Influence of Type and Content of Various Comonomers on Long-Chain Branching of Ethene/α-Olefin Copolymers

Abstract

One polyethylene and nine ethene/α-olefin copolymers differing in amount (0.4−2.9 mol %) and molar mass of the comonomer were characterized by NMR, SEC-MALLS, and rheology. Samples were polymerized using a [Ph2C(2,7-di-t-BuFlu)(Cp)]ZrCl2/MAO catalyst, with octene, octadecene, and hexacosene as comonomers, resulting in polymers of M w ≈ 190 kg/mol. The comonomer content was determined by melt-state NMR. For the homopolymer 0.37 and 0.30 LCB/molecule were found by NMR and SEC-MALLS, respectively. Rheological quantities, such as the zero shear rate viscosity (η0), increased with LCB as compared to linear samples of the same M w. The shape of the viscosity function and the linear steady-state elastic compliance ( ) showed a dependence on comonomer content and length. These findings are used to elucidate the various long-chain branching architectures. The highest comonomer content samples behaved like typical linear polymers in rheological experiments, while those with less comonomer contents were found to be long-chain branched. Besides the comonomer content, the type of comonomer has an influence on the branching structure.

Analytical Rheology of Polymer Melts: State of the Art

“…Cole-Cole plot of G (ω) v/s G (ω), and van GurpPalmen plot of loss angle δ = tan −1 [G (ω)/G (ω)] v/s the complex modulus |G * (ω)| are other alternatives that are very sensitive to changes in relaxation processes [88,[296][297][298][299][300][301]. For example, Robertson et al [302] used the van GurpPalmen plot and correlated the peak in δ at intermediate frequencies with LCB by appealing to blending rules.…”

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

“…Table 1) was measured by solution NMR using the WALTZ-16-program [16]. For L4, melt-state NMR was used [36,37]. Molar mass measurements were carried out by means of a high temperature size exclusion chromatograph (Waters, 150C) equipped with refractive index (RI) and infra-red (IR) (PolyChar, IR4) detectors.…”

“…However, the presence of sizable amounts of long-chain branches can also be safely excluded as the reaction conditions, under which F18G was synthesized inhibit the formation of long-chain branches [36]. Also the value of the zero shear-rate viscosity & 0 of about 9100 Pa·s (at 150°C) and the molar mass M w of 140 kg/mol make the presence of a small amount of LCBs very unlikely, as the expected zero shear-rate viscosity & 0 lin at 140 kg/mol is 30 000 Pa·s [38].…”

Lattice sizes, crystallinities, and spacing between amorphous chains - characterization of ethene-/ɑ-olefin copolymers with various comonomers and comonomer contents measured by wide angle X-ray scattering

“…One parameter influencing the lattice dimensions is the weight average molar mass M w (which strongly influences the rheological properties [27] and thus the chain mobility (and also long-chain branches [12,16,34,41])). For this purpose, several HDPEs (defined by the absence of sizable numbers of short-chain branches) -some slightly long-chain branched-were characterized.…”

“…This affinity of metallocene catalysts to incorporate longer -olefins easily also means that they are able to incorporate vinyl terminated chains, thus producing longchain branched materials [7,[12][13][14][15]. Because of the higher probability of a chain termination upon incorporation of a longer -olefin the production of highly SCB LCBmPE proves difficult [16].…”