Poly(propylene) Heterophasic Copolymers: Molecular Structure Analysis through Fractionation Techniques (original) (raw)
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Macromolecular Symposia, 2012
Impact polypropylene copolymers (ICPs) have complex microstructures compared to homo-or random copolymers of propylene. Standard analytical techniques are unable to unpack the complex structure of impact copolymers, hence the need to fractionate the material. The investigation of poly(propyleneethylene) block copolymers was conducted in order to understand the copolymer composition and the role of particular components by fractionation. Temperature rising elution fractionation (TREF) was used for fractionation of ICPs which involves breaking up the polymer into small fractions that can be analysed further to give more understanding on the complex microstructures. Two ICP samples (ICP1 and ICP2) with different physical properties were fractionated. The bulk samples as well as the resulting fractions were further analysed using DSC, FTIR and DMA. Below 0 8C, the DMA results of the bulk sample with high ethylene content (ICP1) showed both low storage modulus and stiffness which is in line with expectations. However, it was interesting to note that above 0 8C the trend was reversed, thus ICP2 with low ethylene content had lower storage modulus and stiffness. The DSC and FTIR results of the fractions of the two samples revealed different or inhomogeneous distribution of ethylene content between the samples which explained differences in mechanical properties. The findings emphasize the contributions of phase separation and compatibility between the rubber and the matrix towards physical and mechanical properties.
2015
ENGLISH ABSTRACT: Linear low density polyethylene (LLDPE), one of the fastest growing types of polyethylene, is made from the copolymerisation of ethylene and higher 1-olefin comonomers. 1-octene is the comonomer of choice as it gives mechanically better LLDPEs as compared to other 1-olefins. Recently, a shortage of 1-octene has been observed in the global market. Considering the fact that ethylene/1-heptene (EH) copolymers may have properties that are very similar to those of ethylene/1-octene (EO), replacing 1-octene with 1-heptene as the comonomer in the manufacture of commercial linear low density polyethylene (LLDPE) is a viable option. In order to do so, evaluation of microstructural and mechanical properties of both types of resins and their comparison were carried out first. Several LLDPE resins were synthesised using Ziegler-Natta (ZN) and metallocene type catalysts. The LLDPE resins were made using varying amounts of the comonomer to obtain copolymers of different composit...
About morphology in ethylene–propylene(-diene) copolymers-based latexes
Polymer, 2005
Coatings and engineering plastics often require high impact strength. This property can be achieved with tougheners. For the present paper, core-shell impact modifiers were synthesized using ethylene-propylene copolymers (EPM), ethylene-propylene-diene copolymers (EPDM) or a mixture of both types (EP(D)M) as core material, as well as poly(methyl methacrylate) (PMMA) as shell material.
Journal of Applied Polymer Science, 2009
This work highlights an attempt to characterize the degree and nature of long-chain branching (LCB) in an unknown sample of ethylene-propylene-diene rubber (EPDM). Two EPDM rubbers selected for this study were comparable in comonomer compositions but significantly different with respect to molar mass and the presence of LCB. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were used for different characterization techniques. 1H-NMR, and 13C-NMR were used for assessing the comonomer ratios and LCB. Size exclusion chromatography (SEC) equipped with triple detector system was used to determine the molar mass (both absolute and relative) and polydispersity index (PDI). Presence of branching was also detected using sec-viscometry. Rheological analysis has also been used for characterizing LCB. Finally, on the basis of the experimental findings and the available theories, an attempt was made to identify the chemical nature and degree of LCB. This study reveals the possibility of detailed characterization of molecular architecture of EPDM containing LCB by comparing with an essentially linear EPDM in light of an existing theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Synthesis and Characterization of Ethylene/Propylene Copolymers in the Whole Composition Range
Macromolecular Symposia, 2007
Summary: The incorporation of comonomer molecules in the backbone of a homopolymer can influence the final properties of the material, decreasing its crystallinity and the melting and glass transition temperatures, and increasing its impact resistance and transparency. In the present work, ten ethylene/propylene copolymers have been synthesized using a supported metallocene catalytic system covering the whole composition range. Any desired composition was obtained by controlling the feed composition during the reaction. These synthesized copolymers have been characterized by different techniques in order to study the effect of the comonomer incorporation onto their final properties. When the comonomer content is low, the behaviour of the copolymer is similar to that of the corresponding homopolymer. Nevertheless, if the comonomer content increases, the copolymer becomes more amorphous (low crystallization temperature and soft XRD signals) and easily deformable, reaching a behaviour close to that corresponding to an elastomeric material. In order to corroborate these results the samples have been characterized by TREF and GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more than 80% of ethylene are semicrystalline, with elution temperatures typical of this kind of polymers. Molecular weights are higher for homopolymers and they decrease as the comonomer concentration increases, whereas the polydispersity index keeps almost constant at the expected value for this kind of samples.
Structural characterization of reactor blends of polypropylene and ethylene-propylene rubber
Journal of Applied Polymer Science, 2004
Blends of isotactic polypropylene (PP), ethylene-propylene rubber copolymer (EPR), and ethylene-propylene crystalline copolymer (EPC) can be produced through in situ polymerization processes directly in the reactor and blends with different structure and composition can be obtained. In this work we studied the structure of five reactor-made blends of PP, EPR, and EPC produced by a Ziegler-Natta catalyst system. The composition of EPR was related to the ratio between ethylene and propylene used in the copolymerization step. The ethylene content in the EPR was in the range of 50 -70 mol %. The crystallization behav-ior of PP and EPC in the blends was influenced by the presence of the rubber, and some specific interactions between the components could be established. By preparative temperature rising elution fractionation (P-TREF) analysis, the isolation and characterization of crystalline EPC fractions were made.
Journal of Polymer Science Part A: Polymer Chemistry, 2011
Ethylene-propylene-diene terpolymers (EPDM) are generally amorphous and, therefore, do not crystallize from solution. Consequently, fractionation techniques based on crystallization, such as crystallization analysis fractionation or temperature rising elution fractionation, cannot be used to analyze their chemical composition distribution. Moreover, no suitable chromatographic system was known, which would enable to separate them according to their chemical composition. In this study, two different sorbent/solvent systems are tested with regard to the capability to separate EPDM-terpolymers and ethylene-propylene (EP)-copolymers according to chemical composition. While porous graphite/1-decanol system is selective towards ethylene and ethylidene-2-norbornene, carbon coated zirconia/2-ethyl-1-hexanol is preferentially selective towards ethylene. Consequently, the earlier system enables to separate both EP copolymers and EPDM according to the chemical composition and the latter mainly according to the ethylene content. The results prove that the chromatographic separation in both sorbent/solvent systems is not influenced by molar mass of a sample or by its long chain branching. V