect of controlled degradation on the molecular characteristics of heterophasic ethylene–propylene copolymers

“…The most common commercial method to produce these polymers is a sequential two stage polymerization of (first) propylene and then copolymerization of propylene and ethylene in the second reactor. The result of this two stage polymerization process is a highly complex mixture of amorphous, random, and blocky ethylene–propylene copolymers with different chemical composition distributions as well as different molar mass distributions, together with highly isotactic polypropylene and some polyethylene homopolymer . It has been proposed that in this complex mixture of morphologies, the ethylene–propylene segmented or blocky copolymers can act as compatibilizers whereby they enhance the interfacial adhesion between random rubbery copolymers and the polypropylene homopolymer.…”

“…Heterophasic ethylene-propylene copolymers (HEPCs), also known as impact copolymers (ICPs), are widely known to have superior low temperature impact resistance properties over conventional polypropylene (PP). [1][2][3] As a result of these superior properties, coupled with the good mechanical performance, heat resistance, and versatility of conventional polypropylene, HEPCs have seen a growing demand in the market in recent times. The most common commercial method to produce these polymers is a sequential two stage polymerization of (first) propylene and then copolymerization of propylene and ethylene in the second reactor.…”

Preparative TREF ‐ HT‐HPLC ‐ HPer DSC: Linking Molecular Characteristics and Thermal Properties of an Impact Poly(propylene) Copolymer

“…These two factors, the CCD (the chain structure, polymer type, and chain branching) and MMD, primarily influence the thermal properties (melting and crystallization behaviour) of such semi‐crystalline polymers. A variety of techniques has been reported to correlate the molecular characteristics of IPCs with their thermal and mechanical properties . Fractionation of the bulk sample by preparative TREF and further analysis of the separated fraction by conventional analytical techniques such as HT SEC, FTIR, 13 C NMR, and DSC has been found to be an effective method for the detailed analysis of such copolymer system .…”

Molecular composition and properties of impact propylene copolymers

“…The extent of this migration depends on both the nature of the copolymer phase (molecular weight and molecular weight distribution) and the chemical composition distribution of the copolymer phase. The chemical composition aspect is one which will, inter alia, determine whether or not there is some 'compatibilization' between the iPP matrix and the rubbery phase at work [18,19]. There have been a number of papers on morphology of physical blends of iPP with other polymers [20][21][22][23][24][25], as well as the macroscopic relationship between structure and property of the IPCs, and it is clear that the impact properties of these polymers are influenced by the size and distribution of the rubber particles in the polymer after processing [26][27][28][29][30][31][32][33][34].…”