Synthesis and Characterization of Ethylene/Propylene Copolymers in the Whole Composition Range

Abstract

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.

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

“…Linear PE standards (Polymer Standard Service GmbH, Mainz, Germany), isotactic PP standards (American Polymer Standards, Mentor), linear PE with M w 260 kg/mol, iPP 200 kg/mol, and EP copolymers were dissolved in 1-decanol at a concentration of 1-2 mg/mL at 160 C. Samples of EP copolymers were prepared by Suarez 51,52 and described by Coto et al 53,54 The copolymerization reactions were carried out in a stirred tank reactor operating in semicontinuous mode at 70 C and 5 bar. Their molecular characterization data obtained with high-temperature SEC and NMR spectroscopy are summarized in Table I.…”

Molecular characterization of polypropylene heterophasic copolymers by fractionation techniques

“…50 mol.% to get an amorphous state. 4 Comparing the heterophasic copolymers, sample PHC 3 shows the highest T g,EPR value. This fact could be explained by the constriction effect of the higher crystallinity of this sample, which hinders the mobility of amorphous EPR chains and, as consequence increases the glass transition temperature.…”

“…and chemical resistance, such as food and medical packaging and sealing layers. [4][5][6] On the other hand, PP block copolymers, also called polypropylene heterophasic copolymers (PHC), are an intimate blend of homopolymer and an elastomeric material. These elastomers are added to the homopolymer and then blended physically, or are produced through polymerization in situ to get a chemical blend.…”

A fast and reliable procedure to determine the copolymer composition by GPC‐IR: Application to ethylene/propylene copolymers and comparison with 13C NMR

“…The heterogeneous metallocene catalyst used was rac ‐dimethyl‐silylbis(2‐methylindenyl)zirconium dichloride (Boulder Scientific) supported on silica (Grace Davidson) modified with methylaluminoxane (MAO; Witco, 30 wt% in toluene) and it will be named as M1. The conditions of the pretreatment of the support, the determination of the hydroxyl content and the physical properties of the silica in these conditions were reported previously [16], as well as, the immobilization method in order to obtain M1 [17].…”