Crystallization analysis fractionation (CRYSTAF) of poly(ethylene-co-1-octene) made with single-site-type catalysts: A mathematical model for the dependence of composition distribution on molecular weight

Soares, João B. P.; Monrabal, Benjamín; Nieto, Jesús; Blanco, Javier

doi:10.1002/(sici)1521-3935(19980901)199:9<1917::aid-macp1917>3.0.co;2-v

Cited by 46 publications

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“…For ethylene/α-olefin copolymers, the elution curves depend on the length of the longest ethylene sequences in the chains, which is a function of the copolymer molecular weight, α-olefin molar fraction, and reactivity ratios. [24,25] Other factors, such as crystallization kinetics [26,27] and co-crystallization effects [28,29] muddle even more how elution curves are related to copolymer CCDs.…”

Section: Explaining Deconvolution Methodsmentioning

confidence: 99%

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

Soares

2023

Can J Chem Eng

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The deconvolution of the molecular weight distribution (MWD) of polyolefins into Schultz–Flory most probable distributions has become the standard method to identify the number of site types on multiple‐site‐type olefin polymerization catalysts such as Ziegler–Natta, Phillips, and some supported metallocenes. This method has been used to quantify the effect of polymerization conditions and catalyst formulations on polyolefin MWD and olefin polymerization kinetics. Related methods have also been developed to deconvolute other polyolefin microstructure features, such as the chemical composition and comonomer sequence length distributions. In this paper, I explain the premises behind these deconvolution models and review the publications in this area, highlighting the advantages, disadvantages, and misuses of these methods. I also propose a revised formulation on how to model the MWD of polyolefins made with multiple‐site‐type catalysts using ratio distributions for propagation and chain transfer frequencies. The main objective of this overview article is to highlight the strengths, but also show the pitfalls, of polyolefin microstructure deconvolution methods.

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Section: Explaining Deconvolution Methodsmentioning

confidence: 99%

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

Soares

2023

Can J Chem Eng

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“…Note that eq 35 has a conditional summation when c/r = P (cc) . For example, W (0.1) is obtained from the summation of P (10,1) .M (10,1) , P (20,2) .M (20,2) , P (30,3) .M (30,3) , and so on. summations are conditional; they must be calculated using a computer program.…”

Section: Chemical Composition Distributionmentioning

confidence: 99%

“…The molecular weight distribution (MWD) and chemical composition distribution (CCD) of ethylene/1-olefin copolymers determine their properties . The MWD is typically quantified by gel permeation chromatography, − while the CCD can be measured by temperature rising elution fractionation, − crystallization elution fractionation, crystallization analysis fractionation, − and high-temperature thermal gradient interaction chromatography. − However, these analytical techniques can only measure the distribution of the 1-olefin fraction in statistical copolymers. They are inadequate to characterize the features of the OBC microstructure such as the distribution of number of blocks in the copolymer population, the distributions of lengths of hard and soft blocks, and the distribution of chains with specific chemical compositions.…”

Section: Introductionmentioning

confidence: 99%

Using Probability Models to Design the Microstructure of Linear Olefin Block Copolymers

Chayrattanaroj,

Anantawaraskul,

Soares

2024

Macromolecules

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Olefin block copolymers (OBCs)�a new type of linear thermoplastic ethylene/1-olefin elastomer�are made via chainshuttling polymerization using two catalysts with different reactivity ratios and a chain-shuttling agent. The microstructure of the OBCs has been analyzed using standard characterization techniques, but these methods cannot reveal the details of their molecular architectures, such as the distribution of the number of blocks in the polymer population; these finer microstructural features fall in the realm of mathematical models. In this article, we developed probability model equations to describe the microstructure of the OBCs and validated our solutions with Monte Carlo simulations. These new equations describe the distributions of molecular weight, chemical composition, number and length of blocks in OBCs made in a continuous stirred-tank reactor operated at steady-state conditions. We also developed a new method to predict the multimodality of the chemical composition distribution of OBCs (which can be experimentally measured) to assist in the design of new OBC materials.

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“…The CCD of metallocene-type resins has been found experimentally to be broader for the lower M w resins 55 and this has been shown to fit well with Stockmayer's distribution prediction. 88 The commercial introduction of homogeneous singlesite catalysts (metallocenes), which result in resins with narrow CCD and molecular weight distributions, and their combination with Ziegler-type resins, through blending or multiple catalyst -reactor processes, provides broad designing capabilities for new products and the need to determine the percentages of the various components present. In Figure 22 the analysis of a 50 : 50 combination of two metallocene-type resins (with narrow CCD) is shown as an example of the above discussion.…”

Section: Metallocene-type Linear Low-density Polyethylene Resinsmentioning

confidence: 99%

Temperature Rising Elution Fractionation and Crystallization Analysis Fractionation

Monrabal

2000

Encyclopedia of Analytical Chemistry

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Temperature rising elution fractionation (TREF) and crystallization analysis fractionation (CRYSTAF) are separation techniques for the characterization of semicrystalline polymers in terms of chemical composition. TREF has become a powerful tool for preparative polymer fractionation and for the analysis of the chemical composition distribution (CCD) in polyolefins. CRYSTAF, a more recent technique and with a simple hardware design, provides a faster approach for the analysis of the CCD. Both TREF and CRYSTAF separate according to the crystallizability of the polymer molecules, which is influenced by tacticity or the comonomer incorporation into the chain. TREF and CRYSTAF are becoming specially relevant in the characterization of the new and complex polyolefins made with combinations of homogeneous and heterogeneous catalysts.

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Crystallization analysis fractionation (CRYSTAF) of poly(ethylene-co-1-octene) made with single-site-type catalysts: A mathematical model for the dependence of composition distribution on molecular weight

Cited by 46 publications

References 0 publications

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

Polyolefin microstructural deconvolution methods: The good, the bad, and the ugly

Using Probability Models to Design the Microstructure of Linear Olefin Block Copolymers

Temperature Rising Elution Fractionation and Crystallization Analysis Fractionation

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